In-situ Laser Ablation MCICPMS of lead white in paintings

In-situ Laser Ablation MCICPMS of lead white in paintings | 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 Article In-situ Laser Ablation MCICPMS of lead white in paintings Paolo D’Imporzano, Graham A. Hagen-Peter This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9106478/v1 This work is licensed under a CC BY 4.0 License Status: Under Revision Version 1 posted 8 You are reading this latest preprint version Abstract This study develops and validates an in-situ LA-MC-ICPMS method for lead isotope ratios (LIR) measurements of lead carbonate pigments at micrometre scale while consuming only nanogram quantities of material. Two matrix-matched synthetic lead whites (PDLW1 and PDLW2) were produced from metallic lead, converted to carbonate, and characterised by solution MC-ICPMS to define reference isotope compositions. These pigments were then used as calibrants and quality-control reference materials to assess LA performance. LA analyses of epoxy-embedded (binder-free) pigments yield isotope ratios consistent with solution data, demonstrating the method accuracy on lead. LA analyses were performed on samples previously analysed in other study (ref hetero), showing agreement with literature data. The analysis of mock-up cross-sections containing PDLW1 and PDLW2 in oil-paint layers show that oil-rich, pigment-poor domains degrade signal stability and precision, whereas pigment-rich domains provide accurate LIR, proving that this approach is valid to analyse LIR of paint samples. The method was successfully applied to determine the provenance of an anonymous sample believed to be a 16-17th century Italian painting. Finally, LA was used to produce isotopic maps capable of resolving layer-specific LIR. Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 1. Introduction Lead isotope ratio (LIR) analysis of lead white (LW) pigments via multi-collector inductively-coupled-plasma mass-spectrometry (MC-ICPMS) is a robust, well-established methodology for determining pigment provenance [1–7]. Beyond simple material sourcing, this technique successfully reconstructs historical artist movements and socio-economic trade networks, while providing critical analytical data for painting authentication and identification. However, the broader application of this technique in heritage science is currently constrained by significant methodological limitations regarding sample extraction and spatial resolution. The primary limitation of traditional MC-ICPMS is its reliance on invasive sampling and the need to dissolve the sample for analysis. Sampling, whether performed manually by conservators or via micro-scalpel from existing cross-sections [8], remains fundamentally invasive for unique cultural heritage objects. Furthermore, these physical extraction methods suffer from extreme material inefficiency. While a high-precision LIR analysis requires only 50-100 nanograms of lead (ng, which is one billionth of a gram, 10 -9 g lead constitutes approximately of lead white), manual and micro-scalpel methods inevitably extract thousands of nanograms. Consequently, more than of the extracted material is wasted during dissolution, as mechanically isolating exactly of sample is physically unfeasible. A secondary critical limitation is the inadequate spatial resolution inherent in physical sampling. When paint fragments are acquired via manual scraping, the stratigraphic integrity of the painting is lost. If the extracted fragment contains multiple paint layers, containing different historical sources of lead white, the resulting LIR data will merely reflect a homogenised, weighted average rather than a layer-specific isotopic signature. While targeted micro-scalpel sampling from embedded cross-sections improves stratigraphic control, it is still severely limited by the physical dimensions of the tools [8]. Because micro-scalpel blades measure in the tens of micrometres (µm), they frequently exceed the thickness of individual historical paint layers. Consequently, successfully isolating a pure lead white layer without adjacent cross-contamination is difficult and remains heavily dependent on the specific rheological and elasticity/brittleness properties of the aged paint. This study proposes an alternative path to study LIR in lead white samples via MC-ICPMS using in-situ laser ablation (LA) . The use of LA to study LIR in lead white samples can give unparallel benefit compared to classic sampling techniques: it has extremely high spatial resolution, with the laser beam diameter as small as 1 µm, and adjustable repetition rate and fluence (energy per unit area) to sample only the needed material for LIR, without wasting sample material. This resolution also provides the possibility to sample single particles of lead white in a single sample, allowing the comparison of different lead white in painting, as in the case of LW present in ground, prime and highlights, to detect precisely retouching, reuse of canvas and other artist practices. The samples can be, similarly to the use of micro-scalpel [8], sampled from cross-sections, avoiding the necessity of taking new samples from paintings if not needed. The sample can be analysed without sample preparation reducing analysis time. LA of lead white, a lead carbonate that is applied mainly in linseed oil in oil painting, presents specific analytical challenges that must be addressed for reliable heritage science applications. LA-MC-ICPMS inherently yields lower precision (higher external error, ) compared to traditional solution-based analysis due to highly transient signals. This reduced precision can directly limit the ability to resolve minute isotopic differences crucial for determining pigment provenance. To be a viable alternative for painting characterisation, LA analysis must demonstrate sufficient resolving power. For example, distinguishing Venetian from 17th-century Dutch lead white requires resolving a difference of approximately 2700 ppm in the 206 Pb/ 204 Pb ratio [1]. Because solution-based LIR analysis achieves a 2SD of roughly 150 ppm, easily resolving this geographic variation, LA methodologies must be optimised to approach this level of precision. Furthermore, the physical and chemical properties of the carbonate in paint matrix complicate the ablation process. Among others, these so-called “matrix-effects” may include 1) laser-induced elemental and isotopic fractionation during ablation and aerosol transport due to phase changes during the ablation process; 2) sample-dependent differences in isotopic fractionation in the MC-ICPMS due to differences in sample load (“plasma loading”); 3) variable matrix-based interferences, for example organic complexes originating from the organic matrix of the pigmentn(e.g., linseed oil) [9–13]. Finally, the accuracy of LA-MC-ICPMS are currently constrained by the absence of a validated, matrix-matched isotopic reference material for lead carbonate or historical lead white pigments. This work addresses these limitations by developing and validating an in-situ LA-MC-ICPMS approach for LIR analysis of lead white in paint samples. Two lead white reference materials ( PDLW1 and PDLW2 ) were synthesised from metallic lead and converted to carbonates; their isotopic compositions were first established by solution MC-ICPMS and subsequently used as calibrants and quality-control reference materials for LA measurements. These materials were employed to evaluate LA performance on lead carbonates, including signal stability and mass-dependent fractionation, and to assess their suitability as matrix-matched reference materials. To benchmark the proposed approach against established datasets, the 16 th century Venetian lead white samples previously reported in Dimporzano et al. (2021) were re-analysed in this study via solution and by LA and directly compared with literature data [1]. In addition, a stratified mock-up cross-section was prepared consisting of two discrete layers of PDLW1- and PDLW2-based oil paint, separated by zinc white interlayers, to reproduce a realistic multilayer paint stratigraphy. This mock-up was analysed to quantify isotopic fractionation in an oil-bound carbonate matrix and to test the spatial resolving power of LA via isotopic mapping, i.e., the ability to discriminate isotopically distinct lead white domains within a single cross-section. Finally, the validated method was applied to an anonymous paint sample dated to the 16th–17th century, presumably produced in Italy, to identify the isotopic signature of the lead source used in the lead white pigment. 2. Method and materials 2.1- Lead white The lead white pigments used in this study, PDLW1 and PDLW2, were synthesized from metallic lead fishing weights purchased online, manufactured in China. The lead was supplied as small coils approximately 2 cm in height (Figure 1, Metallic lead ). These coils were first analysed to determine their Pb isotopic composition and to assess isotopic homogeneity within each coil; the metal was found to be isotopically homogeneous within individual coils, and two coils with distinct isotopic signatures were selected to produce lead whites with different isotopic compositions (PDLW1 and PDLW2, see supplementary material S1 paragraphF metal LIR vs LW LIR ). To synthesise lead white, the selected coils were suspended above acetic acid at room temperature for two weeks to form lead acetate. The coils were then transferred to a solution of water, sugar, and baking yeast, which generated CO 2 and promoted the conversion of lead acetate to lead carbonate over a further two weeks. The lead white that formed on the surface of the coils was subsequently removed, thoroughly washed, and homogenised (Figure 1, Lead white ). PDLW1 was used as the bracketing standard and PDLW2 as the quality-control material for the laser ablation measurements; this assignment of roles between the two pigments was arbitrary (they could in principle be swapped), whereas the non‑arbitrary decision was to use our own synthetically prepared lead‑white carbonate as the reference matrix to mitigate matrix effects. Lead‑carbonate pigment was considered to be more appropriate for Standard Sample Bracketing (SSB) in LA‑MC‑ICPMS work than a non–matrix-matched silicate glass such as NBS/NIST glasses, because the very large differences in Pb and trace‑element concentrations between glass and lead carbonate (often several orders of magnitude; e.g., NIST 610 with ~430 ug/g Pb and lead white with 70-80 wt% Pb). Significantly different Pb signals resulting from the ablation of Pb white vs glass, or significantly different fluxes of total material into the plasma if the former is compensated by using a larger spot size for the glasses, can lead to differences in the magnitude of instrumental mass-bias between glasses and Pb white. Moreover, using a synthetic Pb carbonate standard better captures the specific ablation behaviour, particle generation, and signal instability associated with the surface structure and crystallographic structure of carbonates and phase differences (e.g. ratios between cerussite/hydrocerussite, presence of partial unreacted lead product as acetates, plumbonacrite, metallic lead and traces of galena) [14–18]. The lead white thus formed was divided in three parts, one to be analysed via solution, one to be compressed and embedded in epoxy to be used as standard and quality control for laser work (Figure 1, PDLW1 LA-standard), and one mixed in linseed oil to form a painting mock-up to assess the LIR in real sample (Figure 1, LA-Oil-paint mock-up). The mock-up consisted of a stock up of 4 different layers of paint on a glass and aged artificially at 40 degrees Celsius. The bottom layer was PDLW1 in Linseed oil, once dry a layer of zinc white was added on top, then a layer of linseed oil with PDLW2 and finally a last layer of zinc white. A third type of lead white, which was already analysed in Dimpo et al 2021, coming from historical Venetian lead white, and here named GN , was also re-analysed in this study. Part of this lead white was also compressed into a pellet and embedded in epoxy to assess the accuracy and precision of laser ablation compared to literature data. 2.2- Instrumentation Lead isotope ratio measurements of solutions were performed in dry plasma using a Thermo Fisher Neoma MC-ICPMS coupled with an Apex omega desolvator (parameters in Table 1). The samples for solution works were introduced as solutions of 25 ppb lead doped with 5 pbb of Thallium (2 mL for each sample was prepared). The Thallium was used to calculate the mass-bias fractionation factor β using the exponential law. The mercury Isotope 202 Hg was monitored and used to remove the isobaric interference (isotope 204 Hg) from the lead isotope 204 Pb. For each run, an in-house quality control standard (“CPI”) and blanks (in solution work blanks were below 50 pg and therefore their contribution to the analysis is considered irrelevant) were also analysed. The replicates of the CPI in-house standard have been used to calculate the external precision of the Neoma in this work. For laser ablation analysis, the ESL (Elemental Scientific Lasers) NWR193UC 193 nm ArF excimer laser ablation system fitted with a TV3 cell was used. Ablations were carried out in a 2-volume chamber in a He atmosphere, and the ablated aerosol was mixed with Ar in a signal-smoothing bulb before introduction into the plasma. The analysis parameters for the Neoma and the LA are reported in Table 1. The PDLW1 was used as a primary standard to correct for instrumental mass bias via a SSB correction (β is calculated using the exponential law and a spline function). Before and after each ablation, a washout time of 70 and 60 seconds was applied to reduce any memory effect (background signal on the 208Pb < 0.001 V). The data were reduced using Iolite 4, via the DRS Pb Isotopes DRS (Beta). For each run, samples were corrected for the baseline (calculated via a spline function), collecting the background signal for 30 seconds before each sample, and the isobaric interference on 204 Pb was corrected for 204 Hg using the 202 Hg. Laser ablation Settings 1 Settings 2 He (L min-1) 0.980 - 01.080 0.980 - 01.080 speed µm/sec 1 2 spot µm 5 5 Energy (J) 0.42 0.51 Hz 7 8 N (dosage) 35 20 N*Energy 10.2 14.7 Neoma Integration time (sec) 0.5 0.25 Ablation time sec ~ 50 ~ 20 Efficency % 0.05-0.3 0.05-0.3 Plasma Solution Laser RF Power (W) 1200 1200 Plasma condition dry plasma Nebulizer Ar flow (L min -1 ) 0.8 Sampling cone Standard Standard Skimmer cone H H Collection Solution Laser Sensitivity (V ppm -1 ) 320 - 400 Blank signal 208 Pb (V) < 0.003 < 0.001 Cycles 40 ~ 80 - 100 block 3 1 Integration time (seconds) 4 0.25-0.5 L4 L3 L2 L1 Center H1 H2 H3 H4 200 Hg 202 Hg 203 Tl 204 Pb 205 Tl 206 Pb 207 Pb 208 Pb 209 Bi Table 1 : Operating conditions used for the LA-MC-ICPMS measurements. The table summarizes the principal laser ablation parameters (spot size, repetition rate, scan speed, carrier gas configuration etc.) and the corresponding MC-ICPMS acquisition settings (cup configuration, integration time, mass etc.) applied for lead