Identification electron capture detector

The chromatogram can finally be used as the series of bands or zones of components or the components can be eluted successively and then detected by various means (e.g. thermal conductivity, flame ionization, electron capture detectors, or the bands can be examined chemically). If the detection is non-destructive, preparative scale chromatography can separate measurable and useful quantities of components. The final detection stage can be coupled to a mass spectrometer (GCMS) and to a computer for final identification. 

An ion mobility spectrometer offers to prospective users an attractive detector for a GC, from the perspective of detection limits and specificity. A mobility spectrometer, even with low resolution, allows interrogation of compound identities and imparts better specificity than the electron-capture detector. When gaseous analytes are delivered individually to IMS, the mobility spectrum contains information for identification, provided that operating conditions are kept constant for the unknown and reference spectra. The connection of a GC column to an ion mobility spectrometer is... 

The electron capture detector (ECD) is most frequently used to identify hexachloroethane. A flame ionization detector (FID) may also be used (NIOSH 1994). When unequivocal identification is required, an MS coupled to the GC column may be employed. 

Gooding et al. [9] used DDT-dehydrochlorinase for the identification of DDT in soils. The enzyme converts DDT to DDE which is then determined gas chromatographically on Chromosorb WHMDS at 190°C using an electron capture detector. 

The best sensitivity for 1,2-dibromoethane quantification is obtained by either electron capture detector (ECD) or Hall electrolytic conductivity detector (HECD) in the halide detection mode, since these detectors are relatively insensitive to nonhalogenated species and very sensitive to halogenated species. Another common detection device is a mass spectrometer (MS) connected to a GC. The GC/MS combination provides unequivocal identification of 1,2-dibromoethane in samples containing multiple components having similar GC elution characteristics (see Table 6-2). To date, GC equipped with either ECD or HECD has provided the greatest sensitivity for detecting... 

The more advanced instrumental methods of analysis, including GC, for the detection and identification of expls are presented (Ref 90) Pyrolysis of expls in tandem with GC/MS was used for the identification of contaminant expls in the environment (Ref 108). Isomer vapor impurities of TNT were characterized by GC-electron capture detector and mass spectrometry (Ref 61). Volatile impurities in TNT and Comp B were analyzed using a GC/MS the GC was equipped with electron capture and flame ionization detectors (Ref 79). The vapors evolved from mines, TNT, acetone, toluene, cyclohexanone and an organosilicon, were analyzed by GC/MS (Ref 78). Red water produced by the sellite purification of crude TNT was analyzed by GC/MS for potentially useful organic compds, 2,4-dinitrotoluene, 3- and 4-sulfonic acids (Ref 124). Various reports were surveyed to determine which methods, including GC/MS, are potential candidates for detection of traces of TNT vapors emitted from land mines factors influencing transportability of TNT vapors thru soil to soil/air interface are dis-... 

It is obvious that unequivocal identification of small quantities of ABA can only be accomplished by combined gas chromatography-mass spectrometry. However, once this has been accomplished in a particular system, routine measurements will in the future probably mostly rely on gas chromatography with electron capture detector and on radioimmunoassay. 

Detectors used to identify DEHP include the electron capture detector (ECD) (Mes et al. 1974 Vessman and Rietz 1974) and the flame ionization detector (FID) (Albro et al. 1984). When unequivocal identification is required, a mass spectrometer (MS) coupled to the GC column might be employed (Ching et al. 1981 a EPA 1986 f Hillman et al. 1975 Sjoberg and Bondesson 1985). Analytical methods for the determination of DEHP in various biological fluids and tissues are summarized inTable7-l. 

Extracts of muscle tissue are usually sufficiently pure for quantitative gas chromatography at this point, but fat-and-viscera samples require further cleanup. The small sample requirement of the electron capture detector permits a close check on the purification without a significant expenditure of sample. Gas chromatography provides tentative identification at this stage, even in impure samples, and guides the ensuing chromatographic cleanup steps. 

Since air samples may contain many substances which give a response with the electron capture detector, samples whose first chromatograms indicated the presence of phenoxy herbicides were analyzed on a second column to reduce the possibility of incorrect identification owing to interfering substances. Criteria for determining whether a chromatograph peak represented only one substance were essentially the same as those outlined by Crippen and Smith (3). 

