Chlorination byproducts of amino acids in natural waters

The chlorination of the amino acids aspartic acid, tyrosine and tryptophan was studied at ambient temperature at pH 1-2 and at neutral pH values by gas chromatography/mass spectrometry. Additional structural information necessary to identify the intermediates was provided by the tandem mass spectrometric analysis of chlorinated tyrosine. Chloroform, dichloroacetonitrile and chloral hydrate were formed as byproducts. The formation of chloral was significantly increased with increase in pH from 7 to 8. The pH dependence was consistent with the proposed reaction pathways. Chlorinated water samples from two different natural lakes and chlorinated effluents from two domestic wastewater treatment plants were analysed for chlorination byproducts. Significant amounts of chloral and dichloroacetonitrile were found in all samples. The presence of dichloroacetonitrile and chloral in chlorinated natural waters implicated amino acids and other nitrogenous compounds as potential precursors in natural waters.