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Following the treatment of the sample with zinc hydroxide, nitrite reacts with potassium iodide in the presence of acetone and sulphuric acid. The released iodine and the propanone derivative resulting from the acetone are extracted in n-hexane. The extract is subjected to gas chromatographic separation and detection using an electron capture detector. The calibration curve was found to be linear...
A chemical sensor for gas phase measurements is reported which combines the principles of chemical separation and fiber optic detection. The analyzer incorporates an annular column Chromatographic sensor, constructed by inserting a polymer-clad optical fiber into a silica capillary. Light from a helium-neon laser is launched down the fiber, producing a steady intensity distribution within the fiber,...
A solvent extraction technique involving no critical clean-up steps was developed for the determination of methylmercury (MeHg) in environmental and biological samples by aqueous phase ethylation, room temperature precollection, gas chromatographic separation and cold vapor atomic fluorescence spectrometric detection. Samples were first digested with KOH-methanol, then acidified prior to extraction...
A method for rapid extraction and determination of some crown ethers in aqueous matrices using octadecyl-bonded silica membrane disks and gas chromatography is presented. Extraction efficiency and the influence of vacuum pressure, pH, and type and least amount of eluting solvent used to extract the crown ethers from the membrane disks were evaluated. Extraction efficiencies > 95% were obtained...
Methods were developed to determine traces of 4,5,6,7-tetrachlorophthalide (fthalide) and 1,4,5,6,7,8,8-heptachloro-2,3-epoxy-2,3,3a,7a-tetrahydro-4,7-methanoindene (heptachlor epoxide) in environmental samples such as river water, sediment and fish. The samples were cleaned up by using convenient disk type solid phase extractors and cartridges and analyzed by GC/MS with selected ion monitoring....
GC/MS and GC/MS/MS in a quadrupole ion trap were used to analyze for anthraquinone, alkyl anthraquinones, benz[a]anthracene-7,12-dione and 9-fluoranone in a sediment obtained from an aluminum smelter settling pond contaminated with polycyclic aromatic hydrocarbons. By standard GC/MS analysis many of these target compounds were either undetectable or their confirmation uncertain because of matrix...
A calibration procedure for solid phase microextraction--gas chromatographic (SPME-GC) analysis of organic vapours in air was described in which GC detector (MS in this case) signal is directly related to concentration of analytes of interest sampled by SPME. Gaseous standard mixtures used for the calibration were generated by means of a home-made permeation-type apparatus described elsewhere, W...
The gas chromatographic detection and quantitative determination of various chlorophenolics as well as resin and fatty acids have been carried out in the chlorination and caustic extraction stage effluents generated in the laboratory by bleaching a bamboo pulp. A number of chlorinated phenols, catechols, guaiacols, syringaldehydes and resin acids as well as non-chlorinated saturated and unsaturated...
Adsorption isotherms for microporous solids have been determined by elution gas chromatography. Adsorbents are of `molecular sieves' type; their utilization in affinity thermal machines is envisaged. These machines work in a relatively high domain of pressure for the adsorbate, so the chromatographic technique is generally inadequate for their study. The possibility of increasing the maximal pressures...
In this paper, separations of organic compounds, such as, n-alkanes, alcohols, ethyl asters of C 1 -C 8 carboxylic acid, halogen derivatives, position-isomers of the replacement aromatic hydrocarbon, optical isomers of ethyl lactate and isoamyl alcohol, etc. were studied using 4'-cholestenoxycarbonyl-benzo-15-crown-5 liquid crystal crown ether (CH-B-15-C-5) as stationary phase in gas-solid...
A simple, rapid and precise gas chromatographic method has been developed for the simultaneous determination of pseudoephedrine hydrochloride and diphenhydramine hydrochloride in cough syrup, using a SS column of 10% OV 1 on chromosorb W-HP (80-100 mesh) and nitrogen as a carrier gas at a flow rate of 30 ml min -1 . The oven temperature was programmed at 135 o C for 1 min, with...
An optimized sample preparation procedure for organotin speciation in sediment samples has been applied to the analysis of sediments collected in the environment. The method is based on tropolone complexation of the ionic organotins, followed by extraction into a hexane-ethylacetate mixture and derivatization by NaBEt 4 . The method was applied to the determination of organotin in various...
Following the deproteination of the milk sample by means of zinc hexacyanoferrate, acetoacetic acid was decarboxylated by heating; the acetone originally present was then determined together with the acetone formed. The essence of the determination was that acetone reacted with bromine in the presence of sulphuric acid, following which, the bromoacetone formed was extracted into toluene, separated...
This article describes a newly developed method of gas chromatography (GC) for the rate study of the reduction of organic compounds by samarium iodide. Solvent extraction was used to reduce the interference of GC analysis by inorganic species. Adequate recoveries ranged from 88.3 to 94.5 % and good linearity ranging from 0.1 to 2.1 mM was determined. An internal standard, decane, was used to enhance...
A subcritical extractor equipped with a three-way inlet valve and an on/off outlet valve has been used for performing subcritical water extractions (SWE) in a continuous manner for the isolation of the essential oil of fennel, a medicinal plant. The target compounds were removed from the aqueous extract by a single extraction with 5 ml hexane, determined by gas-chromatography-flame ionization (GC-FID)...
The economical use of modern analytical instrumentation requires an online-coupling of efficiently working flow-systems which automate both sampling and sample pretreatment. Whenever extraction and preconcentration procedures are necessary the application of chromatomembrane cells proved to be very worthwhile. On this occasion the analyte exchange takes place inside a block of biporous PTFE wherein...
A simple, sensitive method for determining polychlorinated biphenyl (PCB) congeners in industrial product 2,3,5,6-tetrachloro-1,4-benzoquinone with GC/ECD detection has been developed. The method based on liquid-liquid extraction from tetrachlorinated quinone dissolved in N,N-dimethylformamide was found to be efficient for the determination of the levels of the investigated pollutants. A series of...
The fatty acid contents of coffee lipid extracts have been determined by capillary gas chromatography. Ten fatty acids were considered: myristic (C14:0), palmitic (C16:0), palmitoleic (C16:1), stearic (C18:0), oleic (C18:1), linoleic (C18:2), linolenic (C18:3), arachidic (C20:0), eicosenoic (C20:1) and behenic acid (C22:0). The analyzed coffee samples belonged to arabica and robusta varieties and...
An automatic method for the determination of organochlorine pesticides (OCPs) in water samples was developed. The analytes are preconcentrated onto a customized RP-C 18 column and subsequently eluted with 80 μl of ethyl acetate. Gas chromatography with electron capture detection is used for their separation and selective detection. Detection limits for 10 ml sample volumes range from...
An off-line optimization technique based on soft modeling methods has been used to determine the optimum conditions for the separation of eight carbonyl-2,4-dinitrophenylhydrazones by gas chromatography equipped with a nitrogen-phosphorous detector. In this method theoretical simulations of peak retention time and peak width at base-line are coupled to a factorial design to map the chromatographic...
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