Quantification of Xanthates Chemisorbed on Solid Mining Wastes by Evolved Gas Analysis Hyphenation Techniques

Quantification of Xanthates Chemisorbed on Solid Mining Wastes by Evolved Gas Analysis Hyphenation Techniques | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Quantification of Xanthates Chemisorbed on Solid Mining Wastes by Evolved Gas Analysis Hyphenation Techniques Eric R. Dionne, Claude Marengo This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7348102/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 8 You are reading this latest preprint version Abstract The site of a former copper mine, in the process of being decontaminated, needed to be screened for xanthates contamination. It is known that potassium amyl xanthate as well as potassium ethyl xanthate were used in flotation process as collectors during the operation of the mine. The use of common analytical methods for organic contaminants, based on solvent extraction, showed no detectable xanthates contamination. As xanthates are strongly adsorbed on some mineral surfaces in the flotation process of the mineral-rich ore, it was suspected that common analytical methods can’t be applied to such situation. Even the use of acidic media with headspace gas chromatography was not able to detect any significant volatile decomposition products from xanthate-spiked soil samples. Then, thermal decomposition of the surface-bounded contamination, followed by an analysis of the generated vapour, showed significant results. A hyphenated system, composed of a thermogravimetric analyzer, an infrared spectrophotometer and a gas phase chromatograph coupled with a mass spectrometer was ultimately considered. With this multi-instrumental system, an analytical method has been developed and it was found that the xanthate contamination was well over 1 ppm for many samples taken from the former mining site. This article will describe the analytical method that was developed on this hyphenated system to detect, quantify and identify xanthates in environmental samples. Evolved Gas Analysis Gas Chromatography Hyphenated Technology Mass Spectrometry Mining Wastes Thermogravimetric Analysis Xanthates Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Introduction An analytical method, aimed at the quantification of an analyte from a complex environmental matrix, usually considers that the analyte is extractible and transferable into a non-interfering media. It is common to have the targeted analyte dispersed into a matrix with analogues substances. The consequence is generally a significantly reduction of the analyte recovery therefore, the robustness of the analytical method must therefore be monitored to ensure an acceptable recovery. In rarer but not uncommon cases, the analyte can interact strongly with the (organic, inorganic) matrix with the consequence that current extraction methods are useless to isolate the analyte. A good knowledge of the chemistry of contaminants is therefore necessary to identify situations potentially at risk of (chemi-, physi-)sorptions and other matrix effects. In environmental characterization and site remediation activities, this in-depth knowledge can ensure better protection of the environment and public health. This situation happened with contaminated soils with xanthates, a toxic material, from a former open-pit copper (bornite, chalcopyrite) and nickel (pentlandite) mine located in the La Vallée-de-la-Gatineau (a regional county municipality located in the Outaouais region of western Province of Quebec, Canada). Samples were taken from the remaining gangue piles and their composition consists of a granular material (natural soil mixed with mining residues) of grain size corresponds to sand with traces of silt and gravel. Common liquid-solid extraction done on some suspected contaminated samples revealed no xanthate contamination. Was it really the case? Xanthates are known to be toxic to aquatic organisms. They are also known to be biodegradable (Harris, 2000 ). But one of the decomposition products is carbon disulfide (see below), a toxic substance for human. These facts justify the effort to confirm those negative results on the site’s samples before its decommissioning. Alkali metal xanthates are highly soluble amphiphiles that are used as collector agents in the mining industry for the extraction of metals, like gold, copper, lead, or zinc, from sulfide-based ores by the flotation process (Rao, 2004 ; Wills and Finch, 2015 ). They are prepared by reacting an aliphatic alcohol with carbon disulfide (CS 2 ) to obtain the acid form (Harris, 2000 ; Roy, 2000 ). The latter is subsequently reacted with a strong base, such as sodium hydroxide or potassium hydroxide, to form the corresponding carbonodithioate ester. Figure 1 shows some molecular structures of commonly used xanthates in the mining industry. Figures 1 a and 1 b depict examples of the acid form of xanthates (ethyl xanthate and amyl xanthate respectively). Figure 1 c shows an example of a dixanthogen. Figure 1 d represents the amyl xanthate anion (AX − ) structure with its potassium cation, the resulting product of amyl xanthate (acid form) with potassium hydroxide. Since the establishment of the flotation process using sulfur-based organic derivative of carbonic acid (Keller, 1925 ; Lewis, 1925 ), efforts were invested into the elucidation of the interaction between the collector (a xanthate) and the mineral surface. Chen gives a summary of the evolution of the models describing on how a xanthate interacts with the ore surface in a flotation reservoir (Chen, 2021 ). The fact that the metal in a mineral matrix has a different chemical environment from its free metallic counterpart dissolved in pure water can explain why it is a challenge to fully understand the metal collector/mineral surface interactions. Electrochemical and spectrophotometry investigations confirmed the idea that the adsorption of xanthates on a sulfide ore depends on the oxidation of the xanthate and the reduction of the surface of the mineral particles. To confirm this hypothesis, potentiodynamic techniques were used on galena electrode. The results showed the adsorption of an oxidized xanthate radical could lead to the formation of the chemisorbed metal-xanthate pair or to dixantogen multilayers physisorbed on the mineral electrode. Both processes could render the galena electrode surface more hydrophobic thus could be linked to the promoting the flotation process. It was found that oxygen was important to induce the cathodic process on the electrode surface (Woods, 1971 ). Infrared spectroscopy studies confirmed these findings (Allison et al., 1972 ). Follow-up studies were done with the help of surface-specific spectroscopy techniques among bulk analytical techniques. Specifically, UV-visible spectroscopy showed that the dixantogen layers were formed only when xanthates were removed from the solution. This process occurred at a lower potential that the onset potential responsible for the flotation process thus confirming that the redox-induced chemisorption of xanthates on the ore surface was the sole process occurring in the flotation baths (Buckley and Woods, 1997 ). This explains why a simple solid/liquid extraction can’t liberate the adsorbed xanthates from the mineral matrix. The detection and quantification of a possible xanthate contamination must pass through the monitoring of its decomposition products i.e. CS 2 and the corresponding alcohol. Our first attempt to characterise these products from the collected samples was by considering a headspace gas chromatography (GC) coupled to a flame ionization detector (FID). During the analytical method development done directly on potassium amyl xanthate (PAX), potassium ethyl xanthate (PEX) and diethyl dixanthate (DIX), the decomposition was rapid, and the recoveries were complete when the correspondent acidic xanthate solutions (pH = 2) were considered directly in sealed headspace vials. But when an aliquot of a field sample, adjusted at a pH of 2 with an aqueous acidic solution (to promote the decomposition in CS 2 and alcohol), was spiked with a xanthate solution (standard addition method) and then heated at 60°C on a headspace module, no CS 2 nor the alcohol were detected . This situation therefore asked for a more radical methodology of xanthate decomposition from the solid mineral matrix, while still allowing the identification and quantification of the resulting alcohol and CS 2 . Metal xanthates, prepared via complexation with a transition metal salts (Cu 2+ , Pd 2+ , Ni 2+ , etc.), were extensively studied for their thermal behaviour. Thermogravimetric analysis showed that, depending on the length of the alkyl chain, metal xanthates decompose near 200°C (Cavell et al., 1973 ; Pandey et al., 1985 ; Sceney et al., 1973 ). Non commercially apparatuses were designed to thermally decompose a xanthate salt followed by the analysis of the generated gaseous products. (Tydén, 1966 ; Vreugdenhil et al., 1997a ; Vreugdenhil et al., 1997b ). Conversely, commercially available thermogravitational analyser can decompose all the xanthate present in an aliquot of the collected mining waste. An analysis on the thus generated gases would reveal the extent of the contamination, if any. Hyphenated technology makes it possible to meet those needs. A hyphenated system consists of two or more analytical instruments linked together to enhance and complement the obtained data from all instruments of the system. The system considered for our work is located at the MAPLES laboratory (Université de Montréal, Canada). This system is composed of four instruments: a thermogravimetric analyzer (TGA), a Fourier transform infrared spectrophotometer (FTIR), a gas chromatograph and a mass spectrometer. The thermogravimetric analyzer acts like a high-temperature headspace. The infrared spectrophotometer can be used to easily obtain the evolution profile of gases like water vapor, CO 2 , NH 3 , etc. The gas chromatograph is used to separate more complex evolved products and identified with the mass spectrometer who acts as the sole detector. The primary advantage of this hyphenated system is that the sample can be analyzed nearly as is with minimal preanalytical treatments. Few techniques allow this advantage on environmental samples, where the analyte must be extracted from an often heterogeneous and complex matrixes. This system allows, in one experiment, the use of the four instruments to undertake qualitative and quantitative analyzes. The analytical pathway to successfully detect and quantify xanthates chemically bounded on a mineral matrix will be describe in this article. Potassium amyl xanthate was known to be extensively used during the exploitation of the copper mine where the field samples were collected. Therefore, PAX was used to prepare the calibration curve. Consequently, the xanthate content, from the contaminated field samples, was expressed in µg AX − /g of dry sample (equivalent to ppm unit). We also applied the method to the decomposition of potassium ethyl xanthate and diethyldixanthate. As detailed below, the analytical method is based on two hyphenation modes. 1) The TGA-MS mode: used to determine if a field sample is contaminated with xanthate by monitoring the evolution of the ion m / z = 76 linked to the evolution of CS 2 . 2) The TGA-GC/MS mode: used subsequently to confirm the chemical identity of the evolved products. Materials and Methods 1. Chemicals. Potassium amyl xanthate (PAX), (TCI America, ≥ 97.0%, CAS#: 2720-73-2), potassium ethyl xanthate (PEX), (TCI America, ≥ 97.0%, CAS#: 140-89-6), diethyl dixanthate (DIX), (Sigma-Aldrich, CAS#: 502-55-6), sodium hydroxide (BDH, ≥ 98.0%) and methanol (FisherBrand, ACS grade) were purchased and used without further purification. Aqueous solution in this study was prepared with deionized water purified by reversed osmosis. The TGA was purged with nitrogen (99.999%, Linde). Helium (99.999%, Linde) was used as the carrier chromatographic elution. 2. Instrumental Parameters. A picture of the PerkinElmer hyphenated system used in this study is presented in figure S1 (Supporting Information section). The xanthate detection and quantification methods were developed by exploiting both the TGA-MS and the TGA-GC/MS modes. The supporting information section also contains a description of both analytical modes in the context of this work. Are summarized below the instrumental settings for both modes. i) Thermogravimetric Analyser (TGA) — TGA 8000. An aliquot of 70 ± 1 mg of calibration or environmental sample is placed in an alumina TGA. The nitrogen purge is set at 10 ml/min for the sample compartment and at 20 ml/min for the balance compartment. For a CS 2 analysis (quantification and confirmation), the environmental sample is heated from 35°C to 375°C at 20°C/min. For the detection of the other decomposition products (i.e. pentene and pentanol), the field samples were heated from 35°C to 375 at 60°C/min. For the pure xanthates of PAX, PEX and DIX, that were used as references, an aliquot of ≈ 1mg was used with a temperature range that spanned from 35°C to 375°C, heated at 60°C/min. ii) Infrared Spectrophotometer (IR) — Spectrum Two. The infrared spectrophotometer was not considered in the detection nor quantification of xanthates. iii) Gas chromatograph (GC) — Clarus 690. The TGA-MS mode, for xanthate quantification and injection time determination prior a TGA-GC/MS experiment, considers the GC as a transit instrument. Therefore, the GC oven is kept at 250°C (the same temperature as the transfer lines) to prevent condensation of the evolved gas into the restrictor linking the gas switching valves (GSV) to the mass spectrometer. Despite not being used during that mode, carrier gas (helium) must nonetheless flow through the chromatographic column. Helium pressure inside the chromatographic column ( p He ) was set at 8 psi. These settings stay the same regardless of the studied sample by TGA-MS. The chromatographic column used in all TGA-GC/MS experiments was a 20-meter, Rxi 624Sil MS (Restek) with an internal diameter of 180µm and a stationary phase thickness of 1.0 µm. The TGA-GC/MS experiments used to confirm the evolution of carbon disulfide and pentene from the field samples had considered a GC oven kept at 35°C with p He = 8 psi. TGA-GC/MS experiments used to analyse the pure xanthates as well as to detect pentanol evolution considered the following temperature program: isothermal step at 35°C for 5 minutes, then heating of the column to 250°C at 11°C/min ( p He = 20 psi). iv) Mass Spectrometer (MS) — Clarus SQ 8 S. Single ion monitoring (SIM) was used to detect the evolved analytes. The dwell time for all ions considered in this study was 0.100 second. The MS acquisition was done with an EI + ionization mode. Both inlet line temperature and MS source were set at 250°C. The MS was tuned with the multiplier voltage fixed at 2000 V. Scan mode (MS-Scan), with an ion range of m / z = 35 to 300, was considered during the analyte screenings done on the pure xanthates. MS-Scan mode considered a scan duration of 0.35 s and inter-delay delay of 0.05 s with an EI + ionization mode. The mass spectra of each chromatographic peaks were identified using the NIST MS Search version 2.3 database. v) Transfer Lines (TL) — TL9000e. The transfer lines, TGA valve, IR cell and GSV block were heated at 250°C. The flow rate of the TL9000e pump was 21 ml/min representing 70% of the total purge (sample and balance purge), as suggested by the supplier. Those settings were used for both TGA-MS and TGA-GC/MS modes. 