Determination of free chlorine in water by chemiluminescence reaction with hydrogen peroxide

The analytical utility of the hydrogen peroxide—hypochlorite singlet oxygen chemiluminescence reaction for the determination of hypochlorite in water is investigated. Effects of pH and hydrogen peroxide concentration are discussed and interference data for over 35 species in the absence and presence of hypochlorite are provided. The limit of detection is 4 μg l^-1 with a usable non-linear calibration curve up to about 200 μg l^-1. The new method is shown to be relatively free from interferences and to give results for tap water comparable to a standard colorimetric method based on a reaction with N, N-diethyl-p-phenylenediamine.