Simultaneous electrochemical detection of hydroquinone and catechol using a carbon nanotube paste electrode modified with electrochemically polymerized L-alanine

An electrochemical analysis of Hydroquinone (HDQ) and Catechol (CTL) was analyzing in a 0.2 M phosphate buffer solution (PBS) using a modest constructing electrochemically polymerized (EP) L-Alanine (ALN) modified carbon nanotube paste electrode (EP(ALN)MCNTPE). The electrochemical, structural, resistive, and conductive properties of both the EP(ALN)MCNTPE and bare carbon nanotube paste electrode (BCNTPE) surfaces were studied by cyclic voltammetry (CV), Differential pulse voltammetry (DPV), scanning electron microscopy (SEM) and electrochemical impedance Spectroscopy (EIS) techniques. The EP(ALN) presented electrode surface exhibits significantly enhanced peak currents compared to BCNTPE. The optimizing experimental parameters, including PBS in pH, scan rate and concentration variation, also constructed to achieving high selectivity and sensitivity for the analysis of HDQ. The oxidation and reduction peak currents of HDQ exhibited improvement with increasing concentrations ranging from 0.2 µM to 4.0 µM. The achieved lower limit of detection (LOD) and lower limit of quantification (LOQ) were 0.174 µM and 0.582 µM, alone and it shows good analytical responses. The EP(ALN)MCNTPE shows good stability, reproducibility, and repeatability for HDQ. The electrochemically developed sensor proved applicable for both quantitative and qualitative analysis of HDQ in a cosmetic sample.