Field desorption mass spectrometry of metabolites of the anticancer drug cyclophosphamide

Some of the known and important metabolites of cyclophosphamide and the parent drug itself were investigated by low and high resolution field desorption mass spectrometry. The potential of the relatively new analytical method for the determination of the molecular weight and elemental formulae of drugs and drug metabolites was exemplified. This holds for pure, synthetic compounds as well as for contaminated extracts from biological sources. In addition, by thermally-/field-induced fragmentation, diagnostic fragment ions could be produced, providing valuable structural information. Further, an indication on how to distinguish [M]+. and [M + H]+ ions in field desorption mass spectrometry is given. The ability to identify these ions unambiguously is critical for interpretation. Finally, the potential of the method as applied to drug and drug metabolite mixtures is evaluated. The results indicate that field desorption mass spectrometry is a promising tool in metabolism studies.