isotope ratio analysis of lead white 3. Results and discussion 3.1 Solution analyses Table 2 reports the external precision as 2SD for the in-house standard solution, CPI, analysed during the course of this project (6 months c.a. for a total of 203 replicates of the solution) in dry plasma. The data are within error with literature data for the same sample analysed in [1,2,4,7,19–22] (which reports much data on lead isotopes of lead white and other medium as silver and lead glaze). A more detailed discussion on the comparison of this data with literature data is given in the supplementary material S1 paragraph, S hort discussion on the comparison with the Neptune. ²⁰⁶Pb/²⁰⁴Pb 2SD ²⁰⁷Pb/²⁰⁴Pb 2SD ²⁰⁸Pb/²⁰⁴Pb 2SD ²⁰⁸Pb/²⁰⁶Pb 2SD ²⁰⁷Pb/²⁰⁶Pb 2SD Neoma n = 203 CPI in-house Tl 17.9006 0.0015 15.5665 0.0020 38.0230 0.0060 2.12409 0.00018 0.86961 0.00005 ppm 85.1 129.8 159.0 83.5 58.0 Table 2 : results of the analysis of CPI in-house standard over a period of 6 months, n = 203 Comparable external precision was achieved for analysis of the solution of the metal and the pigments of lead white synthesised in this work (PDLW1 and PDLW2), as reported in detail in the supplementary material S1 section Metal LIR vs LW LIR. 3.1 Laser ablation and solution The settings for the laser ablation were chosen following this principle: minimum invasiveness maintaining highest accuracy and reproducibility possible. For this, a series of settings was tested in the course of 8 months. Due to the nature of the carbonates, it was found that low fluence (0.42 to 0.51 J/cm 2 , corresponding to 1-5% of the energy output of the Laser ablation system used in this study, was sufficient to achieve a good signal, between 6-9 V on the 208 Pb). Following the discussion in the supplementary material ( S1, section Decision on the optimal laser ablation settings for lead white and Laser ablation: raster vs Line for a detailed discussion), the results for the best-performing laser ablation settings were PDLW2‑10.2 and PDLW2‑14.7 (corresponding to settings 1 and 2 in Table 1 and LIR reported in Figure 2). The LIR for these two settings are compared to the analysis of the same pigment in solution work to assess the precision and accuracy of LA analysis to the more robust solution analysis, Figure 2. LA analyses were conducted using SSB with PDLW1 as the standard to correct the PDLW2 sample. Using a 5- µm-diameter circular laser spot the ablated area was restricted to a line 50 µm long or to a raster with dimension of 15x15 µm (Image Figure 3) ablating a volume of lead white pigment of ~1.25 *10 -9 cm 3 corresponding to 8 ng ca. (ablation depth estimated to be around 5 µm, detailed discussion in supplementary material S1 Material ablated and efficiency ). The ablation time was around 21 seconds for PDLW2-10.2 and 47 seconds for PDLW2-14.7. PDLW2‑10.2 was tested with 16 replicates over a period of 4 months, while PDLW2‑14.7 was tested with 28 replicates over the same period. The solution analyses were conducted over a period of 6 months on 40 replicates. From Figure 2, both laser settings clearly yield data in good agreement with the solution results. Considering their 2SD, both laser settings display external precision similar to that of solution analysis applied to LIR of lead white in recent years (ref dimpos and Table S1 for CPI analysis on the Neptune). The LA LIR ratios normalised to 204 Pb yielded 2SD values of 150–300 ppm with mean squared weighted deviation (MSWD) between 0.44 and 1.1, whereas solution analyses on the same samples produced smaller 2SD of 80–150 ppm and MSWD of 0.85–1.8. This indicates that the repeatability of laser ablation measurements is predicted by their measurement uncertainties, with no evidence for significant micro-scale heterogeneity or random laser-induced fractionation. Overall, the laser ablation data provide reproducible Pb isotope fingerprints suitable for provenance studies, with roughly twofold lower precision than solution measurements using Tl doping on the same instrument. Taking into account that the amount of sample analysed is only 8 ng and that an average painting sample taken manually can be estimated, for most cases, to be in the range of 5 to 0.01 milligrams, means that using in-situ LA on cross-section is possible to reduce the amount of sample used by 500000 to 1000 times. This procedure therefore drastically reduces the amount of sample needed, preserving most of the sample intact for further analysis, while providing high-precision isotope data comparable with literature data. 3.2 Historical Venetian lead white This study revisits historical lead white recovered from a Venetian shipwreck in the Adriatic Sea, previously characterised [1], and compares those results with new measurements obtained here on the same material (referred as GN in this study). GN was re-analysed by solution MC-ICPMS (Neoma) and by LA-MC-ICPMS on a dedicated epoxy-embedded GN mount, using the same analytical protocol and LA operating conditions (14.7 and 10.2) applied to PDLW1 and PDLW2 and acquired within the same analytical session (Figure 3). The results show that the Neoma solution (GN Figure 3) data are within error with the earlier measurements reported in Dimporzano et al. (2021) (GN D’Imporzano et al. 2021 in Figure 3). The laser ablation data, for both LA settings (GN 10.2 and GN 14.7), are also accurate relative to the Neoma solution measurements, with GN 14.7 setting providing superior accuracy and reproducibility. However, the external error (2SD) for the LA analyses is worse than for newly synthesised PDLW2, with 2SD values for the three LIR being on average about 40 % larger compared to the one reported in Figure 2. This worse precision can be attributed to the history and condition of GN: the pigment remained under seawater for approximately 400 years and, when recovered, exhibited an external black alteration layer that was only partially removed in the material available for this study (no fresh sample was available). Although only visually pure white areas were targeted by laser ablation, nanoscale impurities or residual alteration products may have been present in some regions, thereby influencing the laser ablation and resulting in higher 2SD. This could also explain why the settings 10.2 performed worse than 14.7, as this ablation is faster and can be more susceptible to small local sample phase heterogeneity, resulting in a less stable signal. Despite this, the 14.7 setting yields results that are in good agreement with the solution data and still provide sufficient resolution (approximately 270–390 ppm 2SD for the three 204Pb-normalised LIR) for provenance studies. 3.3 Reducing the ablation size One of the main aims in this study is to reduce the sample usage to a minimum. Therefore, the method was also tested on smaller areas of both PDLW2 and GN. In these tests, the laser was applied either to a raster area of approximately 10 by 10 µm or to a single line of about 20 µm in length, corresponding in both cases to a total ablated mass of roughly 3.25 ng of LW for a 20 seconds ablation time. For this test, only the setting at 14.7 was used, as otherwise the integration time of the analysis would have been too short (10.2 has a speed of 2 µm/s and the total analysis time would have been less than 10 seconds). Consistent with previous results, PDLW2 exhibits better 2SD values than the analysis performed on GN. As expected, the shortened analysis time for the 20 µm length measurements (PDLW2 and GN short in Figure 4) yields a higher 2SD compared to the longer 50 µm laser ablation method, a direct consequence of the total integration time being halved. However, while precision is reduced, the data remain accurate; this makes the method viable for identification and provenance of unique samples containing minute lead white particles, though the longer ablation protocol is recommended for optimal results when enough material is available. 3.4 Mock-up analysis The LA method (14.7), considered more stable for heterogeneous samples as in the case of pigment in oil, was applied to a multi-layered mock-up (Figure 1) containing PDLW2 dispersed in linseed oil and artificially aged for three months at 40°C (each layer was applied after the layer below was hard to touch). The sample consists of four distinct layers applied on glass, alternating between Zinc Oxide, PDLW1, and PDLW2, which were subsequently embedded. The application of the LW pigments resulted in a stratigraphy that is less uniform than that found in masterworks, characterised by significant heterogeneity in particle size and varying pigment density throughout the lead white layers (Figure 6). While this irregularity presents analytical challenges and may differ from real painting samples, it effectively simulates non-idealised conditions, offering valuable insights into Laser Ablation behaviour across a wide range of pigment-to-binder ratios and aiding in the optimisation of sampling strategies for complex real-world samples. Figure 5a presents the LIR data for PDLW2 dispersed in oil, which exhibits a higher 2SD compared to the oil-free reference (PDLW2 14.7). The oil-dispersed dataset splits into two distinct clusters: one consistent with the reference values obtained with standard LA on pure pigment (blue arrow) and a second group showing lower accuracy (red arrow). Visual inspection of the ablation craters (Figure 6b) correlates these clusters with local sample heterogeneity; the accurate data (blue arrows) correspond to areas containing purer lead white agglomerates, whereas the red arrows coincide with pigment-poor, binder-rich areas. This highlights the need to consider matrix-effects when ablating oil painting samples. While signal contributions from oil-rich phases can be excluded during data reduction (e.g., via software Iolite 4; see Supplementary Material S1 section LA in oil samples ), this significantly reduces integration time and increases measurement error. Therefore, precise selection of pigment-rich areas is critical. Ideally, LIR via LA should be preceded by SEM-EDS or FTIR imaging to guide the sampling strategy, ensuring that isotopic data is gathered from optimal locations and can be correlated with the surrounding chemical composition. The application of this method, however, shows that accurate and precise analysis of lead white in linseed oil is possible and accurate when on lead-rich areas. 3.5 Application on Unknown 16-17 th century painting The LA method was applied to a real painting sample, from an unknown artist, identified as probably made in Italy in the 16-17 th century. The sample was an embedded cross-section presenting a thick layer of lead white with small particles evenly diffused in the oil (Figure 7b). The analysis was made using the setting with 14.7 and using an ablation time of 50 second ca., using raster and line ablation patterns and compared with literature data (Figure 6a and 6b). The LA ablation analysis of the real painting sample showed a good repeatability regardless of the sampling geometry and position in the white layer (2SD on 206 Pb/ 204 Pb 0.0049, 207 Pb/ 204 Pb 0.0051 and 208 Pb/ 204 Pb 0.0127, data in supplementary excel file S4 Final data laser , sheet anonymous ) and in line for what found in this study for application of LA ablation on fine pigment in oil paint. From Figure 6a it is also notable that the error (to be conservative the 2SD used was the one calculated for oil samples analysed with LA in section Mock-up analysis, Figure 5a, shown as a cross on the markers of the anonymous sample) is often smaller than the marker itself, meaning that this resolution is more than enough to distinguish macro-differences between the main LIR cluster in Europe. Data compared to the LW database for paintings show that the sample has LIR characteristics of the Italian lead white cluster, as shown in literature, which is distinct compared to the lead found in other regions of Europe. This is evidence that the sample is coming from a painting that can be associated to an Italian painting made in the 16-17 th century. 3.6 Mapping Figure 8 shows the LIR mapping in false colours of the mock-up sample. The analysis was made using laser settings calculated specifically for mapping purposes, obtained using a dedicated Iolite software provided by ESL laser (iolite_optimizer_v0.96). A special designed ESL plasma torch (having a smaller inner tube diameter for sample injection to reduce washout time) was used to improve the washout time. The imaging was performed with raster using a 3 µm spot size (0.5 µm separation between lines to avoid resampling), 20 Hz repetition rate, and 20 µm/s scan speed over a 1 mm × 0.3 mm area. The depth of imaging analysis is calculated to be less than the one presented in the study before (< 5 µm as the dosage used for the mapping is 3, lower than the one used for raster or line analysis), and the surface ablated can be easily polished. Data reduction was carried out using Iolite, applying a 5 V threshold to the 208 Pb signal when the LIR imaging was calculated. This cutoff was essential to mask areas with a higher proportion of matrix to Pb white and to use data more closely signal-matched because of the SSB approach. The 208 Pb distribution map effectively visualizes the stratigraphy, with high-intensity (red-yellow) zones corresponding to lead white layers and low-intensity (blue) regions indicating zinc white. Some mechanical mixing of PDLW2 into the adjacent zinc layer is evident at the interface. Although the two lead pigments appear visually similar in the three LIR over 204 Pb ratios maps, the 206 Pb/ 204 Pb ratio map highlights their isotopic differences more clearly, with PDLW1 showing distinctively lower ratios (blue pixels) compared to PDLW2. Averaging isotopic ratios from two regions-of-interest in the lead-rich areas confirms that accurate LIR values can be extracted from these maps (the areas are the red rectangles highlighted in the 208 Pb Volts map in Figure 7). The method was then tested on a real sample, a cross-section containing LW in two adjacent paint layers: a layer of prime (thickness estimated around 5-8 µm) and a layer of lead white with the same thickness, Figure 8. The sample was provided by ARTDETECT in collaboration with the National Gallery – Alexandros Soutsos Museum, which kindly consented to share the results on the mapping, (not the name of the painting and the values of the analysis, which will be discussed in a specific publication). The investigation was carried out to test if the LW used in the two layers was different, a task possible only using LA analysis due to the paint layer thickness. The first attempt was done using the LA14.7 settings, using a line of 50 µm, on both layers and sampling multiple spots. The results identified the presence of two different lead white, but there was a problem with line_3, 4 and 17. While the sampling spots were on the same lead white rich layer next to each other, Figure 8a, their LIR were different, with line_17 showing values comparable to the value obtained from Line_5 and Line_16 from the prime layer. After visual inspection, it was found that the surface of the cross-section was not perfectly smooth but presented protrusions and pits, which likely caused the laser sampling to be inaccurate and out of focus. Sampling in the range of 5 µm is a challenging task as the focus of the laser ablation system camera and the laser optics is not optimal, when this is combined with a not well-polished surface, it can result in partial or total sampling of the adjacent layers, like in this case. This can explain the anomalous results for line_17, where the laser sampled the prime layer rather than the lead white layer, as visible from the LIR in Figure 8b, where the values for this ablation fall between the values of lines 3, 4, 13, 14, 15 (the lead white layer) and lines 5 and 16 of the prime. To ensure that the two layers were isotopically distinct and confirm that there was not dealing with a complex mixed phase of the two LWs, it was decided to polish the cross-section and to perform an isotopic mapping. As can be seen in Figure 8c, with the map of the three LIRs on ²⁰⁴Pb, and especially on the ²⁰⁶Pb/²⁰⁴Pb one, the presence of two LW in distinct paint is observed (one layer with lower LIR blue pixel, and one with higher LIR, red-yellow pixels). Combining this information, it is therefore possible to state that the LW used in the prime differs from that used in the lead white layer. This demonstrates the method's potential for identifying different lead white sources within a single painting, and this can be a powerful tool, for instance, to distinguish between different, adjacent thin layers containing lead white, while still offering a good indication of the provenance. 