Determination of residual chlorine by folw injection/ electrochemical detector

Abstract

An electrochemical detector for flow injection analysis (FIA) was designed and applied to the determination of residual chlorine. The detector consists of a working electrode (changeable solid electrode), a counter electrode (platinum wire) and a reference electrode {saturated calomel electrode (SCE)}. Evaluation of the detector was carried out using hexacyanoferrate (II). A linear relationship was obtained in the concentration range of 2 × 10-7 to 2 × 10-4 M. The relative standard deviation (RSD) for ten injections was less than 1%. The electrochemical behavior of hypochlorous acid was examined using cyclic voltammetry. At a gold electrode, a reduction wave of hypochlorous acid was observed at +0.3 V vs. SCE. A linear calibration curve was obtained in the concentration range of 0.05 to 2.5 mg l-1 when the gold electrode was applied to the FIA. The RSD was 2.1% for 1 mg l-1 hypochlorous acid. The proposed method was applied to the determination of residual chlorine in tap water. The results agreed well with those obtained by the o-tolidine photometric method.