Direct Simultaneous Electrochemical Determination of Hydroquinone and Catechol at a Poly(glutamic acid) Modified Glassy Carbon Electrode

A simply and high selectively electrochemical method for simultaneous determination of hydroquinone (HQ) and catechol (CC) has been developed at a glassy carbon electrode modified with electropolymerized films of glutamic acid (p-Glu). This p-Glu modified electrode is used to simultaneous electrochemical determination of HQ and CC and shows an excellent electrocatalytical effect on the oxidation of HQ and CC by cyclic voltammetry (CV) in 0.1 M acetate buffer solution (pH 4.5). In differential pulse voltammetric (DPV) measurements, the p-Glu modified electrode could separate the oxidation peak potentials of HQ and CC present in binary mixtures by about 102 mV though the bare electrode gave a single broad response. A successful elimination of the fouling effect by the oxidized product of HQ on the response of CC has been achieved at the p-Pen modified electrode. The determination limit of HQ in the presence of 0.1 M CC was 1.0 × 10-6 M and the determination limit of CC in the presence of 0.1 M HQ was 8.0 × 10-7 M. The proposed method has been applied to simultaneous determination of HQ and CC in a water sample with simplicity and high selectivity.