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Classical electron ionization mass spectra in gas chromatography/mass spectrometry with supersonic molecular beams
Author(s) -
Gordin Alexander,
Fialkov Alexander B.,
Amirav Aviv
Publication year - 2008
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.3654
Subject(s) - chemistry , mass spectrometry , electron ionization , ion source , ionization , mass spectrum , analytical chemistry (journal) , ion , chemical ionization , polyatomic ion , chromatography , organic chemistry
Abstract A major benefit of gas chromatography/mass spectrometry (GC/MS) with a supersonic molecular beam (SMB) interface and its fly‐through ion source is the ability to obtain electron ionization of vibrationally cold molecules (cold EI), which show enhanced molecular ions. However, GC/MS with an SMB also has the flexibility to perform ‘classical EI’ mode of operation which provides mass spectra to mimic those in commercial 70 eV electron ionization MS libraries. Classical EI in SMB is obtained through simple reduction of the helium make‐up gas flow rate, which reduces the SMB cooling efficiency; hence the vibrational temperatures of the molecules are similar to those in traditional EI ion sources. In classical EI‐SMB mode, the relative abundance of the molecular ion can be tuned and, as a result, excellent identification probabilities and very good matching factors to the NIST MS library are obtained. Classical EI‐SMB with the fly‐through dual cage ion source has analyte sensitivity similar to that of the standard EI ion source of a basic GC/MS system. The fly‐through EI ion source in combination with the SMB interface can serve for cold EI, classical EI‐SMB, and cluster chemical ionization (CCI) modes of operation, all easily exchangeable through a simple and quick change (not involving hardware). Furthermore, the fly‐through ion source eliminates sample scattering from the walls of the ion source, and thus it offers full sample inertness, tailing‐free operation, and no ion‐molecule reaction interferences. It is also robust and enables increased column flow rate capability without affecting the sensitivity. Copyright © 2008 John Wiley & Sons, Ltd.