MS/MS of Ions in a Low Pressure Linear Ion Trap using a Pulsed Gas

A pulsed valve was used to increase the pressure within the trapping region of a low-pressure linear ion trap by situating the pulsed valve close to the ion trapping region. The pressure was estimated to increase from a background pressure of 3.5e-5 Torr of nitrogen to 0.49 mTorr at the center of the trap. The increased pressure allowed excitation periods to be reduced from 100 to 25 ms without suffering losses in MS/MS efficiency during dipolar excitation. The reduction in excitation period translates into an increase in the overall duty cycle of the scan. (J Am Soc Mass Spectrom 2009, 20, 1714-1717) (C) 2009 American Society for Mass Spectrometry