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.