Electron capture detector photometric

EC = electrical conductivity detector ECD = electron capture detector FPD = flame photometric detector GC = gas chromatography HPLC = high performance liquid chromatography NPD = nitrogen phosphorus detector TID = thermionic detector UV = ultraviolet spectroscopy... 

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

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,... 

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. 

The pesticides included in this study were fenvalerate, chlordecone (kepone), chlorothalonil, and chlorpyrifos. Fenvalerate is a synthetic pyrethroid insecticide used, for example, for mites on chickens. Its chemical name is cyano(3-phenoxyphenyl)-methyl 4-chloro-alpha-(1-methylethyl)benzeneacetate. Chlordecone is an insecticide, no longer used, and has a chemical name decachloro-octahydro-l,3,4-metheno-2H-cyclobuta(cd)=pentalen-2-one. Chlorothalonil is fungicide used on tomatoes whose chemical name is 2,4,5,6-tetrachloroisophthalonitrile. Chlorpyrifos is an insecticide with a chemical name 0,0-diethyl 0-(3,5,6-trichloro-2-pyridyl)phosphorothioate. Chlorpyrifos is the U. S. Food and Drug Administration chromatographic reference standard since numerous specific detectors (electron capture, flame photometric in both sulfur and phosphorus modes, alkali flame, nitrogen phosphorus, and Hall detectors) are sensitive to it. 

There is one final observation using the bandwidth information The data of Tables IX and X suggest that the flame photometric detector (chlorpyrifos) produces more consistent data than the electron capture detector. The chlorpyrifos data clearly had the narrowest bandwidth yet both the range and sample size of this set were comparable to the others studied. The range of chlorpyrifos was 500 to 1 whereas those of fenvalerate and chlorothalonil were 2000 to 1 and 1000 to 1, resp. Chlorpyrifos had 30 samples whereas the other two had 36 and 30, resp. Chlorpyrifos had 5 analysis levels while the other two had 6 each. More data of this sort is needed to compare various detector systems. 

One advantage of gas chromatography is the availability of detectors which respond specifically to certain types of compound. The best known are the electron capture detector for chlorine compounds and the flame photometric detector for nitrogen and phosphorus compounds. If one wants to detect very small molecules such as water or CSj, the standard flame ionisation detector must be replaced by a thermal conductivity detector. 

Organochlorine pesticides and OPPs have been determined mainly using GC, because of the stability and volatility that most of them show under chromatographic conditions and, particularly, the availability of element-selective detectors that display high selectivity for OCPs (electron-capture detector, ECD), and OPPs (flame photometric detector, FPD, and nitrogen phosphorus detector, NPD). Mass spectrometry-based detection is also more popular in GC than in HPLC (1,2,12,16). 

Various alkyl and aryltin compounds were determined in aquatic matrices, namely sediments, biota and water by means of gas chromatographic methods. In this work, comparisons of single or dual flame photometric detectors and electron capture detectors were reported (Tolosa et al., 1991). Sample preparations included acid digestion, extraction, formation of methyl derivatives and clean-up with alumina prior to gas chromatographic analysis. With the electron capture detector, cold on-column injection of organo-tin chlorides was studied. The conclusion was that a single or dual flame photometric detector equipped with a 600 nm interference filter yielded the best performance for determinations of tin species as methyl derivatives. Detection limits for the method using flame... 

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

Many detectors have been used to detect pesticides and herbicides in SFC. Among these detectors, the flame ionization detector (FID) is most commonly used for detection of a wide range of pesticides and herbicides, with a detection limit ranging from 1 ppm (for carbonfuran) to 80 ppm (for Karmex, Harmony, Glean, and Oust herbicides). The UV detector has frequently been used for the detection of compounds with chromophores. The detection limit was as low as 10 ppt when solid-phase extraction (SPE) was on-line coupled to SFC. The mass spectrometric detector (MSD) has also been used in many applications as a universal detector. The MSD detection limit reached 10 ppb with on-line SFE (supercritical fluid extraction)-SFC. Selective detection of chlorinated pesticides and herbicides has been achieved by an electron-capture detector (ECD). The limit of detection for triazole fungicide metabolite was reported to be 35 ppb. Other detectors used for detection of pesticides and herbicides include thermoionic, infrared, photometric, and atomic emission detectors. 

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). 

Traditionally, gas chromatography (GC) was the preferred approach for the analysis of pollutants in water, due to the high sensitivity and selectivity achieved, thanks to its selective detectors such as the nitrogen-phosphorus (NPD), the flame photometric detector (FPD), and electron-capture detector (ECD), and to the ease of coupling to mass spectrometry (MS). However, high-performance liquid chromatography (HPLC or LC) is the most powerful approach for the determination of polar, nonvolatile, and thermolabile compounds (i.e., those which are not GC amenable). 

The variety of detectors available range from the universal (flame ionization detector) to the specific (electron-capture, thermionic, flame photometric and atomic emission detectors). For example, the electron-capture detector is specific for halogen-containing compounds, e.g. organochlorine pesticides. 

AAS = atomic absorption spectrophotometry EPA = Environmental Protection Agency GC/ECD = gas chromatography/electron capture detector GC/FPD = gas chromatography/flame photometric detector GC/HECD = gas chromatography/ Hall s electrolytic conductivity detector GC/MS = gas chromatography/mass spectrometry GC/PID = gas chromatography/photoionization detector ILS = isotopically labelled standard NR = not reported SCD = Sievers chemiluminescence detector... 

For the GC method, 0-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine can be detected by flame ionization detector, MS/SIM detector, electron-capture detector, or flame photometric detector. 1,2-Diaminobenzene derivatives of MG can be analyzed using a flame ionization detector, MS/SlM, or a specific nitrogen/phosphorus... 

Note EDC, electron-capture detector NPD, nitrogen phosphorus detector FPD, flame photometric detector. 

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