Scrambling versus specific processes in gaseous organic ions during mass spectrometric fragmentation: elucidation of mechanistic origins by isotope labelling - an overview

The use of isotope labelling for the elucidation of mass spectrometric fragmentation mechanisms is demonstrated in various cases of different nature. The intermediacy of ion/neutral (I/N) complexes during fragmentation, being both analytically and fundamentally relevant, is discussed and studies on the regiospecific and irreversible intracomplex hydride transfer reactions within 'designed' deuterium-labelled I/N complexes are reported. By contrast, several types of scrambling processes, being due to reversible isomerization reactions prior to mass spectrometric fragmentation, are presented, exemplifying complete and incomplete, progressive and composite scrambling in gaseous organic ions. Copyright (c) 2007 John Wiley & Sons, Ltd.