The development of dynamic collision induced dissociation (DCID), a novel collisional activation method for quadrupole ion traps (QITs) is described. The effect of experimental parameters such as the excitation frequency, excitation amplitude and mass scanning rate were investigated, as well as the effect of frequency spacing and relative phase angle when a two-frequency excitation waveform is used. With careful selection of the excitation conditions the internal energy deposition was significantly increased when compared to conventional collision induced dissociation (CID). While the maximum ratio of 91/92 reported in the literature for n-butylbenzene, a test molecule, using CID in a QIT is 4.2 (corresponding to ~5 eV internal energy), DCID can achieve ratios of 91/92 as large as 15. DCID fragmentation efficiencies in excess of 60% were achieved for n-butylbenzene and simultaneously efficient and energetic fragmentation may be attained with judicious selection of the DCID waveform.
Upon investigation of excitation at the Ω - ω higher order resonance of the fundamental secular frequency of motion of the precursor ion, large internal energy depositions were possible with a greater flexibility in the selection of experimental parameters. Application of a high amplitude, two-frequency excitation waveform where the two frequencies were spaced at more than 5 kHz resulted in 91/92 fragment ion ratios of n-butylbenzene greater than 3 with concomitant fragmentation efficiencies in excess of 20%. This implies that the internal energy deposited to n-butylbenzene was in excess of 5 eV, which is considerably larger than is generally achievable with conventional CID.
The application of DCID in a pulsed fashion (PqDCID) followed by a fast lowering of the rf amplitude on the ring electrode allowed for mass analysis of low mass product ions. PqDCID was applied to the on-line investigation of tryptic peptides eluting from an HPLC column. PqDCID was successful in accomplishing tandem mass analysis and provided an increased number of peaks in the mass spectrum compared to CID. The ability to analyze low mass product ions such as iTRAQ reporter ions was shown to be applicable for quantitative analysis of iTRAQ-labeled peptides.