A Novel Ion Trap That Enables High Duty Cycle and Wide m/z-range on an Orthogonal Injection TOF Mass Spectrometer

摘要

To improve duty cycle of a quadrupole-TOF mass spectrometer, a short linear ion trap (LIT) is placed between collision cell and ortho-TOF entrance. Ions are trapped axially in the pseudopotential well created by additional RF ("AC") voltage, which is applied to all four rods in the same phase. AC voltage is then ramped down over a period of time tau. Since the effective potential is m/z-dependent, heavy ions leave the trap first; lighter ions exit later, but will eventually catch up with heavy ions due to their higher velocity. tau can be selected to make all ions meet in the centre of the orthoTOF accelerator having the same axial energy. As a result ions within a wide m/z-range are recorded with near 100percent duty cycle, while improving sensitivity by factors from 3 to 14 depending on m/z.