Extended m/z range of coaxial linear ion trap/time-of-flight mass spectrometry using dynamic electric field ejection

Abstract

Linear ion trap/time-of-flight mass spectrometry (LIT/TOFMS) to perform ion accumulation in a separate LIT prior to mass analysis is a more generally accepted method to improve duty cycle. However, a long distance between the accumulation region and the TOF pusher led to time-of-flight dispersion of the injected ions with different m/z, thereby limiting the detectable mass range in a single scan. This paper studies the characteristic behaviors of ion ejection from a segmented LIT through SIMION simulation. A novel dynamic electric field ejection strategy is proposed to broaden the ejection mass range of LIT. By linearly scanning the voltages on the segmented LIT and the ion gate, the axial potential distribution is dynamically adjusted to gradually shift the ion accumulation region toward the TOF pusher. As a result, the ejection distance between the accumulation region and the TOF pusher was slowly shortened, reducing time dispersion among different m/z ions. The simulation results demonstrate that this method significantly improves mass range of the coaxial dual LIT/TOFMS, achieving near 100 % injection efficiency for m/z 130–2000 with a mass window ratio (m/z)_max/(m/z)_min of 15. This technology provides a solution for broadening the mass range of LIT-based hybrid instruments.