HIGH-EFFICIENCY COLLISION-INDUCED DISSOCIATION IN AN RF-ONLY QUADRUPOLE

Collision-induced dissociation (CID), when performed in an RF-only quadrupole is a highly efficient method of fragmenting ions. The low-energy (5-10 eV) CID process may involve direct vibrational excitation by momentum transfer but, in any case, is a very different process from the high-energy (3-10 keV) electronic excitation CID process observed in MIKES and CAMS. Experimental results are presented which demonstrate the efficiency of CID fragmentation (up to 65%), the elimination of scattering losses, and the effects of varying such experimental parameters as choice and pressure of collision gas, ion velocity in the quadrupole, and quadrupole RF voltage and frequency. The appearance of the CID fragmentation spectra is roughly similar to 14-eV EI spectra. The results of digital simulation of ion trajectories in an RF-only quadrupole are presented. The correspondence between simulated and experimental results aids in the understanding of the quadrupole CID process. The high efficiency of the CID process in an RF-only quadrupole is significant in the development of a tandem quadrupole mass spectrometer for selected ion fragmentation studies. © 1979.