Simultaneous determination of cysteine, uric acid and tyrosine using Au-nanoparticles/poly(E)-4-(p-tolyldiazenyl)benzene-1,2,3-triol film modified glassy carbon electrode

A novel Au nanoparticles/poly(E)-4-(p-tolyldiazenyl)benzene-1,2,3-triol (AuNPs/PTAT) film modified glassy carbon electrode (AuNPs/PTAT/GCE) was fabricated for the simultaneous determination of three antioxidants named, cysteine (Cys), uric acid (UA) and tyrosine (Tyr). The bare glassy carbon electrode (GCE) fails to separate the oxidation peak potentials of these molecules, while PTAT film modified electrode can resolve them. Electrochemical impedance spectroscopy (EIS) study indicates that the charge transfer resistance of bare electrode increased as (E)-4-(p-tolyldiazenyl)benzene-1,2,3-triol was electropolymerized at the bare electrode. Furthermore, EIS exhibits enhancement of electron transfer kinetics between analytes and electrode after electrodeposition of Au nanoparticles. Differential pulse voltammetry results show that the electrocatalytic current increases linearly in the ranges of 2-540 μmol L− 1 for Cys, 5-820 μmol L− 1 for UA and 10-560 μmol L− 1 for Tyr with detection limits (S/N = 3) of 0.04 μmol L− 1, 0.1 μmol L− 1 and 2 μmol L− 1 for Cys, UA and Tyr, respectively. The proposed method was successfully applied for simultaneous determination of Cys, UA and Tyr in human urine samples.