Department of Chemistry, Washington State University, Pullman, WA 99164, USA.
Analyst. 2019 Nov 4;144(22):6660-6670. doi: 10.1039/c9an01585j.
For time dispersive ion mobility experiments detail control over the mechanism of ion beam modulation is necessary to establish optimum performance as this parameter greatly influences the temporal width of the ion beam arriving at the detector. When sampling continuous ion sources the temporal sampling or the incoming ion beam is often achieved by the electronic modulation of a grid or electric field. Not surprisingly, the rate at which a given ion population traverses this gating region is directly proportional to an ion's population and the applied electric field. This scenario establishes conditions where discrimination of the incoming ion beam may occur when the ion gate modulation rate is minimized. Recent developments in the mechanical construction of ion gates and their subsequent operation suggest that the mobility discrimination during ion gating may be minimized, however, it is remains unclear how this behavior will translate to ion beam multiplexing approaches. In this present work, we compare the performance levels of the tri-state ion shutter (3S-IS) to the two-state ion shutter (2S-IS) using a series of Fourier transform ion mobility mass spectrometry (FT-IMMS) experiments. The performance of the two different shutter operating principles were evaluated using ion multiplexing using tetraalkylammonium salts (TXA ions; T5-T8, T10, T12) bradykinin, and a set of reversed sequence isomeric pentapeptides using a variety of different ion gate frequency sweeps. Noticeable increases in ion throughput were observed for the 3S-IS with 95% and 45% increases in ion counts for the T5 and T12 ions respectively compared to the 2S-IS. Similarly, a 27% and 55% increase in ion counts was observed for the [M + 2H]2+ and [M + H]+ ions of bradykinin, respectively. In addition, a 10% increase in resolving power was also observed for the 3S-IS compared to the 2S-IS. Overall, utilization of the 3S-IS effectively minimizes both discrimination of slower ions and the impact of gate depletion effect common to traditional ion gating techniques.
对于时间色散离子淌度实验，为了获得最佳性能，需要对离子束调制的机制进行详细控制，因为该参数极大地影响到达检测器的离子束的时间宽度。在对连续离子源进行采样时，通常通过对栅极或电场进行电子调制来实现入射离子束的时间采样或采样。毫不奇怪，给定离子群体穿过该门控区域的速度与离子的群体和所施加的电场成正比。在这种情况下，当离子门调制率最小化时，可能会发生对入射离子束的歧视。离子门的机械结构的最新发展及其随后的操作表明，在离子门控期间，迁移率的歧视可能最小化，但是，尚不清楚这种行为将如何转化为离子束复用方法。在本工作中，我们使用一系列傅里叶变换离子淌度质谱（FT-IMMS）实验比较了三态离子快门（3S-IS）和两态离子快门（2S-IS）的性能水平。使用四烷基铵盐（TXA 离子；T5-T8、T10、T12）缓激肽和一组反向序列异构五肽，通过各种不同的离子门频率扫描，评估了两种不同快门操作原理的性能。与 2S-IS 相比，对于 T5 和 T12 离子，3S-IS 的离子通过量分别增加了 95％和 45％，而对于 3S-IS 的离子通过量分别增加了 95％和 45％。同样，缓激肽的[M + 2H]2+和[M + H]+离子的离子计数也分别观察到 27％和 55％的增加。此外，与 2S-IS 相比，3S-IS 的分辨率也提高了 10％。总体而言，与传统的离子门控技术相比，3S-IS 的使用有效地最小化了较慢离子的歧视和门损耗效应的影响。
