Electron capture negative ionization

Dirtu AC, Roosens L, Geens T, Gheorghe A, Neels H, Covad A (2008) Simultaneous determination of bisphenol A, triclosan, and tetrabromobisphenol A in human serum using solid-phase extraction and gas chromatography-electron capture negative-ionization mass spectrometry. Anal Bioanal Chem 391 1175-1181... 

During the analysis of PBDE in the particle phase of atmosphere samples from various sites in the United States, Hoh et al. [60] noticed a significant, unknown, bromine-containing gas chromatographic (GC) peak in some samples. To identify this unknown substance, full-scan mass spectra were obtained in both electron-impact and electron-capture negative ionization modes. Based on this analysis, it was suspected that this GC peak might be... 

Reported recovery and precision were generally good for measurements in air and gaseous waste emissions (Cooke et al. 1988 Fairless et al. 1987 Oehme et al. 1986), but severe sample loss can occur (Bingham et al. 1989 Rappe et al. 1988). Electron capture, negative ionization, low resolution MS has also been used to quantify CDDs in ambient air however, 2,3,7,8-TCDD is difficult to detect using this method and results must be confirmed with HRGC (Koester et al. 1992). 

ECNI-MS electron-capture negative ionization-mass spectrometry... 

In this section only the most recent methods (post 1990) for extraction and quantitative determination of PCAs in commercial products and environmental samples are discussed. While extraction and isolation techniques have relied mainly on techniques already developed for POPs, there have been major advances in the quantification of PCAs using gas chromatography mass spectrometry in electron capture negative ionization mode (GC-ECNIMS). No attempt will be made to discuss older methods of analysis such as thin-layer chromatography [13,50], and neutron activation methods [51]. 

GC-coupled mass spectrometry with electron ionization (EI-MS) or with electron capture, negative ionization (ECNI-MS), and GC with electron capture detection (ECD) have been the major techniques for the analysis of aryl methyl sulfone fractions isolated from tissue (Sect. 5.1). GC/ECD detection and identification of MeS02-PCBs relies on a comparison of GC retention times relative to authentic standards, which is dependent on the absence of co-eluting interfe-rents. GC/MS techniques have provided important structural information for MeS02-PCBs, especially in the absence of authentic standards. 

Lee et al. [41] developed a method for the quantitative analysis of enantiomers and regioisomers of fatty acids, hydroxy fatty acids, and related substances, including several HETEs and prostaglandins. The method is based on pre-column derivatization to pentafluorobenzyl derivatives and subsequent LC-MS analysis in an organic mobile phase using electron-capture negative-ionization (ECNI). The method is applied to lipidomic profiling, for instance of rat epithehal cells. 

ECD = electron capture detection ECNI = electron capture negative ionization HRGC = high resolution gas chromatography MS = mass spectrometry... 

Owing to their high electronegativity, detection of CPs is usually achieved either by electron capture or by mass spectrometric detectors. While electron ionization (El) has been applied to the analysis of CPs, electron capture negative ionization (ECNl) has been used much more frequently. This section will cover detection methods that have been used in CP analysis. 

Fig. 7 Electron capture negative ionization (ECNI) mass spectrum of pentachlorodecane [60]...

Moore S, Vromet L, Rondeau B (2004) Comparison of metastable atom bombardment and electron capture negative ionization for the analysis of polychloroaUcanes. Chemosphere 54 453 59... 

In electron capture negative ionization, thermal electrons are generated by colhsion of electrons emitted from the filament with buffer gas molecules located at high pressure in the ionization chamber of the source. 

Others. El, electron impact ionization ECNI, electron capture negative ionization HR, high resolution LR, low resolution LVI, large volume injection PICI, positive ion chemical ionization. 

Zhu, J., M. J. Mulvihil R. J. Norstrom, 1994. Characterization oftechnical toxaphene using combined high-performance liquid chromatography-gas chromatography-electron capture negative ionization mass spectrometry techniques. J. Chromatogr. 669 103-117. 

Names that attempt to better describe the ionization process include electron capture negative ionization (ECNI) and electron resonance capture negative ionization. 

CI-MS is a powerful tool for steric structure identification that often allows differentiation between isomers. In addition, compound selectivity or sensitivity can be increased by choice of reagent gases with different proton affinities and ion-molecule reaction properties. However, in practice, only few reagent gases are used such as methane or isobutene. Occasionally, ammonia with a higher proton affinity than methane is employed to enhance selectivity. Methane and argon are most frequently used in electron capture negative ionization (ECNI). 

ECD, Electron capture detection ECNI, electron capture negative ionization El, electron ionization FID, flame ionization detection MS, mass spectrometry MSD, mass selective detection. 

Dirtu AC, Ravindra K, Roosens L, Van Grieken R, Neels H, Blust R, Covaci A. Fast analysis of decabrominated diphenyl ether using low pressure gas chromatography-electron-capture negative ionization mass spectrometry. J Chromatog A. 2008 1186 295-301. 

GC analysis of nonvolatile compounds such as quinolinic acid requires a derivatization step. Heyes and Markey (68) have reported quantification of quinolinic acid in rat brain, whole blood, and plasma after quinolinic acid derivatization to its hexafluoroisopropyl (HFIP) ester and GC electron capture negative ionization (Cl) MS with [ 0]quinolinic acid as an internal standard. Negative Cl efficiently forms a characteristic molecular anion and consequently negative Cl GC/... 

Nakano et al. compared the bioavailability of PN and PN-glucoside by administration of the respective deuterium-labeled vitamers to healthy volunteers (157). Urine samples were collected for 48 h after administration of the dose, and 4-PA was isolated as described by Hachey et al. (155) and evaporated to dryness. Isolated 4-PA was converted to the 3-0-acetyl-4-PA lactone derivative, and GC-MS analysis was performed in the electron capture negative ionization mode with SIM at mh 207 and 209 for the nonlabeled and PH2] 4-PA lactone derivatives, respectively. Using this technique, Nakano et al. found that the bioavailability of PN-glucoside was about 50% relative to PN. 

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