Hall detector

ELCD, HECD Electrolytic conductivity (Hall) detector Thermal generation of inorganic ions... 

In the purge-and-trap procedure, vials filled to the brim with the water samples are loaded into an auto-sampler, and then when the unit is operating, samples are drawn, one by one, into a tube where helium sparging occurs. Because the THMs are volatile, the helium sparging draws them out of the samples. The helium-THM gaseous mixture then flows through a trap in which the THMs are adsorbed and concentrated. This is followed by a desorption step in which the desorbed THMs are guided to the GC column. A Hall detector is used. 

The Hall detector has an excellent ability to detect small concentrations and excellent selectivity, giving a peak for only those components that produce ions in the reaction chamber. It is a destructive detector. 

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. 

For 1,2-DCP, the Hall detector response was linear in the range of 6.93 to 347 yg/mL (34.7 to 1735 ng injected). A plot of peak area versus concentration in this range (as determined with the Perkin-Elmer Sigma 10 Data System) yielded a correlation coefficient (r) of 1.0000. 

Sen [9] has reviewed methods for the determination of nonvolatile N-nilroso compounds in crops, whilst Usero [10] used GC with a Hall detector to determine N-nitroso compounds. 

Hallett, D.J., Norstrom, R.J., Onuska, F.I., Comba, M.E., Sampson, R., 1976. Mass spectral confirmation and analysis by hall detector of mirex and photomirex in herring gulls from Lake Ontario. J. Agric. Food Chem. 24, 1189-1193. 

Other important GC detectors include the thermionic detector, the electrolytic conductivity or Hall detector, and the photoionization detector. The thermionic detector is similar in construction to the FID. With the thermionic detector, nitrogen- and phosphorus-containing compounds produce increased currents in a flame in which an alkali metal salt is vaporized. The thermionic detector is widely used for organophosphorus pesticides and pharmaceutical compounds. 

The most common carrier gases (mobile phase) are nitrogen and helium. Hydrogen and air are used for the flame ionization detector and ultrapure hydrogen (99.9999%) and ultrapure nitrogen (99.999%) are required for the Hall detector. The type of carri - "as to be employed presents some choice, but it usually is dictated by the type of detector... 

What is the purpose of the Sr(OH)2 scrubber when using the Hall detector in the N mode ... 

The noise level gets quite high unless ultrahigh purity gases are used with the Hall detector. What is meant by "ultrahigh" purity ... 

Depending upon both the time and equipment available, 2 mL samples of two beers, preferably one domestic and one foreign, will be purged and trapped, and the components separated and detected. These beers will then be set in strong sunlight for at least 1 hour, and the process repeated, particularly if sulfur compounds are of interest. Isoamyl acetate should be used to set full-scale deflection, if the FID is used, and dimethyl sulfide, if the Hall detector is used. 

Figure E45-2. Hall detector chromatographs of Negro Modelo beer (top) and Genessee 12 Horse beer bottom).

Figure E45-1 shows the chromatograms of three beers using an FID detector. Figure E45-2 shows chromatographs of one beer under different storage time, light and dark exposure, and using a Hall detector.

Electrolytic conductivity detector (Hall detector) relies on the absorption of ionizable gases into liquid for conductivity measurement. These detectors are rarely advocated in EPA methods probably because the electrolyte must be kept extremely clean. 

The use of electrolytic conductivity detectors (HECDs, also known as Hall detectors) for the analysis of organic sulfur compounds is limited, probably because they require high maintenance. The electrolyte must be kept extremely clean and its sulfur specificity is limited by high concentrations of cotrapped carbon dioxide. Despite these problems, HECD performed well in the sulfur detection mode. ... 

Detection systems Halogen-containing herbicides are detected at the picogram level with the BCD ( Ni). Low limits are also obtained in some cases with selective nitrogen-phosphorus detector (NPD) or electrolytic conductivity (Hall) detector (ELCD) detection (Ing). Mass spectrometric detection is widely used due to its universal character as well as for its intrinsic sensitivity and selectivity. Both FI and Cl (using methane or isobutane as reagent gases) are used for ionization. Specific ions monitored in the... 

Compounds that contain halogens and are aromatic display response on both (e.g., chlorobenzene) detectors. Compounds that have a double bond, such as vinyl chloride, are ionized on the PID (11.7 keV), but show a much weaker response than on the Hall detector. Common quality control samples such as a method blank, a matrix spike and a matrix spike duplicate, and a laboratory control sample are required when analyzing samples by this method. A continuing calibration or check standard is injected every 12 h to verify the calibration. 

The Hall detector has a comparable function to the ELCD and is a typical detector for packed or halfmil columns (0.53 mm internal diameter) because of the large volume of its measuring cell. Because of the latter significant peak... 

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