Bath gas temperature and the appearance of ion trap tandem mass spectra of high-mass ions

Abstract

Bath gas temperature effects upon the appearance of ion trap tandem mass spectra of protonated leucine enkephalin have been studied under a variety of ion activation conditions and over a bath gas temperature range of 298–486 K. Bath gas temperature was found to have two possible effects upon the identities and abundances of product ions observed in tandem mass spectra. At high parent ion dissociation rates (>10 s −1) and short activation times (<30 ms), bath gas temperature principally affects the appearance of tandem mass spectra via its role in determining the kinetics for first generation product ion cooling. In the case of protonated leucine enkephalin, this is primarily reflected in the extent to which the first generation b 4 + ion fragments further to yield the a 4 + ion, the energy supplied for this process arising from the parent ion internal energy. Bath gas temperature is most likely to be an important factor in the appearance of tandem mass spectra collected under the conditions just mentioned, when a first generation product ion tends to fragment at rates comparable to or greater than the parent ion dissociation rate. At low parent ion dissociation rates (>10 s −1), relatively long ion activation times (<100 ms), and elevated bath gas temperatures, dissociation resulting from thermal activation of the first and higher generation fragments can make significant contributions to the tandem mass spectra.