Department of Chemistry, Indiana University, Bloomington, Indiana 47405, United States.
Anal Chem. 2015;87(10):5132-8. doi: 10.1021/ac504555u. Epub 2015 Apr 30.
A new means of acquiring overtone mobility spectrometry (OMS) data sets that allows distributions of ions for a prescribed overtone number is described. In this approach, the drift fields applied to specific OMS drift regions are varied to make it possible to select different ions from a specific overtone that is resonant over a range of applied frequencies. This is accomplished by applying different fields for fixed ratios of time while scanning the applied frequency. The ability to eliminate peaks from all but a single overtone region overcomes a significant limitation associated with OMS analysis of unknowns, especially in mixtures. Specifically, a priori knowledge via selection of the overtone used to separate ions makes it possible to directly determine ion mobilities for unknown species and collision cross sections (assuming that the ion charge state is known). We refer to this selection method of operation as selected overtone mobility spectrometry (SOMS). A simple theoretical description of the SOMS approach is provided. Simulations are carried out and discussed in order to illustrate the advantages and disadvantages of SOMS compared with traditional OMS. Finally, the SOMS method (and its distinction from OMS) is demonstrated experimentally by examining a mixture of peptides generated by enzymatic digestion of the equine cytochrome c with trypsin.
一种新的获取泛音移动谱（OMS）数据集的方法，该方法允许为指定的泛音数分配离子分布。在这种方法中，改变施加到特定 OMS 漂移区域的漂移场，使得可以从在应用频率范围内共振的特定泛音中选择不同的离子。这是通过在扫描应用频率的同时，以固定的时间比施加不同的场来实现的。消除除单个泛音区域之外的所有峰的能力克服了与 OMS 对未知物分析相关的一个重大限制，特别是在混合物中。具体来说，通过选择用于分离离子的泛音，可以预先了解离子的迁移率和碰撞截面（假设离子电荷状态已知）。我们将这种操作的选择方法称为选择泛音迁移谱（SOMS）。提供了对 SOMS 方法的简单理论描述。进行了模拟并进行了讨论，以说明与传统 OMS 相比，SOMS 的优缺点。最后，通过检查用胰蛋白酶酶解马细胞色素 c 生成的肽混合物，实验证明了 SOMS 方法（及其与 OMS 的区别）。
