MDS Analytical Technologies, 71 Four Valley Drive, Concord, Ontario, Canada L4K 4V8.
Anal Chem. 2010 Mar 1;82(5):1867-80. doi: 10.1021/ac902571u.
In differential mobility spectrometry (also referred to as high-field asymmetric waveform ion mobility spectrometry), ions are separated on the basis of the difference in their mobility under high and low electric fields. The addition of polar modifiers to the gas transporting the ions through a differential mobility spectrometer enhances the formation of clusters in a field-dependent way and thus amplifies the high- and low-field mobility difference, resulting in increased peak capacity and separation power. Observations of the increase in mobility field dependence are consistent with a cluster formation model, also referred to as the dynamic cluster-decluster model. The uniqueness of chemical interactions that occur between an ion and cluster-forming neutrals increases the selectivity of the separation, and the depression of low-field mobility relative to high-field mobility increases the compensation voltage and peak capacity. The effect of a polar modifier on the peak capacity across a broad range of chemicals has been investigated. We discuss the theoretical underpinnings which explain the observed effects. In contrast to the result with a polar modifier, we find that using mixtures of inert gases as the transport gas improves the resolution by reducing the peak width but has very little effect on the peak capacity or selectivity. The inert gas helium does not cluster and thus does not reduce low-field mobility relative to high-field mobility. The observed changes in the differential mobility alpha parameter exhibited by different classes of compounds when the transport gas contains a polar modifier or has a significant fraction of inert gas can be explained on the basis of the physical mechanisms involved in the separation processes.
在差分迁移率谱法（也称为高场非对称波形离子迁移率谱法）中，离子根据在高电场和低电场下迁移率的差异进行分离。在将离子传输到差分迁移率谱仪的气体中添加极性修饰剂，以场依赖的方式增强团簇的形成，从而放大高场和低场迁移率的差异，从而增加峰容量和分离能力。观察到迁移率场依赖性的增加与团簇形成模型一致，也称为动态团簇解团簇模型。离子与形成团簇的中性物质之间发生的化学相互作用的独特性提高了分离的选择性，而低场迁移率相对于高场迁移率的降低增加了补偿电压和峰容量。已经研究了极性修饰剂对广泛化学物质的峰容量的影响。我们讨论了解释观察到的效应的理论基础。与使用极性修饰剂的结果相反，我们发现使用惰性气体混合物作为传输气体通过减小峰宽来提高分辨率，但对峰容量或选择性几乎没有影响。惰性气体氦不会形成团簇，因此不会降低低场迁移率相对于高场迁移率。当传输气体包含极性修饰剂或含有大量惰性气体时，不同类别的化合物的差分迁移率 α 参数表现出的观察到的变化可以根据分离过程中涉及的物理机制来解释。
