Control of ion distortion in field asymmetric waveform ion mobility spectrometry via variation of dispersion field and gas temperature
Control of ion distortion in field asymmetric waveform ion mobility spectrometry via variation of dispersion field and gas temperature
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DOI：
10.1021/ac800655d
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发表时间：
2008-10-01
影响因子：
7.4
通讯作者：
Smith, Richard D.
中科院分区：
文献类型：
--
作者：
Robinson, Errol W.;Shvartsburg, Alexandre A.;Smith, Richard D.
场不对称波形离子迁移谱（FAIMS）已成为一种具有广泛用途的分析工具，特别是与质谱联用。特别有希望的是使用FAIMS和2-D离子迁移率方法，该方法将FAIMS与常规IMS联合收割机结合以解析和表征蛋白质和其它大分子构象。然而，FAIMS操作需要强电场，并且离子不可避免地通过与缓冲气体分子的高能碰撞而被加热。这可能会导致离子异构化或解离，从而扭曲FAIMS（及后续阶段）的分离特性或降低仪器灵敏度。由于FAIMS采用周期性波形，因此这些过程是由最大场强时的离子温度还是平均场强控制一直存在争议。在这里，我们通过测量紧凑的泛蛋白离子几何形状的展开作为波形振幅（色散场，E-D）和气体温度T的函数来解决这个问题。通过匹配结构转变对E-D和T的依赖性来量化场加热：将E-D从12增加到16或从16增加到20 kV/cm相当于将（N-2）气体加热类似于15-25 ℃。任何E-D的场加热的幅度可以使用双温理论来估计，并且将E-D提高4kV/cm将加热增加类似于FAIMS循环中的最大15-30摄氏度和平均场的4-8摄氏度。因此，FAIMS中离子的异构化似乎是由波形峰值处的激发决定的。
Field asymmetric waveform ion mobility spectrometry (FAIMS) has emerged as an analytical tool of broad utility, especially in conjunction with mass spectrometry. Of particular promise is the use of FAIMS and 2-D ion mobility methods that combine FAIMS with conventional IMS to resolve and characterize protein and other macromolecular conformers. However, FAIMS operation requires a strong electric field, and ions are inevitably heated by energetic collisions with buffer gas molecules. This may induce ion isomerization or dissociation, which distort the separation properties of FAIMS (and subsequent stages) or reduce instrumental sensitivity. As FAIMS employs a periodic waveform, whether those processes are controlled by ion temperature at maximum or average field intensity has been debated. Here we address this issue by measuring the unfolding of compact ubiquitin ion geometries as a function of waveform amplitude (dispersion field, E-D) and gas temperature, T. The field heating is quantified by matching the dependences of structural transitions on E-D and T: increasing E-D from 12 to 16 or from 16 to 20 kV/cm is equivalent to heating the (N-2) gas by similar to 15-25 degrees C. The magnitude of field heating for any E-D can be estimated using the two-temperature theory, and raising E-D by 4 kV/cm augments heating by similar to 15-30 degrees C for maximum and similar to 4-8 degrees C for average field in the FAIMS cycle. Hence, isomerization of ions in FAIMS appears to be determined by the excitation at waveform peaks.