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Anal Chem

Title:		Manipulation of Ion Conversion in Dichloromethane-Enhanced Vacuum Ultraviolet Photoionization Mass Spectrometry of Oxygenated Volatile Organic Compounds
Author(s):		Yu Y; Jiang J; Hua L; Xu Y; Chen C; Chen Y; Li H;
Address:		"CAS Key Laboratory of Separation Science for Analytical Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, People's Republic of China. University of Chinese Academy of Sciences, Beijing 100049, People's Republic of China. Liaoning Key Laboratory for Mass Spectrometry Technology and Instrumentation, Dalian 116023, People's Republic of China"
Journal Title:		Anal Chem
Year:		2023
Volume:		20230815
Issue:		34
Page Number:		12940 - 12947
DOI:		10.1021/acs.analchem.3c02644
ISSN/ISBN:		1520-6882 (Electronic) 0003-2700 (Linking)
Abstract:		"The ion conversion processes in CH(2)Cl(2)-enhanced vacuum ultraviolet photoionization of oxygenated volatile organic compounds (OVOCs) have been systematically studied by regulating the pressure, humidity, and reaction time in the ionization source of a time-of-flight mass spectrometer. As the ionization source pressure increased from 100 to 1100 Pa, the main characteristic ions changed from CH(2)Cl(+) to CH(2)Cl(+)(H(2)O), CH(2)OH(+), and C(2)H(4)OH(+) and then to the hydrated hydronium ions H(3)O(+)(H(2)O)(n) (n = 1, 2, 3). The total ion current (TIC) almost remained unchanged even if the humidity increased from 44 to 3120 ppmv, indicating interconversion between ions through ion-molecule reactions. The intensity of protonated methanol/ethanol (sample S) ion was almost linearly correlated with the intensity of H(3)O(+)(H(2)O)(n), which pointed to the proton transfer reaction (PTR) mechanism. The reaction time was regulated by the electric field strength in the ionization region. The intensity variation trends of different ions with the reaction time indicated that a series of step-by-step ion-molecule reactions occurred in the ionization source, i.e., the primary ion CH(2)Cl(+) reacted with H(2)O and converted to the intermediate product ions CH(2)OH(+) and C(2)H(4)OH(+), which then further reacted with H(2)O and led to the production of H(3)O(+), and finally, the protonated sample ion SH(+) was obtained through PTR with H(3)O(+), as the ion-molecule reactions progressed. This study provides valuable insights into understanding the formation mechanism of some unexpected intermediate product ions and hydrated hydronium ions in dopant-enhanced VUV photoionization and also helps to optimize experimental conditions to enhance the sensitivity of OVOCs"
Keywords:
Notes:		"PubMed-not-MEDLINEYu, Yi Jiang, Jichun Hua, Lei Xu, Yiqian Chen, Chuang Chen, Yi Li, Haiyang eng 2023/08/15 Anal Chem. 2023 Aug 29; 95(34):12940-12947. doi: 10.1021/acs.analchem.3c02644. Epub 2023 Aug 15"