Rapid determination of residual chlorine by flow injection analysis

Abstract

Flow injection determination of residual chlorine in solution has been carried out spectrophotometrically by methyl orange decolorisation and by formation of a yellow complex with o-tolidine. The carrier streams are 0.180 mM methyl orange in pH 2 buffer solution or 0.01 M hydrochloric acid, and 3.0 mMo-tolidinium dichloride (in 2 M hydrochloric acid), respectively. A sampling rate of 288 samples per hour has been obtained with the latter reagent and the detection limit is 0.08 p.p.m. of chlorine. Influence of flow parameters such as flow-rate, tube length and diameter and the effect of interferents on the determination have been investigated. A study of the hyprochlorite-ammonium-o-tolidine reaction system has been performed and a method for the simultaneous determination of NH4+ and OCl– is described.