Electron capture negative ionization ECNI

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. 

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

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). 

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]. 

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

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

The main alternative MS techniques currently used for analyzing PCBs at trace level are negative chemical ionization MS (NCI-MS) and high-resolution MS (HRMS). Usually, both techniques provide much higher sensitivity than EI-MS but the complexity of use and the high cost of purchase and maintenance restrict their use in routine analyses of PCBs. The recent introduction of improved bench-top MS for electron capture nagative ionization (ECNI) may increase the use of this technique. 

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. 

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

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... 

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