Selective Detection of p ‐Phenylenediamine in Hair Dyes Based on a Special CE Mechanism Using MnO 2 Nanowires

We report a novel approach for selective determination of p ‐phenylenediamine in hair dyes using β ‐MnO 2 nanowires modified glassy carbon (GC) electrodes through an electrochemical co‐deposition process with chitosan hydrogel. A special CE (chemical reaction and electron transfer) process on the surface of β ‐MnO 2 nanowires modified GC electrode is proposed and proved by cyclic voltammetry and UV‐Vis spectroscopy in the presence of p ‐phenylenediamine. p ‐Phenylenediamine can react with MnO 2 nanowires to produce diimine and the equilibrium of the two‐electron and two‐proton redox process of p ‐phenylenediamine on the electrode is changed, and consequently the reductive current is enhanced significantly. At a constant potential of 0 V vs. SCE, other main components of hair dyes including o ‐, m ‐phenylenediamine, catechol, resorcinol, and p ‐dihydroxybenzene do not interfere in the determination of p ‐phenylenediamine in the amperometric measurement because of their much lower chemical reaction activities with MnO 2 nanowires. It shows a determination range of 0.2–150 μM and a low detection limit of 50 nM to response p ‐phenylenediamine. This modified electrode is successfully used to analyze the amount of p ‐phenylenediamine in hair dyes without preseparation procedures.