Fundamental studies of ion injection and trapping of electrosprayed ions on a quadrupole ion trap
Fundamental studies of ion injection and trapping of electrosprayed ions on a quadrupole ion trap
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DOI：
10.1016/s1387-3806(98)14268-9
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发表时间：
1999-08-23
影响因子：
1.8
通讯作者：
Yost, RA
中科院分区：
文献类型：
--
作者：
Quarmby, ST;Yost, RA
四极离子阱是一种高度通用且灵敏的分析质谱仪。由于离子阱提供的优点，人们对将其与电喷雾等电离技术耦合产生了浓厚的兴趣，电喷雾在离子阱外部形成离子。在这项工作中，采用模拟和实验来研究将电喷雾离子注入 Finnigan MAT LCQ LC/MSn 质谱仪中的四极离子阱。选择 SIMION v6.0 进行模拟研究是因为它允许模拟包括端盖孔在内的实际离子阱电极几何形状。端盖孔削弱了孔附近区域的射频捕获场；当离子像在离子注入中那样具有较大的轴向偏移时，这种场的扭曲就很重要。此外，电场会穿透端盖孔并影响接近离子阱的离子。在离子阱外部开始模拟离子的结果与实验获得的注入过程中 q(z) 影响的离子注入数据非常吻合。根据这些模拟，开发了捕获注入离子的过程模型。即使使用常用的适度氦气缓冲气体压力（大约 1 mTorr）也可以捕获注入的离子，因为离子在某些 q(z) 值和初始射频相位下自然会长时间（因此距离）振荡。这使得足够的碰撞发生以抑制离子的多余动能。 (Int J Mass Spectrom 190/191 (1999) 81-102) (C) 1999 Elsevier Science B.V.
The quadrupole ion trap is a highly versatile and sensitive analytical mass spectrometer. Because of the advantages offered by the ion trap, there has been intense interest in coupling it to ionization techniques such as electrospray which form ions externally to the ion trap. In this work, simulation and experiment were employed to study the injection of electrosprayed ions into the quadrupole ion trap in a Finnigan MAT LCQ LC/MSn mass spectrometer. SIMION v6.0 was chosen for the simulation studies because it allowed the actual ion trap electrode geometry including endcap holes to be simulated. The endcap holes weaken the rf trapping field in the region near the holes; this distortion of the field is important when ions have large axial excursions as they do in ion injection. In addition, the field penetrates out the endcap holes and affects ions as they approach the ion trap. The results of simulating ions started outside the ion trap agreed well with experimentally obtained ion injection data of the effect of q(z) during injection. From these simulations, a model for the process by which injected ions are trapped was developed. Injected ions can be trapped even with the modest helium buffer gas pressures commonly used (approximate to 1 mTorr) because ions naturally oscillate for long times (and therefore distances) at certain q(z) values and initial rf phases. This allows enough collisions to occur to damp the ions' excess kinetic energy. (Int J Mass Spectrom 190/191 (1999) 81-102) (C) 1999 Elsevier Science B.V.