Athula Attygalle
Stevens Institute of Technology, USA
Posters & Accepted Abstracts: Int J Drug Dev & Res
Same drug molecule sometimes generates entirely different mass spectra depending on the instrumental parameters and sample preparation methods used. We demonstrate that this is primarily due to the co-existence of different protonated forms (protomers) or deprotonated forms (deprotomers) of the same molecule. The co-existence of protomers or deprotomers can be demonstrated by ion-mobility mass spectrometry. By this method, millisecond difference in arrival times of different protomers to the detector can be measured. The separated protomers can be fragmented individually and a unique spectrum can be obtained for each protomer. For example, difloxacin, a fluoroquinolone antibiotic was shown to exist as a mixture of two protomers: an O-protomer, due to pronation at the carbonyl group, and an N-protomer due to protonation on the N atom. Upon fragmentation, the O-protomer undergoes the loss of a water molecule exhibiting two signals at m/z 400 and m/z 382, whereas the N-protomer fragments by a loss of a CO2 molecule. The commonly published spectrum in mass spectrometric databases for this antibiotic is actually a composite of two overlapping spectra. Data obtained from many similar examples will be presented. aattygal@stevens.edu
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