3. Calibration Samples Preparation. i) Control sample. The calibration samples are prepared by spiking (i.e., standard addition method) a precise quantity of a control sample (“blank”) with a potassium amyl xanthate stock solution. To avoid signal variability between the calibration samples and field samples, the blank sample was an environmental sample collected from the same field and that had a granular and mineralogical matrix akin to the environmental samples to be analysed. The control sample must be chosen carefully. Obviously, it must be free of xanthate contamination or at lease has a contamination under the detection limit; it must also be free of organic interferences (traces of hydrocarbons for example). To ensure that the control sample meets these criteria, washing the control sample is carried out before its fortification with PAX additions. Approximatively 10 g of control sample (particle size ≤ 0.5 mm) is placed on a filtering crucible of medium porosity. The control sample is washed trice with water then trice with ethanol. The washed control sample is then spread on an aluminum weighting dish and dried under vacuum (≈ 1.0 × 10 − 3 Torr) at room temperature for 60 minutes. Once dry, the control sample is gently ground with a pestle. The control sample was analysed by TGA-MS (MS-SIM, m / z = 76) to certify that the sample is free of xanthate or has a non-detectable quantity of xanthates. Figure S4 shows a TGA-MS profile on a cleaned control sample aliquot. ii) PAX spiking of control samples. A solution of 2500 ppm of PAX is prepared fresh and used immediately. To impede the protonation of AX − (aq) anions, the PAX solution was brought to pH = 10 with a 0.01 M sodium hydroxide aqueous solution. Four daughter solutions were prepared with the alkaline PAX stock solution: 5 ppm, 15 ppm, 125 ppm and 245 ppm. ii) Spiking of the Control Sample Aliquots. The analytical method developed herein considered calibration samples with their xanthate concentration expressed in µg AX − / g of dry material. The AX − source is the PAX aqueous solution prepared above. The mass contribution coming from the potassium cations must be ignored. From the PAX dissolution stoichiometry, one mole of PAX allows the formation of one mole of AX − . Eq. 1 gives the factor needed to convert a mass of PAX into its AX − equivalent. An aliquot of 2.00 g of the dry control sample is weighed in an aluminum weighting dish and 500 µL of a PAX daughter solution (table S1 ) is poured dropwise over it to completely moisten the dish content then dried under vacuum (≈ 1.0 × 10 − 3 Torr) at room temperature for 60 minutes. Once dry, the calibration sample is homogenized by light grinding using a pestle. The dry, fortified sample is transferred into an amber glass vial fitted with a screw cap equipped with a septum. It is important to store the calibration samples in a freezer (< -20°C) immediately after preparation or when not in use. 4. Calibration Curve. The TGA-MS mode is the one recommended for xanthates quantification in the field samples and the calibration curve was prepared using this mode. It was found that CS 2 is the common evolved molecule whatever the xanthate (see Results and Discussion section). The calibration curve was then based on the specific detection of the molecular ion ( m / z = 76) of carbon disulfide. The bottom graphs seen at Fig. 2 show the raw TGA-MS profiles obtained from the analysis of the four calibration samples. The profiles were smoothed, corrected for the noise and the peak area was integrated. These treatments were done with TurboMass (version 6.1), the software controlling both the GC and the MS. The top graphs of Fig. 2 represent the corrected TGA-MS profiles with their area integrated (represented by the solid filling). Each calibration samples were analysed in triplicate. The average and standard deviation values were plotted and linear fitted to produce the calibration curve (Fig. 3 ) used to quantify the xanthates in the field samples. 5. Storage and preparation of the field samples for hyphenation analysis. Field samples were stored in amber glass jars and transported from the site to the laboratory in coolers kept at a temperature < 4°C. Upon arrival, the samples were continuously stored in a freezer (< -20°C). Prior its use, the amber glass jar is thawed for 15 minutes at room temperature. The field sample weight introduced in the TGA furnace (≈ 70 mg) is relatively small compared to the size (≈ 200 g) collected at the site. It is therefore critical that the aliquot transferred in the TGA crucible is representative of the jar content collected on the field. To assure this, each field samples were treated as follow: Approximately 80 g of the field sample was spread on a watch glass. Large clumps of the sample were crushed with a spatula. Approximately 4.0 g of the watch glass content was taken and deposited in an aluminum weighting dish. The representativeness of the field sample is ensured by taking ≈ 0.4 g from 10 different locations on the watch glass (see figure S5 A). Only the fraction composed with small particle size was considered; rocks and aggregates > 0.5 mm were avoided as much as possible. The aliquot was then dried under vacuum (≈ 1.0 × 10 − 3 Torr) at room temperature for 60 minutes. The dry aliquot was crushed gently in the aluminum dish with a pestle. Figure S2 B shows an example of a dry aliquot prepared from the field sample shown in figure S2 A. The aliquot was then transferred into an amber glass vial fitted with a screw cap. When not used, the vials were stored at -20°C. Before its analysis, the vial content was thawed at room temperature for ≈ 15 min. Results and Discussion 1. Evolved Products Identification from Xanthates. Because all xanthates are deemed harmful to the environment, the herein method don’t focus on the specific identification of the xanthate(s) from the tested samples but rather track the evolution of a specific analyte, i.e. carbon disulfide, that can be linked to the presence of xanthates. The history of the copper mine where the field samples originate tells that potassium amyl xanthate (PAX) was extensively used throughout its operation. This is the reason why PAX was chosen for the calibration samples preparation. Therefore, the tracking of carbon disulfide evolution from the calibration samples gave quantification results expressed in AX − equivalent unit of concentration. In the case where the xanthate usage history of a site is unknown, can the proposed approach usable? This question was answered by considering two other xanthates: potassium ethyl xanthate (PEX) and diethyl dixanthate (DIX). Like PAX, PEX and DIX were analysed by TGA-MS in their normal state (“pure” form) which is solid for PAX and PEX and semi-liquid for DIX. The only parameters that were changed from the environmental sample’s method described above was the weight of the xanthate in the TGA pan (≈ 3 mg instead of 70 mg) and the TGA heating rate (60°C/min instead of 20°C/min); a faster heating rate prevents a broadening of the TGA-MS profile. Section S6 shows the TGA-MS profiles on the studied xanthates. It is possible to observe that the molar mass of the xanthate influences the position of the profile apex. This fact reinforces the choice of using a TGA-MS experiment to quantify the xanthate: if a mixture of xanthate should be present, the analyst just needs to let the MS detect all the ions to obtain the complete profile as shown in Fig. 2 . Nonetheless, the PEX and DIX behave thermally like the PAX: they show a single decomposition event occurring in a relatively narrow range near 225°C, and importantly, they all produce ions with a m / z ratio of 76. To confirm that they all generate carbon disulfide, TGA-GC/MS experiments need to be done. Section S7 gives the TGA-GC/MS results on the three xanthates. The chromatograms show that indeed, DIX and PEX generate carbon disulfide. When the area of the chromatographic peak for carbon disulfide is normalized by the one of the other components detected, carbon disulfide is the major product evolved in the case of PEX. In the case of PAX and DIX, diamyl sulfide and diethyl xanthate are the most important evolved products respectively. As expected, pentanol is a product of PAX decomposition but its amount detected by the MS is ≈ 50% less than the carbon disulfide. As for ethanol, it was not detected in the PEX chromatogram. 2. Carbon Disulfide Recovery by TGA-MS Assays and Detection Limit Determination. When it was determined that carbon disulfide was the primary analyte used for the xanthate determination, recovery assays were conducted, and the limit of detection determined. Recovery measurements were undertaken to validate the calibration curve preparation method. Table S3 compiles the results of these tests. Manual additions of solid PAX < 30 µg in the TGA pan is challenging. An aqueous solution (pH = 10) of PAX was used to obtain quantity of dry AX ‒ equivalent ≤ 50 µg AX−/g. The TGA pan content was decomposed thermally by the TGA-MS method used to prepare the calibration curve, therefore by considering a heating rage between 35°C to 375°C at 20°C/min with a SIM-MS method specific to the ion m / z = 76. The AX ‒ quantities used for the recovery assays span over the range of concentrations depicted by the calibration curve (Fig. 3 ). With a recovery % average of 106 ± 9%, the CS 2 detection method and its conversion into an equivalent quantity of AX − can be assumed to be valid. The detection limit was determined by considering the TGA-MS signal of ion m/z = 76 obtained with the calibration sample at 1.01 µg AX − /g, the sample with the lowest PAX concentration. Table S4 gives the values obtained on nine replicates. The detection limit is calculated using Eq. 2, where σ is the standard deviation. The product of the standard deviation with the factor 3 gives a value in a.u., which when converted to µg AX ‒ /g of sample by the calibration relationship mentioned in the legend of table S3, gives a detection limit of 0.74 µg AX ‒ /g. The variation coefficient was also calculated, using Eq. 3 where σ is the standard deviation and µ is the average. Using the average standard deviation on the nine replicates, the variation coefficient is 42%. This value being relatively small, the detection limit was set at 1 µg AX ‒ /g. 3. Analytes for Xanthate Contamination Confirmation by TGA-GC/MS. The quantification method outlined in this report for xanthate-bound on a mineral matrix is solely based on the TGA-MS mode. The MS spectrum of a TGA-MS profile can be screened by an MS database, but no chemical certification can be achieved. An aliquot of the evolved products must therefore be injected on a chromatographic column. i) Carbon disulfide. Because CS 2 is the quantification analyte, its presence in the TGA-MS profile must be confirmed in. As explained in section S2, the injection on the chromatographic column coincides with the apex of the profile. As shown in Fig. 4 D, the retention time ( t r ) for CS 2 is 4.33 minutes (with p He = 8 psi). Based on many injections, carbon disulfide retention time showed a variation between 4.30 minutes to 4.40 minutes, based on the PAX level in the sample. Therefore, a chromatographic peak, obtained with a SIM method, centered between 4.30 minutes to 4.40 minutes will confirm the evolution of carbon disulfide. ii) Pentanol. Using carbon disulfide as the confirmation analyte for xanthate presence has its drawback for environmental samples: CS 2 can be generated by the degradation of organic material produced by anaerobic processes in the soil (Megonigal et al., 2003 ). To fulfil the demand from the engineering firm asking for the analyzes, a confirmation analyte, not produced by natural processes, has been search. The choice of that secondary analyte implies a knowledge or a good assumption of the xanthate(s) potentially contaminating the site. The obvious choice, in the case of PAX contamination, is the monitoring of pentanol. Pentanol has a mass spectrum depicting three principal ions: m/z = 42, 55, 70. Those ions come form the aliphatic chain attached to the hydroxyl group. Industrial sites usually contain petroleum hydrocarbon residues in their soils. This mining site is no exception to this fact. Therefore, those three ions could originate from heavy hydrocarbons residues instead from PAX. Because of such interference, pentanol could no be used as a quantification analyte but can be a reasonable confirmation candidate. The calibration samples (1.01 µg AX ‒ /g, 3.03 µg AX ‒ /g, 25.23 µg AX ‒ /g and 252.3 µg AX ‒ /g) used to prepare the calibration curve for carbon sulfide quantification were used to monitor the evolution of pentanol at different concentrations of AX ‒ . An approach modeled on the one used for CS 2 was developed to study the production of pentanol: TGA-MS profiles were first recorded by considering the three ions simultaneously with independent SIM methods. Then, an injection on the chromatographic column was undertaken. Table S2 shows that the retention time of pentanol evolved from pure PAX is 14.2 min when a carrier pressure of 20 psi is considered. To help with the comparison with the pure PAX chromatogram, this pressure was used with the calibration samples. Using a heating rate of 20°C/min (as for CS 2 ) was first considered, but the resulting TGA-MS profiles (from the monitoring of the m/z = 55 fragment) had their apex at ≈ 13 min. Since this step is solely done to determine the injection time on the GC column, the process of pentanol detection could be accelerated. Figure S8 shows TGA-MS profiles in function of the TGA heating rate with a SIM method considering the ion m/z = 55. To avoid thermal decomposition of possible hydrocarbon contamination possibly present in the field samples, 60°C/min was chosen for the pentanol screening. Figure S9 shows the chromatograms obtained following on the GC column injection. The calibration sample at 252.3 µg AX − / g depicts an intense peak at 14.9 min identified as pentanol. In the case of the other samples, a peak is present at 14.9 minutes, but it is weak, and the corresponding MS spectrum was unidentifiable as pentanol and embedded in the contaminations emanating from the control sample used to prepare the calibration samples. If the control sample (solvent washed) still emanates background contamination, it is reasonable to consider higher emanation from the (untreated) environmental samples. Pentanol is therefore a confirmation analyte suitable for highly PAX contaminated samples (see next section below). A study to determine the threshold PAX concentration for pentanol detection by TGA-GC/MS mode was not undertaken. iii) Pentene. Inspecting the chromatograms of figure S9, one can observe peaks with retention times < 3 min. Table S2 indicates that 1-pentene and 2-pentene are produced when pure PAX is heated in the purge condition used to analyse the soil samples. Those species are among the first molecules to eluate from the Rxi 624 Sil MS column. The pentene detected form pure PAX must come from the thermal conversion of the evolved pentanol. DFT calculations showed that pentanol, when heated, can be converted into 1- and 2-pentene via a dehydration reaction (Zhao et al., 2012 ). Figure 4 shows the chromatograms of the evolved species coming from a pure PAX aliquot under a carrier gas pressure of 8 psi. The inset focuses on the two pentene isomers. It shows that the pentene chromatographic signal consists of 3 peaks: one peak identified by the NIST data base to 1-pentene and two peaks identified as 2-pentene isomers. Figure S10 focuses on the first 5 minutes of the chromatograms depicted at figure S9 for pentanol evolution detection. The triplet linked to the pentene isomers evolution is visible at every AX ‒ concentration from the four calibration samples. Because of its fast elution in the chromatographic column and evolution at every concentration, pentene was considered as the secondary analyte to confirm the xanthate contamination in environmental samples with an AX ‒ contamination higher than the detection limit. 