4. Conclusion Thes study successfully shows that, when calibrated with synthetic lead carbonate reference pigments (PDLW1 and PDLW2), LA-MC-ICPMS yields accurate lead isotope ratios for lead white at micrometre-scale spatial resolution while consuming only nanogram quantities of material, therefore using ~ 500000-1000 times less sample than traditional LIR analysis, making the approach micro-invasive and compatible with the practical constraints of cultural heritage sampling. The method does not require new sample as it can operate directly on cross-sections, ablating only around 5 µm in depth. LA results are in agreement with solution MC-ICPMS and demonstrate that the method can produce reliable isotope ratios in a carbonate matrix without measurable bias under the operating conditions tested; the principal limitation is that external precision remains poorer than solution analysis on the same instrument. This, however, still provides the resolution typically needed to provenance pigments. Re-analysis of historical lead white (GN) confirms accuracy on complex heritage material and comparability with prior datasets, while also highlighting a key caveat: alteration layers, residual impurities and micro-scale heterogeneity can increase measurement uncertainties, requiring careful targeting. The mock-up cross-section experiments show that oil-rich matrices are a significant analytical challenge for LA on lead carbonate: LIR precision and accuracy are worsened when ablating binder-rich, pigment-poor areas. At the same time, the results also demonstrate the method’s practical success in realistic conditions: accurate LIR are obtained when pigment-rich agglomerates are targeted, and oil contributions can be screened during data reduction, albeit at the cost of shorter usable integration time and therefore larger uncertainty. A key limitation in oil paints is that analytical performance becomes strongly dependent on micro-texture and pigment concentration; consequently, a robust workflow should include prior micro-analytical characterisation (e.g., SEM-EDS and/or FTIR imaging) to optimize ablation placement and to contextualize intra-layer variability. At the same time, this requirement underscores a major advantage of in-situ LA-based LIR analysis: it can be integrated with complementary micro-scale techniques on the same cross-section, enabling correlative, stratigraphy-resolved datasets that may provide new constraints on material choices, paint preparation, and workshop practice. The application to an anonymous 16-17 th century paint cross-section further supports the feasibility of this method to real samples: the lead white layer produced internally consistent LIR across different ablation geometries and positions, and the resulting isotopic signature is consistent with Venetian LW found in Italy during that period. Isotopic mapping demonstrates that LA-MC-ICPMS can generate spatially resolved LIR images that identify LIR differences between layers containing different types of lead white. This is a powerful tool that can be used in order to detect the presence of different LW in different layers, as ground, prime and paint layers, as shown in the application of the method to a real sample, which identified the presence of different types of LW in two thin adjacent paint layers (~ 8 µm thickness). Overall, the method provides an effective route to minimally invasive, spatially resolved LIR analysis of lead white in paintings and the workflow can be transferable to other media. In particular, it should be evaluated on frescoes and mural paintings where pigment presence is high. Further work should focus on strengthening the validation of matrix-matched standards and independent comparison with established reference approaches (e.g., double-spike TIMS), together with broader inter-session datasets to refine external reproducibility and uncertainty models. The use of new laser ablation systems, such as femto-second pulsed lasers, should also be addressed in future applications to verify if the use of shorter pulse duration can limit matrix effects, thereby improving accuracy and precision. 5. Software and data The Neoma data were collected using Qtegra software. The LA data are reduced using the Software Iolite 4, using the DRS Pb Isotopes DRS (Beta). The statistical analysis is done in RStudio using the package ggplot2 (code R in the Supplementary material S2 and S3). The data produced in this study are reported in the supplementary material S4 as an Excel file, Final data laser paper. Declarations Author Contributions Statement: P.D. Developed the method, performed LA-MC-ICPMS analyses, and wrote the first draft of the manuscript. Produced and characterised the synthetic reference materials, and prepared the paint mock-ups. G.H. contributed to method development, LA method setting up, data interpretation and manuscript revision. All authors reviewed and approved the final version. Acknowledgment: Many thanks to Andrea Baldi, Susan A. Rigter and Kimiya Setayeshmehr at the Physics and Astronomy department at VU Amsterdam for the help with the Alpha‑Step D‑500 surface profilometer. Bauke Lacet from the Vrije Universiteit for the embedding of the samples. Thanks to Anna Tummers from ARTDETECT and the National Gallery – Alexandros Soutsos Museum Greece. Adam Duglas for the help with the LA system and the program to calculate the right parameters for the LA imaging. Use of Artificial Intelligence Large language model (LLM) tools were used solely for language checking and editing. Competing interests The authors have no competing interests as defined by Springer, or other interests that might be perceived to influence the results and/or discussion reported in this paper. Funding sources This research was funded by Nederlandse Organisatie voor Wetenschappelijk Onderzoek. References D’imporzano P, Batur K, Keune K, Koornneef JM, Hermens E, Noble P, et al. Lead isotope heterogeneity in lead white: From lead white raw pigment to canvas. Microchemical Journal. Elsevier; 2021;163:105897. D’Imporzano P, Davies GR. Lead Isotope Ratios of Lead White: From Provenance to Authentication. In: Colombini MP, Degano I, Nevin A, editors. Analytical Chemistry for the Study of Paintings and the Detection of Forgeries [Internet]. Cham: Springer International Publishing; 2022. p. 447–71. https://doi.org/10.1007/978-3-030-86865-9_14 KEISCH B, CALLAHAN RC. Lead Isotope Ratios in Artists’ Lead White: a Progress Report. Archaeometry. 1976;18:181–93. https://doi.org/10.1111/j.1475-4754.1976.tb00159.x D’Imporzano P, Keune K, Koornneef JM, Hermens E, Noble P, Vandivere ALS, et al. Time-dependent variation of lead isotopes of lead white in 17th century Dutch paintings. Sci Adv. American Association for the Advancement of Science; 2021;7:eabi5905. Fabian D, Fortunato G. Tracing white: a study of lead white pigments found in seventeenth-century paintings using high precision lead isotope abundance ratios. Trade in artists’ materials: markets and commerce in Europe to. 2010;1700:426–43. Fortunato G, Ritter A, Fabian D. Old Masters{’} lead white pigments: investigations of paintings from the 16th to the 17th century using high precision lead isotope abundance ratios. Analyst [Internet]. The Royal Society of Chemistry; 2005;130:898–906. https://doi.org/10.1039/B418105K Pastorelli G, Miranda ASO, Clerici EA, d’Imporzano P, Hansen BV, Janssens K, et al. Darkening of lead white in old master drawings and historic prints: A multi-analytical investigation. Microchemical Journal. Elsevier; 2024;109912. D’Imporzano P, Keune K, Koornneef JM, Hermens E, Noble P, van Zuilen K, et al. Micro-invasive method for studying lead isotopes in paintings*. Archaeometry. 2020; https://doi.org/10.1111/arcm.12549 Lin J, Yang A, Lin R, Mao J, Hu Z, Liu Y. Review on in situ Isotopic Analysis by LA-MC-ICP-MS. Journal of Earth Science [Internet]. 2023;34:1663–91. https://doi.org/10.1007/s12583-023-2002-4 Guillong M, Wotzlaw J-F, Looser N, Laurent O. Evaluating the reliability of U–Pb laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) carbonate geochronology: matrix issues and a potential calcite validation reference material. Geochronology [Internet]. Copernicus Publications; 2020;2:155–67. https://doi.org/10.5194/gchron-2-155-2020 Zhang W, Hu Z. A critical review of isotopic fractionation and interference correction methods for isotope ratio measurements by laser ablation multi-collector inductively coupled plasma mass spectrometry. Spectrochim Acta Part B At Spectrosc [Internet]. 2020;171:105929. https://doi.org/https://doi.org/10.1016/j.sab.2020.105929 Danyushevsky L V, Thompson JM. GGR Handbook of Rock and Mineral Analysis Chapter 12 Laser Ablation-ICP-MS for the In Situ Analysis of Geological Samples. Geostand Geoanal Res [Internet]. John Wiley & Sons, Ltd; 2025;49:457–93. https://doi.org/https://doi.org/10.1111/ggr.70004 Sylvester PJ. Matrix effects in laser ablation–ICP–MS. 2008; Guillong M, Wotzlaw J-F, Looser N, Laurent O. Evaluating the reliability of U–Pb laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) carbonate geochronology: matrix issues and a potential calcite validation reference material. Geochronology. Copernicus GmbH; 2020;2:155–67. Nuriel P, Wotzlaw J-F, Ovtcharova M, Vaks A, Stremtan C, Šala M, et al. The use of ASH-15 flowstone as a matrix-matched reference material for laser-ablation U-Pb geochronology of calcite. Geochronology. Copernicus Publications Göttingen, Germany; 2021;3:35–47. Roberts NMW, Drost K, Horstwood MSA, Condon DJ, Chew D, Drake H, et al. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) U–Pb carbonate geochronology: strategies, progress, and limitations. Geochronology. Copernicus Publications Göttingen, Germany; 2020;2:33–61. Weber M, Lugli F, Jochum KP, Cipriani A, Scholz D. Calcium carbonate and phosphate reference materials for monitoring bulk and microanalytical determination of Sr isotopes. Geostand Geoanal Res. Wiley Online Library; 2018;42:77–89. Gonzalez V, Fazlic I, Cotte M, Vanmeert F, Gestels A, De Meyer S, et al. Lead (II) Formate in Rembrandt’s Night Watch: Detection and Distribution from the Macro‐to the Micro‐scale. Angewandte Chemie. Wiley Online Library; 2023;135:e202216478. Merkel SW, D’Imporzano P, Van Zuilen K, Kershaw J, Davies GR. “Non-invasive” portable laser ablation sampling for lead isotope analysis of archaeological silver: a comparison with bulk and in situ laser ablation techniques. J Anal At Spectrom. Royal Society of Chemistry; 2022;37:148–56. van Loon A, Vandivere A, Delaney JK, Dooley KA, De Meyer S, Vanmeert F, et al. Beauty is skin deep: the skin tones of Vermeer’s Girl with a Pearl Earring. Herit Sci [Internet]. 2019;7:102. https://doi.org/10.1186/s40494-019-0344-0 D’imporzano P, Reiling HM, Merkel S, van Iperen JM, Garachon I, Keune K, et al. Lead isotope analysis of lead-tin-glaze via on-site portable laser ablation sampling of 17-18th century Delftware (earthenware). J Archaeol Sci. Elsevier; 2026;185:106443. Klaver M, Smeets RJ, Koornneef JM, Davies GR, Vroon PZ. Pb isotope analysis of ng size samples by TIMS equipped with a 10 13 Ω resistor using a 207 Pb–204 Pb double spike. J Anal At Spectrom. Royal Society of Chemistry; 2016;31:171–8. Additional Declarations No competing interests reported. Supplementary Files S4Finaldatalaserpaper.xlsx S3PlotsMSDWseparate.r S2PlotsMSDWplottogether.r S1Supplementarymaterial.docx S5LAsettingsparameters.xlsx Cite Share Download PDF Status: Under Revision Version 1 posted Editorial decision: Revision requested 17 Apr, 2026 Reviews received at journal 08 Apr, 2026 Reviewers agreed at journal 19 Mar, 2026 Reviewers agreed at journal 17 Mar, 2026 Reviewers invited by journal 16 Mar, 2026 Editor assigned by journal 16 Mar, 2026 Submission checks completed at journal 16 Mar, 2026 First submitted to journal 12 Mar, 2026 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-9106478","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":607897375,"identity":"78634552-4d0f-42c0-a2e4-84439b2ee14e","order_by":0,"name":"Paolo D’Imporzano","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAuklEQVRIiWNgGAWjYFCCxAYgYZMAZicUEK8lLYGBDaTFgCgtYPMPQ7QwEKPFnD25dXNBxfk8fvnuxA8PDBjk+cUO4Ndi2fOw7faMM7eLJdt4N0sAHWY4c3YCfi0GNxLbbvO23U7ccIx3A0hLgsFt4rScA2nZ/IMULQdAWrYRZwvUL8mJM9tyt1kkGEgQ9os5e/qz2wUVdon9zGc33/xRYSPPL03IYUDMjMSXwK8cm5ZRMApGwSgYBZgAAJxbSCTqTp4sAAAAAElFTkSuQmCC","orcid":"","institution":"Vrije Universiteit Amsterdam","correspondingAuthor":true,"prefix":"","firstName":"Paolo","middleName":"","lastName":"D’Imporzano","suffix":""},{"id":607897376,"identity":"9d7190b6-ac97-4ace-8432-53fd83618819","order_by":1,"name":"Graham A. Hagen-Peter","email":"","orcid":"","institution":"Vrije Universiteit Amsterdam","correspondingAuthor":false,"prefix":"","firstName":"Graham","middleName":"A.","lastName":"Hagen-Peter","suffix":""}],"badges":[],"createdAt":"2026-03-12 15:24:49","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-9106478/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-9106478/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":104971026,"identity":"9ab466e5-2928-4faf-85c0-8f9e57267528","added_by":"auto","created_at":"2026-03-19 10:59:47","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":102311,"visible":true,"origin":"","legend":"\u003cp\u003ePhotographs of the PDLW1 reference material at successive preparation stages (left to right): metallic lead precursor, synthesised lead white pigment, epoxy-embedded pellet for use as an LA standard, and lead white dispersed in linseed oil applied on glass to produce a mock-up paint sample.