Ratiometric electrochemical sensing platform based on N-doped MOF-derived CoNi/C for the determination of p-phenylenediamine in hair dyes.

A stable ratiometric electrochemical sensing platform is introduced for the determination of p-phenylenediamine (PPD). Specifically, the proposed sensing platform employs nitrogen-doped MOF pyrolysis-derived CoNi/C (N-CoNi/C) which was deployed as the sensing agent and methylene blue (MB) as the internal reference, and the MB combined with N-CoNi/C nanomaterials by a simple immersion adsorption process. Full characterization of N-CoNi/C was carried out with respect to morphology, composition, and electrochemical behavior, and the sensing performance of the ratiometric electrochemical sensing platform was evaluated. Complete separation of the oxidation peaks of PPD and MB was achieved using the MB/N-CoNi/C composite modified glassy carbon electrode (MB/N-CoNi/C/GCE) and their ratio signals were used for quantitative determination of PPD. The electrical signal was linearly related to the concentration of PPD in the concentration range 0.3-100 µM, with a fitted correlation coefficient of 0.9987 and a detection limit of 0.091 µM (S/N = 3). Additionally, the sensor has been successfully used for the determination of PPD in commercial hair dyes with a recovery rate of over 95%.