4 Field Samples Analysis. It is with the knowledge acquired by the TGA-MS and TGA-GC/MS experimentations done on the calibration samples that we tackled the task of detecting and quantifying PAX in the collected samples from the field of the decommissioned mine site. A total of 104 field samples were submitted to MAPLES laboratory. The samples were collected from two distinct sampling events on the mining site. The first lot had 30 samples, while the second one had 74 samples. Systematically, two TGA-MS assays were realized on all samples. When a sample depicted a positive signal linked to CS 2 evolution, an injection on the chromatographic column was carried out (TGA-GC/MS assay). The MS was set to detect specifically fragments with m/z = 76. A chromatographic peak with a retention time ≈ 4.33 ± 0.06 minutes confirmed the evolution of carbon disulfide. Table 1 compiles the xanthate quantification results on samples that were confirmed to produce CS 2 by TGA-GC/MS. Because reporting a xanthate contaminated sample could have important economical implications in term of soil decontamination, a cautious approach toward our results were preconized. It is with this approach in mind that the TGA-GC/MS results were screened for pentene evolution. After analysing the two lots, four analytical scenarios were observed and are summarized below. Table 1 AX − quantification results on the positive field samples based on TGA-MS assays for specific CS 2 detection (fragment m/z = 76). Contaminated Sample Number AX − Concentration (µg AX − /g) of Dry Field Sample Variation Coefficient /% Analytical Scenario # Assay 1 Assay 2 Assay 3 Assay 4 Assay 5 Average Standard Deviation Lot #1 1 17.86 13.56 13.84 — — 15.1 2.4 16 3 2 10.56 7.91 10.98 — — 9.8 1.7 17 3 3 5.65 6.97 — — — 6.3 0.9 15 2 4 5.24 5.03 — — — 5.1 0.1 3 2 5 7.72 8.09 — — — 7.9 0.3 3 2 6 2.82 5.11 — — — 4.0 1.6 41 2 7 38.34 24.92 25.54 24.69 — 28.4 6.7 23 4 8 47.49 67.06 49.59 40.50 40.55 49.0 10.9 22 3 9 59.23 62.96 73.39 — — 65.2 7.3 11 4 10 20213 14308 16580 — — 17034 2978 17 4 11 14.86 11.49 6.57 20.51 7.47 12.2 5.7 47 3 12 21.30 21.40 44.30 15.44 — 25.6 12.8 50 3 Lot # 2 1 a < 1 9.16 < 1 3.67 — 6.4 3.9 61 3 2 7.25 16.31 5.28 5.57 — 8.6 5.2 61 3 3 12.76 17.17 11.31 10.78 — 13.0 2.9 22 3 4 2.75 4.63 2.77 — — 3.4 1.1 32 3 5 8.18 7.98 8.26 — — 8.1 0.1 2 2 6 10.70 12.13 16.50 — — 13.1 3.0 23 3 7 a 2.16 2.12 < 1 — — 2.1 0.0 1 2 8 5.11 5.00 5.03 — — 5.0 0.1 1 2 9 4.23 4.38 4.17 — — 4.3 0.1 3 2 10 a 1 1 < 1 — — 1 0.0 0 2 11 8.88 4.53 9.78 5.44 — 7.2 2.6 36 3 12 7.59 3.69 3.29 2.93 — 4.4 2.2 49 2 13 3.29 3.84 2.98 — — 3.4 0.4 13 2 14 30.72 18.48 22.22 — — 23.8 6.3 26 2 a Average and standard deviation are calculated using the concentration valued higher than the detection limit. 1) Analytical scenario 1: Undetectable xanthate contamination. Absent from Table 1 are the 77 samples who showed a contamination, if present, below the detection limit of 1 µg AX − / g of dry sample. Figure 5 portrays a typical TGA-MS profile obtained on such sample with a SIM method specific to ion m/z = 76: Near the 13-minute mark (corresponding to a temperature ≈ 375°C at the TGA), a large peak appears. TGA-MS runs with longer acquisition times on such samples show that the signal curvature only tends to increase and never decrease to complete the profile’s peak. The source of the curvature of the baseline probably comes from natural contaminations which can generate ions m/z = 76 that are not linked to the evolution of CS 2 from the thermal decomposition of xanthates. The other possibility observed was a signal for m/z = 76 like the one depicted at figure S4a. 2) Analytical scenario 2: False positive. Several samples gave a positive TGA-MS profile for the m/z = 76 ion. Figure 6 portrays an example of TGA-MS profile and TGA-GC/MS results for such samples. It is possible to detect the evolution of CS 2 by TGA-GC/MS assay, but a xanthate contamination confirmation by the detection of pentene is not possible. In addition, these samples show a relatively low AX − concentration – the only exception being sample 14 from lot #2. Samples from this scenario depict TGA-MS profile for the fragment m/z = 76 with their peak appearing at a time ≥ 13 minutes and are noisy. An injection on the chromatographic column produces a chromatogram that can be associated with a CS 2 evolution. However, the intensity of the chromatogram is weak. Furthermore, the TGA-GC/MS profiles associated to ions m/z = 42, 55 and 70 show no signature of a pentene evolution: for this case, the chromatograms only show noise in the region between 3.0 and 4.0 min. The CS 2 is therefore suspected to come from a natural source and not from PAX. 3) Analytical scenario 3: Probable xanthate contamination. Figure 7 shows an example of the case where the TGA-MS and TGA-GC/MS results for CS 2 give MS signals that point to xanthate contamination: the TGA-MS profile is intense and relatively low in noise, as the chromatogram obtained by the TGA-GC/MS mode. However, the chromatograms linked to pentene evolution are less certain. Unlike to analytical scenario 2, the chromatograms show a certain fingerprint that can be linked to pentene production: The chromatograms show a clear doublet in the region between 3.0 and 4.0 min. The first peak has an average apex time of 3.33 min and 3.84 min for the second peak. From the inserts of Fig. 4 (pure PAX, obtained with the same GC conditions as the environmental samples) the first peak has an apex average of 3.25 min and 3.70 min for the second one. With a peak-to-peak average difference of ≈ 0.1 min, the doublet can be linked to pentene evolution. Our cautious approach prevents us from declaring these samples contaminated since the multiplicity on the second pentene peak is not visible. This case represents samples that demonstrate both TGA-MS and TGA-GC/MS results that meet all criteria for the presence of xanthate as obtained during the analysis of the calibration samples. As shown in Table 1 , the samples that meet this situation are in the minority. Figure 8 shows the most contaminated sample of the two batches analyzed in this study. This is the only sample on which pentanol was undoubtedly identified, i.e., with multiplicity on the second peak from the pentene doublet. Analyzes on more than a hundred samples confirmed the presence of amyl xanthate contamination in only a small fraction of them and amyl xanthate contamination concentration was rather low. This is not surprising since xanthates are biodegradable. Nevertheless, considerable savings for the rehabilitation of the site became possible by significantly reducing the quantities of materials confirmed of being contaminated with xanthates. To complement our findings, a half-life study of degradation of amyl xanthate in the certified contaminated field samples was conducted. Those samples were kept dry and in amber vial, at room temperature. The half-life in that is estimated to be six months for 40% of the samples while the other samples showed significantly longer stability (not detectable over three months), which confirms some persistence of xanthate, but also a rather slow potential for release of toxic degradation products into the environment. Conclusion A method to quantify xanthates contamination bounded strongly to a mineral matrix mixed to refractory materials is proposed. The novelty is the utilization of a hyphenated system composed of a thermogravimetric analyzer linked to a gas chromatograph coupled to a mass spectrometer as the detector. The method was developed by considering the detection of carbon disulfide as the quantification analyte since all xanthates studied (potassium amyl xanthate, ethyl amyl xanthate and diethyl dixanthate) are known to produce this molecule when heated. Two hyphenated modes were exploited. The TGA-MS mode proved to be suitable for the quantification of a thermally generated analyte based on CS 2 recovery % average of 106 ± 9%. The thus obtained MS signal profile can be integrated like a chromatographic peak and the calculated area can be used to prepare a calibration curve. The TGA-GC/MS mode was useful to confirm the degradation products based on the retention time on the chromatographic column. In the case for this study, CS 2 was the sole quantification analyte. This mode was also useful to detect the production of another decomposition species confirming that the CS 2 was produced by the xanthate decomposition and not from another organic source. This hyphenated system was able to provide a calibration curve with a good linearity with good recovery values on the CS 2 . Due to its versatility, such system could easily be exploited to detect other types of chemisorbed or physisorbed organic material on a refractory, solid matrix. The herein method would only be modified to adapt the TGA heating range to encompass the complete decomposition of the contamination and the SIM TGA-MS method would be modified to reflect the quantification analyte (i.e., a specie that gives an intense MS response). When field samples from a mining site known to be contaminated by potassium amyl xanthate (a compound known to be biodegradable) were analysed, the TGA-GC/MS results used to confirm the evolution of pentene had to be inspected carefully to prevent deeming certain samples of being contaminated with xanthate. A cautious approach was preconized throughout the study of the environmental samples. Based on a systematic approach, four different analytical scenarios were established to let the project managers determine their own limit to decide which zones of the mining site would be decontaminated. Declarations Author Contribution E.R.D. wrote the manuscript and supporting information text. E.R.D. prepared all the figures. C.M. revised and corrected the manuscript, the supporting information and the figures. Acknowledgement E. D. and C. M. want to acknowledge the significant contribution of Yanick Gauthier on this project (initial headspace experiments and field samples preparation method). References Allison SA, Goold LA, Nicol MJ, Granville A (1972) A determination various solution, products of the products of reaction between sulfide minerals and aqueous xanthate and a correlation of the with electrode rest potentials. Metall Trans 3:2613-2618. https://doi.org/10.1007/BF02644237 Buckley AN, Woods R (1997) Chemisorption—the thermodynamically favoured process in the interaction of thiol collectors with sulphide minerals. Int J Miner Process 51:15-26. https://doi.org/10.1016/S0301-7516(97)00016-1 Cavell KJ, Sceney CG, Hill JO, Magee RJ (1973) Thermal studies on nickel alkyl xanthate complexes. Thermochim Acta 5:319-328. https://doi.org/10.1016/0040-6031(73)85010-5 Chen J (2021) The interaction of flotation reagents with metal ions in mineral surfaces: A perspective from coordination chemistry. Miner Eng 171:107067. https://doi.org/10.1016/j.mineng.2021.107067 Harris GH (2000) Xanthates. Kirk-Othmer Encyclopedia of Chemical Technology. John Wiley & Sons, New York Keller CH (1925) Froth-flotation concentration of ores. U.S. Pat., 1554216 Lewis CP (1925) Concentration of Ores. U.S. Pat., 1554220 Megonigal JP, Hines ME, Visscher PT (2003) 8.08 - Anaerobic Metabolism: Linkages to Trace Gases and Aerobic Processes. In: Holland HD, Turekian KK (eds). Treatise on Geochemistry. Pergamon, Oxford. pp 317-424 Pandey OP, Sengupta SK, Tripathi SC (1985) Thermochemistry of metal xanthato complexes. A review. Thermochim Acta 96:155-167. https://doi.org/10.1016/0040-6031(85)80018-6 Rao SR (2004) Flotation Surfactants. Surface Chemistry of Froth Flotation: Volume 1: Fundamentals. Springer US, Boston. pp 385-478 Roy K-M (2000) Xanthates. Ullmann's Encyclopedia of Industrial Chemistry. Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim. pp 633-642 Sceney CG, Hill JO, Magee RJ (1973) Thermal studies on palladium alkyl xanthates. Thermochim Acta 6:111-117. https://doi.org/10.1016/0040-6031(73)80010-3 Tydén I (1966) Gas chromatographic study of the pyrolysis of potassium salts of xanthic acids. Talanta 13:1353-1360. Vreugdenhil AJ, Brienne SHR, Butler IS, Finch JA, Markwell RD (1997a) Infrared spectroscopic determination of the gas-phase thermal decomposition products of metal-ethyldithiocarbonate complexes. Spectrochim Acta A Mol Biomol Spectrosc 53:2139-2151. https://doi.org/10.1016/S1386-1425(97)00144-3 Vreugdenhil AJ, Brienne SHR, Markwell RD, Butler IS, Finch JA (1997b) Headspace analysis gas-phase infrared spectroscopy: a study of xanthate decomposition on mineral surfaces. J Mol Struct 405:67-77. https://doi.org/10.1016/S0022-2860(96)09449-5 Wills BA, Finch J (2015) Wills' Mineral Processing Technology: an Introduction to the Practical Aspects of ore Treatment and Mineral Recovery. Butterworth-Heinemann Woods R (1971) Oxidation of ethyl xanthate on platinum, gold, copper, and galena electrodes. Relation to the mechanism of mineral flotation. J Phys Chem 75:354-362. https://doi.org/10.1021/j100673a011 Zhao L, Ye L, Zhang F, Zhang L (2012) Thermal Decomposition of 1-Pentanol and Its Isomers: A Theoretical Study. J Phys Chem A 116:9238-9244. https://doi.org/10.1021/jp305885s Additional Declarations No competing interests reported. 