Gas chromatography-negative ion chemical ionization mass spectrometry as a powerful tool for the detection of mercapturic acids and DNA and protein adducts as biomarkers of exposure to halogenated olefins.

The studies on metabolism of halogenated olefins presented here outline the advantages of modern mass spectrometry. The perchloroethene (PER) metabolite N-acetyl-S-(trichlorovinyl)-L-cysteine (N-ac-TCVC) is an important biomarker for the glutathione dependent biotransformation of PER. In urine of rats and humans exposed to PER, N-ac-TCVC was quantified as methyl ester after BF3-MeOH derivatization by gas chromatography with chemical ionization and negative ion detection mass spectrometry (GC-NCI-MS). The detection limit was 10 fmol/microliter injected solution using [2H3]N-ac-TCVC methyl ester as the stable isotope internal standard. Cleavage of S-(trichlorovinyl)-L-cysteine by beta-lyase enzymes results in an electrophilic and highly reactive thioketene which reacts with nucleophilic groups in DNA and proteins. Protein adduct formation was shown in kidney mitochondria by identification of dichloroacetylated lysine after derivatization with 1,1,3,3-tetrafluoro-1,3-dichloroacetone by GC-NCI-MS. In addition, chlorothioketene was generated in organic solvents and reacted with cytosine to give N4-chlorothioacetyl cytosine. After derivatization with pentafluorobenzyl bromide this compound exhibited good gas chromatographic properties and was detectable with a limit of detection of 50 fmol/injected volume. The detection of chemically induced protein modifications in the target organ of toxic metabolite formation and the study of DNA modifications with chemically generated metabolites provide important information on organ toxicity and possible tumorigenicity of halogenated olefins.