\u003c/p\u003e","description":"","filename":"1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-9106478/v1/3c84a199185afe4354d3e965.jpg"},{"id":104971030,"identity":"70d320fc-537d-4ad2-a66e-41bf27ca9c2d","added_by":"auto","created_at":"2026-03-19 10:59:47","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":146225,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003e(a)\u003c/strong\u003e\u0026nbsp;Summary of laser operating conditions and corresponding analytical performance for PDLW2, including mean LIR values, 2SD, and MSWD for solution MC-ICPMS (PDLW2-solution) and two LA-MC-ICPMS settings (PDLW2-10.2 and PDLW2-14.7) based on \u003csup\u003e204\u003c/sup\u003ePb. Ellipses represent the method-specific covariance (95%). Solution measurements show lower 2SD, while all three datasets agree within uncertainty.\u0026nbsp;\u003cstrong\u003e(b)\u003c/strong\u003e\u0026nbsp;Reflected-light microscope image acquired on the LA system showing representative ablation features in the lead white pigment; the ablation depth is estimated at approximately 5 µm.\u003c/p\u003e","description":"","filename":"2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-9106478/v1/ead672a3db6ab1fa1e3c3deb.jpg"},{"id":104971028,"identity":"b0b4dcbd-8b9f-4368-a88f-4d86d768e1d3","added_by":"auto","created_at":"2026-03-19 10:59:47","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":159097,"visible":true,"origin":"","legend":"\u003cp\u003eSummary of the analysis on GN, including mean LIR values, 2SD, and MSWD for solution MC-ICPMS (GN) and two LA-MC-ICPMS settings (GN 10.2 and GN 14.7) based on \u003csup\u003e204\u003c/sup\u003ePb and literature data taken from GN in D’Imporzano et al. 2021. Ellipses represent the method-specific covariance (95%). Solution measurements show lower 2SD, while all four datasets agree within uncertainty.\u0026nbsp;\u003c/p\u003e","description":"","filename":"3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-9106478/v1/25b8debed1dbb2c52467c760.jpg"},{"id":105562775,"identity":"a385850b-c3e6-4fc6-91bf-d9b608591ab3","added_by":"auto","created_at":"2026-03-27 12:44:39","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":148060,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003e(a)\u003c/strong\u003e\u0026nbsp;Summary of laser operating conditions and corresponding analytical performance for PDLW2, including mean LIR values, 2SD, and MSWD for solution MC-ICPMS (PDLW2-solution) and two LA-MC-ICPMS ablation areas; long corresponding to a 50 second analysis time and ablation patterns as shown in Figure 2b, and short which is 20 second analysis and around half of the long method. The LIR are based on \u003csup\u003e204\u003c/sup\u003ePb. Ellipses represent the method-specific covariance (95%). PDLW2 short show worse 2SD compared to PDLW2 long, as expected by shorter analysis time, but the values are still within error of the solution values.\u0026nbsp;\u003cstrong\u003e(b)\u003c/strong\u003e\u0026nbsp;Summary of laser operating conditions and corresponding analytical performance for GN which show identical patterns as discussed for PDLW2\u003c/p\u003e","description":"","filename":"4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-9106478/v1/e24b62a120c1aa66cc0f3b5d.jpg"},{"id":104971032,"identity":"b71ca576-fae6-486c-8978-83c994da3d25","added_by":"auto","created_at":"2026-03-19 10:59:47","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":164034,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003e(a)\u003c/strong\u003e\u0026nbsp;Summary of laser operating conditions and corresponding analytical performance for PDLW2 in the mock-up and embedded pure pigment, including mean LIR values, 2SD, and MSWD; PDLW2-Oil corresponding to analysis of the mock-up, and PDLW2 14.7 corresponding to standard LA on the embedded pure pigment. The LIR are based on \u003csup\u003e204\u003c/sup\u003ePb. Ellipses represent the method-specific covariance (95%).\u0026nbsp;\u003cstrong\u003e(b)\u003c/strong\u003e\u0026nbsp;Image taken with the LA system integrated microscope of the mock-up areas ablated during a session. The ablations were done to test the accuracy of the method when different ratios of pigment/oil were ablated.\u003c/p\u003e","description":"","filename":"5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-9106478/v1/dfdca8ad73c3d06d9cab9418.jpg"},{"id":104971034,"identity":"1441c5ff-45ee-4756-a2f1-762987f0dc82","added_by":"auto","created_at":"2026-03-19 10:59:47","extension":"jpg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":114451,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003e(a)\u003c/strong\u003e LIR biplots showing the results obtained for the anonymous painting compared to literature data for lead white LIR [1,2,4–7] \u003cstrong\u003e(b)\u003c/strong\u003e Image taken with the LA system integrated microscope of the anonymous paint sample showing ablation location and pattern.\u003c/p\u003e","description":"","filename":"6.jpg","url":"https://assets-eu.researchsquare.com/files/rs-9106478/v1/d6e58a0cc05644059d2629c0.jpg"},{"id":105034840,"identity":"011a7002-d65b-4177-8739-98eff690d083","added_by":"auto","created_at":"2026-03-20 07:24:27","extension":"jpg","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":179270,"visible":true,"origin":"","legend":"\u003cp\u003eFalse-colour maps of the \u003csup\u003e208\u003c/sup\u003ePb signal intensity (V) and the corresponding lead isotope ratios (LIR) calculated over the same mapped area. LIR pixels were computed only where the \u003csup\u003e208\u003c/sup\u003ePb signal exceeded a 5 V threshold. In The \u003csup\u003e208\u003c/sup\u003ePb intensity map there are two regions-of-interest highlighted in red, corresponding to the\u0026nbsp;PDLW1 (lower layer)\u0026nbsp;and\u0026nbsp;PDLW2 (upper layer). Mean LIR values extracted from these regions are shown in the biplots below: the mapped layer averages are consistent with the bulk LIR signatures of PDLW1 and PDLW2, albeit with larger uncertainties.\u003c/p\u003e","description":"","filename":"7.jpg","url":"https://assets-eu.researchsquare.com/files/rs-9106478/v1/6ea294609fd9c081ff51cd84.jpg"},{"id":104971036,"identity":"5b5fbc5d-28aa-4037-8d6a-f66f78068cfc","added_by":"auto","created_at":"2026-03-19 10:59:47","extension":"jpg","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":102828,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003e(a)\u003c/strong\u003e microscope image of the cross-section showing the two different painting layers and the ablated area; \u003cstrong\u003e(b)\u003c/strong\u003e LIR data obtained using the LA14.7, the analyses were able to identify the presence of two different LW; \u003cstrong\u003e(c)\u003c/strong\u003e Mapping of the lead cross-section showing the presence of two layers of paint containing two different types of lead white.\u003c/p\u003e","description":"","filename":"8.jpg","url":"https://assets-eu.researchsquare.com/files/rs-9106478/v1/644ac95512ce18f1d5b3b302.jpg"},{"id":106092944,"identity":"6058205d-32a4-4f69-8cd2-4a4d43bb56f8","added_by":"auto","created_at":"2026-04-03 11:31:11","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1782163,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9106478/v1/66d1ddc6-932d-49b0-88ed-2fbd2a73c226.pdf"},{"id":105035270,"identity":"c3b3eabc-1d77-4001-9cc2-bb7e07ede956","added_by":"auto","created_at":"2026-03-20 07:25:46","extension":"xlsx","order_by":0,"title":"","display":"","copyAsset":false,"role":"supplement","size":118441,"visible":true,"origin":"","legend":"","description":"","filename":"S4Finaldatalaserpaper.xlsx","url":"https://assets-eu.researchsquare.com/files/rs-9106478/v1/47ec22db7ebdbc76dcb60c0f.xlsx"},{"id":105035248,"identity":"233f2edd-e90b-4f9a-a07b-a70c3f786da7","added_by":"auto","created_at":"2026-03-20 07:25:44","extension":"r","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":8789,"visible":true,"origin":"","legend":"","description":"","filename":"S3PlotsMSDWseparate.r","url":"https://assets-eu.researchsquare.com/files/rs-9106478/v1/3f27cfaebcf554c9605ac028.r"},{"id":105035099,"identity":"f25bc6dd-3d39-410d-9b4c-611b95413434","added_by":"auto","created_at":"2026-03-20 07:25:29","extension":"r","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":8436,"visible":true,"origin":"","legend":"","description":"","filename":"S2PlotsMSDWplottogether.r","url":"https://assets-eu.researchsquare.com/files/rs-9106478/v1/e1850c7e7522f6a20580c7b4.r"},{"id":105035305,"identity":"7548358d-bf4d-4052-9688-b7723ce621f8","added_by":"auto","created_at":"2026-03-20 07:25:49","extension":"docx","order_by":3,"title":"","display":"","copyAsset":false,"role":"supplement","size":3259741,"visible":true,"origin":"","legend":"","description":"","filename":"S1Supplementarymaterial.docx","url":"https://assets-eu.researchsquare.com/files/rs-9106478/v1/fcc6cbc84cfba076498b013b.docx"},{"id":105035326,"identity":"477ceea7-2cf0-444e-97c3-64ef3a8524ee","added_by":"auto","created_at":"2026-03-20 07:25:51","extension":"xlsx","order_by":4,"title":"","display":"","copyAsset":false,"role":"supplement","size":646505,"visible":true,"origin":"","legend":"","description":"","filename":"S5LAsettingsparameters.xlsx","url":"https://assets-eu.researchsquare.com/files/rs-9106478/v1/bdba07de0b0192f2e7e3c433.xlsx"}],"financialInterests":"No competing interests reported.","formattedTitle":"In-situ Laser Ablation MCICPMS of lead white in paintings","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003e\u003cstrong\u003eLead isotope ratio (LIR)\u003c/strong\u003e analysis of \u003cstrong\u003elead white\u0026nbsp;(LW)\u003c/strong\u003e pigments via \u003cstrong\u003emulti-collector inductively-coupled-plasma mass-spectrometry (MC-ICPMS)\u003c/strong\u003e is a robust, well-established methodology for determining pigment provenance\u0026nbsp;[1\u0026ndash;7]. Beyond simple material sourcing, this technique successfully reconstructs historical artist movements and socio-economic trade networks, while providing critical analytical data for painting authentication and identification. However, the broader application of this technique in heritage science is currently constrained by significant methodological limitations regarding sample extraction and spatial resolution.\u003c/p\u003e\n\u003cp\u003eThe primary limitation of traditional MC-ICPMS is its reliance on invasive sampling and the need to dissolve the sample for analysis. Sampling, whether performed manually by conservators or via micro-scalpel from existing cross-sections\u0026nbsp;[8], remains fundamentally invasive for unique cultural heritage objects. Furthermore, these physical extraction methods suffer from extreme material inefficiency. While a high-precision LIR analysis requires only\u0026nbsp;50-100 nanograms of lead (ng, which is one billionth of a gram, 10\u003csup\u003e-9\u0026nbsp;\u003c/sup\u003eg lead constitutes approximately\u0026nbsp;\u003cimg width=\"58\" height=\"19\" src=\"data:image/png;base64,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\" alt=\"image\"\u003e\u0026nbsp;of lead white), manual and micro-scalpel methods inevitably extract thousands of nanograms. Consequently, more than\u0026nbsp;\u003cimg width=\"29\" height=\"19\" src=\"data:image/png;base64,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\" alt=\"image\"\u003e\u0026nbsp;of the extracted material is wasted during dissolution, as mechanically isolating exactly\u0026nbsp;\u003cimg width=\"43\" height=\"19\" src=\"data:image/png;base64,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\" alt=\"image\"\u003e\u0026nbsp;of sample is physically unfeasible.\u003c/p\u003e\n\u003cp\u003eA secondary critical limitation is the inadequate spatial resolution inherent in physical sampling. When paint fragments are acquired via manual scraping, the stratigraphic integrity of the painting is lost. If the extracted fragment contains multiple paint layers, containing different historical sources of lead white, the resulting LIR data will merely reflect a homogenised, weighted average rather than a layer-specific isotopic signature. While targeted micro-scalpel sampling from embedded cross-sections improves stratigraphic control, it is still severely limited by the physical dimensions of the tools\u0026nbsp;[8]. Because micro-scalpel blades measure in the tens of micrometres (\u0026micro;m), they frequently exceed the thickness of individual historical paint layers. Consequently, successfully isolating a pure lead white layer without adjacent cross-contamination is difficult and remains heavily dependent on the specific rheological and elasticity/brittleness properties of the aged paint.\u003c/p\u003e\n\u003cp\u003eThis study proposes an alternative path to study LIR in lead white samples via MC-ICPMS using in-situ \u003cstrong\u003elaser ablation (LA)\u003c/strong\u003e. The use of LA to study LIR in lead white samples can give unparallel benefit compared to classic sampling techniques: it has extremely high spatial resolution, with the laser beam diameter as small as 1\u0026nbsp;\u0026micro;m, and adjustable repetition rate and fluence (energy per unit area) to sample only the needed material for LIR, without wasting sample material. This resolution also provides the possibility to sample single particles of lead white in a single sample, allowing the comparison of different lead white in painting, as in the case of LW present in ground, prime and highlights, to detect precisely retouching, reuse of canvas and other artist practices. The samples can be, similarly to the use of micro-scalpel\u0026nbsp;[8], sampled from cross-sections, avoiding the necessity of taking new samples from paintings if not needed. The sample can be analysed without sample preparation reducing analysis time.\u003c/p\u003e\n\u003cp\u003eLA of lead white, a lead carbonate that is applied mainly in linseed oil in oil painting, presents specific analytical challenges that must be addressed for reliable heritage science applications. LA-MC-ICPMS inherently yields lower precision (higher external error,\u0026nbsp;\u003cimg width=\"27\" height=\"19\" src=\"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAACgAAAAcCAMAAAAkyw3kAAAAAXNSR0IArs4c6QAAAIFQTFRFAAAAAAAAAAA6AABmADo6ADqQAGa2OgAAOjoAOjpmOmZmOmaQOma2OpDbZgAAZjoAZjo6ZmY6ZmZmZpC2ZpDbZrb/kDoAkGY6kLbbkNv/tmYAtmY6tpBmtra2trbbttv/tv//25A627aQ29v/2////7Zm/9uQ/9u2/9vb//+2///bb3OFCgAAAAF0Uk5TAEDm2GYAAAAJcEhZcwAAFiUAABYlAUlSJPAAAAAZdEVYdFNvZnR3YXJlAE1pY3Jvc29mdCBPZmZpY2V/7TVxAAAA+UlEQVQ4T+1SC5KCMAxNCiu6Kq51wRW/uBa09z/g5gPYjs7sATQzlLR9yctLCvCidt2NEc3s8p98h8kRfIUfjLxuMwqaHsltyCNLZcPmzIbWW86/NsfU2jGagoHGWrskeETmSwZWOOfYJktOtAgHtAscBVVJRkUD+PVkMwA7sh7rJKzLKId9RoBaecR8SWQiIF396tEdePcolXJC+0VCe9VaYxgCdYfj3Oc1C32eseZ2BHbOsHhG7ehYK90f1GFpj2JueS9quIuAOguySor2ZUEffmsPAuqh4U5GSiZjQ/Npl8hNfRhhFQDB80vCyY/2NH4Ukd73Ju7AHwjoE/pyZOh5AAAAAElFTkSuQmCC\" alt=\"image\"\u003e) compared to traditional solution-based analysis due to highly transient signals. This reduced precision can directly limit the ability to resolve minute isotopic differences crucial for determining pigment provenance. To be a viable alternative for painting characterisation, LA analysis must demonstrate sufficient resolving power. For example, distinguishing Venetian from 17th-century Dutch lead white requires resolving a difference of approximately 2700 ppm in the \u003csup\u003e206\u003c/sup\u003ePb/\u003csup\u003e204\u003c/sup\u003ePb ratio\u0026nbsp;[1]. Because solution-based LIR analysis achieves a 2SD of roughly 150 ppm,\u0026nbsp;easily resolving this geographic variation, LA methodologies must be optimised to approach this level of precision.