JMSSJ On-line

JMSSJ On-line, Vol. 49 (2001) No. 5, pp. 201-206

A New GC/MS System Equipped with a Supersonic Molecular Beam Sample Introduction System		>> Full Text PDF >> References
*Ai TAHARA^a), Hiroshi KISHI^a), and Toshihiro FUJII^b)** ^a) Department of Materials Chemistry and Bioengineering, Oyama National College of Technology (771 Nakakuki, Oyama, Tochigi 323-0806, Japan)* ^b) Department of Chemical Environment, National Institute for Environmental Studies (16-2 Onogawa, Tsukuba, Ibaraki 305-0053, Japan)

The effect of vibrational supercooling in supersonic molecular beam (SMB) on the electron impact mass spectrometry (EIMS) was demonstrated for a number of organics, (i) hydrocarbons, (ii) monoterpenes, and (iii) fatty acid esters. With SMB/EIMS, all of these compounds showed enhanced molecular ion intensities whereas the fragment ion intensities were greatly suppressed. Effect of electron impact energy was also examined. With increase in electron energy, fragment ion intensity increased for (i) hydrocarbon and (ii) aliphatic alcohol, whereas fatty acid methyl ester showed opposite behavior. At 20 eV, peak intensities of McLafferty rearrangement (m/z 74) and molecular ion were 100% and 55%, respectively, whereas at 70 eV, they were 25% and 100%, respectively. Sensitivity for GC/MS mode was also examined.

Key words: Molecular ion intensity enhancement, Supersonic molecular beam, Vibrational supercooling, Electron ionization, Gas chromatography/mass spectrometry.