Mass Spectrometry

Biography

Biography: Athula Attygalle

Abstract

 The preferred charge sites of protonated or deprotonated molecules in the gas phase has been a topic of extensive research. In fact, the exact location of the initial charge site of the precursor ion is requisite that should be addressed before any pragmatic interpretation of a fragmentation spectrum is attempted.  Although the challenge appears seemingly simple, in reality it is not at all a trivial problem. One often assumes that the charge location can be easily predicted by knowing the gas-phase acidity or basicity of various groups present in a polyfunctional molecule.  However, in reality this a very challenging problem because generalizations valid for solution-based chemistry cannot be extended directly to gas-phase phenomena.  For example, there is sufficient experimental evidence to demonstrate that deprotonated p-hydroxybenzoic acid exists in gas phase as a mixture of carboxylate and phenoxide forms.  Analogously, protonated aniline exists as mixture of nitrogen- or ring-protonated forms.  Ion-mobility mass spectrometry (IM-MS) provides a way to determine relative population ratios of protomers or deprotomers that coexist under mass spectrometric ion generation conditions.  Employing IM-MS separation, we demonstrate that mass spectrometric source conditions used for gas-phase ion generation play an important role on the relative ratios of isomeric protomers and deprotomers that coexist under a specific set of experimental conditions.