\u003c/p\u003e\n\u003cp\u003eFurthermore, the physical and chemical properties of the carbonate in paint matrix complicate the ablation process. Among others, these so-called \u0026ldquo;matrix-effects\u0026rdquo; may include 1) laser-induced elemental and isotopic fractionation during ablation and aerosol transport due to phase changes during the ablation process; 2) sample-dependent differences in isotopic fractionation in the MC-ICPMS due to differences in sample load (\u0026ldquo;plasma loading\u0026rdquo;); 3) variable matrix-based interferences, for example organic complexes originating from the organic matrix of the pigmentn(e.g., linseed oil)\u0026nbsp;[9\u0026ndash;13].\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eFinally, the accuracy of LA-MC-ICPMS are currently constrained by the absence of a validated, matrix-matched isotopic reference material for lead carbonate or historical lead white pigments.\u003c/p\u003e\n\u003cp\u003eThis work addresses these limitations by developing and validating an\u0026nbsp;in-situ LA-MC-ICPMS\u0026nbsp;approach for LIR analysis of lead white in paint samples. Two lead white reference materials (\u003cstrong\u003ePDLW1\u003c/strong\u003e and \u003cstrong\u003ePDLW2\u003c/strong\u003e) were synthesised from metallic lead and converted to carbonates; their isotopic compositions were first established by\u0026nbsp;solution MC-ICPMS\u0026nbsp;and subsequently used as\u0026nbsp;calibrants and quality-control reference materials\u0026nbsp;for LA measurements. These materials were employed to evaluate LA performance on lead carbonates, including signal stability and mass-dependent fractionation, and to assess their suitability as matrix-matched reference materials.\u003c/p\u003e\n\u003cp\u003eTo benchmark the proposed approach against established datasets, the 16\u003csup\u003eth\u003c/sup\u003e century Venetian lead white samples previously reported in Dimporzano et al. (2021) were re-analysed in this study via solution and by LA and directly compared with literature data\u0026nbsp;[1]. In addition, a stratified mock-up cross-section was prepared consisting of two discrete layers of PDLW1- and PDLW2-based oil paint, separated by zinc white interlayers, to reproduce a realistic multilayer paint stratigraphy. This mock-up was analysed to quantify isotopic fractionation in an oil-bound carbonate matrix and to test the spatial resolving power of LA via isotopic mapping, i.e., the ability to discriminate isotopically distinct lead white domains within a single cross-section.\u003c/p\u003e\n\u003cp\u003eFinally, the validated method was applied to an anonymous paint sample dated to the 16th\u0026ndash;17th century, presumably produced in Italy, to identify the isotopic signature of the lead source used in the lead white pigment.\u003c/p\u003e"},{"header":"2. Method and materials","content":"\u003cp\u003e2.1- Lead white\u003c/p\u003e\n\u003cp\u003eThe lead white pigments used in this study, PDLW1 and PDLW2, were synthesized from metallic lead fishing weights purchased online, manufactured in China. The lead was supplied as small coils approximately 2 cm in height (Figure 1, \u003cem\u003eMetallic lead\u003c/em\u003e). These coils were first analysed to determine their Pb isotopic composition and to assess isotopic homogeneity within each coil; the metal was found to be isotopically homogeneous within individual coils, and two coils with distinct isotopic signatures were selected to produce lead whites with different isotopic compositions (PDLW1 and PDLW2, see supplementary material S1 paragraphF \u003cem\u003emetal LIR vs LW LIR\u003c/em\u003e). To synthesise lead white, the selected coils were suspended above acetic acid at room temperature for two weeks to form lead acetate. The coils were then transferred to a solution of water, sugar, and baking yeast, which generated CO\u003csub\u003e2\u003c/sub\u003e and promoted the conversion of lead acetate to lead carbonate over a further two weeks. The lead white that formed on the surface of the coils was subsequently removed, thoroughly washed, and homogenised (Figure 1, \u003cem\u003eLead white\u003c/em\u003e).\u003c/p\u003e\n\u003cp\u003ePDLW1 was used as the bracketing standard and PDLW2 as the quality-control material for the laser ablation measurements; this assignment of roles between the two pigments was arbitrary (they could in principle be swapped), whereas the non‑arbitrary decision was to use our own synthetically prepared lead‑white carbonate as the reference matrix to mitigate matrix effects. Lead‑carbonate pigment was considered to be more appropriate for \u003cstrong\u003eStandard Sample Bracketing (SSB)\u003c/strong\u003e in LA‑MC‑ICPMS work than a non\u0026ndash;matrix-matched silicate glass such as NBS/NIST glasses, because the very large differences in Pb and trace‑element concentrations between glass and lead carbonate (often several orders of magnitude; e.g., NIST 610 with ~430 ug/g Pb and lead white with 70-80 wt% Pb). Significantly different Pb signals resulting from the ablation of Pb white vs glass, or significantly different fluxes of total material into the plasma if the former is compensated by using a larger spot size for the glasses, can lead to differences in the magnitude of instrumental mass-bias between glasses and Pb white. Moreover, using a synthetic Pb carbonate standard better captures the specific ablation behaviour, particle generation, and signal instability associated with the surface structure and crystallographic structure of carbonates and phase differences (e.g. ratios between cerussite/hydrocerussite, presence of partial unreacted lead product as acetates, plumbonacrite, metallic lead and traces of galena)\u0026nbsp;[14\u0026ndash;18].\u003c/p\u003e\n\u003cp\u003eThe lead white thus formed was divided in three parts, one to be analysed via solution, one to be compressed and embedded in epoxy to be used as standard and quality control for laser work (Figure 1, PDLW1 LA-standard), and one mixed in linseed oil to form a painting mock-up to assess the LIR in real sample (Figure 1, LA-Oil-paint mock-up). The mock-up consisted of a stock up of 4 different layers of paint on a glass and aged artificially at 40 degrees Celsius. The bottom layer was PDLW1 in Linseed oil, once dry a layer of zinc white was added on top, then a layer of linseed oil with PDLW2 and finally a last layer of zinc white.\u003c/p\u003e\n\u003cp\u003eA third type of lead white, which was already analysed in Dimpo et al 2021, coming from historical Venetian lead white, and here named \u003cstrong\u003eGN\u003c/strong\u003e, was also re-analysed in this study. Part of this lead white was also compressed into a pellet and embedded in epoxy to assess the accuracy and precision of laser ablation compared to literature data.\u003c/p\u003e\n\u003cp\u003e2.2- Instrumentation\u003c/p\u003e\n\u003cp\u003eLead isotope ratio measurements of solutions were performed in dry plasma using a Thermo Fisher Neoma MC-ICPMS coupled with an Apex omega desolvator (parameters in Table 1). The samples for solution works were introduced as solutions of 25 ppb lead doped with 5 pbb of Thallium (2 mL for each sample was prepared). The Thallium was used to calculate the mass-bias fractionation factor\u0026nbsp;\u0026beta; using the exponential law.\u0026nbsp;The mercury Isotope \u003csup\u003e202\u003c/sup\u003eHg was monitored and used to remove the isobaric interference (isotope \u003csup\u003e204\u003c/sup\u003eHg) from the lead isotope \u003csup\u003e204\u003c/sup\u003ePb. For each run, an in-house quality control standard (\u0026ldquo;CPI\u0026rdquo;) and blanks (in solution work blanks were below 50 pg and therefore their contribution to the analysis is considered irrelevant) were also analysed. The replicates of the CPI in-house standard have been used to calculate the external precision of the Neoma in this work.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eFor laser ablation analysis, the ESL (Elemental Scientific Lasers) NWR193UC \u0026nbsp; 193 nm ArF excimer laser ablation system fitted with a TV3 cell was used. Ablations were carried out in a 2-volume chamber in a He atmosphere, and the ablated aerosol was mixed with Ar in a signal-smoothing bulb before introduction into the plasma. The analysis parameters for the Neoma and the LA are reported in Table 1. The PDLW1 was used as a primary standard to correct for instrumental mass bias via a SSB correction (\u0026beta; is calculated using the exponential law and a spline function). Before and after each ablation, a washout time of 70 and 60 seconds was applied to reduce any memory effect (background signal on the 208Pb \u0026lt; 0.001 V). The data were reduced using Iolite 4, via the DRS Pb Isotopes DRS (Beta). For each run, samples were corrected for the baseline (calculated via a spline function), collecting the background signal for 30 seconds before each sample, and the isobaric interference on \u003csup\u003e204\u003c/sup\u003ePb was corrected for \u003csup\u003e204\u003c/sup\u003eHg using the \u003csup\u003e202\u003c/sup\u003eHg.\u003c/p\u003e\n\u003ctable border=\"0\" cellspacing=\"0\" cellpadding=\"0\" width=\"507\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"2\" valign=\"bottom\" style=\"width: 195px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eLaser ablation\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 97px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 97px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eSettings 1\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 117px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eSettings 2\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\" style=\"width: 183px;\"\u003e\n \u003cp\u003e\u003cem\u003eHe (L min-1)\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 11px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 97px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 97px;\"\u003e\n \u003cp\u003e0.980 - 01.080\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 117px;\"\u003e\n \u003cp\u003e0.980 - 01.080\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"2\" valign=\"bottom\" style=\"width: 195px;\"\u003e\n \u003cp\u003e\u003cem\u003espeed \u0026micro;m/sec\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 97px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 97px;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 117px;\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\" style=\"width: 183px;\"\u003e\n \u003cp\u003e\u003cem\u003espot \u0026micro;m\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 11px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 97px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 97px;\"\u003e\n \u003cp\u003e5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 117px;\"\u003e\n \u003cp\u003e5\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\" style=\"width: 183px;\"\u003e\n \u003cp\u003e\u003cem\u003eEnergy (J)\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 11px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 97px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 97px;\"\u003e\n \u003cp\u003e0.42\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 117px;\"\u003e\n \u003cp\u003e0.51\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\" style=\"width: 183px;\"\u003e\n \u003cp\u003e\u003cem\u003eHz\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 11px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 97px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 97px;\"\u003e\n \u003cp\u003e7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 117px;\"\u003e\n \u003cp\u003e8\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\" style=\"width: 183px;\"\u003e\n \u003cp\u003e\u003cem\u003eN (dosage)\u0026nbsp;\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 11px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 97px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 97px;\"\u003e\n \u003cp\u003e35\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 117px;\"\u003e\n \u003cp\u003e20\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\" style=\"width: 183px;\"\u003e\n \u003cp\u003e\u003cem\u003eN*Energy\u0026nbsp;\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 11px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 97px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 97px;\"\u003e\n \u003cp\u003e10.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 117px;\"\u003e\n \u003cp\u003e14.7\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"3\" valign=\"bottom\" style=\"width: 292px;\"\u003e\n \u003cp\u003e\u003cem\u003eNeoma Integration time (sec)\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 97px;\"\u003e\n \u003cp\u003e0.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 117px;\"\u003e\n \u003cp\u003e0.25\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"2\" valign=\"bottom\" style=\"width: 195px;\"\u003e\n \u003cp\u003e\u003cem\u003eAblation time sec\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 97px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 97px;\"\u003e\n \u003cp\u003e~ 50\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 117px;\"\u003e\n \u003cp\u003e~ 20\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\" style=\"width: 183px;\"\u003e\n \u003cp\u003e\u003cem\u003eEfficency %\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 11px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 97px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 97px;\"\u003e\n \u003cp\u003e0.05-0.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 117px;\"\u003e\n \u003cp\u003e0.05-0.3\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\" style=\"width: 183px;\"\u003e\n \u003cp\u003e\u003cstrong\u003ePlasma\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 11px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 97px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 97px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eSolution\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 117px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eLaser\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\" style=\"width: 183px;\"\u003e\n \u003cp\u003e\u003cem\u003eRF Power (W)\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 11px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 97px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 97px;\"\u003e\n \u003cp\u003e1200\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 117px;\"\u003e\n \u003cp\u003e1200\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"2\" valign=\"bottom\" style=\"width: 195px;\"\u003e\n \u003cp\u003e\u003cem\u003ePlasma condition\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 97px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 97px;\"\u003e\n \u003cp\u003edry plasma\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 117px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"2\" valign=\"bottom\" style=\"width: 195px;\"\u003e\n \u003cp\u003e\u003cem\u003eNebulizer Ar flow (L min\u003csup\u003e-1\u003c/sup\u003e)\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 97px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 97px;\"\u003e\n \u003cp\u003e0.