Determination of residual chlorine in natural waters by X-ray fluorescence spectrometry

Abstract

A method for the determination of total residual chlorine (TRC) in natural water is described. Potassium iodide is added to water samples on-site followed by filtration with active charcoal filters to collect iodine generated by TRC oxidation. The filters are subsequently analysed for iodine content in the laboratory by X-ray fluorescence spectrometry. The iodine recovery is better than 96%, the TRC detection limit being approximately 40 µg l^–1. The within-batch relative standard deviation is 23% at 0.16 mg l^–1 of TRC and 60% at lower concentrations. The method is rapid (less than 10 min per sample), virtually free from interferences and the samples remain stable for at least 1 month.