Determination of a bound musk xylene metabolite in carp hemoglobin as a biomarker of exposure by gas chromatography-mass spectrometry using selected ion monitoring.

Musk xylene (MX) is widely used as a fragrance ingredient in commercial toiletries. Identification and quantitation of a bound 4-amino-MX (AMX) metabolite was carried out by gas chromatography-mass spectrometry (GC-MS) with selected ion monitoring (SIM). Detection of AMX occurred after the cysteine adducts in carp hemoglobin (Hb), derived from the nitroso metabolite, were released by alkaline hydrolysis. The released AMX metabolite was extracted into n-hexane. The extract was preconcentrated by evaporation and analyzed by GC-SIM-MS. The concentration of AMX metabolite was found to range from 6.0 to 30.6 ng/g in the carp Hb, collected from the Las Vegas Wash and Lake Mead, NV areas. The presence of an AMX metabolite in the carp Hb was confirmed when similar mass spectral features and the same retention time of the AMX metabolite were obtained for both standard AMX and carp Hb extract solutions. In the nonhydrolyzed and reagent blank extracts, the AMX metabolite was not detected.