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 117px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"2\" valign=\"bottom\" style=\"width: 195px;\"\u003e\n \u003cp\u003e\u003cem\u003eSampling cone\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 97px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 97px;\"\u003e\n \u003cp\u003eStandard\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 117px;\"\u003e\n \u003cp\u003eStandard\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"2\" valign=\"bottom\" style=\"width: 195px;\"\u003e\n \u003cp\u003e\u003cem\u003eSkimmer cone\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 97px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 97px;\"\u003e\n \u003cp\u003eH\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 117px;\"\u003e\n \u003cp\u003eH\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\" style=\"width: 183px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eCollection\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 11px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 97px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 97px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eSolution\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 117px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eLaser\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"2\" valign=\"bottom\" style=\"width: 195px;\"\u003e\n \u003cp\u003e\u003cem\u003eSensitivity (V ppm\u003csup\u003e-1\u003c/sup\u003e)\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 97px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 97px;\"\u003e\n \u003cp\u003e320 - 400\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 117px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"2\" valign=\"bottom\" style=\"width: 195px;\"\u003e\n \u003cp\u003e\u003cem\u003eBlank signal \u003csup\u003e208\u003c/sup\u003ePb (V)\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 97px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 97px;\"\u003e\n \u003cp\u003e\u0026lt; 0.003\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 117px;\"\u003e\n \u003cp\u003e\u0026lt; 0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\" style=\"width: 183px;\"\u003e\n \u003cp\u003e\u003cem\u003eCycles\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 11px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 97px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 97px;\"\u003e\n \u003cp\u003e40\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 117px;\"\u003e\n \u003cp\u003e~ 80 - 100\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\" style=\"width: 183px;\"\u003e\n \u003cp\u003e\u003cem\u003eblock\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 11px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 97px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 97px;\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 117px;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"2\" valign=\"bottom\" style=\"width: 195px;\"\u003e\n \u003cp\u003e\u003cem\u003eIntegration time (seconds)\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 97px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 97px;\"\u003e\n \u003cp\u003e4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 117px;\"\u003e\n \u003cp\u003e0.25-0.5\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n\u003ctable border=\"0\" cellspacing=\"0\" cellpadding=\"0\" width=\"100%\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\" style=\"width: 10px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eL4\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 10px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eL3\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 10px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eL2\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 10px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eL1\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 10px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eCenter\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 10px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eH1\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 12px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eH2\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 13px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eH3\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 10px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eH4\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\" style=\"width: 10px;\"\u003e\n \u003cp\u003e\u003csup\u003e200\u003c/sup\u003eHg\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 10px;\"\u003e\n \u003cp\u003e\u003csup\u003e202\u003c/sup\u003eHg\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 10px;\"\u003e\n \u003cp\u003e\u003csup\u003e203\u003c/sup\u003eTl\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 10px;\"\u003e\n \u003cp\u003e\u003csup\u003e204\u003c/sup\u003ePb\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 10px;\"\u003e\n \u003cp\u003e\u003csup\u003e205\u003c/sup\u003eTl\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 10px;\"\u003e\n \u003cp\u003e\u003csup\u003e206\u003c/sup\u003ePb\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 12px;\"\u003e\n \u003cp\u003e\u003csup\u003e207\u003c/sup\u003ePb\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 13px;\"\u003e\n \u003cp\u003e\u003csup\u003e208\u003c/sup\u003ePb\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 10px;\"\u003e\n \u003cp\u003e\u003csup\u003e209\u003c/sup\u003eBi\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 1\u003c/strong\u003e: Operating conditions used for the LA-MC-ICPMS measurements. The table summarizes the principal laser ablation parameters (spot size, repetition rate, scan speed, carrier gas configuration etc.) and the corresponding MC-ICPMS acquisition settings (cup configuration, integration time, mass etc.) applied for lead isotope ratio analysis of lead white\u003c/p\u003e"},{"header":"3.\tResults and discussion","content":"\u003cp\u003e3.1 Solution analyses\u003c/p\u003e\n\u003cp\u003eTable 2 reports the external precision as 2SD for the in-house standard solution, CPI, analysed during the course of this project (6 months c.a. for a total of 203 replicates of the solution) in dry plasma. The data are within error with literature data for the same sample analysed in\u0026nbsp;[1,2,4,7,19\u0026ndash;22]\u0026nbsp;(which reports much data on lead isotopes of lead white and other medium as silver and lead glaze). A more detailed discussion on the comparison of this data with literature data is given in the supplementary material S1 paragraph, S\u003cem\u003ehort discussion on the comparison with the Neptune.\u003c/em\u003e\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" align=\"\" width=\"110%\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 11px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd style=\"width: 11px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd style=\"width: 8px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026sup2;⁰⁶Pb/\u0026sup2;⁰⁴Pb\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 6px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e2SD\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026sup2;⁰⁷Pb/\u0026sup2;⁰⁴Pb\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 6px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e2SD\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026sup2;⁰⁸Pb/\u0026sup2;⁰⁴Pb\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 6px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e2SD\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026sup2;⁰⁸Pb/\u0026sup2;⁰⁶Pb\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 6px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e2SD\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026sup2;⁰⁷Pb/\u0026sup2;⁰⁶Pb\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 6px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e2SD\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 11px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eNeoma n = 203\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 11px;\"\u003e\n \u003cp\u003eCPI in-house Tl\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8px;\"\u003e\n \u003cp\u003e17.9006\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 6px;\"\u003e\n \u003cp\u003e0.0015\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8px;\"\u003e\n \u003cp\u003e15.5665\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 6px;\"\u003e\n \u003cp\u003e0.0020\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8px;\"\u003e\n \u003cp\u003e38.0230\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 6px;\"\u003e\n \u003cp\u003e0.0060\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8px;\"\u003e\n \u003cp\u003e2.12409\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 6px;\"\u003e\n \u003cp\u003e0.00018\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8px;\"\u003e\n \u003cp\u003e0.86961\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 6px;\"\u003e\n \u003cp\u003e0.00005\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 11px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd style=\"width: 11px;\"\u003e\n \u003cp\u003eppm\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd style=\"width: 6px;\"\u003e\n \u003cp\u003e85.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd style=\"width: 6px;\"\u003e\n \u003cp\u003e129.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd style=\"width: 6px;\"\u003e\n \u003cp\u003e159.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd style=\"width: 6px;\"\u003e\n \u003cp\u003e83.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd style=\"width: 6px;\"\u003e\n \u003cp\u003e58.0\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u003cstrong\u003eTable 2\u003c/strong\u003e: results of the analysis of CPI in-house standard over a period of 6 months, n = 203\u003c/p\u003e\n\u003cp\u003eComparable external precision was achieved for analysis of the solution of the metal and the pigments of lead white synthesised in this work (PDLW1 and PDLW2), as reported in detail in the supplementary material S1 section \u003cem\u003eMetal LIR vs LW LIR.\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003e3.1 Laser ablation and solution\u003c/p\u003e\n\u003cp\u003eThe settings for the laser ablation were chosen following this principle: minimum invasiveness maintaining highest accuracy and reproducibility possible. For this, a series of settings was tested in the course of 8 months. Due to the nature of the carbonates, it was found that low fluence (0.42 to 0.51 J/cm\u003csup\u003e2\u003c/sup\u003e, corresponding to 1-5% of the energy output of the Laser ablation system used in this study, was sufficient to achieve a good signal, between 6-9 V on the \u003csup\u003e208\u003c/sup\u003ePb). Following the discussion in the supplementary material ( S1, section \u003cem\u003eDecision on the optimal laser ablation settings for lead white\u003c/em\u003e and \u003cem\u003eLaser ablation: raster vs Line\u003c/em\u003e for a detailed discussion), the results for the best-performing laser ablation settings were PDLW2‑10.2 and PDLW2‑14.7 (corresponding to settings 1 and 2 in Table 1 and LIR reported in Figure 2). The LIR for these two settings are compared to the analysis of the same pigment in solution work to assess the precision and accuracy of LA analysis to the more robust solution analysis, Figure 2.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eLA analyses were conducted using SSB with PDLW1 as the standard to correct the PDLW2 sample. \u0026nbsp; Using a 5-\u0026nbsp;\u0026micro;m-diameter circular laser spot the ablated area was restricted to a line 50\u0026nbsp;\u0026micro;m long or to a raster with dimension of 15x15\u0026nbsp;\u0026micro;m (Image Figure 3) ablating a volume of lead white pigment of ~1.25 *10\u003csup\u003e-9\u003c/sup\u003e cm\u003csup\u003e3\u003c/sup\u003e corresponding to 8 ng ca. (ablation depth estimated to be around 5\u0026nbsp;\u0026micro;m, detailed discussion in supplementary material S1 \u003cem\u003eMaterial ablated and efficiency\u003c/em\u003e). The ablation time was around 21 seconds for PDLW2-10.2 and 47 seconds for PDLW2-14.7. PDLW2‑10.2 was tested with 16 replicates over a period of 4 months, while PDLW2‑14.7 was tested with 28 replicates over the same period. The solution analyses were conducted over a period of 6 months on 40 replicates.\u003c/p\u003e\n\u003cp\u003eFrom Figure 2, both laser settings clearly yield data in good agreement with the solution results. Considering their 2SD, both laser settings display external precision similar to that of solution analysis applied to LIR of lead white in recent years (ref dimpos and Table S1 for CPI analysis on the Neptune).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe LA LIR ratios normalised to \u003csup\u003e204\u003c/sup\u003ePb yielded 2SD values of 150\u0026ndash;300 ppm with \u003cstrong\u003emean squared weighted deviation (MSWD)\u003c/strong\u003e between 0.44 and 1.1, whereas solution analyses on the same samples produced smaller 2SD of 80\u0026ndash;150 ppm and MSWD of 0.85\u0026ndash;1.8. This indicates that the repeatability of laser ablation measurements is predicted by their measurement uncertainties, with no evidence for significant micro-scale heterogeneity or random laser-induced fractionation. Overall, the laser ablation data provide reproducible Pb isotope fingerprints suitable for provenance studies, with roughly twofold lower precision than solution measurements using Tl doping on the same instrument.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eTaking into account that the amount of sample analysed is only 8 ng and that an average painting sample taken manually can be estimated, for most cases, to be in the range of 5 to 0.01 milligrams, means that using in-situ LA on cross-section is possible to reduce the amount of sample used by 500000 to 1000 times. This procedure therefore drastically reduces the amount of sample needed, preserving most of the sample intact for further analysis, while providing high-precision isotope data comparable with literature data.