The development of an analytical method for urinary metabolites of the riot control agent 2-chlorobenzylidene malononitrile (CS)

•A sensitive analytical method for 2-chlorohippuric acid in urine is reported.•2-Chlorohippuric acid is a human urinary metabolite of the riot control agent CS.•2-Chlorohippuric acid can be detected in human urine 20h after mild exposures to CS.•2-Chlorobenzyl-N-acetylcysteine, a CS metabolite in the rat, was not detected. The analysis of biomedical samples such as urine and blood can provide evidence of exposure to chemicals for a range of applications including occupational exposure monitoring, detection of drugs of abuse, performance enhancement in sport and investigations of poisoning and incapacitation. This paper reports the development of an analytical method for two suspected urinary metabolites of the riot control agent 2-chlorobenzylidene malononitrile (CS): 2-chlorohippuric acid and 2-chlorobenzyl-N-acetylcysteine. 2-Chlorohippuric acid was identified in all 2h post-exposure samples from a set of urine samples taken from army recruits exposed to low levels of thermally dispersed CS during training. 2-Chlorobenzyl-N-acetylcysteine, a metabolite known to be formed in the rat, was not identified in any of the samples. The lower limit of detection (LLOD) for 2-chlorohippuric acid and 2-chlorobenzyl-N-acetylcysteine was 1ng/ml and 0.5ng/ml in pooled urine from the pre-exposed subjects. 2-Chlorohippuric acid was rapidly excreted but was detectable in the urine of 17 of the 19 subjects tested 20h after exposure.