Electron impact ionization library searches

Based on a new technology, particle beam enhanced liquid chromatography-mass spectrometry expands a chemist s ability to analyse a vast variety of substances. Electron impact spectra from the system are reproducible and can be searched against standard or custom libraries for positive compound identification. Chemical ionization spectra can also be produced. Simplicity is a key feature. A simple adjustment to the particle beam interface is all it takes. 

Gas Chromatography-Mass Spectrometry. A VG Trio-2 mass spectrometer was directly coupled with the Hewlett-Packard 589 R gas chromatograph, equipped with a 30 m x 0.32 mm DB-WAX capillary column (J and W. Scientific bonded polyethylene glycol phase). The carrier gas was He at 2.3 ml/min. The injector and transfer temperature was programmed as follows 30 C (2 min isothermal), to 38°C at l°C/min, then to 180°C at 2°C/min. The instrument was operated in the electron-impact mode at an ionization voltage of 70eV. Quantitative analysis by peak area, plots of chromatograms, and library search results were obtained. 

The application of mass spectrometry, including electron impact (El) studies, to the analysis of hydrocarbon fractions obtained from petroleum is as old as the earliest exploitation of the technique. Almost all of the ionization methods known have been applied to saturated hydrocarbons. The number of papers dealing with one or another aspect of the MS of alkanes and cycloalkanes is enormous. However, the computerized compilation of the mass spectra in libraries such as NBS makes the search easier ... 

Qian et al carried out a rapid identification of polymers using a technique based on ion source direct pyrolysis mass spectrometry and library searching. Polymers were pyrolysed using a coiled filament designed for desorption chemical ionization/desorption electron ionization applications. Pyrolysis products were ionized at 70 ev electron impact. This yielded highly reproducible spectra characteristic of the polymer. Using these techniques and library searching a comprehensive library of 150 polymers was developed. 

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