\u003c/p\u003e\n\u003cp\u003e3.2 Historical Venetian lead white\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThis study revisits historical lead white recovered from a Venetian shipwreck in the Adriatic Sea, previously characterised\u0026nbsp;[1], and compares those results with new measurements obtained here on the same material (referred as GN in this study). GN was re-analysed by solution MC-ICPMS (Neoma) and by LA-MC-ICPMS on a dedicated epoxy-embedded GN mount, using the same analytical protocol and LA operating conditions (14.7 and 10.2) applied to PDLW1 and PDLW2 and acquired within the same analytical session (Figure 3). The results show that the Neoma solution (GN Figure 3) data are within error with the earlier measurements reported in Dimporzano et al. (2021) (GN D\u0026rsquo;Imporzano et al. 2021 in Figure 3). The laser ablation data, for both LA settings (GN 10.2 and GN 14.7), are also accurate relative to the Neoma solution measurements, with GN 14.7 setting providing superior accuracy and reproducibility. However, the external error (2SD) for the LA analyses is worse than for newly synthesised PDLW2, with 2SD values for the three LIR being on average about 40 % larger compared to the one reported in Figure 2. This worse precision can be attributed to the history and condition of GN: the pigment remained under seawater for approximately 400 years and, when recovered, exhibited an external black alteration layer that was only partially removed in the material available for this study (no fresh sample was available). Although only visually pure white areas were targeted by laser ablation, nanoscale impurities or residual alteration products may have been present in some regions, thereby influencing the laser ablation and resulting in higher 2SD. This could also explain why the settings 10.2 performed worse than 14.7, as this ablation is faster and can be more susceptible to small local sample phase heterogeneity, resulting in a less stable signal.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eDespite this, the 14.7 setting yields results that are in good agreement with the solution data and still provide sufficient resolution (approximately 270\u0026ndash;390 ppm 2SD for the three \u003csup\u003e204Pb-normalised\u003c/sup\u003e LIR) for provenance studies.\u003c/p\u003e\n\u003cp\u003e3.3 Reducing the ablation size\u003c/p\u003e\n\u003cp\u003eOne of the main aims in this study is to reduce the sample usage to a minimum. Therefore, the method was also tested on smaller areas of both PDLW2 and GN. In these tests, the laser was applied either to a raster area of approximately 10 by 10\u0026nbsp;\u0026micro;m or to a single line of about 20\u0026nbsp;\u0026micro;m in length, corresponding in both cases to a total ablated mass of roughly 3.25 ng of LW for a 20 seconds ablation time. For this test, only the setting at 14.7 was used, as otherwise the integration time of the analysis would have been too short (10.2 has a speed of 2\u0026nbsp;\u0026micro;m/s and the total analysis time would have been less than 10 seconds).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eConsistent with previous results, PDLW2 exhibits better 2SD values than the analysis performed on GN. As expected, the shortened analysis time for the 20 \u0026micro;m length measurements (PDLW2 and GN short in Figure 4) yields a higher 2SD compared to the longer 50 \u0026micro;m laser ablation method, a direct consequence of the total integration time being halved. However, while precision is reduced, the data remain accurate; this makes the method viable for identification and provenance of unique samples containing minute lead white particles, though the longer ablation protocol is recommended for optimal results when enough material is available.\u003c/p\u003e\n\u003cp\u003e3.4 Mock-up analysis\u003c/p\u003e\n\u003cp\u003eThe LA method (14.7), considered more stable for heterogeneous samples as in the case of pigment in oil, was applied to a multi-layered mock-up (Figure 1) containing PDLW2 dispersed in linseed oil and artificially aged for three months at 40\u0026deg;C (each layer was applied after the layer below was hard to touch). The sample consists of four distinct layers applied on glass, alternating between Zinc Oxide, PDLW1, and PDLW2, which were subsequently embedded. The application of the LW pigments resulted in a stratigraphy that is less uniform than that found in masterworks, characterised by significant heterogeneity in particle size and varying pigment density throughout the lead white layers (Figure 6). While this irregularity presents analytical challenges and may differ from real painting samples, it effectively simulates non-idealised conditions, offering valuable insights into Laser Ablation behaviour across a wide range of pigment-to-binder ratios and aiding in the optimisation of sampling strategies for complex real-world samples.\u003c/p\u003e\n\u003cp\u003eFigure 5a presents the LIR data for PDLW2 dispersed in oil, which exhibits a higher 2SD compared to the oil-free reference (PDLW2 14.7). The oil-dispersed dataset splits into two distinct clusters: one consistent with the reference values obtained with standard LA on pure pigment (blue arrow) and a second group showing lower accuracy (red arrow). Visual inspection of the ablation craters (Figure 6b) correlates these clusters with local sample heterogeneity; the accurate data (blue arrows) correspond to areas containing purer lead white agglomerates, whereas the red arrows coincide with pigment-poor, binder-rich areas. This highlights the need to consider matrix-effects when ablating oil painting samples. While signal contributions from oil-rich phases can be excluded during data reduction (e.g., via software Iolite 4; see Supplementary Material S1 section \u003cem\u003eLA in oil samples\u003c/em\u003e), this significantly reduces integration time and increases measurement error. Therefore, precise selection of pigment-rich areas is critical. Ideally, LIR via LA should be preceded by SEM-EDS or FTIR imaging to guide the sampling strategy, ensuring that isotopic data is gathered from optimal locations and can be correlated with the surrounding chemical composition. The application of this method, however, shows that accurate and precise analysis of lead white in linseed oil is possible and accurate when on lead-rich areas.\u003c/p\u003e\n\u003cp\u003e3.5 Application on Unknown 16-17\u003csup\u003eth\u003c/sup\u003e century painting\u003c/p\u003e\n\u003cp\u003eThe LA method was applied to a real painting sample, from an unknown artist, identified as probably made in Italy in the 16-17\u003csup\u003eth\u003c/sup\u003e century. The sample was an embedded cross-section presenting a thick layer of lead white with small particles evenly diffused in the oil (Figure 7b). The analysis was made using the setting with 14.7 and using an ablation time of 50 second ca., using raster and line ablation patterns and compared with literature data (Figure 6a and 6b).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe LA ablation analysis of the real painting sample showed a good repeatability regardless of the sampling geometry and position in the white layer (2SD on \u003csup\u003e206\u003c/sup\u003ePb/\u003csup\u003e204\u003c/sup\u003ePb 0.0049, \u003csup\u003e207\u003c/sup\u003ePb/\u003csup\u003e204\u003c/sup\u003ePb 0.0051 and \u003csup\u003e208\u003c/sup\u003ePb/\u003csup\u003e204\u003c/sup\u003ePb 0.0127, data in supplementary excel file S4 \u003cem\u003eFinal data laser\u003c/em\u003e, sheet \u003cem\u003eanonymous\u003c/em\u003e) and in line for what found in this study for application of LA ablation on fine pigment in oil paint. From Figure 6a it is also notable that the error (to be conservative the 2SD used was the one calculated for oil samples analysed with LA in section Mock-up analysis, Figure 5a, shown as a cross on the markers of the anonymous sample) is often smaller than the marker itself, meaning that this resolution is more than enough to distinguish macro-differences between the main LIR cluster in Europe.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eData compared to the LW database for paintings show that the sample has LIR characteristics of the Italian lead white cluster, as shown in literature, which is distinct compared to the lead found in other regions of Europe. This is evidence that the sample is coming from a painting that can be associated to an Italian painting made in the 16-17\u003csup\u003eth\u003c/sup\u003e century.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e3.6 Mapping\u003c/p\u003e\n\u003cp\u003eFigure 8 shows the LIR mapping in false colours of the mock-up sample. The analysis was made using laser settings calculated specifically for mapping purposes, obtained using a dedicated Iolite software provided by ESL laser (iolite_optimizer_v0.96). A special designed ESL plasma torch (having a smaller inner tube diameter for sample injection to reduce washout time) was used to improve the washout time. The imaging was performed with raster using a 3 \u0026micro;m spot size (0.5 \u0026micro;m separation between lines to avoid resampling), 20 Hz repetition rate, and 20 \u0026micro;m/s scan speed over a 1 mm \u0026times; 0.3 mm area. The depth of imaging analysis is calculated to be less than the one presented in the study before (\u0026lt; 5 \u0026micro;m as the dosage used for the mapping is 3, lower than the one used for raster or line analysis), and the surface ablated can be easily polished. Data reduction was carried out using Iolite, applying a 5 V threshold to the \u003csup\u003e208\u003c/sup\u003ePb signal when the LIR imaging was calculated. This cutoff was essential to mask areas with a higher proportion of matrix to Pb white and to use data more closely signal-matched because of the SSB approach.\u003c/p\u003e\n\u003cp\u003eThe \u003csup\u003e208\u003c/sup\u003ePb distribution map effectively visualizes the stratigraphy, with high-intensity (red-yellow) zones corresponding to lead white layers and low-intensity (blue) regions indicating zinc white. Some mechanical mixing of PDLW2 into the adjacent zinc layer is evident at the interface. Although the two lead pigments appear visually similar in the three LIR over \u003csup\u003e204\u003c/sup\u003ePb ratios maps, the \u003csup\u003e206\u003c/sup\u003ePb/\u003csup\u003e204\u003c/sup\u003ePb ratio map highlights their isotopic differences more clearly, with PDLW1 showing distinctively lower ratios (blue pixels) compared to PDLW2. Averaging isotopic ratios from two regions-of-interest in the lead-rich areas confirms that accurate LIR values can be extracted from these maps (the areas are the red rectangles highlighted in the \u003csup\u003e208\u003c/sup\u003ePb Volts map in Figure 7).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe method was then tested on a real sample, a cross-section containing LW in two adjacent paint layers: a layer of prime (thickness estimated around 5-8 \u0026micro;m) and a layer of lead white with the same thickness, Figure 8. The sample was provided by ARTDETECT in collaboration with the National Gallery \u0026ndash; Alexandros Soutsos Museum, which kindly consented to share the results on the mapping, (not the name of the painting and the values of the analysis, which will be discussed in a specific publication). The investigation was carried out to test if the LW used in the two layers was different, a task possible only using LA analysis due to the paint layer thickness. The first attempt was done using the LA14.7 settings, using a line of 50 \u0026micro;m, on both layers and sampling multiple spots. The results identified the presence of two different lead white, but there was a problem with line_3, 4 and 17. While the sampling spots were on the same lead white rich layer next to each other, Figure 8a, their LIR were different, with line_17 showing values comparable to the value obtained from Line_5 and Line_16 from the prime layer. After visual inspection, it was found that the surface of the cross-section was not perfectly smooth but presented protrusions and pits, which likely caused the laser sampling to be inaccurate and out of focus. Sampling in the range of 5 \u0026micro;m is a challenging task as the focus of the laser ablation system camera and the laser optics is not optimal, when this is combined with a not well-polished surface, it can result in partial or total sampling of the adjacent layers, like in this case. This can explain the anomalous results for line_17, where the laser sampled the prime layer rather than the lead white layer, as visible from the LIR in Figure 8b, where the values for this ablation fall between the values of lines 3, 4, 13, 14, 15 (the lead white layer) and lines 5 and 16 of the prime. To ensure that the two layers were isotopically distinct and confirm that there was not dealing with a complex mixed phase of the two LWs, it was decided to polish the cross-section and to perform an isotopic mapping. As can be seen in Figure 8c, with the map of the three LIRs on \u0026sup2;⁰⁴Pb, and especially on the \u0026sup2;⁰⁶Pb/\u0026sup2;⁰⁴Pb one, the presence of two LW in distinct paint is observed (one layer with lower LIR blue pixel, and one with higher LIR, red-yellow pixels). Combining this information, it is therefore possible to state that the LW used in the prime differs from that used in the lead white layer.\u003c/p\u003e\n\u003cp\u003eThis demonstrates the method\u0026apos;s potential for identifying different lead white sources within a single painting, and this can be a powerful tool, for instance, to distinguish between different, adjacent thin layers containing lead white, while still offering a good indication of the provenance.\u0026nbsp;\u003c/p\u003e"},{"header":"4. Conclusion","content":"\u003cp\u003eThes study successfully shows that, when calibrated with synthetic lead carbonate reference pigments (PDLW1 and PDLW2), LA-MC-ICPMS yields accurate lead isotope ratios for lead white at micrometre-scale spatial resolution while consuming only nanogram quantities of material, therefore using ~ 500000-1000 times less sample than traditional LIR analysis, making the approach micro-invasive and compatible with the practical constraints of cultural heritage sampling. The method does not require new sample as it can operate directly on cross-sections, ablating only around 5\u0026nbsp;\u0026micro;m in depth.\u003c/p\u003e\n\u003cp\u003eLA results are in agreement with solution MC-ICPMS and demonstrate that the method can produce reliable isotope ratios in a carbonate matrix without measurable bias under the operating conditions tested; the principal limitation is that\u0026nbsp;external precision remains poorer than solution analysis on the same instrument. This, however, still provides the resolution typically needed to provenance pigments. Re-analysis of historical lead white (GN) confirms accuracy on complex heritage material and comparability with prior datasets, while also highlighting a key caveat:\u0026nbsp;alteration layers, residual impurities and micro-scale heterogeneity can increase measurement uncertainties, requiring careful targeting.