Sulfur-doped reduced graphene oxide@chitosan composite for the selective and sensitive electrochemical detection of Hg2+ in fish muscle

Abstract

In this study, a glassy carbon electrode was modified with sulfur-doped reduced graphene oxide (S-rGO) and then combined with chitosan (CTS) to produce an electrochemical sensor. There is a favorable interaction between Hg2+ and S-rGO, due to the strong affinity between sulfur and mercury. This effect was exploited for the selective and sensitive electrochemical determination of trace amounts of Hg2+ in fish muscle samples by differential pulse anodic stripping voltammetry (DPASV). The factors that can affect the sensitivity and precision of the modified electrode were investigated through the optimization of various parameters, such as S-rGO concentration, solution pH, deposition potential, accumulation potential, accumulation time, and supporting electrolytes. By introducing S-rGO to enrich and amplify the electrochemical signal, the sensing strategy allowed to detect a range from 0.125 to 6 μM Hg2+ with a detection limit of 1.6 nM. The sensor also showed excellent selectivity towards Hg2+ in the presence of interfering metal ions, such as Fe3+, Zn2+, Mg2+, Mn2+, As3+, Na+, Cd2+ and CO2+. The practical feasibility of the proposed sensor was assessed in fish muscle samples with satisfactory results compared with that of atomic fluorescence spectrometry. Moreover, this work demonstrated a simple and reliable method for improving the electrochemical performance of Hg2+ sensor, which paves the way for many promising potential applications in the field of environmental testing.