Simulation of duty cycle-based trapping and ejection of massive ions using linear digital quadrupoles: The enabling technology for high resolution time-of-flight mass spectrometry in the ultra high mass range

Duty cycle-based trapping and extraction processes have been investigated for linear digitally driven multipoles by simulating ion trajectories. The duty cycles of the applied waveforms were adjusted so that an effective trapping or ejection electric field was created between the rods and the grounded end cap electrodes. By manipulating the duty cycles of the waveforms, the potentials of the multipole rods can be set equal for part of the waveform cycle. When all rods are negative for this period, the device traps positive ions and when all are positive, it ejects them in focused trajectories. Four Linac II electrodes [1] have been added between the quadrupole rods along the asymptotes to create an electric field along the symmetry axis for collecting the ions near the exit end cap electrode and prompt ejection. This method permits the ions to be collected and then ejected in a concentrated and collimated plug into the acceleration region of a time-of-flight mass spectrometer (TOFMS). Our method has been shown to be independent of mass. Because the resolution of orthogonal acceleration TOFMS depends primarily on the dispersion of the ions injected into the acceleration region and not on the ion mass, this technology will enable high resolution in the ultrahigh mass range (m/z > 20,000).

Graphical abstractFigure optionsDownload full-size imageDownload high-quality image (153 K)Download as PowerPoint slideHighlights► The duty cycle of the waveforms applied to a digital ion guide can be used to trap and eject ions. ► Adding Linac electrodes to the guide permits ion to be trapped and collected in front of the exit end cap electrode. ► Collected ions can be ejected in plug with well-collimated trajectories into the acceleration region of an oa-TOFMS. ► Trapping, collecting and ejection by this method permits ions of ANY mass-to-charge ratio to be injected into a oa-TOFMS in collimated trajectories with controlled kinetic energy distributions. ► This technology will enable high resolution TOFMS in the ultra high mass range (m/z > 20 kDa).