Negative ion chemical ionisation

M. Kala, M. Kochanowski. The Determination of A9-Tetrahydrocannabinol (9THC) and 11-nor-9-Carboxy-A9-Tetrahydrocannabinol (THCCOOH) in Blood and Urine Using Gas Chromatography Negative Ion Chemical Ionisation Mass Spectrometry (GC-MS-NCI), Chemical Analysis (Warsaw), 51, 2006. 

Niederer [100] used ion trap mass spectrometry and negative ion chemical ionisation to determine nitro- and oxypolyaromatic hydrocarbons in soils. Meyer et al. [101] have described a simple and reproducible method which provides the simultaneous determination of polycyclic aromatic hydrocarbons and het-eropolycyclic aromatic hydrocarbons (N, S, O) and their metabolites in contaminated soils. Contaminants extracted from the soil sample were separated by polarity and acid-base characteristics using solid-phase extraction on silica gel and a strong basic anion exchange material. A subfraction containing PANHs and neutral metabolites was subsequently fractionated into neutral and basic... 

Yu Ma and Bayne [198] differentiated different aroclors in soil using linear discrimination and analyses by electron-capture negative-ion chemical ionisation mass spectrometry. 

Chemical ionisation, electron impact ionisation and field ionisation have been used to obtain molecular fragmentation patterns in speciation studies involving GC-MS. However, the systems used often lacked sensitivity. This area has expanded recently as inexpensive, smaller and more sensitive instruments have become available (Zufiaurre et al., 1997). Tributyl tin and triphenyl tin compounds have recendy been determined in seawater using GC negative ion chemical ionisation MS (Mizuishi et al., 1998). Of particular interest are those mass spectrometers in which the sample is broken down into elemental form. 

Mizuishi, K., Takeuchi, M. and Hobo, T. (1998) Trace metal analysis of tributyltin and triphenyltin compounds in seawater by gas chromatography-negative ion chemical ionisation mass spectrometry./. Chromatogr. A, 800, 267-273. 

Barcelo [13] characterised selected pesticides by negative ion chemical ionisation thermospray high performance liquid chromatography-mass spectrometry. Ions observed... 

Ethylene thiourea Negative ion chemical ionisation Derivativisation with 3,5 bis (trifluoromethyl) benzyl bromide 50ppt [345]... 

Ethylene, Elexane dibromide, 1,2 dibromo-3-chloropropane Negative ion chemical ionisation GC-MS using isobutane as reagent gas 0.1 P [43]... 

Gas Chromatography-Mass Spectrometry Negative-ion chemical ionisation mass spectrom-etry is the best method to identify a wide range of synthetic corticosteroids in horse urine (E. Houghton et at, Biomed. Mass Spectrom., 1982, 9, 459-465). Method. Extract 10 ml of urine with 25 ml of methylene chloride, separate the solvent layer, dry over anhydrous sodium sulphate, and evaporate to dryness in a rotary film evaporator at 30° to 40°. Heat the residue with 100 p.1 of an 8% solution of methoxyamine hychochloride in dry pyridine in a reaction tube at 80° for 30 minutes, add 50 pi of trimeOiylsilylimidazole, [Pg.98]

The combination of both modes of operation, positive and negative offers complementary information. This is why most modern instruments offer the possibihty of recording what is known as a PPINICI spectrum, the acronym being derived from pulsed positive ion/ negative ion chemical ionisation. This method allows for the automated quasi-simultaneous recording of positive ion and negative ion spectra. 

Hubbard, W. C., Hundley, T. R., Oriente, A. and MacGlashan, D. W. Jr (1996) Quantitation of l-stearoyl-2-arachidonoyl-5Ai-3-glycerol in human basophils via gas chromatography-negative ion chemical ionisation mass spectrometry. Anal Biochem., 236, 309-21. 

Kallio, H. and Currie, G. (1993a) Analysis of low erucic acid turnip rapeseed oil (Brassica campesteris) by negative ion chemical ionisation tandem mass spectrometry. A method giving information on the fatty acid composition in positions sn-2 and sn- /3 of triacylglycerols. Lipids, 28, 207-15. 

Laakso, P. and Kallio, H. (1996) Optimization of the mass spectrometric analysis of triacylglycerols using negative ion chemical ionisation with ammonia. Lipids, 31, 33-42. 

Schweer, H., Watzer, B. and Seyberth, H. W. (1994) Determination of seven prostanoids in 1 ml of urine by gas chromatography-negative ion chemical ionisation triple stage quadrupole mass spectrometry. J. Chromatogr. B, 652, 221-7. 

LAS and dialkyltetralin sulphonates are converted to their sulphonyl chlorides by reaction with phosphorus pentachloride and then to their trifluoroethyl derivatives by reaction with trifluoroethanol. These derivatives are separated on a 15 m x 0.25 mm i.d. (0.25 micron film) of DB-5 temperature programmed from 125°C (1 min) to 230°C at 5°C per min with a final hold of 5 min. Helium is the carrier gas and detection is by negative-ion chemical ionisation mass spectrometry [3]. 

Nevertheless, scanned mass spectra may not give the entire information due to the loss of molecular ions (e.g., esters). In this case, the application of chemical ionisation (Cl) mode using reagent gases in GC-MS will provides valuable additional information. For sesquiterpenes, the use of ammonia is superior to isobutane. An additional method is negative ion chemical ionisation (NCI) with OH as the reactant ion can be used [56,57]. 

Bowadt, F.E. et al (1993) Combined positive and negative ion chemical ionisation for the analysis of PCB S, in ISth International Symposium on Capillary Chromatography, Riva del Garda, May 1993 (ed. P. Sandra), Huethig. 

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