Shvartsburg Alexandre A, Tang Keqi, Smith Richard D
Biological Systems Analysis and Mass Spectrometry, Pacific Northwest National Laboratory, 3335 Q Ave., (K8-98), P. O. Box 999, 99352, Richland, WA, USA.
J Am Soc Mass Spectrom. 2005 Sep;16(9):1447-1455. doi: 10.1016/j.jasms.2005.04.003.
The use of field asymmetric waveform ion mobility spectrometry (FAIMS) has rapidly grown with the advent of commercial FAIMS systems coupled to mass spectrometry. However, many fundamental aspects of FAIMS remain obscure, hindering its technological improvement and expansion of analytical utility. Recently, we developed a comprehensive numerical simulation approach to FAIMS that can handle any device geometry and operating conditions. The formalism was originally set up in one dimension for a uniform gas flow and limited to ideal asymmetric voltage waveforms. Here we extend the model to account for a realistic gas flow velocity distribution in the analytical gap, axial ion diffusion, and waveform imperfections (e.g., noise and ripple). The nonuniformity of the gas flow velocity profile has only a minor effect, slightly improving resolution. Waveform perturbations are significant even at very low levels, in some cases approximately 0.01% of the nominal voltage. These perturbations always improve resolution and decrease sensitivity, a trade-off controllable by variation of noise or ripple amplitude. This trade-off is physically inferior to that obtained by adjusting the gap width and/or asymmetric waveform frequency. However, the disadvantage is negligible when the perturbation period is much shorter than the residence time in FAIMS, and ripple adjustment appears to offer a practical method for modifying FAIMS resolution.
随着与质谱联用的商用场不对称波形离子迁移谱（FAIMS）系统的出现，FAIMS的应用迅速增加。然而，FAIMS的许多基本方面仍不清楚，这阻碍了其技术改进和分析用途的扩展。最近，我们开发了一种针对FAIMS的综合数值模拟方法，该方法可以处理任何设备几何形状和操作条件。该形式最初是在一维中针对均匀气流建立的，并且仅限于理想的不对称电压波形。在这里，我们扩展了模型，以考虑分析间隙中实际的气流速度分布、轴向离子扩散和波形缺陷（例如噪声和纹波）。气流速度分布的不均匀性影响较小，只会略微提高分辨率。即使在非常低的水平下，波形扰动也很显著，在某些情况下约为标称电压的0.01%。这些扰动总是会提高分辨率并降低灵敏度，这种权衡可以通过改变噪声或纹波幅度来控制。这种权衡在物理上不如通过调整间隙宽度和/或不对称波形频率获得的权衡。然而，当扰动周期比在FAIMS中的停留时间短得多时，这种缺点可以忽略不计，并且纹波调整似乎提供了一种修改FAIMS分辨率的实用方法。
