Determination of the N-acetyl metabolites of 4,4'-methylene dianiline and 4,4'-methylene-bis(2-chloroaniline) in urine.

A sensitive and specific gas chromatographic/mass spectrometric assay is described for the determination of N-acetyl 4,4'-methylene dianiline (N-acetyl MDA) and N-acetyl 4,4'-methylene-bis(2-chloroaniline) (N-acetyl MbOCA) in urine. The method is based on the solvent extraction of the compounds together with deuterium-labelled internal standards, the compounds being separated and detected by capillary gas chromatography/mass spectrometry as their pentafluoropropyl derivatives. The method has been applied to the detection of N-acetyl MbOCA and N-acetyl MDA in the urine of workers occupationally exposed to MbOCA and MDA. The results show that whilst N-acetyl MbOCA is a relatively minor urinary metabolite a significant proportion of MDA is excreted as the N-acetylated compound.