Gas-chromatographic determination of selenium as an organo-selenium compound with acetophenone

A gas-chromatographic method with electron-capture detection is presented for the determination of selenium after reaction with acetophenone to obtain an organo-selenium compound. This compound is extracted into benzene and chromatographed on an alumina column. The relative standard deviation for the average value (5 mug) is +/-6% (n = 8, P = 95%). The method has been applied to the determination of selenium in metals, alloys, ores and biological samples.     

Gas-chromatographic determination of ultramicro amounts of selenium in pure sulphuric acid

Ultramicro amounts of selenium in pure sulphuric acid are converted into selenous acid with a bromine-bromide redox buffer solution. The selenous acid reacts quantitatively with 4-nitro-o-phenyl-enediamine to form 5-nitropiaselenol which can be extracted into toluene. The extract is very sensitive to electron-capture detection in gas chromatography, and the sensitivity is higher than that of 5-chloro-or 4, 5-dichloro-piaselenol. The calibration curve (peak heights) is linear up to 0.15 mug of selenium in 1 ml of toluene. Pure sulphuric acid, commercially available, contains 10(-6)$ 10(-5) % selenium.     

Gas-chromatographic determination of deltamethrin in crops

A rapid and economical method is described for the determination of deltamethrin in wheat, rice, peanuts and corn. It is based on simultaneous extraction and clean-up on a column packed with alumina and silica gel using n-hexane-ethyl ether (8:2, v/v), followed by a derivatization step and gas-chromatographic analysis. Recoveries from fortified cereal and peanut samples were determined at four concentration levels and ranged from 73 to 109%. The detection limits were 0.01 to 0.03 mg/ kg. This method simplifies the traditional procedures in terms of sample size, solvent consumption and analysis time. Received: 25 March 1997 / Revised: 3 June 1997 / Accepted: 4 June 1997     

Gas-chromatographic determination of deltamethrin in crops

A rapid and economical method is described for the determination of deltamethrin in wheat, rice, peanuts and corn. It is based on simultaneous extraction and clean-up on a column packed with alumina and silica gel using n-hexane-ethyl ether (8:2, v/v), followed by a derivatization step and gas-chromatographic analysis. Recoveries from fortified cereal and peanut samples were determined at four concentration levels and ranged from 73 to 109%. The detection limits were 0.01 to 0.03 mg/ kg. This method simplifies the traditional procedures in terms of sample size, solvent consumption and analysis time. Received: 25 March 1997 / Revised: 3 June 1997 / Accepted: 4 June 1997     

Gas-chromatographic determination of 1,1-dimethylhydrazine in water

A gas-chromatographic procedure for the determination of 1,1-dimethylhydrazine in water was developed on the basis of its reaction with 4-nitrobenzaldehyde yielding the corresponding hydrazone, the extraction of the latter from water with an organic solvent, its subsequent preconcentration by evaporation, and the determination on a gas chromatograph with a nitrogen-phosphorus detector. The determination limit of 1,1-dimethylhydrazine is 0.03 μg/L. The relative error of the determination is no larger than 22% in the concentration range 0.06–0.60 μg/L and 33% at a level of 0.03 μg/L.     

Gas-chromatographic determination of carbon-containing impurities in high-purity sulfur

A gas-chromatographic procedure was developed for the determination of carbon-containing impurities in sulfur with a detection limit of 6 x 10^-6%. Carbon-containing substances and elemental carbon can be effectively separated from sulfur samples as CO₂ and COS.     

Gas-chromatographic determination of nitrophenols after derivatisation with diazomethane

Summary A method is described to determine nitrophenols and two herbicides (Bromoxynil, Ioxynil) in precipitation, with GC-PND and GC-MS. First, the micropollutants were extracted by a mixture of pentane and ether (1/1), concentrated by rotary evaporator, then methylated by diazomethane. The extraction and reaction yields were measured. The resulting recoveries were between 75 and 100% for the mononitrophenols and about 70% for methylnitrophenols. The detection limits were about 0.25 g/l for most substances.     

Gas-chromatographic determination of organomercury(II) compounds

Gas chromatography has proved to be an invaluable technique not only for the identification and determination of organomercury(II) compounds but also for differentiating inorganically bound from organically bound mercury. It also offers a possible route for determining various inorganic species through their conversion into organomercury(II) compounds. These procedures and the chemical and instrumental problems associated with them are reviewed.     

Gas-chromatographic determination of α,β-unsaturated carboxylic acids

Procedures for the gas-chromatographic determination of α,β-unsaturated carboxylic acids as the methyl esters of α,β-dibromocarboxylic acids or the methyl esters of corresponding morpholine derivatives were developed using treatment with diazomethane.     

Gas-chromatographic determination of airborne monoethanolamine using reagent-coated adsorbent tubes

A sampling and analytical procedure was developed for the monitoring of airborne monoethanolamine (MEA). The analyte is collected by drawing air through the adsorbent tubes containing XAD-4 resin coated with cyclohexanone as a derivatising reagent. Derivatisation takes place during sampling. After desorption with methanol, the MEA derivative was quantified by gas chromatography using a thermionic specific detector (TSD) in the nitrogen mode. Application of cyclohexanone as a derivatising reagent gives a more stable product and TSD allows subsequent GC analysis in the presence of excess reagent. The structure of the MEA derivative was confirmed by mass spectrometry. The lower limit of detection for MEA was 1 g and the detector response was linear between 5 and 200 g. The working range of the method is 0.5 to 20 mg/m³ in a 10 l air sample. Collected samples were stable for at least 2 weeks at 4°C and room temperature. The efficiency of sampling was evaluated using a Test Atmosphere Generation System.Presented at the Lab-Ex 1990 Conference in Palais de Congres, Montreal, during October 23–24, 1990     

Gas-chromatographic method for the determination of thiopental in serum

Conclusion The procedure presented is a practical and reliable method for the determination of thiopental in barbiturate loading therapy that can be run on every gas-chromatograph equipped with a flame ionization detector. The sample clean-up is easy and no derivatisation is necessary. Pentobarbital — a metabolite of thiopental — can be determined quantitatively at the same time under the gas-chromatographic conditions described. This is especially advantageous in the case of small clearance rates, which can lead to an accumulation of barbiturates. The use of the method may be expanded to pharmacokinetic studies, where very low concentrations are to be measured by use of an alkali flame ionization detector.

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Gas-chromatographische Methode zur Bestimmung von Thiopental im Serum

     

Gas-chromatographic determination of chlorostyrene and dichlorostyrene isomers in workplace air

Conditions for a gas-chromatographic determination of vapors and aerosols of p-chlorostyrene and 2,6-dichlorostyrene contained in workplace air samples were determined. The method is based on the adsorption of p-chlorostyrene and 2,6-dichlorostyrene on activated charcoal and fiberglass, desorption with toluene and analysis of the obtained solution by capillary gas chromatography with flame ionization detection (FID). The determination limit of the method is 5 mg m^–3 for each substance. Received: 13 December 1999 / Revised: 6 March 2000 / Accepted: 7 March 2000