Organic silicon compounds, electron impact

ELECTRON IMPACT IONIZATION OF ORGANIC SILICON COMPOUNDS... 

Electron Impact Ionization of Organic Silicon Compounds, Rolf Basner, Martin Schmidt, Hans Deutsch and Kurt Becker... 

Different capillary columns are available for organic acid separation and analysis. In our laboratory, the gas chromatography column in all GC-MS applications is crosslinked 5% phenyl (poly)methyl silicone, 25 m internal diameter 0.20 mm stationary phase film thickness 0.33 pm (Agilent HP-5, DB-5, or equivalent). Several instrument configurations are commercially available, which allow for positive identification of compounds by their mass spectra obtained in the electron impact ionization mode. A commercially available bench-top GC-MS system with autosampler (Agilent 6890/5973, or equivalent) is suitable. Software for data analysis is available and recommended. The use of a computer library of mass spectra for comparison and visualization of the printed spectra is required for definitive identification and interpretation of each patient specimen. 

Some compounds can be easily detected by both CGC and high-pressure liquid chromatography (HPLC), for instance, cocaine, which has characteristic electron-impact mass and UV fluorescence spectra (Fernandez et al., 2009). Inert nonpolar or low-polar silicone phases have chromatographic features suitable for separation and analysis by CGC. In addition, dedicated base-treated stationary phases are now used to improve the identification and quantification of compoimds. HPLC analyses are done by reversed-phase elution with buffered water/organic solvent mixtures. In contrast, numerous native drags and almost all metabolites require chemical derivatization before analysis [e.g., with trifluoroacetic anhydride, A -methyl-7V-trimethylsilyltrifluoroacetamide, or iV-(r-butyldimethylsilyl)-Af-methyltrifluoroacetamide, which is usually used for cannabinoids] this improves the analytical performance of the method and drastically reduces the risk of misinterpretation and misidentification of the compoimds. 

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