Thermionic chromatography

Analysis for the butanals is most conveniendy carried out by gas chromatography. Trace quantities of -butyraldehyde (18 ppb) in exhaust gases have been determined employing a combination of capillary gas chromatography with thermionic detection (35). Sinulady, trace amounts of -butyraldehyde in cigarette smoke and coffee aroma have been determined by various capillary gc techniques (36,37). 

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... 

Nitenpyram and its metabolites. The metabolites of nitenpyram, CPMA and CPMF, are determined by HPLC under the same conditions as for the parent nitenpyram. The retention times of nitenpyram, CPMA, and CPMF are 9.2,7.9 and 5.3 min, respectively. However, these compounds are unstable and need to be derivatized to a more stable compound, CPF, prior to analysis. It is necessary to remove acetone from the extract before derivatization, because a by-product can be formed in the presence of acetone thus impacting the recovery of CPF. Nitenpyram is more effectively determined using HPLC, whereas CPF, as the analyte of nitenpyram and its metabolites, is more effective by gas chromatography/flame thermionic detection (GC/FTD). 

The sample is homogenized with acetonitrile. An aliquot of the extract is evaporated to dryness and the residual material is dissolved in ethyl acetate-toluene (3 1, v/v), and subjected to cleanup by gel permeation chromatography (GPC). After GPC, the sample is subjected to an alumina and Florisil SPE cleanup procedure. The concentrated eluate is analysed by gas chromatography/thermionic nitrogen-specific detection (GC/TSD). 

Transfer the concentrate into a 200-mL separatory funnel using two portions of 20 mL of n-hexane. Add 100 mL of saturated sodium chloride aqueous solution and extract twice with 100 mL of n-hexane by shaking for 5 min and allow the phases to separate. After dehydration of the n-hexane extract with 10 g of anhydrous sodium sulfate, concentrate the extract to dryness below 40 °C with a rotary evaporator. Transfer the residue with three portions of 5 mL of n-hexane into a glass column containing 10 g of Florisil (deactivated by water at a rate of 1%). Elute with 100 mL of n-hexane-ethyl acetate (9 1, v/v) and then with 100 mL of n-hexane-ethyl acetate (7 3, v/v). Concentrate the second eluate to dryness and dissolve the residue in 10 mL of n-hexane and analysis by gas chromatography/flame thermionic detection (GC/FTD). 

The flame ionization detector Is the most popular of the flame-based detectors. Apart from a reduction in sensitivity compared to expectations based on gas chromatographic response factors [138] and incompatibility with the high flow rates of conventional bore columns (4-5 mm I. 0.), the flame ionization detector is every bit as easy to use in SFC as it is in gas chromatography [148,149]. It shows virtually no response to carbon dioxide, nitrous oxide and sulfur hexafluoride mobile phases but is generally incompatible with other mobile phases and mixed mobile phases containing organic modifiers except for water and formic acid, other gas chromatographic detectors that have been used in SFC include the thermionic ionization detector (148,150], ... 

Shinohara et al. [299] have described a procedure based on gas chromatography for the determination of traces of two, three, and five-ring azarenes in seawater. The procedure is based on the concentration of the compounds on Amberlite XAD-2 resin, separation by solvent partition [300], and determination by gas chromatography-mass spectrometry with a selective ion monitor. Detection limits by the flame thermionic detector were 0.5-3.0 ng and those by gas chromatography-mass spectrometry were in the range 0.02-0.5 ng. The preferred solvent for elution from the resin was dichloromethane and the recoveries were mainly in the range 89-94%. 

Lores et al. [382] discussed the determination of the organophosphate insecticide fenthion in seawater. The method comprises a solvent extraction followed by silica gel clean-up procedure prior to determination by gas chromatography with thermionic detection. Detection levels of 0.01 pg/1 were achieved. 

Thornton JS, Anderson CA. 1968. Determination of residues of Di-Syston and metabolites by thermionic emission flame gas chromatography. J Agric Food Chem 16 895-898. 

The main analytical technique for pesticides is gas chromatography using a variety of detectors such as electron capture for halogenated compounds, thermionic for compounds containing either phosphorus or nitrogen, and flame photometric for compounds containing sulphur or phosphorus. 

Ryan, D., Marriott P. (2006) Studies on thermionic ionisation detection in comprehensive two-dimensional gas chromatography. J. Sep. Sci. 29 2375-2382.D... 

Cl = chemical ionization CI-NI = monitoring negative ions in the chemical ionization mode GC = gas chromatogmphy HPLC = high performance hquid chromatography MS = mass spectrometry pmol = picomole SPE = solid-phase extraction TSD = thermionic specific detection... 