Traditional detectors (i.e., FID electron capture detector, BCD nitrogen-phosphorous detector, NPD) supply only retention data. However, in many cases this is not enough for proper identification of analytes. Application of GC coupled with an MS detector gives much more information (i.e., the mass spectmm of each compound). GC-MS is a well known and frequently used technique that combines the highly effective separation of GC with the high sensitivity and selectivity of MS. Moreover, improvements in analytical instruments based on different types of mass analyzers (ion trap, quadrupole, and TOF) and the development of hybrid Q-TOF has enhanced the analytical capabilities of modem hardware. Different kinds of mass spectrometers are presented in Table 14.2 [119]. 

Tn recent years much concern has risen, especially in o Bcial regulatory circles, about the problem of misidentification or uncertain identification in pesticide residue analysis. Since the introduction of the electron-capture detector (EC) in 1960 (i) and its rapid exploitation for the determination of organochlorine residues by gas-liquid chromatography (GLC) (2) the combined EC-GLC system has become, from 1963, the most commonly used end-method for quantitative pesticide residue analysis. It was quickly discovered that even after the application of the more common clean-up techniques (3, 5, 4) EC-GLC interferences occurred not only from peak-overlap of the various pesticides themselves (6, 7) but also from extraneous contamination—e,g, the laboratory or... 

Thermal conductivity detectors have been discussed in detail by Ingraham (107), who also described their application to thermodynamic and kinetic measurements. In this same book. Lodding (4) describes the gas density detector as well as several ionization detectors, such as the argon ionization detector, the electron capture detector, and others. Flame ionization detectors have been described in detail by Brody and Chaney (108) and Johnson (109). The latter also discusses other types of detectors. Malone and McFad-den (110) described many different types of special identification detectors, such as those listed in Table 8.3. Numerous texts on gas chromatography describe a wide variety of detectors, many of them useful in EGD and EGA. 

GC continues to play an important role in the identification and quantification of ubiquitous pollutants in the environment. GC coupled with an electron capture detector (ECD) or a mass spectrometric detector (MSD) has been widely applied for the quantification of PCBs. 

GC is the most commonly used technique. It has, thanks to capillary columns, a very good resolution and enables, when coupled with other specific detectors such as the electron capture detector (BCD), nitrogen phosphorus detector (NPD), flame photometric detector (FPD), pulsed flame photometer (PFPD) and AED separation, identification, and quantification of OPPs containing halogenated groups, or phosphorus or sulfur atoms. 

Gas chromatography has been the most frequently used technique for the determination of organic mercury compounds. In conventional GC, the compounds are chromatographed as halogenides, and determined by use of the highly halogene-sensi-tive electron capture detector (ECD). Better mercury specificity is obtained with detectors based on the principles of AAS, AFS or OES, but, for positive identification of the compounds, mass selective detectors have to be used. 

Chemical analysis of hazardous substances in air, water, soil, sediment, or solid waste can best be performed by instrumental techniques involving gas chromatography (GC), high-performance liquid chromatography (HPLC), GC/mass spectrometry (MS), Fourier transform infrared spectroscopy (FTIR), and atomic absorption spectrophotometry (AA) (for the metals). GC techniques using a flame ionization detector (FID) or electron-capture detector (BCD) are widely used. Other detectors can be used for specific analyses. However, for unknown substances, identification by GC is extremely difficult. The number of pollutants listed by the U.S. Environmental Protection Agency (EPA) are only in the hundreds — in comparison with the thousands of harmful... 

Laboratory air is routinely monitored quarterly by the NIOSH charcoal tube sampling procedure. Laboratory air is drawn through the tube for an 8 hour period and the charcoal adsorbant is extracted with carbon disulfide or other suitable solvents. The extract is analyzed by gas chromatography using both flame ionization and electron capture detectors. Chromatograms from each sample are compared to those of blank samples collected prior to initiation of Hazardous Materials Laboratory operations. Standard analytical techniques (HPLC, GC/MS, etc.) are used, as required, for identification, confirmation and quantitation. 

Detection systems usually employed in GC for the analysis of solvents in paints are the flame ionization detector (FID) and the electron-capture detector, but coupled GC and Fourier transform infrared spectroscopy (FTIR) or GC with mass spectrometry (GC-MS) offer improved peak identification capability. 

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