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Simultaneous determination of catechol (CC) and hydroquinone (HQ) were investigated by voltammetry based on glassy carbon electrode (GCE) modified by poly (diallyldimethylammonium chloride) (PDDA) functionalized graphene (PDDA-G). The modified electrode showed excellent sensitivity and selectivity properties for the two dihydroxybenzene isomers. In 0.1 mol/L phosphate buffer solution (PBS, pH 7.0), the oxidation peak potential difference between CC and HQ was 108 mV, and the peaks on the PDDA-G/GCE were three times as high as the ones on graphene-modified glass carbon electrode. Under optimized conditions, the PDDA-G/GCE showed wide linear behaviors in the range of 1×10 −6 −4×10 −4 mol/L for CC and 1×10 −6 −5×10 −4 mol/L for HQ, with the detection limits 2.0×10 −7 mol/L for CC and 2.5×10 −7 mol/L for HQ (S/N=3) in mixture, respectively. Some kinetic parameters, such as the electron transfer number (n), charge transfer coefficient (α), and the apparent heterogeneous electron transfer rate constant (k s ), were calculated. The proposed method was applied to simultaneous determine CC and HQ in real water samples of Yellow River with satisfactory results.

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