Highly-Sensitive Simultaneous Determination of p-Phenylenediamine and Hydroquinone by Recognizing Electrochemical Reduction Responses on Bare GCE

Juanjuan Gao ^a,1, Weiqing Zhu ^a,1, Haiou Song ^{b, c,}*^,z, and Shupeng Zhang ^a,c*^,z

¹ J.J. Gao and W.Q. Zhu contributed equally to this work.

ABSTRACT

p-Phenylenediamine (PPD) and hydroquinone (HQ) are hair dye precursors for permanent dyeing and are used globally. We report a novel and economic approach for the selective and simultaneous detection of the cathodic peaks of PPD and HQ by using a bare glassy carbon electrode, compared with modified electrodes that are obtained by tedious or expensive functionalized and that failed to achieve a peak-to-peak separation of PPD and HQ. Linear relationships between the simultaneous cathodic peak current and PPD and HQ concentrations were obtained for 0.5–400 μM and 5–4,000 μM with detection limits (S/N = 3) of 0.163 and 0.353 μM, respectively. The glassy carbon electrode sensor was applied to determine PPD and HQ in Nanjing river water with a recovery for these two analogues of 98.7 – 103.9% and 98.0 – 102.4%, respectively.

Conclusions

Three advantages were apparent in this study: a low detection limit could be achieved for PPD; the reduction peak-peak separation of PPD and HQ could be achieved regardless of their extremely similar redox potentials, and the successful completion of the simultaneous detection of the two with a lower detection limit;and we discovered, serendipitously, that pure bare electrodes enable the simultaneous analysis of these two analogues, whereas traditional modified sensors that are obtained by using tedious or expensive functionalized materials do not. This provided a novel idea for the simultaneous detection of relative targets in which the oxidation peak potential is too difficult but the reduction peak is easy to be separated.