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J Mass Spectrom

Title:		Evidence for electron-based ion generation in radio-frequency ionization
Author(s):		Olaitan AD; Zekavat B; Solouki T;
Address:		"Baylor University, Chemistry and Biochemistry, Waco, TX, United States"
Journal Title:		J Mass Spectrom
Year:		2016
Volume:		51
Issue:		1
Page Number:		12 - 19
DOI:		10.1002/jms.3703
ISSN/ISBN:		1096-9888 (Electronic) 1076-5174 (Linking)
Abstract:		"Radio-frequency ionization (RFI) is a novel ionization method coupled to mass spectrometry (MS) for analysis of semi-volatile and volatile organic compounds (VOCs). Despite the demonstrated capabilities of RFI MS for VOC analysis in both positive- and negative-ion modes, mechanism of RFI is not completely understood. Improved understanding of the ion generation process in RFI should expand its utility in MS. Here, we studied the possibility of electron emission in RFI using both direct charged particle current measurements and indirect electron detection in a 9.4-T Fourier transform-ion cyclotron resonance (FT-ICR) mass spectrometer. We show that RF-generated electrons can be trapped in the ICR cell and, subsequently, reacted with neutral hexafluorobenzene (C6 F6 ) molecules to generate C6 F6 (?╖+-) . Intensity of observed C6 F6 (?╖+-) species correlated with the number of trapped electrons and decreased as a function of electron quenching period. We also measured the electron attachment rate constant of hexafluorobenzene using a post-RF electron trapping experiment. Measured electron attachment rate constant of hexafluorobenzene (1.19 (+/-0.53) x 10(-9) cm(3) molecule(-1) s(-1) ) for post-RF FT-ICR MS agreed with the previously reported value (1.60 (+/-0.30) x 10(-9) cm(3) molecule(-1) s(-1) ) from low-pressure ICR MS measurements. Experimental results from direct and indirect electron measurements suggest that RFI process involves RF-generated electrons under ultrahigh vacuum conditions"
Keywords:		Cyclotrons *Electrons Equipment Design Fluorocarbons/*chemistry Fourier Analysis Ions/*chemistry Mass Spectrometry/*instrumentation Radio Waves Volatile Organic Compounds/chemistry electron attachment hexafluorobenzene mass spectrometry (MS) negative-ion;
Notes:		"MedlineOlaitan, Abayomi D Zekavat, Behrooz Solouki, Touradj eng Research Support, U.S. Gov't, Non-P.H.S. England 2016/01/13 J Mass Spectrom. 2016 Jan; 51(1):12-9. doi: 10.1002/jms.3703"