Julian Ryan R, Mabbett Sarah R, Jarrold Martin F
Department of Chemistry, Indiana University, Bloomington, Indiana 47405, USA.
J Am Soc Mass Spectrom. 2005 Oct;16(10):1708-12. doi: 10.1016/j.jasms.2005.06.012.
A modified ion funnel is described. Counterintuitively, increased spacing between electrodes results in enhanced "focusing" of the ions through the funnel. Consequently, the internal diameter (i.d.) of the funnel need not decrease to the conductance limit (as in previous designs). A simple dc-only lens, which also serves as the conductance limit, combined with the natural flow of gas is used to extract the ions from the funnel. Ions with mass to charge ratios varying between 75 and 3000 m/z are passed through the funnel with no apparent discrimination. The funnel can be operated under mild conditions that preserve weakly bound noncovalent complexes. After testing several designs, a thin closely spaced dc lens was found to be the best solution for extracting ions. A simple method for simulating ion trajectories at nonzero pressures based on ion mobility and explicit diffusion is described. This theoretical approach was used to design and calculate ion trajectories for the modified funnel presented here. Finally, the increased spacing between electrodes in the current funnel significantly relaxes machining constraints, reduces cost, and enhances ease of use versus previous funnel designs.
本文描述了一种改进的离子漏斗。与直觉相反，电极之间间距的增加会增强离子通过漏斗的“聚焦”效果。因此，漏斗的内径无需减小到传导极限（如先前设计那样）。一个仅由直流电源供电的简单透镜，它同时也作为传导极限，与气体的自然流动相结合，用于从漏斗中提取离子。质荷比在75至3000 m/z之间变化的离子能够无明显歧视地通过漏斗。该漏斗可在温和条件下运行，从而保留弱结合的非共价复合物。在测试了几种设计后，发现一个薄的、间距紧密的直流透镜是提取离子的最佳解决方案。本文描述了一种基于离子迁移率和显式扩散来模拟非零压力下离子轨迹的简单方法。这种理论方法被用于设计和计算此处介绍的改进漏斗的离子轨迹。最后，与先前的漏斗设计相比，当前漏斗中电极之间间距的增加显著放宽了加工限制，降低了成本，并提高了易用性。