Kale, endive, carrots, lettuce, apples, potatoes, strawberries Extraction of crops with ethyl acetate and granular sodium sulfate, filtration, concentration with K-D. Sweep codistillation cleanup for GC. Florisil partition chromatography for polarographic confirmation. GC/KCI thermionic detector or GC/FPD polarographic confirmatory method No data for GC polarographic 0.2 ppm based on 1 g crop in 1 mL cell No data AOAC 1990... 

Numerous non-fatty crops Extraction with acetonitrile and partition into petroleum ether. Concentration using K-D and purification using Florisil column chromatography. GC/KCI thermionic detector identifications by combinations of gas, thin layer, and paper chromatography No data >80 AOAC 1990... 

Three standardized methods were found in the Official Methods ofAnalysis of the Association of Official Analytical Chemists (AOAC 1990). The first of these methods is based on the extraction of crops (kale, endive, carrots, lettuce, apples, potatoes, and strawberries) with ethyl acetate and isolation of the residue followed by a sweep codistillation cleanup prior to GC/thermionic detection (Method 968.24). The second of these methods utilizes Florisil column chromatography clean-up followed by GC/FPD (Method 970.53). In the third method (Method 970.52), the sample is extracted with acetonitrile, and the residue is partitioned into petroleum ether followed by Florisil clean-up and GC/KC1 thermionic detection. Identifications are based on combinations of gas, thin-layer, and paper chromatography. The recovery for diazinon in this method is stated to be greater than 80% no data on limits of detection were given. 

Gas chromatographic methods have been successfully used for the determination of penicillin molecules bearing neutral side-chains in milk and tissues (95, 97), but cannot be used for amphoteric -lactams. Gas chromatography of penicillin residues is further complicated by the necessity for derivatization with diazomethane. This derivatization step is particularly important because it not only leads to formation of the volatile penicillin methyl esters but also improves their chromatographic properties (thermal stability and decreased polarity). Using a fused-silica capillary column in connection with a thermionic nitrogen-selective detector, excellent separation and sensitivity figures were obtained. 

Nitrogen-containing explosives [249] and trinitrotoluene [250] have been determined in soil by gas chromatography with thermionic NP detection and reverse-phase high-performance liquid chromatography. Warmont et al. [251] used tunable infrared laser detection to study the pyrolysis products of explosives in soil. 

Miscellaneous - Gas liquid chromatography with thermionic detection ... 

Triazole type, pyrimidine type (retardants) Plants Ethylene dichloride extraction Silica gel chromatography with N-thermionic detection [169]... 

Albanis, T.A. and D.G. Hela (1995). Multi-residue pesticide analysis in environmental water samples using solid-phase extraction discs and gas chromatography with flame thermionic and mass-selective detection. J. of Chromatogr. A, 707 283-292. 

Riva, M., Cafisano, A. Compact dual channel flame ionisation — cum — thermionic detector for high specifity chromatography analysis. J. Chromatog. 36,269 (1968). 

Karlsson et al. reported the supercritical fluid chromatography of methaqualone, cotinine, and reclopride, among other compounds, using capillary columns of different polarities [19]. Detection was either thermionic nitrogen-phosphorus or flame ionization. Supercritical nitrous oxide was used as the mobile phase. The detection limits obtained were in the range of 2-4 ppm and the precision was in the range of 3-12%. 

P. Patterson, Recent advances in thermionic ionization detection for gas chromatography, J. Chromatogr. Sci., 24 4152 (1986). 

Verwej et al. [175] have described a procedure for the determination of PH3-containing insecticides in surface water. In this procedure the insecticide is hydrolysed to methylphosphonic acid, and the acid is concentrated by anion exchange and converted to the dimethyl ester. After clean-up on a microsilica gel column the ester is analysed by gas chromatography using a thermionic phosphorus-specific detector. Detection limit is lnmol L 1. 

Funazo et al. [794] have also described a more sensitive gas chromatographic procedure capable of determining down to 3gg L 1 total cyanide in waste waters. The method is based on the derivatisation of cyanide to benzonitrile, which is extracted with benzene and determined by flame thermionic gas chromatography. In the derivatisation reaction, aqueous cyanide reacts with aniline and sodium nitrite in the presence of copper(II) sulphate and forms benzonitrile. 

U.A.Th. Brinkman, Verification of nonproduction of chemical warfare agents I. Determination of organophosphorus compounds by microcolumn liquid chromatography with flame photometric or thermionic detection, J. Microcol. Sep., 4, 465-475 (1992). 

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