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Structure of the Cluster Ions of Ketones in the Gas Phase According to Ion Mobility Spectrometry and Ab Initio Calculations

Investigation of the state of volatile organic compounds such as ketones in the gas phase has become an active area of fundamental and applied research. Rationalization of ionization, charge transfer, cluster formation, and hydration is very important in physical and structural chemistry, biochemistry, and development of analytical procedures (ion mobility and mass spectrometry).

Ion mobility spectrometry is used to describe the ion drift in the gas phase under the action of an electric field across the chamber filled with a gas. Ions with different structures have different scattering cross sections in a gas and hence different drift rates [1, 2]. Ion mobility spectrometry is currently used to solve many applied problems such as foodstuffs quality analysis [3, 4], explosives detection [5], and medical diagnostics [6]. The equilibrium gas phase over the aqueous solutions of volatile organic components can be regarded as a model of biological assays, e.g., exhaled air because of its close composition and humidity [6, 7].

Ion mobility spectrometry combined with mass spectrometry is a powerful method for analysis of complex mixtures and structural analysis in addition to X-ray diffraction and NMR [8–12]. An analysis of ion mobility spectra also allows one to solve the fundamental problems: structure determination of complex molecules [13] and atomic clusters [14, 15] and studies of the space charge effect on the shape of the ion spectrum [16, 17].

Studies of homologous series [18–20] reveal the correlation between the molecular mass and ion mobility of organic compounds in the gas phase. Ab initio quantum-chemical simulations allow verification of assumptions on the molecular, ion, and cluster structure, charge transfer, cluster formation, and hydration [21] based on the experimental ion mobilities. The approach to structure determination based on comparison of the values calculated theoretically with those calculated from experimental data is most correct.

Our previous communication [20] reported on the structure of the dimer and monomer ions formed by aldehydes in the gas phase by ion mobility spectrometry combined with ab initio quantum-chemical calculations. The present communication is devoted to a study of the state of ionized ketones during their drift in an ion mobility spectrometer.

Structure of the Cluster Ions of Ketones in the Gas Phase According.pdf

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