Boundary-activated dissociation of peptide ions in a quadrupole ion trap.

Boundary-activated dissociation (BAD) of peptides has been investigated as an alternative to the use of resonant excitation to effect collision-induced dissociation in the quadrupole ion trap. BAD's nonresonant excitation mechanism overcomes a major drawback in resonant excitation, namely, the variation of the resonant excitation frequency as a function of ion space charging. As with resonant excitation, the pulsed introduction of heavy gases (argon, xenon) extends the applicability of BAD when tandem mass spectrometry is performed on peptide ions. The presence of heavy gases during ion activation allows greater internal energy deposition and also enables BAD to be performed at much lower trapping field strengths (lower q values) than previously reported for this technique. This extends the mass range over which product ions can be collected.