Nitro musk metabolites bound to carp hemoglobin: Determination by GC with two MS detection modes. Eims versus electron capture negative ion MS

Nitroaromatic compounds including synthetic nitro musks are important raw materials and intermediates in the synthesis of explosives, dyes, pesticides, and pharmaceutical and personal-care products (PPCPs). The nitro musks such as musk xylene (MX) and musk ketone (MK) are extensively used as fragrance ingredients in PPCPs and other commercial toiletries. Identification and quantification of a bound 4-amino-MX (4-AMX) metabolite as well as a 2-amino-MK (2-AMK) metabolite were carried out by gas chromatography-mass spectrometry (GCMS), with selected ion monitoring (SIM) in both the electron ionization (EIMS) and electron capture (EC) negative ion chemical ionization (NICIMS) modes. Detection of 4-AMX and 2-AMK occurred after the cysteine adducts in carp hemoglobin, derived from the nitroso metabolites, were released by alkaline hydrolysis. The released metabolites were extracted into n-hexane. The extract was preconcentrated by evaporation, and analyzed by GC-SIM-MS. A comparison between the EI and EC approaches was made. EC NICIMS detected both metabolites whereas only 4-AMX was detected by EIMS. The EC NICIMS approach exhibited fewer matrix responses and provided a lower detection limit. Quantitation in both approaches was based on an internal standard and a calibration plot.