Simultaneous detection of dopamine and ascorbic acid by a thread-based microfluidic device and multiple pulse amperometry

In this work, the simultaneous determination of ascorbic acid (AA) and dopamine (DA) was proposed using a simple and inexpensive microfluidic device. Microfluidic devices are totally suitable to couple with electrochemical detectors such as screen-printed electrodes (SPE) and offer many advantages: portability, high sample throughput and low reagent consumption. Here, a 3D-printed microfluidic device (µTED) was developed using textile threads as microfluidic channels and an unmodified SPE as amperometric detector. By using the multiple pulse amperometry (MPA), two potential values (0.65 V and − 0.10 V) were chosen. The current signals generated in the reduction of dopamine o-quinone were used to calculate a correction factor for the ascorbic acid oxidation signals, allowing the simultaneous quantification. The proposed microfluidic device provided a stable flowrate of carrier solution and low consumption of samples and reagents (volume of injection of 2.0 µL). Using the best set of experimental conditions, a linear dynamic range (LDR) between 50 and 900 µmol L − 1 for DA and AA were achieved. Sensitivities of 2.24 µA L µmol − 1 and 5.09 µA L µmol − 1 as well as limits of detection (LOD) of 2.60 µmol L − 1 and 1.54 µmol L − 1 were calculated for AA and DA, respectively. The proposed method was successfully applied for simultaneous determination of AA and DA in commercial blood serum sample spiked at three concentration levels. In addition, MPA showed to be a very simple way to perform simultaneous determination of AA and DA without the need of previous separations or the use of chemically modified electrodes.