\u003c/p\u003e\n\u003cp\u003eThe mock-up cross-section experiments show that\u0026nbsp;oil-rich matrices are a significant analytical challenge\u0026nbsp;for LA on lead carbonate: LIR precision and accuracy are worsened when ablating\u0026nbsp;binder-rich, pigment-poor areas. At the same time, the results also demonstrate the method\u0026rsquo;s practical success in realistic conditions:\u0026nbsp;accurate LIR are obtained when pigment-rich agglomerates are targeted, and oil contributions can be screened during data reduction, albeit at the cost of shorter usable integration time and therefore larger uncertainty. A key limitation in oil paints is that analytical performance becomes strongly dependent on\u0026nbsp;micro-texture\u0026nbsp;and\u0026nbsp;pigment concentration; consequently, a robust workflow should include prior micro-analytical characterisation (e.g., SEM-EDS and/or FTIR imaging) to optimize ablation placement and to contextualize intra-layer variability. At the same time, this requirement underscores a major advantage of in-situ LA-based LIR analysis: it can be integrated with complementary micro-scale techniques on the\u0026nbsp;same cross-section, enabling correlative, stratigraphy-resolved datasets that may provide new constraints on material choices, paint preparation, and workshop practice.\u003c/p\u003e\n\u003cp\u003eThe application to an anonymous 16-17\u003csup\u003eth\u003c/sup\u003e century paint cross-section further supports the feasibility of this method to real samples: the lead white layer produced internally consistent LIR across different ablation geometries and positions, and the resulting isotopic signature is consistent with Venetian LW found in Italy during that period.\u003c/p\u003e\n\u003cp\u003eIsotopic mapping demonstrates that LA-MC-ICPMS can generate spatially resolved LIR images that identify LIR differences between layers containing different types of lead white. This is a powerful tool that can be used in order to detect the presence of different LW in different layers, as ground, prime and paint layers, as shown in the application of the method to a real sample, which identified the presence of different types of LW in two thin adjacent paint layers (~\u0026nbsp;8\u0026nbsp;\u0026micro;m thickness).\u003c/p\u003e\n\u003cp\u003eOverall, the method provides an effective route to minimally invasive, spatially resolved LIR analysis of lead white in paintings and the workflow can be transferable to other media. In particular, it should be evaluated on frescoes and mural paintings where pigment presence is high. Further work should focus on strengthening the validation of matrix-matched standards and independent comparison with established reference approaches (e.g., double-spike TIMS), together with broader inter-session datasets to refine external reproducibility and uncertainty models. The use of new laser ablation systems, such as femto-second pulsed lasers, should also be addressed in future applications to verify if the use of shorter pulse duration can limit matrix effects, thereby improving accuracy and precision.\u003c/p\u003e"},{"header":"5. Software and data","content":"\u003cp\u003eThe Neoma data were collected using Qtegra software. The LA data are reduced using the Software Iolite 4, using the DRS Pb Isotopes DRS (Beta). The statistical analysis is done in RStudio using the package ggplot2 (code R in the Supplementary material S2 and S3). The data produced in this study are reported in the supplementary material S4 as an Excel file, \u003cem\u003eFinal data laser paper.\u003c/em\u003e\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003eAuthor Contributions Statement:\u003c/p\u003e\n\u003cp\u003eP.D. Developed the method, performed LA-MC-ICPMS analyses, and wrote the first draft of the manuscript. Produced and characterised the synthetic reference materials, and prepared the paint mock-ups. G.H. contributed to method development, LA method setting up, data interpretation and manuscript revision. All authors reviewed and approved the final version.\u003c/p\u003e\n\u003cp\u003eAcknowledgment:\u003c/p\u003e\n\u003cp\u003eMany thanks to Andrea Baldi, Susan A. Rigter and Kimiya Setayeshmehr at the Physics and Astronomy department at VU Amsterdam for the help with the Alpha‑Step D‑500 surface profilometer. Bauke Lacet from the Vrije Universiteit for the embedding of the samples. Thanks to Anna Tummers from ARTDETECT and the National Gallery \u0026ndash; Alexandros Soutsos Museum Greece. Adam Duglas for the help with the LA system and the program to calculate the right parameters for the LA imaging.\u003c/p\u003e\n\u003cp\u003eUse of Artificial Intelligence\u003c/p\u003e\n\u003cp\u003eLarge language model (LLM) tools were used solely for language checking and editing.\u003c/p\u003e\n\u003cp\u003eCompeting interests\u003c/p\u003e\n\u003cp\u003eThe authors have no competing interests as defined by Springer, or other interests that might be perceived to influence the results and/or discussion reported in this paper.\u003c/p\u003e\n\u003cp\u003eFunding sources\u003c/p\u003e\n\u003cp\u003eThis research was funded by Nederlandse Organisatie voor Wetenschappelijk Onderzoek.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eD\u0026rsquo;imporzano P, Batur K, Keune K, Koornneef JM, Hermens E, Noble P, et al. Lead isotope heterogeneity in lead white: From lead white raw pigment to canvas. Microchemical Journal. Elsevier; 2021;163:105897. \u003c/li\u003e\n\u003cli\u003eD\u0026rsquo;Imporzano P, Davies GR. Lead Isotope Ratios of Lead White: From Provenance to Authentication. In: Colombini MP, Degano I, Nevin A, editors. Analytical Chemistry for the Study of Paintings and the Detection of Forgeries [Internet]. Cham: Springer International Publishing; 2022. p. 447\u0026ndash;71. https://doi.org/10.1007/978-3-030-86865-9_14\u003c/li\u003e\n\u003cli\u003eKEISCH B, CALLAHAN RC. Lead Isotope Ratios in Artists\u0026rsquo; Lead White: a Progress Report. Archaeometry. 1976;18:181\u0026ndash;93. https://doi.org/10.1111/j.1475-4754.1976.tb00159.x\u003c/li\u003e\n\u003cli\u003eD\u0026rsquo;Imporzano P, Keune K, Koornneef JM, Hermens E, Noble P, Vandivere ALS, et al. Time-dependent variation of lead isotopes of lead white in 17th century Dutch paintings. Sci Adv. American Association for the Advancement of Science; 2021;7:eabi5905. \u003c/li\u003e\n\u003cli\u003eFabian D, Fortunato G. Tracing white: a study of lead white pigments found in seventeenth-century paintings using high precision lead isotope abundance ratios. Trade in artists\u0026rsquo; materials: markets and commerce in Europe to. 2010;1700:426\u0026ndash;43. \u003c/li\u003e\n\u003cli\u003eFortunato G, Ritter A, Fabian D. Old Masters{\u0026rsquo;} lead white pigments: investigations of paintings from the 16th to the 17th century using high precision lead isotope abundance ratios. Analyst [Internet]. The Royal Society of Chemistry; 2005;130:898\u0026ndash;906. https://doi.org/10.1039/B418105K\u003c/li\u003e\n\u003cli\u003ePastorelli G, Miranda ASO, Clerici EA, d\u0026rsquo;Imporzano P, Hansen BV, Janssens K, et al. Darkening of lead white in old master drawings and historic prints: A multi-analytical investigation. Microchemical Journal. Elsevier; 2024;109912. \u003c/li\u003e\n\u003cli\u003eD\u0026rsquo;Imporzano P, Keune K, Koornneef JM, Hermens E, Noble P, van Zuilen K, et al. Micro-invasive method for studying lead isotopes in paintings*. Archaeometry. 2020; https://doi.org/10.1111/arcm.12549\u003c/li\u003e\n\u003cli\u003eLin J, Yang A, Lin R, Mao J, Hu Z, Liu Y. Review on in situ Isotopic Analysis by LA-MC-ICP-MS. Journal of Earth Science [Internet]. 2023;34:1663\u0026ndash;91. https://doi.org/10.1007/s12583-023-2002-4\u003c/li\u003e\n\u003cli\u003eGuillong M, Wotzlaw J-F, Looser N, Laurent O. Evaluating the reliability of U\u0026ndash;Pb laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) carbonate geochronology: matrix issues and a potential calcite validation reference material. Geochronology [Internet]. Copernicus Publications; 2020;2:155\u0026ndash;67. https://doi.org/10.5194/gchron-2-155-2020\u003c/li\u003e\n\u003cli\u003eZhang W, Hu Z. A critical review of isotopic fractionation and interference correction methods for isotope ratio measurements by laser ablation multi-collector inductively coupled plasma mass spectrometry. Spectrochim Acta Part B At Spectrosc [Internet]. 2020;171:105929. https://doi.org/https://doi.org/10.1016/j.sab.2020.105929\u003c/li\u003e\n\u003cli\u003eDanyushevsky L V, Thompson JM. GGR Handbook of Rock and Mineral Analysis Chapter 12 Laser Ablation-ICP-MS for the In Situ Analysis of Geological Samples. Geostand Geoanal Res [Internet]. John Wiley \u0026amp; Sons, Ltd; 2025;49:457\u0026ndash;93. https://doi.org/https://doi.org/10.1111/ggr.70004\u003c/li\u003e\n\u003cli\u003eSylvester PJ. Matrix effects in laser ablation\u0026ndash;ICP\u0026ndash;MS. 2008; \u003c/li\u003e\n\u003cli\u003eGuillong M, Wotzlaw J-F, Looser N, Laurent O. Evaluating the reliability of U\u0026ndash;Pb laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) carbonate geochronology: matrix issues and a potential calcite validation reference material. Geochronology. Copernicus GmbH; 2020;2:155\u0026ndash;67. \u003c/li\u003e\n\u003cli\u003eNuriel P, Wotzlaw J-F, Ovtcharova M, Vaks A, Stremtan C, \u0026Scaron;ala M, et al. The use of ASH-15 flowstone as a matrix-matched reference material for laser-ablation U-Pb geochronology of calcite. Geochronology. Copernicus Publications G\u0026ouml;ttingen, Germany; 2021;3:35\u0026ndash;47. \u003c/li\u003e\n\u003cli\u003eRoberts NMW, Drost K, Horstwood MSA, Condon DJ, Chew D, Drake H, et al. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) U\u0026ndash;Pb carbonate geochronology: strategies, progress, and limitations. Geochronology. Copernicus Publications G\u0026ouml;ttingen, Germany; 2020;2:33\u0026ndash;61. \u003c/li\u003e\n\u003cli\u003eWeber M, Lugli F, Jochum KP, Cipriani A, Scholz D. Calcium carbonate and phosphate reference materials for monitoring bulk and microanalytical determination of Sr isotopes. Geostand Geoanal Res. Wiley Online Library; 2018;42:77\u0026ndash;89. \u003c/li\u003e\n\u003cli\u003eGonzalez V, Fazlic I, Cotte M, Vanmeert F, Gestels A, De Meyer S, et al. Lead (II) Formate in Rembrandt\u0026rsquo;s Night Watch: Detection and Distribution from the Macro‐to the Micro‐scale. Angewandte Chemie. Wiley Online Library; 2023;135:e202216478. \u003c/li\u003e\n\u003cli\u003eMerkel SW, D\u0026rsquo;Imporzano P, Van Zuilen K, Kershaw J, Davies GR. \u0026ldquo;Non-invasive\u0026rdquo; portable laser ablation sampling for lead isotope analysis of archaeological silver: a comparison with bulk and in situ laser ablation techniques. J Anal At Spectrom. Royal Society of Chemistry; 2022;37:148\u0026ndash;56. \u003c/li\u003e\n\u003cli\u003evan Loon A, Vandivere A, Delaney JK, Dooley KA, De Meyer S, Vanmeert F, et al. Beauty is skin deep: the skin tones of Vermeer\u0026rsquo;s Girl with a Pearl Earring. Herit Sci [Internet]. 2019;7:102. https://doi.org/10.1186/s40494-019-0344-0\u003c/li\u003e\n\u003cli\u003eD\u0026rsquo;imporzano P, Reiling HM, Merkel S, van Iperen JM, Garachon I, Keune K, et al. Lead isotope analysis of lead-tin-glaze via on-site portable laser ablation sampling of 17-18th century Delftware (earthenware). J Archaeol Sci. Elsevier; 2026;185:106443. \u003c/li\u003e\n\u003cli\u003eKlaver M, Smeets RJ, Koornneef JM, Davies GR, Vroon PZ. Pb isotope analysis of ng size samples by TIMS equipped with a 10 13 \u0026Omega; resistor using a 207 Pb\u0026ndash;204 Pb double spike. J Anal At Spectrom. Royal Society of Chemistry; 2016;31:171\u0026ndash;8. \u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"npj-heritage-science","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"hsci","sideBox":"Learn more about [Heritage Science](http://heritagesciencejournal.springeropen.com)","snPcode":"40494","submissionUrl":"https://submission.nature.com/new-submission/40494/3","title":"npj Heritage Science","twitterHandle":"@SpringerOpen","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"BMC/SO AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-9106478/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-9106478/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThis study develops and validates an in-situ LA-MC-ICPMS method for lead isotope ratios (LIR) measurements of lead carbonate pigments at micrometre scale while consuming only nanogram quantities of material. Two matrix-matched synthetic lead whites (PDLW1 and PDLW2) were produced from metallic lead, converted to carbonate, and characterised by solution MC-ICPMS to define reference isotope compositions. These pigments were then used as calibrants and quality-control reference materials to assess LA performance. LA analyses of epoxy-embedded (binder-free) pigments yield isotope ratios consistent with solution data, demonstrating the method accuracy on lead. LA analyses were performed on samples previously analysed in other study (ref hetero), showing agreement with literature data. The analysis of mock-up cross-sections containing PDLW1 and PDLW2 in oil-paint layers show that oil-rich, pigment-poor domains degrade signal stability and precision, whereas pigment-rich domains provide accurate LIR, proving that this approach is valid to analyse LIR of paint samples. The method was successfully applied to determine the provenance of an anonymous sample believed to be a 16-17th century Italian painting. Finally, LA was used to produce isotopic maps capable of resolving layer-specific LIR.\u003c/p\u003e","manuscriptTitle":"In-situ Laser Ablation MCICPMS of lead white in paintings","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-03-19 10:59:42","doi":"10.21203/rs.3.rs-9106478/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2026-04-17T17:42:37+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-04-08T20:47:18+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"129447069977455158595182384622141198541","date":"2026-03-19T08:38:47+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"195206295551481841012639973545775953299","date":"2026-03-18T00:26:31+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-03-16T15:52:39+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-03-16T06:41:16+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2026-03-16T06:41:05+00:00","index":"","fulltext":""},{"type":"submitted","content":"npj Heritage Science","date":"2026-03-12T15:18:15+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"npj-heritage-science","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"hsci","sideBox":"Learn more about [Heritage Science](http://heritagesciencejournal.springeropen.com)","snPcode":"40494","submissionUrl":"https://submission.nature.com/new-submission/40494/3","title":"npj Heritage Science","twitterHandle":"@SpringerOpen","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"BMC/SO AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"1de77dae-b1a0-4ebd-8c22-46b5a0c698a2","owner":[],"postedDate":"March 19th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"in-revision","subjectAreas":[],"tags":[],"updatedAt":"2026-04-17T17:54:02+00:00","versionOfRecord":[],"versionCreatedAt":"2026-03-19 10:59:42","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-9106478","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-9106478","identity":"rs-9106478","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}