In the present study reported, fully electrochemical methodology was used to prepare a new nanocomposite on a glassy carbon electrode. Cysteic acid was formed by electrochemical oxidation of L-cysteine on the surface of a glassy carbon electrode (GCE) and used as a proper polymeric framework for deposition of Au nanoparticles (AuNPs). Field emission scanning electron microscopy (FESEM) was used for the surface characterization. It was shown that this composite electrode not only separates the voltammetric signals of hydroquinone (HQ) and catechol (CC), but also shows higher oxidation current for these molecules. Under the optimized condition, a linear dynamic range of 0.09 mu mol dm(-3) to 39.2 mu mol dm(-3) range for hydroquinone with the detection limit of 20 nM and from 0.09 mu mol dm(-3) to 39.2 mu mol dm(-3) for catechol with the detection limit of 60 nM were obtained. The proposed method was evaluated by determination of HQ and CC in rain and tap water samples with satisfactory results (recovery > 96%). (C) 2017 The Electrochemical Society. All rights reserved.