Determination of residual chlorine by derivatisation with 2,6-dimethylphenol and gas chromatographic separation

Residual chlorine in aqueous solution is converted to 4-chloro-2,6-dimethylphenol, which is extracted into hexane and determined by gas chromatography. Relative standard deviations (n = 5) are 0.36–1.1% for chlorine concentrations of 8.6–0.01 mg l^-1 and chlorine recoveries are 99.2–101%. In the presence of dichromate (30 mg l^-1), relative standard deviations (n = 5) are 1.19–2.71% for chlorine concentrations of 9.3–0.1 mg l^-1. Oxidants and coloured solutes do not interfere.