Determination of total phenols in environmental wastewater by flow-injection analysis with a biamperometric detector

Abstract.

A flow injection (FI) method with a biamperometric detector, based on the biamperometry for an irreversible redox couple, is described for the determination of phenols in environmental wastewater. The method relies on coupling of the oxidation of phenols at one platinum-wire electrode with the reduction of MnO₄ ^– at another platinum wire electrode to enable biamperometric detection with an applied potential difference of 0 V. The linear dynamic range for the dependence of current on phenol concentration was from 1.0×10^–6 to 1.0×10^–4 mol L^–1, with a detection limit of 4.0×10^–7 mol L^–1 (signal-to-noise ratio, S/N=3). In comparison with the 4-aminoantipyrine (4-AAP) standard method and the 3-methyl-2-benzothiazoline hydrazone (MBTH) method the proposed method can be used to detect many para-substituted phenols that do not react with 4-AAP and MBTH, and response factors are higher for most of the phenols tested. The method, which is simple, economic, and rapid (180 samples h^–1), has been applied to the analysis of four wastewater samples. The results obtained were compared with those from 4-AAP method. The recoveries obtained by adding phenol standards to samples ranged from 94.3 to 105.2% with a standard deviation of 3.6%.