Shvartsburg Alexandre A, Tang Keqi, Smith Richard D
Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington, USA.
J Am Soc Mass Spectrom. 2004 Oct;15(10):1487-1498. doi: 10.1016/j.jasms.2004.06.018.
Field asymmetric waveform ion mobility spectrometry (FAIMS) is rapidly gaining acceptance as a robust, versatile tool for post-ionization separations prior to mass-spectrometric analyses. The separation is based on differences between ion mobilities at high and low electric fields, and proceeds at atmospheric pressure. Two major advantages of FAIMS over condensed-phase separations are its high speed and an ion focusing effect that often improves sensitivity. While selected aspects of FAIMS performance are understood empirically, no physical model rationalizing the resolving power and sensitivity of the method and revealing their dependence on instrumental variables has existed. Here we present a first-principles computational treatment capable of simulating the FAIMS analyzer for virtually any geometry (including the known cylindrical and planar designs) and arbitrary operational parameters. The approach involves propagating an ensemble of ion trajectories through the device in real time under the influence of applied asymmetric potential, diffusional motion incorporating the high-field and anisotropic phenomena, and mutual Coulomb repulsion of ionic charges. Calculations for both resolution and sensitivity are validated by excellent agreement with measurements in different FAIMS modes for ions representing diverse types and analyte classes.
场不对称波形离子迁移谱（FAIMS）作为一种强大且通用的工具，在质谱分析前的电离后分离中迅速获得认可。该分离基于离子在高电场和低电场下迁移率的差异，并在大气压下进行。FAIMS相对于凝聚相分离的两个主要优点是其高速以及通常能提高灵敏度的离子聚焦效应。虽然FAIMS性能的某些方面是通过经验理解的，但尚未存在一种物理模型来合理化该方法的分辨率和灵敏度，并揭示它们对仪器变量的依赖性。在此，我们提出一种第一性原理计算方法，能够模拟几乎任何几何形状（包括已知的圆柱形和平面设计）和任意操作参数的FAIMS分析仪。该方法涉及在施加的不对称电势、包含高场和各向异性现象的扩散运动以及离子电荷的相互库仑排斥的影响下，实时传播一组离子轨迹通过该装置。通过与不同FAIMS模式下代表不同类型和分析物类别的离子的测量结果高度吻合，验证了分辨率和灵敏度的计算结果。
