Structural characterization of drugs and oxygenated metabolites by laser microprobe mass spectrometry (LAMMA).

Laser microprobe mass analysis (LAMMA) was used for the structural characterization of polyfunctional drugs and their oxygenated metabolites, in particular the N-oxides. The spectra usually yield the molecular weight as well as intense fragments. The structural information is characteristically distributed between the positive and negative ions. To rationalize the unfamiliar fragmentation, tentative pathways are introduced. Key elements are the formation of odd-electron molecular (and fragment) ions, the correlation between cations and anions, as well as the three-dimensional representation of structures. The combination of mild desorption and abundant fragmentation makes LAMMA a valuable tool in the study of N-oxides.