Negative chemical ionisation

Table 5.4.4 Characteristic negative chemical ionisation mass fragments for pentafluorobenzyl bromide-trimethylsilylimidazole (TMSi)derivatives of known BAs (reprinted from [18])...

Derivatised GA and Cr are measured by GC-MS by the injection of 1 pi into the GC-MS system operating in the negative chemical ionisation mode. The injection temperature is 250°C, the transfer line temperature is 260°C and the oven temperature is programmed starting at 100°C for 1 min followed by a linear ramp of 5°C/min to 260°C. A mixture of 95% methane, 5% ammonia is used as reagent gas. A polar GC column (e.g. SGE, BPX-70) is used to allow proper chromatography, which is neces-... 

Examples of this type of herbicide are imazapyr, m-imazamethabenz, p-imazamethabenz, m,p-imazamethabenzmethyl, imazethapyr and imazaquin. Imazapyr has been determined at the xg/kg level in 0.1 M ammonium acetate extracts of soil by microwave-assisted extraction using electron capture negative chemical ionisation mass spectrometry [432]. High-performance liquid chromatography with UV detection at 250 nm has been used to determine imazapyr in methanol extracts of soil [433]. 

Dougherty, R. C. (1981). Negative chemical ionisation mass spectrometry. Anal. Chem. 53, 625A-636A. 

Stan, H. J., and Scheutwinkel-Reich, M. (1980). Detection of hydroxy fatty acids in biological samples using capillary gas chromatography in combination with positive and negative chemical ionisation mass spectrometry. Lipids 15, 1044-1050. 

Zakett, D., Ciupek, J. D., and Cooks, R. G. (1981). Determination of polycyclic aromatic hydrocarbons in solvent-refined coal by negative chemical ionisation-charge inversion mass spectrometry/mass spectrometry. Anal. Chem. 53, 723-726. 

Xiao, X.-Y. McCaUey, D.V. McEvoy, J. Analysis of estrogen in river water and effluents using solid-phase extraction and gas chromatography-negative chemical ionisation mass spectrometry of the pentafluorobenzyl derivatives. J. Chromatogr., A 2001, 923, 195-204. 

It is interesting to note that the very natm e of Cl, namely to produce low energy ions, renders negative chemical ionisation a very useful technique. Unlike El, Cl allows for the generation of stable negative ion species. The ionisation processes that take place are similar to those just described actually they are their electronic counterpart as evidenced by equations (17) through (21). 

Castells P, Santos EJ, Galceran MT (2004) Solid-phase extraction versus solid-phase microextraction for the determination of chlorinated paraffins in water using gas chromatography-negative chemical ionisation mass spectrometry. J Chromatogr A 1025 157-162... 

In summary, for the many applications with a limited (100-300 Da) mass range, rapid-scanning qMS is a useful alternative to ToF MS. Peak skewing issues have to be carefully monitored to ensure proper identification and may require the use of specific mass spectral libraries. Several qMS systems also offer the option of doing negative chemical ionisation (NCI) in addition to electron... 

Gallon, A. A. and Pryor, W. A. (1993) The identification of the allylic nitrite and nitro derivatives of methyl linoleate and methyl linolenate by negative chemical ionisation mass spectrometry. Lipids, 28, 125-33. 

Kuksis, A., Marai, L. and Myher, J. J. (1991a) Reversed phase liquid chromatography-mass spectrometry of complex mixtures of natural triacylglycerols with chloride attachment negative chemical ionisation. J. Chromatogr., 588, 73-87. 

Hendriks, H., Bos, R., and Bruins, A.P. 1985. Analysis of the essential oil Eupatorium can-nabiuam by combined gas chromatography—mass spectrometry using electron impact and negative chemical ionisation. Planta Medica, 51, 541-542. 

The Cobalt Triad. - Oxidative addition reactions between hydrocarbon radicals and complexed cobalt(II) centres in the gas phase have been studied using negative chemical ionisation mass spectrometry. The gas-phase chemistry of Co with a series of 1-chloro-n-alkanes and alcohols has been investigated, and it has been found that for RCl, as the chain length increases, Co insertion into internal C-C bonds becomes preferred to insertion... 

Stan, H.-J. and Kellner, G. (1981) Analysis of organophosphoric pesticide residues in food by GC-MS using positive and negative chemical ionisation, in Recent Developments in Food Analysis (eds W. Bakes, P.B. Czedik-Eysenberg, and W. Pfannhauser), Verlag Chemie, Weinheim. 

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