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12:07:35","extension":"png","order_by":23,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":86208,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage9.png","url":"https://assets-eu.researchsquare.com/files/rs-7348102/v1/0f8fc3eca9f7c924ba101256.png"},{"id":92943696,"identity":"58fe59a1-e519-498f-b745-f9c12af48110","added_by":"auto","created_at":"2025-10-07 11:59:31","extension":"png","order_by":24,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":11532,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinegroupimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-7348102/v1/4cfef4a472e3ccc85ae8e4f1.png"},{"id":92943699,"identity":"01828a9a-ab23-43be-8f8f-ebf68672f880","added_by":"auto","created_at":"2025-10-07 11:59:31","extension":"png","order_by":25,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":1874,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-7348102/v1/283a33c7fa4178ae7e1c8371.png"},{"id":92943690,"identity":"de6eb440-92ce-4baa-b62b-8ed04c3d73cf","added_by":"auto","created_at":"2025-10-07 11:59:31","extension":"xml","order_by":26,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":106518,"visible":true,"origin":"","legend":"","description":"","filename":"6fa1694d6209458d82189dfcb65830d91structuring.xml","url":"https://assets-eu.researchsquare.com/files/rs-7348102/v1/3fb6cb1b14c30eb868da5239.xml"},{"id":92944628,"identity":"fd7fb0ca-7c3e-4b91-aec4-ab3bb70794bd","added_by":"auto","created_at":"2025-10-07 12:15:34","extension":"html","order_by":27,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":112575,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-7348102/v1/ff13674f8ef0e208f8b5f16c.html"},{"id":92944473,"identity":"0a21a7fb-9c7f-4541-bbdb-bbb27d80b25b","added_by":"auto","created_at":"2025-10-07 12:07:30","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":20029,"visible":true,"origin":"","legend":"\u003cp\u003eMolecular structures of common xanthates: (a) ethyl xanthate (EX). (b) \u003cem\u003en\u003c/em\u003e-Amyl xanthate (AX). (c) Diethyl dixanthate (DIX). (d) Potassium amyl xanthate (PAX) where the amyl xanthate anion (AX−) is shown to counterbalance the potassium cation.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-7348102/v1/ee55f2a6238a34af29056a54.png"},{"id":92944478,"identity":"078f86fb-1200-4261-b655-a60df4138391","added_by":"auto","created_at":"2025-10-07 12:07:31","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":87797,"visible":true,"origin":"","legend":"\u003cp\u003eTGA-MS profiles (MS-SIM, \u003cem\u003em\u003c/em\u003e/\u003cem\u003ez\u003c/em\u003e= 76) obtained from standard samples analyzed promptly after their preparation. Top traces: Corrected and integrated profiles. Bottom traces: raw profiles as obtained. The time at the apex as well as the integration value are indicated respectively on the corrected profiles. (a) 1.01 μg AX−/g; (b) 3.03 μg AX−/g; (c) 25.25 μg AX−/g; (d) 49.50 μg AX− / g.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-7348102/v1/1fd09bc0f68d06161fcd9c34.png"},{"id":92943669,"identity":"9dd28b29-caef-44f8-b674-cdda0f2ffa80","added_by":"auto","created_at":"2025-10-07 11:59:30","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":14165,"visible":true,"origin":"","legend":"\u003cp\u003eA calibration curve obtained from the integration of the TGA-MS (MS-SIM, \u003cem\u003em\u003c/em\u003e/\u003cem\u003ez\u003c/em\u003e = 76) profiles of freshly prepared standard samples. The line represents the linear regression on the data. Error bars represent standard deviation from three measurements.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-7348102/v1/d467b4ed68aaeb5c86fd0b57.png"},{"id":92943665,"identity":"d6e6b62a-0ea1-4b4f-9add-6cb1afc56988","added_by":"auto","created_at":"2025-10-07 11:59:29","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":97689,"visible":true,"origin":"","legend":"\u003cp\u003eTGA-GC/MS results on ≈1 mg pure PAX aliquot (TGA heating rate: 60°C/min; \u003cem\u003ep\u003c/em\u003e\u003csub\u003eHe\u003c/sub\u003e = 8 psi). The bottom chromatograms are acquired by MS scan.\u0026nbsp; Top chromatograms were acquired simultaneously with a MS-SIM method: (a) \u003cem\u003em\u003c/em\u003e/\u003cem\u003ez\u003c/em\u003e = 42, (b) \u003cem\u003em\u003c/em\u003e/\u003cem\u003ez\u003c/em\u003e = 55, (c) \u003cem\u003em\u003c/em\u003e/\u003cem\u003ez\u003c/em\u003e = 70, (d) \u003cem\u003em\u003c/em\u003e/\u003cem\u003ez\u003c/em\u003e = 76. The inserts magnify the pentene peaks.\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-7348102/v1/cbc29cc8e834279a32a8633e.png"},{"id":92943673,"identity":"b8c9170b-75ff-49d0-a28e-fc9899b1b3a2","added_by":"auto","created_at":"2025-10-07 11:59:30","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":38493,"visible":true,"origin":"","legend":"\u003cp\u003eAnalytical scenario 1: undetectable xanthate contamination. Example of a TGA-MS profile (MS-SIM, \u003cem\u003em\u003c/em\u003e/\u003cem\u003ez\u003c/em\u003e = 76) from a field sample containing a level of xanthate bellow the detection limit of 1 μg AX\u003csup\u003e‒\u003c/sup\u003e/g. On such profile, no peak, from the CS\u003csub\u003e2\u003c/sub\u003e detection, is noticeable between 5 minutes and 13 minutes.\u0026nbsp;\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-7348102/v1/a0500411003e52055b8866e5.png"},{"id":92943685,"identity":"81474143-e5b6-4702-9fe2-ab35da285e2a","added_by":"auto","created_at":"2025-10-07 11:59:30","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":143904,"visible":true,"origin":"","legend":"\u003cp\u003eAnalytical scenario 2: false positive (lot#2, sample 9). (A) Bottom trace: CS\u003csub\u003e2\u003c/sub\u003e detection by TGA-MS. Top trace: TGA-MS profile after baseline correction and integration. The dashed line corresponds to the injection time on the GC column for the CS\u003csub\u003e2\u003c/sub\u003e confirmation. (B) Resulting chromatogram obtained by TGA-GC/MS at 10.0 min. (C) TGA-MS profile for pentene detection. The dashed line represents the injection time on the GC column for the pentene confirmation. (D) TGA-GC/MS chromatograms after an injection at 8.1 min (\u003cem\u003ep\u003c/em\u003e\u003csub\u003eHe \u003c/sub\u003e= 8 psi). The shaded section, between 3.0 and 4.0, highlights the pentene peaks.\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-7348102/v1/aaa44e3fb4a7cf571972b63c.png"},{"id":92943672,"identity":"bb054642-1371-4337-b522-64639a32dc74","added_by":"auto","created_at":"2025-10-07 11:59:30","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":145548,"visible":true,"origin":"","legend":"\u003cp\u003eAnalytical scenario 3: probable xanthate contamination (lot#2, sample 2). (A) Bottom trace: CS\u003csub\u003e2\u003c/sub\u003e detection by TGA-MS. Top trace: TGA-MS profile after baseline correction and integration. The dashed line corresponds to the injection time on the GC column for the CS\u003csub\u003e2\u003c/sub\u003e confirmation. (B) Resulting chromatogram obtained by TGA-GC/MS at 12.6 min. (C) TGA-MS profile for pentene detection. The dashed line represents the injection time on the GC column for the pentene confirmation. (D) TGA-GC/MS chromatograms after an injection at 8.1 min (\u003cem\u003ep\u003c/em\u003e\u003csub\u003eHe \u003c/sub\u003e= 8 psi). The shaded section, between 3.0 and 4.0, highlights the pentene peaks.\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-7348102/v1/5a3ff276e2233dc63c891837.png"},{"id":92943676,"identity":"b216797a-e6a5-4a96-a6cd-fd5f9ffdc1a5","added_by":"auto","created_at":"2025-10-07 11:59:30","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":122622,"visible":true,"origin":"","legend":"\u003cp\u003eAnalytical scenario 4: confirmed xanthate contamination (lot#1, sample 10). (A) Bottom trace: CS\u003csub\u003e2\u003c/sub\u003e detection by TGA-MS. Top trace: TGA-MS profile after baseline correction and integration. The dashed line corresponds to the injection time on the GC column for the CS\u003csub\u003e2\u003c/sub\u003e confirmation. (B) Resulting chromatogram obtained by TGA-GC/MS after an injection at 7.3 min. (C) TGA-MS profile for pentene detection. The dashed line represents the injection time on the GC column for the pentene confirmation. (D) TGA-GC/MS chromatograms after an injection at 6.2 min (\u003cem\u003ep\u003c/em\u003e\u003csub\u003eHe \u003c/sub\u003e= 8 psi). The shaded section, between 3.0 and 4.0, highlights the pentene peaks.\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-7348102/v1/9502b43b169ebd2e253c604a.png"},{"id":92946137,"identity":"da2e04f2-4567-46b5-bdb5-0609df20db06","added_by":"auto","created_at":"2025-10-07 12:34:51","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1424311,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7348102/v1/727e46e5-168a-4a54-8016-edba3361c3cd.pdf"},{"id":92943670,"identity":"4530587c-0419-4ae3-a8ad-947ddafec154","added_by":"auto","created_at":"2025-10-07 11:59:30","extension":"docx","order_by":0,"title":"","display":"","copyAsset":false,"role":"supplement","size":20773074,"visible":true,"origin":"","legend":"","description":"","filename":"SupportingInformationXanthates.docx","url":"https://assets-eu.researchsquare.com/files/rs-7348102/v1/a3891d7a0454549f8f9b746d.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Quantification of Xanthates Chemisorbed on Solid Mining Wastes by Evolved Gas Analysis Hyphenation Techniques","fulltext":[{"header":"Introduction","content":"\u003cp\u003eAn analytical method, aimed at the quantification of an analyte from a complex environmental matrix, usually considers that the analyte is extractible and transferable into a non-interfering media. It is common to have the targeted analyte dispersed into a matrix with analogues substances. The consequence is generally a significantly reduction of the analyte recovery therefore, the robustness of the analytical method must therefore be monitored to ensure an acceptable recovery. In rarer but not uncommon cases, the analyte can interact strongly with the (organic, inorganic) matrix with the consequence that current extraction methods are useless to isolate the analyte. A good knowledge of the chemistry of contaminants is therefore necessary to identify situations potentially at risk of (chemi-, physi-)sorptions and other matrix effects. In environmental characterization and site remediation activities, this in-depth knowledge can ensure better protection of the environment and public health. This situation happened with contaminated soils with xanthates, a toxic material, from a former open-pit copper (bornite, chalcopyrite) and nickel (pentlandite) mine located in the La Vall\u0026eacute;e-de-la-Gatineau (a regional county municipality located in the Outaouais region of western Province of Quebec, Canada). Samples were taken from the remaining gangue piles and their composition consists of a granular material (natural soil mixed with mining residues) of grain size corresponds to sand with traces of silt and gravel. Common liquid-solid extraction done on some suspected contaminated samples revealed no xanthate contamination. Was it really the case? Xanthates are known to be toxic to aquatic organisms. They are also known to be biodegradable (Harris, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2000\u003c/span\u003e). But one of the decomposition products is carbon disulfide (see below), a toxic substance for human. These facts justify the effort to confirm those negative results on the site\u0026rsquo;s samples before its decommissioning.\u003c/p\u003e\u003cp\u003eAlkali metal xanthates are highly soluble amphiphiles that are used as collector agents in the mining industry for the extraction of metals, like gold, copper, lead, or zinc, from sulfide-based ores by the flotation process (Rao, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2004\u003c/span\u003e; Wills and Finch, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). They are prepared by reacting an aliphatic alcohol with carbon disulfide (CS\u003csub\u003e2\u003c/sub\u003e) to obtain the acid form (Harris, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2000\u003c/span\u003e; Roy, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2000\u003c/span\u003e). The latter is subsequently reacted with a strong base, such as sodium hydroxide or potassium hydroxide, to form the corresponding carbonodithioate ester. Figure\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e shows some molecular structures of commonly used xanthates in the mining industry. Figures\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea and \u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb depict examples of the acid form of xanthates (ethyl xanthate and amyl xanthate respectively). Figure\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ec shows an example of a dixanthogen. Figure\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ed represents the amyl xanthate anion (AX\u003csup\u003e\u0026minus;\u003c/sup\u003e) structure with its potassium cation, the resulting product of amyl xanthate (acid form) with potassium hydroxide. Since the establishment of the flotation process using sulfur-based organic derivative of carbonic acid (Keller, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e1925\u003c/span\u003e; Lewis, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e1925\u003c/span\u003e), efforts were invested into the elucidation of the interaction between the collector (a xanthate) and the mineral surface. Chen gives a summary of the evolution of the models describing on how a xanthate interacts with the ore surface in a flotation reservoir (Chen, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). The fact that the metal in a mineral matrix has a different chemical environment from its free metallic counterpart dissolved in pure water can explain why it is a challenge to fully understand the metal collector/mineral surface interactions. Electrochemical and spectrophotometry investigations confirmed the idea that the adsorption of xanthates on a sulfide ore depends on the oxidation of the xanthate and the reduction of the surface of the mineral particles. To confirm this hypothesis, potentiodynamic techniques were used on galena electrode. The results showed the adsorption of an oxidized xanthate radical could lead to the formation of the chemisorbed metal-xanthate pair or to dixantogen multilayers physisorbed on the mineral electrode. Both processes could render the galena electrode surface more hydrophobic thus could be linked to the promoting the flotation process. It was found that oxygen was important to induce the cathodic process on the electrode surface (Woods, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e1971\u003c/span\u003e). Infrared spectroscopy studies confirmed these findings (Allison et al., \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1972\u003c/span\u003e). Follow-up studies were done with the help of surface-specific spectroscopy techniques among bulk analytical techniques. Specifically, UV-visible spectroscopy showed that the dixantogen layers were formed only when xanthates were removed from the solution. This process occurred at a lower potential that the onset potential responsible for the flotation process thus confirming that the redox-induced \u003cem\u003echemisorption\u003c/em\u003e of xanthates on the ore surface was the sole process occurring in the flotation baths (Buckley and Woods, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e1997\u003c/span\u003e). This explains why a simple solid/liquid extraction can\u0026rsquo;t liberate the adsorbed xanthates from the mineral matrix. The detection and quantification of a possible xanthate contamination must pass through the monitoring of its decomposition products i.e. CS\u003csub\u003e2\u003c/sub\u003e and the corresponding alcohol.