Electronic chemical detectors

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. 

ECD = electron capture detector GC = gas chromatography HPLC = high-performance liquid chromatography MC = microcoulometric detector MS = mass spectrometry NICI = negative ion chemical ionization RSD = relative standard deviation SPE = solid phase extraction... 

Pressures Helium—60 psig, Hydrogen—10 psig Quantitative determinations of purity were made at the Analytical Laboratory of Dow Chemical Co. by GLC using flame ionization and electron capture detectors. Unknown samples were compared with prepared standards containing the compounds in question. 

The structure-selective, electron-capture detector (ECD) is the second aost widely used ionization detector [115-118]. It owes Buch of its popularity to its unsurpassed sensitivity to a wide range of toxic and biologically active coapounds. Consequently, it is widely used in trace analysis for the detemination of pesticides, herbicides and industrial chemicals in the... 

GC is coupled with many detectors for the analysis of pesticides in wastewater. At the present time the most popular is GC-MS, which will be discussed in more detail later in this section. The flame ionization detector (FID) is another nonselective detector that identifies compounds containing carbon but does not give specific information on chemical structure (but is often used for quantification because of the linear response and sensitivity). Other detectors are specific and only detect certain species or groups of pesticides. They include electron capture,nitrogen-phosphorus, thermionic specific, and flame photometric detectors. The electron capture detector (ECD) is very sensitive to chlorinated organic pesticides, such as the organochlorine compounds (OCs, DDT, dieldrin, etc.). It has a long history of use in many environmental methods,... 

Qin BH, Yu BB, Zhang Y, Lin XC. Residual analysis of organochlorine pesticides in soil by gas chromatograph-electron capture detector (gc-ecd) and gas chromatograph-negative chemical ionization mass spectrometry (GC-NCI-MS). Environ. Forensics 2009 10 331-335. 

Elimination of wet chemical sample preparation enables a complete analysis to be performed and data to be quickly analyzed. The detection limits are in the low part-per-million range using mass spectrometric detection. Alternatively, detection of compounds can be achieved by all common gas chromatography detectors (flame ionization detector, electron capture detector and flame photometric detector), and detection limits are determined by the method of detection employed. 

Many substances are not initially appropriate for gas chromatography because of their relatively high boiling points or insolubility. In such cases it is often possible to modify the compound chemically and render it more amenable to separation. In some instances, the chemical modification is used to enable easier detection of the compound, e.g. the introduction of a halogen for use with electron capture detectors. 

MS, Mass spectrometry El, electron impact Cl, chemical ionization MID, multiple ion detection PICI, positive-ion chemical ionization NICI, negative-ion chemical ionization SIM, selected ion nmonitoring TSP, thermospray PPINICI, pulsed positive ion-negative ion chemical ionization ECD, electron-capture detector NPD, nitrogen/phosphorous detector NSTD, nitrogen-selective thermionic detector FT-IR, Fourier transform infrared spectrometry. 

Excellent separation of sulfonamides can be achieved on conventional or fused silica capillary columns, the preferred type been the DB-5 capillary column. Following separation, electron-capture detector (254, 271) can be used for the determination of these drugs with good sensitivity and specificity. To confirm the presence of sulfonamides residues in edible animal products, mass spectrometric detectors are also frequently employed. Typical examples of such applications are those coupling gas chromatography with mass spectrometry via a chemical ionization (224, 254, 271) or electron impact (223, 256, 261) interface. 

ECD = electron capture detector FID = flame ionization detector GC = gas chromatography HRGC = high resolution gas chromatography LC-APCI-MS = liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry LSE = liquid-solid extraction MS = mass spectrometry PVC = polyvinyl chloride SFE = supercritical fluid extraction... 

TCD) detector or the flame-ionization (FID) detector, which are the two most common detectors in gas chromatography, respond to all (organic) compounds except the carrier gas. On the contrary, a selective detector responds to a range of compounds with a common physical or chemical property. Representatives of the latter group of detectors are the nitrogen-phosphorus detector (NPD), the electron capture detector (ECD), the mass selective detector (MSD) and - last, but not least - the tandem mass spectrometer (MS/MS). 

Chemical oxygen demand ( ) Electron capture detector ( ) Flame ionization detector... 

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