Faculty of Advanced Technologies and Chemistry, Military University of Technology, ul. gen. Sylwestra Kaliskiego 2, 00-908 Warsaw, Poland.
Anal Chem. 2023 Jun 6;95(22):8505-8511. doi: 10.1021/acs.analchem.3c00435. Epub 2023 May 23.
Ions in the ion mobility spectrometry (IMS) are mostly hydrated. A single peak in the drift time spectrum is usually generated by a mixture of ions differing in the number of attached water molecules. Under real IMS detector operating conditions, ions change their composition during movement in the drift region due to the changes in the number of water molecules attached to the ion. The impact of water vapor on the drift times of small ions at different temperatures was studied experimentally using an ion mobility spectrometer. The experiments were carried out for hydronium, ammonium, oxygen, chloride, bromide, and iodide ions. A theoretical model was developed, allowing us to calculate the effective mobility of ions for a given concentration of water vapor and temperature. The basic assumption adopted in this model was the linear dependence of the effective mobility coefficient on the mobility of ions with a certain degree of hydration. The weighting factors in this relationship are the abundances of individual types of ions. These parameters were determined by calculations based on the thermodynamics of the formation and disintegration of ionic clusters. From the known values of temperature, pressure, and humidity, the values of effective mobilities can be predicted quite accurately. The dependencies of reduced mobilities on the average degree of hydration were also determined. For these dependencies, the measurement points on the graphs are gathered along specific lines. This means that the average degree of hydration unambiguously determines the value of reduced mobility for a given type of ions.
在离子淌度谱（IMS）中，离子大多是水合的。在漂移时间谱中，单个峰通常是由附着水分子数量不同的离子混合物产生的。在实际 IMS 检测器工作条件下，由于附着在离子上的水分子数量的变化，离子在漂移区运动时会改变其组成。本研究使用离子淌度谱仪实验研究了水蒸气对不同温度下小离子漂移时间的影响。实验针对水合氢离子、铵离子、氧离子、氯离子、溴离子和碘离子进行。建立了一个理论模型，允许我们根据水蒸气浓度和温度计算离子的有效迁移率。该模型的基本假设是有效迁移系数与一定程度水合的离子迁移率呈线性关系。该关系中的权重因子是各种类型离子的丰度。这些参数是基于离子簇形成和解体的热力学计算确定的。从已知的温度、压力和湿度值，可以相当准确地预测有效迁移率的值。还确定了减少迁移率与平均水合度的关系。对于这些关系，图上的测量点沿着特定的线聚集。这意味着对于给定类型的离子，平均水合度明确地决定了减少迁移率的值。