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eOur first attempt to characterise these products from the collected samples was by considering a headspace gas chromatography (GC) coupled to a flame ionization detector (FID). During the analytical method development done directly on potassium amyl xanthate (PAX), potassium ethyl xanthate (PEX) and diethyl dixanthate (DIX), the decomposition was rapid, and the recoveries were complete when the correspondent acidic xanthate solutions (pH\u0026thinsp;=\u0026thinsp;2) were considered directly in sealed headspace vials. But when an aliquot of a field sample, adjusted at a pH of 2 with an aqueous acidic solution (to promote the decomposition in CS\u003csub\u003e2\u003c/sub\u003e and alcohol), was spiked with a xanthate solution (standard addition method) and then heated at 60\u0026deg;C on a headspace module, \u003cem\u003eno CS\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e \u003cem\u003enor the alcohol were detected\u003c/em\u003e. This situation therefore asked for a more radical methodology of xanthate decomposition from the solid mineral matrix, while still allowing the identification and quantification of the resulting alcohol and CS\u003csub\u003e2\u003c/sub\u003e.\u003c/p\u003e\u003cp\u003eMetal xanthates, prepared via complexation with a transition metal salts (Cu\u003csup\u003e2+\u003c/sup\u003e, Pd\u003csup\u003e2+\u003c/sup\u003e, Ni\u003csup\u003e2+\u003c/sup\u003e, etc.), were extensively studied for their thermal behaviour. Thermogravimetric analysis showed that, depending on the length of the alkyl chain, metal xanthates decompose near 200\u0026deg;C (Cavell et al., \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e1973\u003c/span\u003e; Pandey et al., \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e1985\u003c/span\u003e; Sceney et al., \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e1973\u003c/span\u003e). Non commercially apparatuses were designed to thermally decompose a xanthate salt followed by the analysis of the generated gaseous products. (Tyd\u0026eacute;n, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e1966\u003c/span\u003e; Vreugdenhil et al., \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e1997a\u003c/span\u003e; Vreugdenhil et al., \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e1997b\u003c/span\u003e). Conversely, commercially available thermogravitational analyser can decompose all the xanthate present in an aliquot of the collected mining waste. An analysis on the thus generated gases would reveal the extent of the contamination, if any. Hyphenated technology makes it possible to meet those needs. A hyphenated system consists of two or more analytical instruments linked together to enhance and complement the obtained data from all instruments of the system. The system considered for our work is located at the MAPLES laboratory (Universit\u0026eacute; de Montr\u0026eacute;al, Canada). This system is composed of four instruments: a thermogravimetric analyzer (TGA), a Fourier transform infrared spectrophotometer (FTIR), a gas chromatograph and a mass spectrometer. The thermogravimetric analyzer acts like a high-temperature headspace. The infrared spectrophotometer can be used to easily obtain the evolution profile of gases like water vapor, CO\u003csub\u003e2\u003c/sub\u003e, NH\u003csub\u003e3\u003c/sub\u003e, etc. The gas chromatograph is used to separate more complex evolved products and identified with the mass spectrometer who acts as the sole detector. The primary advantage of this hyphenated system is that the sample can be analyzed nearly \u003cem\u003eas is\u003c/em\u003e with minimal preanalytical treatments. Few techniques allow this advantage on environmental samples, where the analyte must be extracted from an often heterogeneous and complex matrixes. This system allows, in one experiment, the use of the four instruments to undertake qualitative and quantitative analyzes. The analytical pathway to successfully detect and quantify xanthates chemically bounded on a mineral matrix will be describe in this article. Potassium amyl xanthate was known to be extensively used during the exploitation of the copper mine where the field samples were collected. Therefore, PAX was used to prepare the calibration curve. Consequently, the xanthate content, from the contaminated field samples, was expressed in \u003cem\u003e\u0026micro;g AX\u003c/em\u003e\u003csup\u003e\u003cem\u003e\u0026minus;\u003c/em\u003e\u003c/sup\u003e\u003cem\u003e/g of dry sample\u003c/em\u003e (equivalent to ppm unit). We also applied the method to the decomposition of potassium ethyl xanthate and diethyldixanthate.\u003c/p\u003e\u003cp\u003eAs detailed below, the analytical method is based on two hyphenation modes. 1) The TGA-MS mode: used to determine if a field sample is contaminated with xanthate by monitoring the evolution of the ion \u003cem\u003em\u003c/em\u003e/\u003cem\u003ez\u003c/em\u003e\u0026thinsp;=\u0026thinsp;76 linked to the evolution of CS\u003csub\u003e2\u003c/sub\u003e. 2) The TGA-GC/MS mode: used subsequently to confirm the chemical identity of the evolved products.\u003c/p\u003e"},{"header":"Materials and Methods","content":"\u003ch3\u003e1. Chemicals.\u003c/h3\u003e\n\u003cp\u003ePotassium amyl xanthate (PAX), (TCI America, \u0026ge; 97.0%, CAS#: 2720-73-2), potassium ethyl xanthate (PEX), (TCI America, \u0026ge; 97.0%, CAS#: 140-89-6), diethyl dixanthate (DIX), (Sigma-Aldrich, CAS#: 502-55-6), sodium hydroxide (BDH, \u0026ge; 98.0%) and methanol (FisherBrand, ACS grade) were purchased and used without further purification. Aqueous solution in this study was prepared with deionized water purified by reversed osmosis. The TGA was purged with nitrogen (99.999%, Linde). Helium (99.999%, Linde) was used as the carrier chromatographic elution.\u003c/p\u003e\n\u003ch3\u003e2. Instrumental Parameters.\u003c/h3\u003e\n\u003cp\u003eA picture of the PerkinElmer hyphenated system used in this study is presented in figure \u003cspan class=\"InternalRef\"\u003eS1\u003c/span\u003e (Supporting Information section). The xanthate detection and quantification methods were developed by exploiting both the TGA-MS and the TGA-GC/MS modes. The supporting information section also contains a description of both analytical modes in the context of this work. Are summarized below the instrumental settings for both modes.\u003c/p\u003e\n\u003cp\u003e\u003cspan\u003e\u003c/span\u003e\u003c/p\u003e\n\u003cp\u003e\u003cspan type=\"ItalicUnderline\" class=\"ItalicUnderline\" name=\"Emphasis\"\u003ei) Thermogravimetric Analyser (TGA) \u0026mdash; TGA 8000.\u003c/span\u003e An aliquot of 70\u0026thinsp;\u0026plusmn;\u0026thinsp;1 mg of calibration or environmental sample is placed in an alumina TGA. The nitrogen purge is set at 10 ml/min for the sample compartment and at 20 ml/min for the balance compartment. For a CS\u003csub\u003e2\u003c/sub\u003e analysis (quantification and confirmation), the environmental sample is heated from 35\u0026deg;C to 375\u0026deg;C at 20\u0026deg;C/min. For the detection of the other decomposition products (i.e. pentene and pentanol), the field samples were heated from 35\u0026deg;C to 375 at 60\u0026deg;C/min. For the pure xanthates of PAX, PEX and DIX, that were used as references, an aliquot of \u0026asymp;\u0026thinsp;1mg was used with a temperature range that spanned from 35\u0026deg;C to 375\u0026deg;C, heated at 60\u0026deg;C/min.\u003c/p\u003e\u003cspan\u003e\n \u003cp\u003e\u003cspan type=\"ItalicUnderline\" class=\"ItalicUnderline\" name=\"Emphasis\"\u003eii) Infrared Spectrophotometer (IR) \u0026mdash; Spectrum Two.\u003c/span\u003e The infrared spectrophotometer was not considered in the detection nor quantification of xanthates.\u003c/p\u003e\n\u003c/span\u003e\u003cspan\u003e\n \u003cp\u003e\u003cspan type=\"ItalicUnderline\" class=\"ItalicUnderline\" name=\"Emphasis\"\u003eiii) Gas chromatograph (GC) \u0026mdash; Clarus 690.\u003c/span\u003e The TGA-MS mode, for xanthate quantification and injection time determination prior a TGA-GC/MS experiment, considers the GC as a transit instrument. Therefore, the GC oven is kept at 250\u0026deg;C (the same temperature as the transfer lines) to prevent condensation of the evolved gas into the restrictor linking the gas switching valves (GSV) to the mass spectrometer. Despite not being used during that mode, carrier gas (helium) must nonetheless flow through the chromatographic column. Helium pressure inside the chromatographic column (\u003cem\u003ep\u003c/em\u003e\u003csub\u003eHe\u003c/sub\u003e) was set at 8 psi. These settings stay the same regardless of the studied sample by TGA-MS.\u003c/p\u003e\n\u003c/span\u003e\n\u003cp\u003e\u003c/p\u003e\n\u003cp\u003eThe chromatographic column used in all TGA-GC/MS experiments was a 20-meter, Rxi 624Sil MS (Restek) with an internal diameter of 180\u0026micro;m and a stationary phase thickness of 1.0 \u0026micro;m. The TGA-GC/MS experiments used to confirm the evolution of carbon disulfide and pentene from the field samples had considered a GC oven kept at 35\u0026deg;C with \u003cem\u003ep\u003c/em\u003e\u003csub\u003eHe\u003c/sub\u003e = 8 psi. TGA-GC/MS experiments used to analyse the pure xanthates as well as to detect pentanol evolution considered the following temperature program: isothermal step at 35\u0026deg;C for 5 minutes, then heating of the column to 250\u0026deg;C at 11\u0026deg;C/min (\u003cem\u003ep\u003c/em\u003e\u003csub\u003eHe\u003c/sub\u003e = 20 psi).\u003c/p\u003e\n\u003cp\u003e\u003cspan\u003e\u003c/span\u003e\u003c/p\u003e\n\u003cp\u003e\u003cspan type=\"ItalicUnderline\" class=\"ItalicUnderline\" name=\"Emphasis\"\u003eiv) Mass Spectrometer (MS) \u0026mdash; Clarus SQ 8 S.\u003c/span\u003e Single ion monitoring (SIM) was used to detect the evolved analytes. The dwell time for all ions considered in this study was 0.100 second. The MS acquisition was done with an EI\u0026thinsp;+\u0026thinsp;ionization mode. Both inlet line temperature and MS source were set at 250\u0026deg;C. The MS was tuned with the multiplier voltage fixed at 2000 V. Scan mode (MS-Scan), with an ion range of \u003cem\u003em\u003c/em\u003e/\u003cem\u003ez\u003c/em\u003e\u0026thinsp;=\u0026thinsp;35 to 300, was considered during the analyte screenings done on the pure xanthates. MS-Scan mode considered a scan duration of 0.35 s and inter-delay delay of 0.05 s with an EI\u0026thinsp;+\u0026thinsp;ionization mode. The mass spectra of each chromatographic peaks were identified using the NIST MS Search version 2.3 database.\u003c/p\u003e\u003cspan\u003e\n \u003cp\u003e\u003cspan type=\"ItalicUnderline\" class=\"ItalicUnderline\" name=\"Emphasis\"\u003ev) Transfer Lines (TL) \u0026mdash; TL9000e.\u003c/span\u003e The transfer lines, TGA valve, IR cell and GSV block were heated at 250\u0026deg;C. The flow rate of the TL9000e pump was 21 ml/min representing 70% of the total purge (sample and balance purge), as suggested by the supplier. Those settings were used for both TGA-MS and TGA-GC/MS modes.\u003c/p\u003e\n\u003c/span\u003e\n\u003cp\u003e\u003c/p\u003e\n\u003cp\u003e\u003cspan\u003e\u003c/span\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e3. Calibration Samples Preparation.\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003c/p\u003e\n\u003cp\u003e\u003cspan\u003e\u003c/span\u003e\u003c/p\u003e\n\u003cp\u003e\u003cspan type=\"ItalicUnderline\" class=\"ItalicUnderline\" name=\"Emphasis\"\u003ei) Control sample.\u003c/span\u003e The calibration samples are prepared by spiking (i.e., standard addition method) a precise quantity of a control sample (\u0026ldquo;blank\u0026rdquo;) with a potassium amyl xanthate stock solution. To avoid signal variability between the calibration samples and field samples, the blank sample was an environmental sample collected from the same field and that had a granular and mineralogical matrix akin to the environmental samples to be analysed. The control sample must be chosen carefully. Obviously, it must be free of xanthate contamination or at lease has a contamination under the detection limit; it must also be free of organic interferences (traces of hydrocarbons for example). To ensure that the control sample meets these criteria, washing the control sample is carried out before its fortification with PAX additions. Approximatively 10 g of control sample (particle size\u0026thinsp;\u0026le;\u0026thinsp;0.5 mm) is placed on a filtering crucible of medium porosity. The control sample is washed trice with water then trice with ethanol. The washed control sample is then spread on an aluminum weighting dish and dried under vacuum (\u0026asymp;\u0026thinsp;1.0 \u0026times; 10\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e Torr) at room temperature for 60 minutes. Once dry, the control sample is gently ground with a pestle. The control sample was analysed by TGA-MS (MS-SIM, \u003cem\u003em\u003c/em\u003e/\u003cem\u003ez\u003c/em\u003e\u0026thinsp;=\u0026thinsp;76) to certify that the sample is free of xanthate or has a non-detectable quantity of xanthates. Figure S4 shows a TGA-MS profile on a cleaned control sample aliquot.\u003c/p\u003e\u003cspan\u003e\n \u003cp\u003e\u003cspan type=\"ItalicUnderline\" class=\"ItalicUnderline\" name=\"Emphasis\"\u003eii) PAX spiking of control samples.\u003c/span\u003e A solution of 2500 ppm of PAX is prepared fresh and used immediately. To impede the protonation of AX\u003csup\u003e\u0026minus;\u003c/sup\u003e\u003csub\u003e(aq)\u003c/sub\u003e anions, the PAX solution was brought to pH\u0026thinsp;=\u0026thinsp;10 with a 0.01 M sodium hydroxide aqueous solution. Four daughter solutions were prepared with the alkaline PAX stock solution: 5 ppm, 15 ppm, 125 ppm and 245 ppm.\u003c/p\u003e\n\u003c/span\u003e\u003cspan\u003e\n \u003cp\u003e\u003cspan type=\"ItalicUnderline\" class=\"ItalicUnderline\" name=\"Emphasis\"\u003eii) Spiking of the Control Sample Aliquots.\u003c/span\u003e The analytical method developed herein considered calibration samples with their xanthate concentration expressed in \u0026micro;g AX\u003csup\u003e\u0026minus;\u003c/sup\u003e / g of dry material. The AX\u003csup\u003e\u0026minus;\u003c/sup\u003e source is the PAX aqueous solution prepared above. The mass contribution coming from the potassium cations must be ignored. From the PAX dissolution stoichiometry, one mole of PAX allows the formation of one mole of AX\u003csup\u003e\u0026minus;\u003c/sup\u003e. Eq.\u0026nbsp;1 gives the factor needed to convert a mass of PAX into its AX\u003csup\u003e\u0026minus;\u003c/sup\u003e equivalent.