Determination of S-benzyl-N-acetyl-L-cysteine by gas chromatography/mass spectrometry as a new marker of toluene exposure.

We investigated by gas chromatography/mass spectrometry if S-benzyl-N-acetyl-L-cysteine (SBAC) is excreted into the urine of six printing workers and 20 sniffers after exposure to toluene. SBAC was extracted from 10 mL urine with chloroform and back extracted into 1M sodium bicarbonate. After acidfying, the sample was reextracted with ethyl acetate. The SBAC in urine was also measured by selected ion monitoring methods, using deuterium-labeled SBAC as an internal standard. An excellent linearity was obtained from 0.01 to 3.0 mg/L (r = 0.998). Urinary concentrations of SBAC were determined quantitatively in all samples from sniffers and printing workers (n = 26, 0.02-43.29 mg/L) but were not determined in the urine of persons not exposed to toluene (n = 40). The results of this experiment indicate that SBAC is excreted as a minor metabolite of toluene in human urine. The analysis of urinary SBAC is a useful tool in identifying toluene exposure.