Selective electrochemical sensor based on the electropolymerized p-coumaric acid for the direct determination of L-cysteine

Novel electrochemical sensor based on poly(p-coumaric acid) electrodeposited on the surface of multi-walled carbon nanotubes modified glassy carbon electrode (poly(p-coumaric acid)/MWNT/GCE) has been developed for the direct determination of L-cysteine. Poly(p-coumaric acid) has been obtained by potentiodynamic electrolysis under the optimized conditions (0.10 mM p-coumaric acid in 0.1 M NaOH using 5 cycles in the potential window of 0-1.0 V and the scan rate of 25 mV s(-1)) providing highest voltammetric response of L-cysteine. Sensor surface has been studied by scanning electron microscopy (SEM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The porous structure of polymeric film provides 6.9-fold increase in effective surface area and 4.2-fold lower charge transfer resistance in comparison to GCE. Under conditions of DPV, the sensor response is linear in the ranges of 7.5-50 and 50-1000 mu M of L-cysteine with the detection and quantification limits of 1.1 and 3.6 mu M, respectively. The excellent sensor selectivity to L-cysteine in the presence of glucose, uric and ascorbic acids, dopamine, L-tyrosine and S-containing substances (homocysteine, glutathione, L-methionine, L-cystine and alpha-lipoic acid) has been observed. Applicability of the sensor to real samples analysis has been shown on example of human urine. (c) 2018 Elsevier Ltd. All rights reserved.