Indirect determination of chloride by gas-diffusion flow injection with amperometric detection

Abstract

A rapid, indirect gas-diffusion flow injection (FI) method with amperometric detection has been developed for the selective and sensitive determination of Cl–. The method is based on permanganate oxidation of Cl– to chlorine. The chlorine diffuses through the micro-porous membrane and is quantified amperometrically at a platinum working electrode. Calibration graphs were linear up to the maximum concentration of Cl– investigated (10 mmol dm–3). The precision of the technique was better than a relative standard deviation of 1% at 2 mmol dm–3 levels and better than 2% at 10 µmol dm–3, with a throughput of 30 samples h–1. At elevated temperatures (50 °C) and higher acidities (5 mol dm–3 H2SO4), the detection limit was 0.1 µmol dm–3(0.7 ng of Cl–). The effects of temperature, sample acidity, working potential and interferents on the FI signals were studied. The method was successfully applied to the determination of Cl– in natural and tap waters.