Analysis of urinary N-acetyl-S-(N-methylcarbamoyl)cysteine, the mercapturic acid derived from N,N-dimethylformamide

Human biotransformation of the industrial solvent N,N-dimethylformamide giv es raise to N-acetyl-S-(N-methylcarbamoyl)cysteine (AMCC) which has the lon gest half-life (about 23 h) among urinary metabolites of N,N-dimethylformam ide. It could be used for monitoring industrial exposure over several workd ays, by measuring it in urine samples collected at the end of the working w eek. This is consistent with the suggestions of the American Conference of Governmental Industrial Hygienists, which established a limit of 40 mg/l fo r the year 2000. An easy, cheap and user-friendly method has been developed for determination of urinary AMCC. Unlike currently available methods, it requires neither a time-consuming preparation phase nor gas chromatographic analysis with a nitrogen-phosphorus or mass detector. The method uses high -performance liquid chromatography (HPLC), with an UV detector at 436 nm. A 10-mul volume of urine is added to a carbonate-hydrogen carbonate buffer a nd mixed with a dabsyl chloride solution in acetonitrile. The reaction betw een AMCC and the reagent is performed at 70 degreesC for 10 min. The 'dabsy lated' product is stable for at least 12 h. After brief centrifugation, the solution is ready for HPLC analysis using a C-18 column (250X4.6 mm, 5 mum ). The method is sensitive (detection limit 1.8 mg/l) and specific. It iden tified urinary AMCC in urine of 40 subjects not exposed to N,N-dimethylform amide with a median concentration of 3.9 mg/l. In urine samples from 20 wor kers exposed to N,N-dimethylformamide (5-40.8 mg/m(3)), AMCC concentrations ranged from 16 to 170 mg/l. Industrial toxicology laboratories with limite d instrumentation will be able to use it in the biological monitoring of wo rkers exposed to N,N-dimethylformamide. (C) 2001 Elsevier Science B.V. All rights reserved.