\u003c/p\u003e\n\u003c/span\u003e\n\u003cp\u003e\u003c/p\u003e\n\u003cp\u003e\u003cimg src=\"data:image/png;base64,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\"\u003e\u003c/p\u003e\n\u003cp\u003eAn aliquot of 2.00 g of the dry control sample is weighed in an aluminum weighting dish and 500 \u0026micro;L of a PAX daughter solution (table \u003cspan class=\"InternalRef\"\u003eS1\u003c/span\u003e) is poured dropwise over it to completely moisten the dish content then dried under vacuum (\u0026asymp;\u0026thinsp;1.0 \u0026times; 10\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e Torr) at room temperature for 60 minutes. Once dry, the calibration sample is homogenized by light grinding using a pestle. The dry, fortified sample is transferred into an amber glass vial fitted with a screw cap equipped with a septum. It is important to store the calibration samples in a freezer (\u0026lt; -20\u0026deg;C) immediately after preparation or when not in use.\u003c/p\u003e\n\u003ch3\u003e4. Calibration Curve.\u003c/h3\u003e\n\u003cp\u003eThe TGA-MS mode is the one recommended for xanthates quantification in the field samples and the calibration curve was prepared using this mode. It was found that CS\u003csub\u003e2\u003c/sub\u003e is the common evolved molecule whatever the xanthate (see Results and Discussion section). The calibration curve was then based on the specific detection of the molecular ion (\u003cem\u003em\u003c/em\u003e/\u003cem\u003ez\u003c/em\u003e\u0026thinsp;=\u0026thinsp;76) of carbon disulfide. The bottom graphs seen at Fig. \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e show the raw TGA-MS profiles obtained from the analysis of the four calibration samples. The profiles were smoothed, corrected for the noise and the peak area was integrated. These treatments were done with TurboMass (version 6.1), the software controlling both the GC and the MS. The top graphs of Fig. \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e represent the corrected TGA-MS profiles with their area integrated (represented by the solid filling). Each calibration samples were analysed in triplicate. The average and standard deviation values were plotted and linear fitted to produce the calibration curve (Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e) used to quantify the xanthates in the field samples.\u003c/p\u003e\n\u003ch3\u003e5. Storage and preparation of the field samples for hyphenation analysis.\u003c/h3\u003e\n\u003cp\u003eField samples were stored in amber glass jars and transported from the site to the laboratory in coolers kept at a temperature\u0026thinsp;\u0026lt;\u0026thinsp;4\u0026deg;C. Upon arrival, the samples were continuously stored in a freezer (\u0026lt; -20\u0026deg;C). Prior its use, the amber glass jar is thawed for 15 minutes at room temperature.\u003c/p\u003e\n\u003cp\u003eThe field sample weight introduced in the TGA furnace (\u0026asymp;\u0026thinsp;70 mg) is relatively small compared to the size (\u0026asymp;\u0026thinsp;200 g) collected at the site. It is therefore critical that the aliquot transferred in the TGA crucible is representative of the jar content collected on the field. To assure this, each field samples were treated as follow: Approximately 80 g of the field sample was spread on a watch glass. Large clumps of the sample were crushed with a spatula. Approximately 4.0 g of the watch glass content was taken and deposited in an aluminum weighting dish. The representativeness of the field sample is ensured by taking\u0026thinsp;\u0026asymp;\u0026thinsp;0.4 g from 10 different locations on the watch glass (see figure S5 A). Only the fraction composed with small particle size was considered; rocks and aggregates\u0026thinsp;\u0026gt;\u0026thinsp;0.5 mm were avoided as much as possible. The aliquot was then dried under vacuum (\u0026asymp;\u0026thinsp;1.0 \u0026times; 10\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e Torr) at room temperature for 60 minutes. The dry aliquot was crushed gently in the aluminum dish with a pestle. Figure S2 B shows an example of a dry aliquot prepared from the field sample shown in figure S2 A. The aliquot was then transferred into an amber glass vial fitted with a screw cap. When not used, the vials were stored at -20\u0026deg;C. Before its analysis, the vial content was thawed at room temperature for \u0026asymp;\u0026thinsp;15 min.\u003c/p\u003e"},{"header":"Results and Discussion","content":"\u003ch3\u003e1. Evolved Products Identification from Xanthates.\u003c/h3\u003e\n\u003cp\u003eBecause all xanthates are deemed harmful to the environment, the herein method don\u0026rsquo;t focus on the specific identification of the xanthate(s) from the tested samples but rather track the evolution of a specific analyte, i.e. carbon disulfide, that can be linked to the presence of xanthates. The history of the copper mine where the field samples originate tells that potassium amyl xanthate (PAX) was extensively used throughout its operation. This is the reason why PAX was chosen for the calibration samples preparation. Therefore, the tracking of carbon disulfide evolution from the calibration samples gave quantification results expressed in AX\u003csup\u003e\u0026minus;\u003c/sup\u003e equivalent unit of concentration. In the case where the xanthate usage history of a site is unknown, can the proposed approach usable? This question was answered by considering two other xanthates: potassium ethyl xanthate (PEX) and diethyl dixanthate (DIX).\u003c/p\u003e\n\u003cp\u003eLike PAX, PEX and DIX were analysed by TGA-MS in their normal state (\u0026ldquo;pure\u0026rdquo; form) which is solid for PAX and PEX and semi-liquid for DIX. The only parameters that were changed from the environmental sample\u0026rsquo;s method described above was the weight of the xanthate in the TGA pan (\u0026asymp;\u0026thinsp;3 mg instead of 70 mg) and the TGA heating rate (60\u0026deg;C/min instead of 20\u0026deg;C/min); a faster heating rate prevents a broadening of the TGA-MS profile. Section S6 shows the TGA-MS profiles on the studied xanthates. It is possible to observe that the molar mass of the xanthate influences the position of the profile apex. This fact reinforces the choice of using a TGA-MS experiment to quantify the xanthate: if a mixture of xanthate should be present, the analyst just needs to let the MS detect all the ions to obtain the complete profile as shown in Fig. \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e. Nonetheless, the PEX and DIX behave thermally like the PAX: they show a single decomposition event occurring in a relatively narrow range near 225\u0026deg;C, and importantly, they all produce ions with a \u003cem\u003em\u003c/em\u003e/\u003cem\u003ez\u003c/em\u003e ratio of 76. To confirm that they all generate carbon disulfide, TGA-GC/MS experiments need to be done. Section S7 gives the TGA-GC/MS results on the three xanthates. The chromatograms show that indeed, DIX and PEX generate carbon disulfide. When the area of the chromatographic peak for carbon disulfide is normalized by the one of the other components detected, carbon disulfide is the major product evolved in the case of PEX. In the case of PAX and DIX, diamyl sulfide and diethyl xanthate are the most important evolved products respectively. As expected, pentanol is a product of PAX decomposition but its amount detected by the MS is \u0026asymp;\u0026thinsp;50% less than the carbon disulfide. As for ethanol, it was not detected in the PEX chromatogram.\u003c/p\u003e\n\u003ch3\u003e2. Carbon Disulfide Recovery by TGA-MS Assays and Detection Limit Determination.\u003c/h3\u003e\n\u003cp\u003eWhen it was determined that carbon disulfide was the primary analyte used for the xanthate determination, recovery assays were conducted, and the limit of detection determined. Recovery measurements were undertaken to validate the calibration curve preparation method. Table S3 compiles the results of these tests. Manual additions of solid PAX\u0026thinsp;\u0026lt;\u0026thinsp;30 \u0026micro;g in the TGA pan is challenging. An aqueous solution (pH\u0026thinsp;=\u0026thinsp;10) of PAX was used to obtain quantity of dry AX\u003csup\u003e‒\u003c/sup\u003e equivalent\u0026thinsp;\u0026le;\u0026thinsp;50 \u0026micro;g AX\u0026minus;/g. The TGA pan content was decomposed thermally by the TGA-MS method used to prepare the calibration curve, therefore by considering a heating rage between 35\u0026deg;C to 375\u0026deg;C at 20\u0026deg;C/min with a SIM-MS method specific to the ion \u003cem\u003em\u003c/em\u003e/\u003cem\u003ez\u003c/em\u003e\u0026thinsp;=\u0026thinsp;76. The AX\u003csup\u003e‒\u003c/sup\u003e quantities used for the recovery assays span over the range of concentrations depicted by the calibration curve (Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e). With a recovery % average of 106\u0026thinsp;\u0026plusmn;\u0026thinsp;9%, the CS\u003csub\u003e2\u003c/sub\u003e detection method and its conversion into an equivalent quantity of AX\u003csup\u003e\u0026minus;\u003c/sup\u003e can be assumed to be valid.\u003c/p\u003e\n\u003cp\u003eThe detection limit was determined by considering the TGA-MS signal of ion m/z\u0026thinsp;=\u0026thinsp;76 obtained with the calibration sample at 1.01 \u0026micro;g AX\u003csup\u003e\u0026minus;\u003c/sup\u003e/g, the sample with the lowest PAX concentration. Table S4 gives the values obtained on nine replicates. The detection limit is calculated using Eq. 2, where \u003cem\u003e\u0026sigma;\u003c/em\u003e is the standard deviation.\u003c/p\u003e\n\u003cdiv class=\"gridtable\"\u003e\n \u003cdiv align=\"left\" class=\"colspec\"\u003e\u003cimg src=\"data:image/png;base64,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\"\u003e\u003c/div\u003e\n\u003c/div\u003e\n\u003cp\u003eThe product of the standard deviation with the factor 3 gives a value in a.u., which when converted to \u0026micro;g AX\u003csup\u003e‒\u003c/sup\u003e/g of sample by the calibration relationship mentioned in the legend of table S3, gives a detection limit of 0.74 \u0026micro;g AX\u003csup\u003e‒\u003c/sup\u003e/g. The variation coefficient was also calculated, using Eq. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e where \u003cem\u003e\u0026sigma;\u003c/em\u003e is the standard deviation and \u003cem\u003e\u0026micro;\u003c/em\u003e is the average.\u003c/p\u003e\n\u003cp\u003e\u003cimg src=\"data:image/png;base64,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\"\u003e\u003c/p\u003e\n\u003cp\u003eUsing the average standard deviation on the nine replicates, the variation coefficient is 42%. This value being relatively small, the detection limit was set at 1 \u0026micro;g AX\u003csup\u003e‒\u003c/sup\u003e/g.\u003c/p\u003e\n\u003ch3\u003e3. Analytes for Xanthate Contamination Confirmation by TGA-GC/MS.\u003c/h3\u003e\n\u003cp\u003eThe quantification method outlined in this report for xanthate-bound on a mineral matrix is solely based on the TGA-MS mode. The MS spectrum of a TGA-MS profile can be screened by an MS database, but no chemical certification can be achieved. An aliquot of the evolved products must therefore be injected on a chromatographic column.\u003c/p\u003e\n\u003cp\u003e\u003cspan\u003e\u003c/span\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ei) Carbon disulfide.\u003c/strong\u003e Because CS\u003csub\u003e2\u003c/sub\u003e is the quantification analyte, its presence in the TGA-MS profile must be confirmed in. As explained in section S2, the injection on the chromatographic column coincides with the apex of the profile. As shown in Fig. \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003eD, the retention time (\u003cem\u003et\u003c/em\u003e\u003csub\u003er\u003c/sub\u003e) for CS\u003csub\u003e2\u003c/sub\u003e is 4.33 minutes (with \u003cem\u003ep\u003c/em\u003e\u003csub\u003eHe\u003c/sub\u003e = 8 psi). Based on many injections, carbon disulfide retention time showed a variation between 4.30 minutes to 4.40 minutes, based on the PAX level in the sample. Therefore, a chromatographic peak, obtained with a SIM method, centered between 4.30 minutes to 4.40 minutes will confirm the evolution of carbon disulfide.\u003c/p\u003e\n\u003cp\u003e\u003c/p\u003e\n\u003cp\u003e\u003cspan\u003e\u003c/span\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eii) Pentanol.\u003c/strong\u003e Using carbon disulfide as the confirmation analyte for xanthate presence has its drawback for environmental samples: CS\u003csub\u003e2\u003c/sub\u003e can be generated by the degradation of organic material produced by anaerobic processes in the soil (Megonigal et al., \u003cspan class=\"CitationRef\"\u003e2003\u003c/span\u003e). To fulfil the demand from the engineering firm asking for the analyzes, a confirmation analyte, not produced by natural processes, has been search. The choice of that secondary analyte implies a knowledge or a good assumption of the xanthate(s) potentially contaminating the site. The obvious choice, in the case of PAX contamination, is the monitoring of pentanol.\u003c/p\u003e\n\u003cp\u003e\u003c/p\u003e\n\u003cp\u003ePentanol has a mass spectrum depicting three principal ions: \u003cem\u003em/z\u003c/em\u003e\u0026thinsp;=\u0026thinsp;42, 55, 70. Those ions come form the aliphatic chain attached to the hydroxyl group. Industrial sites usually contain petroleum hydrocarbon residues in their soils. This mining site is no exception to this fact. Therefore, those three ions could originate from heavy hydrocarbons residues instead from PAX. Because of such interference, pentanol could no be used as a quantification analyte but can be a reasonable confirmation candidate. The calibration samples (1.01 \u0026micro;g AX\u003csup\u003e‒\u003c/sup\u003e/g, 3.03 \u0026micro;g AX\u003csup\u003e‒\u003c/sup\u003e/g, 25.23 \u0026micro;g AX\u003csup\u003e‒\u003c/sup\u003e/g and 252.3 \u0026micro;g AX\u003csup\u003e‒\u003c/sup\u003e/g) used to prepare the calibration curve for carbon sulfide quantification were used to monitor the evolution of pentanol at different concentrations of AX\u003csup\u003e‒\u003c/sup\u003e. An approach modeled on the one used for CS\u003csub\u003e2\u003c/sub\u003e was developed to study the production of pentanol: TGA-MS profiles were first recorded by considering the three ions simultaneously with independent SIM methods. Then, an injection on the chromatographic column was undertaken. Table S2 shows that the retention time of pentanol evolved from pure PAX is 14.2 min when a carrier pressure of 20 psi is considered. To help with the comparison with the pure PAX chromatogram, this pressure was used with the calibration samples. Using a heating rate of 20\u0026deg;C/min (as for CS\u003csub\u003e2\u003c/sub\u003e) was first considered, but the resulting TGA-MS profiles (from the monitoring of the \u003cem\u003em/z\u003c/em\u003e\u0026thinsp;=\u0026thinsp;55 fragment) had their apex at \u0026asymp;\u0026thinsp;13 min. Since this step is solely done to determine the injection time on the GC column, the process of pentanol detection could be accelerated. Figure S8 shows TGA-MS profiles in function of the TGA heating rate with a SIM method considering the ion \u003cem\u003em/z\u003c/em\u003e\u0026thinsp;=\u0026thinsp;55. To avoid thermal decomposition of possible hydrocarbon contamination possibly present in the field samples, 60\u0026deg;C/min was chosen for the pentanol screening. Figure S9 shows the chromatograms obtained following on the GC column injection. The calibration sample at 252.3 \u0026micro;g AX\u003csup\u003e\u0026minus;\u003c/sup\u003e / g depicts an intense peak at 14.9 min identified as pentanol. In the case of the other samples, a peak is present at 14.9 minutes, but it is weak, and the corresponding MS spectrum was unidentifiable as pentanol and embedded in the contaminations emanating from the control sample used to prepare the calibration samples. If the control sample (solvent washed) still emanates background contamination, it is reasonable to consider higher emanation from the (untreated) environmental samples. Pentanol is therefore a confirmation analyte suitable for \u003cem\u003ehighly PAX contaminated\u003c/em\u003e samples (see next section below). A study to determine the threshold PAX concentration for pentanol detection by TGA-GC/MS mode was not undertaken.