ECNI

Particle-beam (PB) Electron-capture (ECNI) Fourie-transform (FT)... 

Flow limitations restrict application of the DFI interface for pSFC-MS coupling. pSFC-DFI-MS with electron-capture negative ionisation (ECNI) has been reported [421], The flow-rate of eluent associated with pSFC (either analytical scale - 4.6 mm i.d. - or microbore scale 1-2 mm, i.d.) renders this technique more compatible with other LC-MS interfaces, notably TSP and PB. There are few reports on workable pSFC-TSP-MS couplings that have solved real analytical problems. Two interfaces have been used for pSFC-EI-MS the moving-belt (MB) [422] and particle-beam (PB) interfaces [408]. pSFC-MB-MS suffers from mechanical complexity of the interface decomposition of thermally labile analytes problems with quantitative transfer of nonvolatile analytes and poor sensitivity (low ng range). The PB interface is mechanically simpler but requires complex optimisation and poor mass transfer to the ion source results in a limited sensitivity. Table 7.39 lists the main characteristics of pSFC-PB-MS. Jedrzejewski... 

ECNI Electron capture negative ionisation ESIMS Electrospray ionisation mass... 

Both PCI and ECNI/MS are very sensitive to the presence of contaminating water or oxygen molecules, which can greatly decrease sensitivity as well as contaminate the source itself. 

Endogenous Neurochemicals Amino acids Pentafluorobenzyl Chloroformate ECNI Simpson et al. (1996)... 

Antidepressants Antipsychotics (review) Dopamine, norsalsolinol, and ECNI Watson et al. (1990)... 

Geens T, Neels H, Covad A (2009) Sensitive and selective method for the determination of bisphenol-A and triclosan in serum and urine as pentafluorobenzoate-derivatives using GC-ECNI/MS. J Chromatogr B Anal Technol Biomed Life Sci 877 4042-4046... 

Environmental Cancer Risk, Nutrition, and Individual Susceptibility (ECNIS) Studying use of biomarkers of exposure and susceptibility and bioindicators of disease in molecular epidemiology of cancer (ECNIS 2005). 

ECNIS. 2005. Environmental Cancer Risk, Nutrition and Individual Susceptibility [online]. Available http //www.ecnis.org/ [accessed Sept. 26, 2005]. 

ECNI electron capture negative-chemical ionization... 

Electron capture negative chemical ionization (ECNI) with methane as reagent gas was used to analyze 17 halogenated diphenylethene, -ethane and -ethanol derivatives such as DDE (150), DDD (151), DDT (152) and dicofol (153)335. Both the ethylenic double bond... 

Fig. 3a-d. Mass spectra of a TCPM in the El mode b TCPM in the ECNI mode... 

ECNI-MS),311,313,346,348 (TCPMe,EI-MS),and346,348 (TCPMe,ECNI-MS). Much more fragmentation is observed in the El spectra when compared to the ECNI spectra (Fig. 3). As is to be expected, the most prominent peaks in the ECNI spectra are due to the molecular ions. 

The use of ECD detection causes a small loss in sensitivity (Table 1), but a considerable loss in selectivity. Therefore, ECD can be used for screening of TCPM and TCPMe, but confirmation by GC/ECNI-MS or GC/EI-MS, respectively, will often be essential. 

A recent method of detection is electron capture negative ionisation (ECNI) as ionization technique in combination with GC-MS analysis. This method is advantageous because it offers a high sensitivity for compounds with four or more bromine atoms [36]. The sensitivity of ECNI for these compounds is approximately 10 times higher than with the use of an electron capture detector (ECD) [5]. In the analytical method which was developed to quantitate PCBs and PBBs in human serum, GC/ECD was used [30]. Because the response, and therefore the sensitivity, of the ECD depends on the position of the halogen on the biphenyl nucleus as well as the number of halogen atoms, it is necessary to run a standard for each compound to be determined [2], The use of narrow bore (0.15 mmi.d.) capillary columns is advised to obtain the required resolution [5]. 

Both GC-ECD and GC-MS with El or ECNI maybe used for the final analysis of PBDEs [5]. ECNI-MS is a very sensitive method for many halogenated compounds [1]. Using GC-MS, the type of reaction gas can influence the data. A study of PBDE residues in guillemot eggs showed an increase in levels of 2,2, 4,4 -TeBDE, an unidentified PeBDE, and 2,2, 4,4, 5-PeBDE of respectively 10-35%, 25 -80%, and 0-20% after re-analysis using ammonia as reaction gas instead of methane [1]. 

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

Jansson et al. [52] developed a low resolution method for PCA analyses, based on GC/ECNI-MS in the selected ion mode (SIM). In this method, PCAs were selectively removed from other common environmental contaminants by GPC, and quantification was performed by integrating the response of the Clj (m/z 70) ion, an ion that predominates in the mass spectra of individual PCA congeners at high ion source temperatures [54]. 

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