Enhanced sensitivity for the determination of ambiphilic polyaromatic amines by LC-MS/MS after acetylation

A new method for the analysis of aminonitropyrenes and diaminopyrenes was developed for urine and hemoglobin samples using LC-MS/MS. A good separation by LC was only achieved after derivatization of the amino group, which also increased sensitivity to a limit of detection (LOD) of 0.1 pg (on column) for diaminopyrene and 5 pg for aminonitropyrene using electrospray ionization (ESI). Compared to a derivatization with pentafluorobenzoyl chloride yielding only one sensitive MS/MS transition, acetylation offers the advantages of a higher selectivity with two sensitive MS/MS transitions and the possibility of a direct detection of acetylated aminonitropyrenes and diaminopyrenes formed metabolically in vivo. Acetylated diaminopyrene was detected in urine and after hydrolysis of the corresponding hemoglobin adducts followed by acetylation in blood samples of rats after administration of dinitropyrene but not in controls. A method based on GC-MS with negative chemical ionization of the electrophore labelled metabolites was non-selective since only one major ion M - HF]- was formed and some isobaric peaks were observed preventing unequivocal analyte identification at concentrations close to the LOD.