Electron-impact chromatography-mass

J.J. Jimenez, J.L. Bernal, S. Aumente, M.J. delNozal, M.T. Martin, J. Bernal, Quality assurance of commercial beeswax I. Gas chromatography electron impact ionization mass spectrometry of hydrocarbons and monoesters, Journal of Chromatography A, 1024, 147 154 (2004). 

The electron impact ionization mass spectrum of cortisone acetate was obtained using solid probe introduction, using a Shimadzu QP-Class-5000 gas chromatography mass spectrometer system. The most prominent ions observed, and their relative intensities, are shown in Table 6. 

Gas Chromatography Coupled with Electron Impact Ionisation Mass Spectrometry... 

GC-EI-MS gas chromatography coupled with electron impact ionization mass spectrometry... 

The emphasis of this work is on the analysis of plastic additives through gas chromatography/mass spectrometry (GC/MS). GC/MS systems are a common analytical tool in quality control and analytical service laboratories and electron impact (El) mass spectra are recognized as reliable data for the identification of organic compounds. Traditional methods have employed a flame ionization detector (FID) with identifications based solely on GC retention time data. These methods lack the specificity necessary to distinguish between components attributable to the sample matrix or the additive(s). 

Capillary gas chromatography-mass spectrometry is being used to separate and measure the trimethylsilyl (TMS) ethers of organic acids. A capfilary GC column is used that contains an immobilized nonpolar stationary phase. Organic acids are detected by electron impact (El) mass spectrometry performed in the scan mode m/z 50 to m/z 550 to obtain mass spectra. Identification is by comparison to a library of spectra generated by analysis of pure standard compounds integrated by published spectra, when applicable. 

Fig. 11. Comparison of electron impact (El) mass spectrum of the 380/440-400/460 fluorophore and xanthopterin from gas chromatography using trimethylsily (TMS) derivatives base peak, fragment with greatest intensity M+, TMS-molecular ion. Arabic numbers represent the mass/charge ratio (m/z). (R. W. Williams et alunpublished data, 1990.)...

Nieto R, Calder AG, Anderson SE, et al. 1996. Method for the determination of 15NH3 enrichment in biological samples by gas chromatography electron impact ionization mass spectrometry. J Mass Spectrom 31(3) 289-294. 

Moldovan, Z., lover, E., Bayona, J. M. (2002). Systematic characterisation of long-chain aliphatic esters of wool wax by gas chromatography-electron impact ionisation mass spectrometry. Journal of Chromatography A, 952(1-2), 193-204. 

Figure 2 Traces obtained from simultaneous gas chromatography analysis of Maillard headspace, using both API and EIMS detectors. API, atmospheric pressure ionization El, electron impact MS, mass spectrometry.

An on-line chromatography/atmospheric pressure chemical ionization tandem mass spectrometry (LC-APCI/MS/MS) methods was developed for rapid screen of pharmacokinetics of different drugs, including 5 (98RCM1216). The electron impact mass spectrum of 5 and ethyl 9,10-difluoro-3-methyl-7-oxo-2,3-dihydro-7Ff-pyrido[l,2,3- fe]-l,4-benzoxazine-6-carboxylate was reported (97MI28). Electron impact/Fourier transform... 

Chromatography is typically at atmospheric pressure while source pressures in the mass spectrometer are in the range of 2 to 10 Torr for chemical and electron impact ionization, respectively. The interface must be capable of providing an adequate pressure drop between the two instruments and should also maximize the throughput of seuaple idiile maintaining a gas flow rate compatible with the source operating pressure. Further, the Interface should not introduce excessive dead volume at the column exit and should not degrade or modify the chemical constitution of the sample. 

Purdon JG, Pagotto JG, Miller RK. 1989. Preparation, stability, and quantitative analysis by gas chromatography and gas chromatography-electron impact mass spectrometry of tert-butyldimethylsilyl derivatives of some alkylphosphonic and alkyl methylphosphonic acids. J Chromatogr 475 261-272. 

Mass spectrometry is used to identify unknown compounds by means of their fragmentation pattern after electron impact. This pattern provides structural information. Mixtures of compounds must be separated by chromatography beforehand, e.g. gas chromatography/mass spectrometry (GC-MS) because fragments of different compounds may be superposed, thus making spectral interpretation complicated or impossible. To obtain complementary information about complex mixtures as a whole, it may be advantageous to have only one peak for each compound that corresponds to its molecular mass ([M]+). Even for thermally labile, nonvolatile compounds, this can be achieved by so-called soft desorption/ionisation techniques that evaporate and ionise the analytes without fragmentation, e.g. matrix-assisted laser desorption/ionisation mass spectrometry (MALDI-MS). 

Analysis of pesticides (eight in total, namely, molinate, propanil, fenitrothion, malathion, bentazone, cypermetrine, maloxon, and fenitrothion oxon) in biota was accomplished with a method based on pressurized liquid extraction (ASE), followed by SPE clean-up, and analysis by gas chromatography-mass spectrometry with electron impact ionization (GC/MS-EI). 

The carbinolamine metabolite 64 was unstable in organic solvents and on routine chromatography. It was impossible to obtain molecular ions in the mass spectra by electron impact, chemical ionization, Held desorption, or fast-atom bombardment techniques. The apparent molecular ion occurred at m/e 456, consistent with a carbinolamine such as 64, which eliminates water to form an [M — 18] peak. The H-NMR spectrum of this metabolite was similar to that of... 

Note. Abbreviations g.l.c., gas-liquid chromatography e.i.-m.s., electron-impact mass spectrometry c.i.-m.s., chemical-ionization mass spectrometry h.p.l.c., high-performance liquid chromatography h.p.a.e., high pH anion-exchange f.a.b.-m.s., fast-atom-bombardment mass spectrometry l.s.i.-m.s., liquid secondary-ion mass spectrometry n.O.e., nuclear Overhauser enhancement. Details of these methodologies are given in Ref. (3). 

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