Electrochemical sensor based on reduced graphene oxide/carbon black/chitosan composite for the simultaneous determination of dopamine and paracetamol concentrations in urine samples

A sensor based on glassy carbon electrode (GCE) modified within reduced graphene oxide (RGO) and carbon black (CB) in a chitosan film (CTS) is presented. The combination of the nanomaterials with CTS provided a stable dispersion and could be successfully used as electroactive layer. By using the Nicholson method and the results obtained by cyclic voltammetry with the proposed RGO-CB-CTS/GCE, the heterogeneous electron transfer rate constant (k0) of 5.6 × 10− 3 cm s− 1 was obtained. The proposed electrode was applied for the simultaneous determination of dopamine (DA) and paracetamol (PAR). Employing square-wave voltammetry, DA presented an anodic peak at 0.25 V and PAR at 0.50 V vs. Ag/AgCl (3.0 mol L− 1 KCl). The analytical curves obtained were linear in the range from 3.2 × 10− 6 to 3.2 × 10− 5 mol L− 1 and from 2.8 × 10− 6 to 1.9 × 10− 5 mol L− 1 for DA and PAR, respectively, with detection limits of 2.0 × 10− 7 for DA and 5.3 × 10− 8 mol L− 1 for PAR. The developed sensor presented advantages such as simple preparation, low cost of the nanomaterials employed and a fast response. Besides, it could successfully apply in the determination of DA and PAR in biological samples.