Chemical ionization negative

Mixture of reagent gases to obtain PPNICI spectra [56b] 

Ne (or Ar) Charge transfer with Nj (formation Electron capture (formation of M  

CH4 (or iC4H,o) Protonation with CHj (MH and fragment ions) Proton abstraction ([M-H] only) 

Jennings [59a] has shown that other mixtures, such as Nj (or CH ) +N2O to form 0 , may be used. These ions abstract H or according to the position of the double bond in alkene compounds. With this reagent it is possible to demonstrate if the a carbon(s) of a nitrile or ketone function is (are) secondary (or not). In this case, an intense [M-Hj] ion appears. 

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An abundant molecular ion may indicate that an aromatic compound or highly unsaturated ring compound is present. If no molecular ion is observed and one cannot be deduced, the use of chemical ionization (ci), negative chemical ionization (nci), fast atom bombardment (FAB), or electrospray ionization (ESI) should provide a molecular ion. 

Wester PG, J de Boer, UAT Brinkman (1996) Determination of polychlorinated terphenyls in aquatic biota and sediment with gas chromatography/mass spectrometry using negative chemical ionization. Environ Sci Technol 30 473-480. 

Macerated plant material is homogenized with a mixture of methanol and 1.2N hydrochloric acid (HCl) in water (4 1, v/v) and then with methanol. An internal standard solution is added to the filtrate and the filtrate is adjusted to a constant volume. A portion of the filtrate is rotary evaporated to dryness and hexane is added to the extract before a Florisil cleanup procedure is performed. The extract is dissolved in toluene for analysis by GC/MS in the negative chemical ionization (NCI) mode. 

Representative mass spectral conditions (negative chemical ionization) ion source temperature, 150°C ionizing current, 0.20 mamp electron energy, 70 eV methane reagent gas (source pressure 0.5 to 1 torr). 

McClure, TD and Liebler, DC, 1995. Electron capture negative chemical ionization mass spectrometry and tandem mass-spectrometry analysis of beta-carotene, alpha-tocopherol and their oxidation products. J Mass Spectrom 30, 1480-1488. 

Guevremont, R., R.A. Yost, and W.D. Jamieson. 1987. Identification of PCB congeners by collision-induced dissociation of [M-C1+]- from oxygen-enhanced negative chemical ionization mass spectrometry. Biomed. Environ. Mass Spectrom. 14 435-441. 

Qin BH, Yu BB, Zhang Y, Lin XC. Residual analysis of organochlorine pesticides in soil by gas chromatograph-electron capture detector (gc-ecd) and gas chromatograph-negative chemical ionization mass spectrometry (GC-NCI-MS). Environ. Forensics 2009 10 331-335. 

Imazethapyr herbicide has been determined at the pg kg-1 level in soil by microwave assisted extraction using electron capture negative chemical ionization mass spectrometry [176], A soil extract is prepared by extraction with 0.1M ammonium acetate at pHIO or 1M ammonium acetate at pH9.5. 

Parker CE, Haney CA, Hass JR. 1982. High-performance liquid chromatography-negative chemical ionization mass spectrometry of organophosphorous pesticides. J Chromatogr 237 233-248. 

Microwave-assisted extraction coupled with gas chromatography-electron capture negative chemical ionization mass spectrometry (i. e., MAE-GC-EC-NCI-MS) was described for the simplified determination of imidazolinone herbicides in soil at the ppb level [715]. 

Liquid chromatography was developed to analyze carbonyl (2,4-dinitro-phenyl) hydrazones with detection by diode array ultraviolet spectroscopy (DA-UV) and by atmospheric pressure negative chemical ionization (APNCI) mass spectrometry [716]. In addition, LC can be combined with electrospray ionization coupled on-line with a photolysis reactor for better detection and confirmation of photo degradation products [717]. 

Bndzikiewicz, H. Studies in Negative Ion Mass Spectrometry. XI. Negative Chemical Ionization (NCI) of Organic Compounds. Mass Spectrom. Rev. 1986, 5, 345-380. 

Kim Y-S, Zhang H, Kim H-Y. 2000. Profiling neurosteroids in cerebrospinal fluids and plasma by gas chromatography/ electron capture negative chemical ionization mass spectrometry. Anal Biochem 277 187. 

Vallee M, Rivera JD, Koob GF, Purdy RH, Fitzgerald RL. 2000. Quantification of neurosteroids in rat plasma and brain following swim stress and aUopregnanolone administration using negative chemical ionization gas chromatography/ mass spectrometry. Anal Biochem 287 153. 

Hidalgo OH, Lopez MJ, Carazo EA, Larrea MSA, Reuvres TBA. 2003. Determination of dexamethasone in urine by gas chromatography with negative chemical ionization. J Chromatogr B 788 137. 

Fitzgerald RL, Herold DA. 1996. Serum total testosterone immunoassay compared with negative chemical ionization gas chromatography—mass spectrometry. Clin Chem 42 749-755. 

GC = gas chromatography EC = electrochemical (detector ECD = electron capture (detector HCD = Hall conductivity detector HFBA = heptafluorobutyric anhydride HPLC = high performance liquid chromatography NCI-MS = mass spectrometry in the negative chemical ionization mode NPD = nitrogen-phosphorus detector ppb = parts per billion UV = ultraviolet absorption SPE = solid phase extraction wt wt = weight weight... 

An ion containing unpaired electrons in its ground state Electron impact ionization Positive chemical ionization Negative chemical ionization... 

The Finnegan single stage quadrupole powers a very flexible system for several analytical problems. The user has a choice of electron ionization positive chemical ionization or negative chemical ionization. The Quadrupole can be Hnked to gas or Hquid chromatography and several direct insertion probes. The data features powerful, multilayered software using high performance workstations, that make data analysis and instrument control easy. 

A recent review [laj emphasizes the complexity of air pollutant samples and describes some of the techniques which have been recently developed for their analysis. Among these are a number of alternate ionization techniques for mass spectrometry. Positive and negative chemical ionization mass spectrometry (CIMSj are analytical tools which can provide significant assistance in solving these problems. Their application in a number of air pollution studies are discussed in this chapter. 

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