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Influence of Sample Gas Humidity on Product Ion Formation in High Kinetic Energy Ion Mobility Spectrometry (HiKE-IMS)
ACS Environmental Au ( IF 6.7 ) Pub Date : 2022-05-20 , DOI: 10.1021/jasms.2c00099
Christoph Schaefer 1 , Florian Schlottmann 1 , Ansgar T. Kirk 1 , Stefan Zimmermann 1
Affiliation  

High Kinetic Energy Ion Mobility Spectrometers (HiKE-IMS) chemically ionize gaseous samples via reactant ions and separate the generated ions by their motion in a neutral gas under the influence of an electric field. Operation at reduced pressures of 10–40 mbar allows for reaching high reduced electric field strengths (E/N) of up to 120 Td. At these high E/N, the generated ions gain the namesake high kinetic energies, leading to a decrease in cluster size of the reactant ions by increasing the reaction rate of collision-induced cluster dissociation of hydrates. In positive ion polarity and in purified air, H3O+(H2O)n, NO+(H2O)n, and O2+•(H2O)p are the most abundant reactant ions. In this work, we investigate the effect of varying sample gas humidity on product ion formation for several model substances. Results show that increasing the sample gas humidity at high E/N of 120 Td shifts product ion formation from a charge transfer dominated reaction system to a proton transfer dominated reaction system. For HiKE-IMS operated at high E/N, the reduction in cluster size of reactant ions allows ionization of analytes with low proton affinity even at high relative humidity in the sample gas of RH = 75% at 303.15 K and 1013.25 hPa. In contrast to conventional IMS, where increasing the sample gas humidity inhibits ionization for various analytes, increasing sample gas humidity in HiKE-IMS operated at 120 Td is actually beneficial for ionization yield of most analytes investigated in this work as it increases the number of H3O+(H2O)n.

中文翻译:

样气湿度对高动能离子淌度谱仪 (HiKE-IMS) 中产物离子形成的影响

高动能离子淌度谱仪 (HiKE-IMS) 通过反应离子对气态样品进行化学电离,并通过它们在电场影响下在中性气体中的运动分离生成的离子。在 10–40 mbar 的减压下运行允许达到高达 120 Td 的高降低电场强度 ( E / N )。在这些高E / N下,生成的离子获得了同名的高动能,通过增加碰撞诱导的水合物簇解离的反应速率,导致反应离子簇尺寸减小。在正离子极性和净化空气中,H 3 O + (H 2 O) n , NO+ (H 2 O) n和 O 2 +• (H 2 O) p是最丰富的反应离子。在这项工作中,我们研究了不同样气湿度对几种模型物质的产物离子形成的影响。结果表明,在 120 Td 的高E / N下增加样气湿度会使产物离子的形成从电荷转移为主的反应体系转变为质子转移为主的反应体系。用于高E / N运行的 HiKE-IMS,即使在 303.15 K 和 1013.25 hPa 的样品气体中 RH = 75% 的高相对湿度下,反应物离子簇大小的减小也允许对具有低质子亲和力的分析物进行电离。与传统 IMS 相比,增加样气湿度会抑制各种分析物的电离,在 120 Td 下运行的 HiKE-IMS 中增加样气湿度实际上有利于本工作中研究的大多数分析物的电离产率,因为它增加了 H 的数量3 O + (H 2 O) n
更新日期:2022-05-20
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