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eiii) Pentene.\u003c/strong\u003e Inspecting the chromatograms of figure S9, one can observe peaks with retention times\u0026thinsp;\u0026lt;\u0026thinsp;3 min. Table S2 indicates that 1-pentene and 2-pentene are produced when pure PAX is heated in the purge condition used to analyse the soil samples. Those species are among the first molecules to eluate from the Rxi 624 Sil MS column. The pentene detected form pure PAX must come from the thermal conversion of the evolved pentanol. DFT calculations showed that pentanol, when heated, can be converted into 1- and 2-pentene via a dehydration reaction (Zhao et al., \u003cspan class=\"CitationRef\"\u003e2012\u003c/span\u003e). Figure \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e shows the chromatograms of the evolved species coming from a pure PAX aliquot under a carrier gas pressure of 8 psi. The inset focuses on the two pentene isomers. It shows that the pentene chromatographic signal consists of 3 peaks: one peak identified by the NIST data base to 1-pentene and two peaks identified as 2-pentene isomers. Figure S10 focuses on the first 5 minutes of the chromatograms depicted at figure S9 for pentanol evolution detection. The triplet linked to the pentene isomers evolution is visible at every AX\u003csup\u003e‒\u003c/sup\u003e concentration from the four calibration samples. Because of its fast elution in the chromatographic column and evolution at every concentration, \u003cem\u003epentene was considered as the secondary analyte to confirm the xanthate contamination\u003c/em\u003e in environmental samples with an AX\u003csup\u003e‒\u003c/sup\u003e contamination higher than the detection limit.\u003c/p\u003e\n\u003ch3\u003e4 Field Samples Analysis.\u003c/h3\u003e\n\u003cp\u003eIt is with the knowledge acquired by the TGA-MS and TGA-GC/MS experimentations done on the calibration samples that we tackled the task of detecting and quantifying PAX in the collected samples from the field of the decommissioned mine site. A total of 104 field samples were submitted to MAPLES laboratory. The samples were collected from two distinct sampling events on the mining site. The first lot had 30 samples, while the second one had 74 samples. Systematically, two TGA-MS assays were realized on all samples. When a sample depicted a positive signal linked to CS\u003csub\u003e2\u003c/sub\u003e evolution, an injection on the chromatographic column was carried out (TGA-GC/MS assay). The MS was set to detect specifically fragments with \u003cem\u003em/z\u003c/em\u003e\u0026thinsp;=\u0026thinsp;76. A chromatographic peak with a retention time\u0026thinsp;\u0026asymp;\u0026thinsp;4.33\u0026thinsp;\u0026plusmn;\u0026thinsp;0.06 minutes confirmed the evolution of carbon disulfide. Table \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e compiles the xanthate quantification results on samples that were confirmed to produce CS\u003csub\u003e2\u003c/sub\u003e by TGA-GC/MS. Because reporting a xanthate contaminated sample could have important economical implications in term of soil decontamination, a cautious approach toward our results were preconized. It is with this approach in mind that the TGA-GC/MS results were screened for pentene evolution. After analysing the two lots, four analytical scenarios were observed and are summarized below.\u003c/p\u003e\n\u003cdiv class=\"gridtable\"\u003e\n \u003cdiv align=\"left\" class=\"colspec\"\u003e\u003cbr\u003e\u003c/div\u003e\n \u003ctable id=\"Tab1\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eAX\u003csup\u003e\u0026minus;\u003c/sup\u003e quantification results on the positive field samples based on TGA-MS assays for specific CS\u003csub\u003e2\u003c/sub\u003e detection (fragment \u003cem\u003em/z\u003c/em\u003e\u0026thinsp;=\u0026thinsp;76).\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" rowspan=\"2\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003eContaminated Sample Number\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"7\"\u003e\n \u003cp\u003eAX\u003csup\u003e\u0026minus;\u003c/sup\u003e Concentration (\u0026micro;g AX\u003csup\u003e\u0026minus;\u003c/sup\u003e/g) of Dry Field Sample\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003eVariation Coefficient /%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003eAnalytical Scenario #\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAssay 1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAssay 2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAssay 3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAssay 4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAssay 5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAverage\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eStandard Deviation\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" rowspan=\"12\"\u003e\n \u003cp\u003eLot #1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e17.86\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e13.56\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e13.84\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e15.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e10.56\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e7.91\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e10.98\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e9.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e17\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e5.65\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e6.97\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e6.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e5.24\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e5.03\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e5.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e7.72\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e8.09\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e7.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2.82\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e5.11\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e41\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e38.34\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e24.92\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e25.54\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e24.69\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e28.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e6.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e23\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e47.49\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e67.06\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e49.59\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e40.50\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e40.55\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e49.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e10.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e22\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e59.23\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e62.96\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e73.39\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e65.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e7.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e11\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e20213\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e14308\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e16580\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e17034\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2978\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e17\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e11\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e14.86\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e11.49\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e6.57\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e20.51\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e7.47\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e12.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e5.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e47\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e12\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e21.30\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e21.40\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e44.30\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e15.44\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e25.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e12.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e50\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" rowspan=\"14\"\u003e\n \u003cp\u003eLot # 2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026lt;\u0026thinsp;1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e9.16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026lt;\u0026thinsp;1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3.67\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e6.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e61\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e7.25\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e16.31\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e5.28\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e5.57\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e8.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e5.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e61\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e12.76\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e17.17\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e11.31\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e10.78\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e13.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e22\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2.75\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4.63\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2.77\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e32\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e8.18\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e7.98\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e8.26\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e8.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e10.70\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e12.13\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e16.50\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e13.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e23\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e7\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2.16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2.12\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026lt;\u0026thinsp;1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e5.11\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e5.00\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e5.03\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e5.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4.23\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4.38\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4.17\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e10\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026lt;\u0026thinsp;1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e11\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e8.88\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4.53\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e9.78\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e5.44\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e7.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e36\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e12\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e7.59\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3.69\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3.29\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2.93\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e49\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e13\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3.29\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3.84\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2.98\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e13\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e14\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e30.72\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e18.48\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e22.22\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e23.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e6.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e26\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003ctfoot\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"11\"\u003e\u003csup\u003ea\u003c/sup\u003e Average and standard deviation are calculated using the concentration valued higher than the detection limit.\u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tfoot\u003e\n \u003c/table\u003e\n\u003c/div\u003e\n\u003ch3\u003e1) Analytical scenario 1: Undetectable xanthate contamination.