In cyclic ion mobility (cIMS), ions are permitted to travel multiple passes around the drift cell, increasing the distance traveled and the relative separation between ions. This study tests the hypothesis that multiple passes around the cell can also result in improved precision when measuring an ion’s mobility and the collision cross section (^TWCCS) derived therefrom. Experiments were performed with a diverse set of compounds, including 16 polycyclic aromatic hydrocarbons using gas chromatographic atmospheric pressure chemical ionization and a set of drug molecules by direct infusion electrospray ionization. The average periodic drift time, viz., the average time required for the ion to travel around the cIMS cell once, shifts dramatically, approaching part-per-million (ppm) precision as the number of passes increases to ∼100. Extrapolation of the precision of the CCS values with respect to the number of passes led to the prediction that the precision will reach 1000 ppm after 50 passes, 100 ppm after 100 passes, and <10 ppm after 150 passes. Experiments wherein the number of passes exceeded 100 produced ^TWCCS values having within-run precisions ranging between 15 and 117 ppm. The improved precision with an increasing number of passes may be a consequence of mitigating space-charge effects by allowing the ions to occupy a larger region of the cIMS cell. A method is proposed to enable practical measurements of ^TWCCS with ppm precision and is demonstrated to characterize an unknown drug mixture.

中文翻译：

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使用多道循环离子淌度确定离子碰撞截面的精度达到百万分之一

在循环离子淌度 (cIMS) 中，离子可以在漂移池周围多次移动，从而增加移动距离和离子之间的相对分离。这项研究测试了这样一个假设：在测量离子迁移率和由此得出的碰撞截面 ( ^TW CCS) 时，多次绕过电池也可以提高精度。使用气相色谱大气压化学电离对多种化合物进行了实验，其中包括 16 种多环芳烃，以及通过直接输注电喷雾电离对一组药物分子进行了实验。平均周期性漂移时间，即离子绕 cIMS 单元移动一次所需的平均时间，会发生显着变化，随着通过次数增加到~100，精度接近百万分之一 (ppm)。根据通过次数推断 CCS 值的精度，预测 50 次通过后精度将达到 1000 ppm，100 次通过后精度将达到 100 ppm，150 次通过后精度将达到 <10 ppm。通过次数超过 100 次的实验产生的^TW CCS 值的运行内精度范围为 15 至 117 ppm。随着通过次数的增加，精度得到提高，这可能是通过允许离子占据 cIMS 单元更大区域来减轻空间电荷效应的结果。提出了一种能够以 ppm 精度实际测量^TW CCS 的方法，并被证明可以表征未知的药物混合物。