Highly sensitive electrochemical sensor for simultaneous determination of dihydroxybenzene isomers based on Co doped SnO2 nanoparticles

We have fabricated an electrochemical sensor for the simultaneous determination of two dihydroxybenzene isomers of phenolic compounds, hydroquinone (HQ) and catechol (CC) using Co doped SnO2 nanoparticles (Co-SnO2 NPs) for the first time. Cobalt doped SnO2 NPs were synthesized by a microwave irradiation method and characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Square wave voltammetry (SWV) studies yielded two well resolved strong peaks at the 3 wt% Co-SnO2 NP modified glassy carbon electrode (GCE) corresponding to the reduction of HQ and CC at -0.091 V and +0.041 V respectively. Under the optimum conditions, an adequate voltammetric peak to peak separation of 132 mV was found between the two isomeric species owing to the excellent catalytic activity of SnO2 NPs due to cobalt doping. For individual detection, the linear responses of HQ and CC were in the concentration ranges of 0.5-600 and 0.1-600 mu M with the detection limits of 0.45 and 0.094 mu M respectively. For simultaneous detection by synchronous change of the concentrations of HQ and CC, the linear response ranges were in the order of 1-150 mu M each with the detection limits of 0.137 and 0.116 mu M for HQ and CC respectively. With good selectivity and sensitivity, the practical application of the modified electrode has been investigated by the simultaneous determination of HQ and CC in tap water samples using the standard addition method with satisfactory results.