A glassy carbon electrode modified with a composite consisting of gold nanoparticle, reduced graphene oxide and poly(L-arginine) for simultaneous voltammetric determination of dopamine, serotonin and L-tryptophan.

Abstract

A glassy carbon electrode (GCE) was modified with poly(L-arginine) (P-Arg), reduced graphene oxide (rGO) and gold nanoparticle (AuNP) to obtain an electrode for simultaneous determination of dopamine (DA), serotonin (5-HT) and L-tryptophan (L-Trp) in the presence of ascorbic acid (AA). The modified GCE was prepared via subsequent 'layer-by-layer' deposition using an electrochemical technique. The surface morphology of the modified electrode was studied by scanning electron microscopy, and electrochemical characterizations were carried out via cyclic voltammetry and electrochemical impedance spectroscopy. The modified electrode showed excellent electrocatalytic activity toward DA, 5-HT and L-Trp at pH7.0. Figures of merit for the differential pulse voltammetric reponse are as follows: (a) Response to DA is linear in two intervals, viz. 1.0-50nM and 1.0-50μM DA concentration range, the typical working voltage is 202mV (vs. Ag/AgCl), and the detection limit is 1nM (at an S/N ratio of 3). For 5-HT, the respective data are 10 to 500nM and 1.0 to 10μM, 381mV, and 30nM. For L-Trp, the respective data are 10-70nM and 10-100μM, 719mV, and 0.1μM. The modified GCE is fairly selective. It was successfully applied to the simultaneous determination of DA, 5-HT, and L-Trp in spiked urine samples, and high recovery rates were found. Graphical abstract Schematic presentation of the voltammetric sensor based on a glassy carbon electrode modified with poly(L-arginine), reduced graphene oxide (rGO) and gold nanoparticle (GCE/P-Arg/ErGO/AuNP) for simultaneous determination of dopamine (DA), serotonin (5-HT) and L-tryptophan (L-Trp).