BCD - Electron-capture detector

BCD—electron capture detector Ed.—editor(s) or edited by Edn—edition... 

Abbreviations FID flame ionization detector BCD electron capture detector FPD flame photometric detector MS mass spectrometer MED microwave emission detector AAS atomic absorption spectrometer. 

Information for acertain parameter not available, if not given, na, not available DI, deionized water Cl, chemical ionization BCD, electron capture detector El, electron impact ionization FID, flame ionization detector MS, mass spectrometer MtBE, methyl tert-butylether MTBSTE, n-(tert-butyldimethylsilyl)-Wmethylfluoracetamide PDAM, 1-pyrenyldiazomethane PFBBr, pentafluorobenzyl bromide PEBOH, pentafluorobenzyl alcohol SPME, solid-phase microextraction TOPO, tri-n-octylphoshine oxide UASB, upflow anaerobic sludge blanket reactor. 

FIA-FLD flow injection analysis with fluorescence detection, GC gas chromatography, MS mass spectrometry (quadrupole mass filter), BCD electron capture detector, FID flame ionisation detector, LOD limit of detection, HPLC high performance liquid chromatography, TIMS ion trap mass spectrometry... 

GC nitrogen-phosphorus detector (NPD), flame photometric detector (FPD), electron capture detector (BCD), flame ionization detector (FID), mass-spectrometric detector (MS)... 

A technique known as selective electron capti sensitization has been used to increase the response of the BCD weakly electron-capturing compounds [117]. In this mode a standard electron-capture detector is used with a supply of makeup gas doped with a specific sensitizing reagent such as oxygen nitrous oxide. In this way the BCD functions as an ion-aoleculSj... 

Ni electron capture detector (BCD) Selective (halogens and other electron-withdrawing groups) 5 X 10 °... 

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]. 

It was not until the advent of the electron capture detector (BCD) and the development an appropriate BCD cahbration routine when precise and rehable N2O measurements were made possible (Cohen, 1977 BUdns, 1980 Rasmussen et al, 1976 Weiss, 1981). Up to now the use of an BCD in connection with equilibration or purge-and-trap techniques followed by gas chromatographic separation is state of the art for the determination of dissolved NoO (Butler and BUdns, 1991). 

The flame ionization detector (FID), which, for fluorinated compounds, has the advantage of a greater linearity range in spite of its lower sensitivity in comparison with the electron capture detector (BCD), has been extensively applied to organic metal chelates in particular. Comparisons of the different detectors were carried out (Table 1.2) For special analyses such as the determination of SO2 by reaction to SO2F2 with the radioactive F-isotope or by utilization of H-labelled 3-diketon-ates, radiometric measurements for detection are employed ... 

A nonselective detector more sensitive than the RID and easier to use with a small contribution to band broadening is thus desirable in HPLC. The mass spectrometer would be a good solution if it were not so complex [10] and expensive. The electron-capture detector (BCD) [11] and flame-based detectors have been suggested [12]. Both are very sensitive and could be made with very small volumes. Unfortunately, the... 

The electron-capture detector (BCD) is probably the most sensitive GC detector presently available. However, like most high-sensitivity detectors, it is also very specific and will only sense those substances that are electron capturing (e.g., halogenated substances, particularly fiuorinated materials). 

Combinations of highly efficient separation columns, with specific or selective detectors, such as electron capture detector (BCD), GC-mass spectrometer (MS), and GC-Fourier transform infrared (FTIR) detector, make GC a more favorable technique. Multidimensional GC systems, which contain at least two columns operated in series, have also proved to be a powerful tool in the analytical chemistry of complex mixtures. 

The conventional sensitive and specific GC detection such as electron-capture detector (BCD) (see Fig. 2), flame thermionic detector (FTD), and flame photometric detector (FPD) are still widely used in pesticide residue analysis. In recent years, mass spectrometric detection is becoming more and more important. Although other types of mass analyzers are commercially available, the equipment used in modern residue laboratories is based on two major types the classical quadrupole mass analyzers and those based on the ion trap (also called tridimensional quadrupole). 

Electron Capture Detector. The operating principle of the BCD is based on the reaction between electronegative compounds and thermal electrons. The electrons are normally provided from a radioactive source, such as Ni or housed in the detector. A collector electrode is pulsed to... 

Figure 2.16 Electron capture detector(ECD) (a) and photo-ionization detector (PID) (b). The BCD must be installed in an well ventilated position owing to it containing a radioactive source. The PID contains a UV source from which the photons are emitted, having a pre-selected energy, using a filter which prevents undesired carrier gas ionization M + hv M+ - - e ). Examples of filters LiF at ll.SeV, MgFj at 9.6-10 eV, sapphire at 8.4 eV. On contact with the electrodes the molecules return to uncharged state, ionization being therefore reversible. The use of the make-up gas provides an optimal flow.

Responses due to a few unknown compounds are also seen in the chromatogram, but the responses are weak. As a point of reference, the chromatogram for this sample obtained using an electron capture detector (BCD), a detector commonly used for analysis of explosives, contained over 100 peaks. This data-set illustrates the excellent selectivity and sensitivity of the AFP for nitroaromatics. 

FIGURE 3.10 Schematic diagrams of (a) conventional electron capture detector (BCD) (b) pulse discharge BCD. 

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. 

EDCs in the environment are often analyzed using GC or LC based instrumental techniques. GC coupled with an electron capture detector (BCD), a nitrogen-phosphorus detector (NPD), or mass spectrometry (MS) has been the preferred method due to its excellent sensitivity and separation capability on a capillary column. High performance liquid chromatography (HPLC) with various detectors such as ultraviolet detection (UV), fluorescence detection (FLD), MS, and more recently tandem MS (MS/MS) has also been used for analysis of some EDCs, especially for the polar compounds. Analytical techniques for each class of EDCs will be discussed in the following section. 

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