\u003c/h3\u003e\n\u003cp\u003eAbsent from Table \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e are the 77 samples who showed a contamination, if present, below the detection limit of 1 \u0026micro;g AX\u003csup\u003e\u0026minus;\u003c/sup\u003e / g of dry sample. Figure \u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003e portrays a typical TGA-MS profile obtained on such sample with a SIM method specific to ion \u003cem\u003em/z\u003c/em\u003e\u0026thinsp;=\u0026thinsp;76: Near the 13-minute mark (corresponding to a temperature\u0026thinsp;\u0026asymp;\u0026thinsp;375\u0026deg;C at the TGA), a large peak appears. TGA-MS runs with longer acquisition times on such samples show that the signal curvature only tends to increase and never decrease to complete the profile\u0026rsquo;s peak. The source of the curvature of the baseline probably comes from natural contaminations which can generate ions \u003cem\u003em/z\u003c/em\u003e\u0026thinsp;=\u0026thinsp;76 that are not linked to the evolution of CS\u003csub\u003e2\u003c/sub\u003e from the thermal decomposition of xanthates. The other possibility observed was a signal for \u003cem\u003em/z\u003c/em\u003e\u0026thinsp;=\u0026thinsp;76 like the one depicted at figure S4a.\u003c/p\u003e\n\u003ch3\u003e2) Analytical scenario 2: False positive.\u003c/h3\u003e\n\u003cp\u003eSeveral samples gave a positive TGA-MS profile for the \u003cem\u003em/z\u003c/em\u003e\u0026thinsp;=\u0026thinsp;76 ion. Figure \u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003e portrays an example of TGA-MS profile and TGA-GC/MS results for such samples. It is possible to detect the evolution of CS\u003csub\u003e2\u003c/sub\u003e by TGA-GC/MS assay, but a xanthate contamination confirmation by the detection of pentene is not possible. In addition, these samples show a relatively low AX\u003csup\u003e\u0026minus;\u003c/sup\u003e concentration \u0026ndash; the only exception being sample 14 from lot #2. Samples from this scenario depict TGA-MS profile for the fragment \u003cem\u003em/z\u003c/em\u003e\u0026thinsp;=\u0026thinsp;76 with their peak appearing at a time\u0026thinsp;\u0026ge;\u0026thinsp;13 minutes and are noisy. An injection on the chromatographic column produces a chromatogram that can be associated with a CS\u003csub\u003e2\u003c/sub\u003e evolution. However, the intensity of the chromatogram is weak. Furthermore, the TGA-GC/MS profiles associated to ions \u003cem\u003em/z\u003c/em\u003e\u0026thinsp;=\u0026thinsp;42, 55 and 70 show no signature of a pentene evolution: for this case, the chromatograms only show noise in the region between 3.0 and 4.0 min. The CS\u003csub\u003e2\u003c/sub\u003e is therefore suspected to come from a natural source and not from PAX.\u003c/p\u003e\n\u003ch3\u003e3) Analytical scenario 3: Probable xanthate contamination.\u003c/h3\u003e\n\u003cp\u003eFigure \u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003e shows an example of the case where the TGA-MS and TGA-GC/MS results for CS\u003csub\u003e2\u003c/sub\u003e give MS signals that point to xanthate contamination: the TGA-MS profile is intense and relatively low in noise, as the chromatogram obtained by the TGA-GC/MS mode. However, the chromatograms linked to pentene evolution are less certain. Unlike to analytical scenario 2, the chromatograms show a certain fingerprint that can be linked to pentene production: The chromatograms show a clear doublet in the region between 3.0 and 4.0 min. The first peak has an average apex time of 3.33 min and 3.84 min for the second peak. From the inserts of Fig. \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e (pure PAX, obtained with the same GC conditions as the environmental samples) the first peak has an apex average of 3.25 min and 3.70 min for the second one. With a peak-to-peak average difference of \u0026asymp;\u0026thinsp;0.1 min, the doublet can be linked to pentene evolution. Our cautious approach prevents us from declaring these samples contaminated since the multiplicity on the second pentene peak is not visible.\u003c/p\u003e\n\u003cp\u003eThis case represents samples that demonstrate both TGA-MS and TGA-GC/MS results that meet all criteria for the presence of xanthate as obtained during the analysis of the calibration samples. As shown in Table \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e, the samples that meet this situation are in the minority. Figure \u003cspan class=\"InternalRef\"\u003e8\u003c/span\u003e shows the most contaminated sample of the two batches analyzed in this study. This is the only sample on which pentanol was undoubtedly identified, i.e., with multiplicity on the second peak from the pentene doublet.\u003c/p\u003e\n\u003cp\u003eAnalyzes on more than a hundred samples confirmed the presence of amyl xanthate contamination in only a small fraction of them and amyl xanthate contamination concentration was rather low. This is not surprising since xanthates are biodegradable. Nevertheless, considerable savings for the rehabilitation of the site became possible by significantly reducing the quantities of materials \u003cem\u003econfirmed\u003c/em\u003e of being contaminated with xanthates. To complement our findings, a half-life study of degradation of amyl xanthate in the certified contaminated field samples was conducted. Those samples were kept dry and in amber vial, at room temperature. The half-life in that is estimated to be six months for 40% of the samples while the other samples showed significantly longer stability (not detectable over three months), which confirms some persistence of xanthate, but also a rather slow potential for release of toxic degradation products into the environment.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eA method to quantify xanthates contamination bounded strongly to a mineral matrix mixed to refractory materials is proposed. The novelty is the utilization of a hyphenated system composed of a thermogravimetric analyzer linked to a gas chromatograph coupled to a mass spectrometer as the detector. The method was developed by considering the detection of carbon disulfide as the quantification analyte since all xanthates studied (potassium amyl xanthate, ethyl amyl xanthate and diethyl dixanthate) are known to produce this molecule when heated. Two hyphenated modes were exploited. The TGA-MS mode proved to be suitable for the quantification of a thermally generated analyte based on CS\u003csub\u003e2\u003c/sub\u003e recovery % average of 106\u0026thinsp;\u0026plusmn;\u0026thinsp;9%. The thus obtained MS signal profile can be integrated like a chromatographic peak and the calculated area can be used to prepare a calibration curve. The TGA-GC/MS mode was useful to confirm the degradation products based on the retention time on the chromatographic column. In the case for this study, CS\u003csub\u003e2\u003c/sub\u003e was the sole quantification analyte. This mode was also useful to detect the production of another decomposition species confirming that the CS\u003csub\u003e2\u003c/sub\u003e was produced by the xanthate decomposition and not from another organic source. This hyphenated system was able to provide a calibration curve with a good linearity with good recovery values on the CS\u003csub\u003e2\u003c/sub\u003e. Due to its versatility, such system could easily be exploited to detect other types of chemisorbed or physisorbed organic material on a refractory, solid matrix. The herein method would only be modified to adapt the TGA heating range to encompass the complete decomposition of the contamination and the SIM TGA-MS method would be modified to reflect the quantification analyte (i.e., a specie that gives an intense MS response). When field samples from a mining site known to be contaminated by potassium amyl xanthate (a compound known to be biodegradable) were analysed, the TGA-GC/MS results used to confirm the evolution of pentene had to be inspected carefully to prevent deeming certain samples of being contaminated with xanthate. A cautious approach was preconized throughout the study of the environmental samples. Based on a systematic approach, four different analytical scenarios were established to let the project managers determine their own limit to decide which zones of the mining site would be decontaminated.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eE.R.D. wrote the manuscript and supporting information text. E.R.D. prepared all the figures. C.M. revised and corrected the manuscript, the supporting information and the figures.\u003c/p\u003e\u003ch2\u003eAcknowledgement\u003c/h2\u003e\u003cp\u003eE. D. and C. M. want to acknowledge the significant contribution of Yanick Gauthier on this project (initial headspace experiments and field samples preparation method).\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eAllison SA, Goold LA, Nicol MJ, Granville A (1972) A determination various solution, products of the products of reaction between sulfide minerals and aqueous xanthate and a correlation of the with electrode rest potentials. Metall Trans 3:2613-2618. https://doi.org/10.1007/BF02644237\u003c/li\u003e\n\u003cli\u003eBuckley AN, Woods R (1997) Chemisorption\u0026mdash;the thermodynamically favoured process in the interaction of thiol collectors with sulphide minerals. Int J Miner Process 51:15-26. https://doi.org/10.1016/S0301-7516(97)00016-1\u003c/li\u003e\n\u003cli\u003eCavell KJ, Sceney CG, Hill JO, Magee RJ (1973) Thermal studies on nickel alkyl xanthate complexes. 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A review. Thermochim Acta 96:155-167. https://doi.org/10.1016/0040-6031(85)80018-6\u003c/li\u003e\n\u003cli\u003eRao SR (2004) Flotation Surfactants. Surface Chemistry of Froth Flotation: Volume 1: Fundamentals. Springer US, Boston. pp 385-478\u003c/li\u003e\n\u003cli\u003eRoy K-M (2000) Xanthates. Ullmann\u0026apos;s Encyclopedia of Industrial Chemistry. Wiley-VCH Verlag GmbH \u0026amp; Co. KGaA, Weinheim. pp 633-642\u003c/li\u003e\n\u003cli\u003eSceney CG, Hill JO, Magee RJ (1973) Thermal studies on palladium alkyl xanthates. Thermochim Acta 6:111-117. https://doi.org/10.1016/0040-6031(73)80010-3\u003c/li\u003e\n\u003cli\u003eTyd\u0026eacute;n I (1966) Gas chromatographic study of the pyrolysis of potassium salts of xanthic acids. Talanta 13:1353-1360. \u003c/li\u003e\n\u003cli\u003eVreugdenhil AJ, Brienne SHR, Butler IS, Finch JA, Markwell RD (1997a) Infrared spectroscopic determination of the gas-phase thermal decomposition products of metal-ethyldithiocarbonate complexes. Spectrochim Acta A Mol Biomol Spectrosc 53:2139-2151. https://doi.org/10.1016/S1386-1425(97)00144-3\u003c/li\u003e\n\u003cli\u003eVreugdenhil AJ, Brienne SHR, Markwell RD, Butler IS, Finch JA (1997b) Headspace analysis gas-phase infrared spectroscopy: a study of xanthate decomposition on mineral surfaces. J Mol Struct 405:67-77. https://doi.org/10.1016/S0022-2860(96)09449-5\u003c/li\u003e\n\u003cli\u003eWills BA, Finch J (2015) Wills\u0026apos; Mineral Processing Technology: an Introduction to the Practical Aspects of ore Treatment and Mineral Recovery. Butterworth-Heinemann\u003c/li\u003e\n\u003cli\u003eWoods R (1971) Oxidation of ethyl xanthate on platinum, gold, copper, and galena electrodes. Relation to the mechanism of mineral flotation. J Phys Chem 75:354-362. https://doi.org/10.1021/j100673a011\u003c/li\u003e\n\u003cli\u003eZhao L, Ye L, Zhang F, Zhang L (2012) Thermal Decomposition of 1-Pentanol and Its Isomers: A Theoretical Study. J Phys Chem A 116:9238-9244. https://doi.org/10.1021/jp305885s\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"environmental-earth-sciences","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"enge","sideBox":"Learn more about [Environmental Earth Sciences](https://www.springer.com/journal/12665)","snPcode":"12665","submissionUrl":"https://submission.nature.com/new-submission/12665/3","title":"Environmental Earth Sciences","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Evolved Gas Analysis, Gas Chromatography, Hyphenated Technology, Mass Spectrometry, Mining Wastes, Thermogravimetric Analysis, Xanthates","lastPublishedDoi":"10.21203/rs.3.rs-7348102/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7348102/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe site of a former copper mine, in the process of being decontaminated, needed to be screened for xanthates contamination. It is known that potassium amyl xanthate as well as potassium ethyl xanthate were used in flotation process as collectors during the operation of the mine. The use of common analytical methods for organic contaminants, based on solvent extraction, showed no detectable xanthates contamination. As xanthates are strongly adsorbed on some mineral surfaces in the flotation process of the mineral-rich ore, it was suspected that common analytical methods can\u0026rsquo;t be applied to such situation. Even the use of acidic media with headspace gas chromatography was not able to detect any significant volatile decomposition products from xanthate-spiked soil samples. Then, thermal decomposition of the surface-bounded contamination, followed by an analysis of the generated vapour, showed significant results. A hyphenated system, composed of a thermogravimetric analyzer, an infrared spectrophotometer and a gas phase chromatograph coupled with a mass spectrometer was ultimately considered. With this multi-instrumental system, an analytical method has been developed and it was found that the xanthate contamination was well over 1 ppm for many samples taken from the former mining site. This article will describe the analytical method that was developed on this hyphenated system to detect, quantify and identify xanthates in environmental samples.\u003c/p\u003e","manuscriptTitle":"Quantification of Xanthates Chemisorbed on Solid Mining Wastes by Evolved Gas Analysis Hyphenation Techniques","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-10-07 11:59:24","doi":"10.21203/rs.3.rs-7348102/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2026-01-29T22:01:01+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-01-04T15:55:19+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"273313028678922877107102807222270528030","date":"2025-12-08T09:07:18+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"255914696685608348409032950281326117453","date":"2025-09-24T15:22:40+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-09-24T12:01:38+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-08-12T06:31:34+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-08-12T06:30:01+00:00","index":"","fulltext":""},{"type":"submitted","content":"Environmental Earth Sciences","date":"2025-08-11T15:51:08+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"environmental-earth-sciences","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"enge","sideBox":"Learn more about [Environmental Earth Sciences](https://www.springer.com/journal/12665)","snPcode":"12665","submissionUrl":"https://submission.nature.com/new-submission/12665/3","title":"Environmental Earth Sciences","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"04975805-3b56-4135-b6ad-7c7053698785","owner":[],"postedDate":"October 7th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-04-12T10:10:15+00:00","versionOfRecord":[],"versionCreatedAt":"2025-10-07 11:59:24","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7348102","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7348102","identity":"rs-7348102","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}