Accurate Drift Time Determination by Traveling Wave Ion Mobility Spectrometry: The Concept of the Diffusion Calibration
Accurate Drift Time Determination by Traveling Wave Ion Mobility Spectrometry: The Concept of the Diffusion Calibration
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DOI：
10.1021/acs.analchem.6b03215
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发表时间：
2016-12-06
影响因子：
7.4
通讯作者：
De Pauw, Edwin
中科院分区：
文献类型：
--
作者：
Kune, Christopher;Far, Johann;De Pauw, Edwin
离子迁移谱（IMS）是一种气相分离技术，它依赖于离子碰撞截面（CCS）的差异。如果CCS差异低于以CCS/ΔCCS表示的仪器分辨率，未分离构象异构体的离子云会重叠。那么实验到达时间分布（ATD）峰就是由各种成分按其相对强度加权后的叠加。本文介绍了一种使用行波离子迁移谱（TWIMS）对分离不佳或未分离的构象异构体进行精确漂移时间测定的策略。该方法通过一个校准程序，在波高和波速的多种设置范围内，建立了半峰全宽（fwhm）与模型化合物漂移时间之间的联系。我们修改了一个高斯方程，该方程根据我们的校准程序固定fwhm，实现了对ATD峰的去卷积。新的拟合高斯方程仅取决于两个参数：峰顶点（A）和平均漂移时间值（μ）。标准偏差参数（与fwhm相关）成为漂移时间的函数。μ和fwhm之间的这种相关函数是通过TWIMS校准程序获得的，该程序使用在气相中作为单一构象异构体被检测到的离子化合物，在有限且可控的空间电荷效应下确定仪器离子束的最大扩散。这种去卷积过程已被用于凸显冠醚配合物和肽的分离不佳的构象异构体的存在，从而使CCS测定更加准确，与量子化学预测更加吻合。
Ion mobility spectrometry (IMS) is a gas phase separation technique, which relies on differences in collision cross section (CCS) of ions. Ionic clouds of unresolved conformers overlap if the CCS difference is below the instrumental resolution expressed as CCS/Delta CCS. The experimental arrival time distribution (ATD) peak is then a superimposition of the various contributions weighted by their relative intensities. This paper introduces a strategy for accurate drift time determination using traveling wave ion mobility spectrometry (TWIMS) of poorly resolved or unresolved conformers. This method implements through a calibration procedure the link between the peak full width at half-maximum (fwhm) and the drift time of model compounds for wide range of settings for wave heights and velocities. We modified a Gaussian equation, which achieves the deconvolution of ATD peaks where the fwhm is fixed according to our calibration procedure. The new fitting Gaussian equation only depends on two parameters: The apex of the peak (A) and the mean drift time value (mu). The standard deviation parameter (correlated to fwhm) becomes a function of the drift time. This correlation function between mu and fwhm is obtained using the TWIMS calibration procedure which determines the maximum instrumental ion beam diffusion under limited and controlled space charge effect using ionic compounds which are detected as single conformers in the gas phase. This deconvolution process has been used to highlight the presence of poorly resolved conformers of crown ether complexes and peptides leading to more accurate CCS determinations in better agreement with quantum chemistry predictions.