Sensitivity gas chromatograph

Eklund [175] developed a method for sensitive gas chromatographic analysis of monosaccharides in seawater, using trifluoracetyl derivatisation and electron capture detection. It is difficult to determine accurately the monosaccharide concentration by this method because a number of chromatographic peaks result from each monosaccharide. 

Gaynor and MacTavish [207] have described a further sensitive gas chromatographic procedure for the determination in soil of Diclofopmethyl and its hydrolysis product diclofop. 

More recently Hartog and Zwietering (103) used a bromometric technique to measure the small concentrations of olefins formed in the hydrogenation of aromatic hydrocarbons on several catalysts in the liquid phase. The maximum concentration of olefin is a function of both the catalyst and the substrate for example, at 25° o-xylene yields 0.04, 1.4, and 3.4 mole % of 1,2-dimethylcyclohexene on Raney nickel, 5% rhodium on carbon, and 5% ruthenium on carbon, respectively, and benzene yields 0.2 mole % of cyclohexene on ruthenium black. Although the cyclohexene derivatives could not be detected by this method in reactions catalyzed by platinum or palladium, a sensitive gas chromatographic technique permitted Siegel et al. (104) to observe 1,4-dimethyl-cyclohexene (0.002 mole %) from p-xylene and the same concentrations of 1,3- and 2,4-dimethylcyclohexene from wi-xylene in reductions catalyzed by reduced platinum oxide. 

Step 4. Samples are analyzed for tracer and hydrocarbon vapors by means of a very sensitive gas chromatograph the presence of tracer vapors, which can be detected in the low parts-per-triUion, provides unambiguous information about the occurrence of leakage and its location. 

J. M. Moore, Rapid and sensitive gas chromatographic quantitation of morphine, codeine and 06-acetylmorphine in illicit heroin using an electron capture detector, J. Chromatogr., 747 327 (1978). 

The combination of these microextraction techniques that combine sampling, extraction and pre-concentration into a sigle step, with high sensitive gas chromatograph detectors such as mass spectrometer is the way to determine compounds at levels of ng L 1 that could be important for wine aroma characterization. 

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. 

All the binary Cu/ZnO catalysts were found highly selective toward methanol without DME, methane, or higher alcohols and hydrocarbons detected in the product by sensitive gas chromatographic methods (59). Several of the composites were also found to be very active when subjected to a standard test with synthesis gas C0/C02/H2 = 24/6/70 at gas hourly space velocity of 5000 hr- pressure 75 atm, and temperature 250°C. The activities, expressed as carbon conversions and yields, are summarized in Table VIII. The end members of the series, pure copper and pure zinc oxide, were inactive under these testing conditions, and maximum activity was obtained for the composition Cu/ZnO = 30/70. The yields per unit weight, per unit area of the catalyst or the individual components, turnover rates per site titratable by irreversible oxygen and by irreversible carbon monoxide, are graphically... 

An elaborate apparatus for the diminished-pressure distillation is not required to obtain a product of excellent purity sensitive gas-chromatographic analyses could detect no more than a doubtful trace of the cis isomer in the crude mixture, and other possible contaminants boil at least 45° (760 mm.) below the product. The submitters usually employed an 8 x 300 mm., vacuum-jacketed, silvered column with a helical, Nichrome-wire heat transfer insert. They consistently obtained a product which analyzed at least 99% pure using vapor phase... 

Valentour, J.C., Aggarwal, V., Sunshine, I. (1974). Sensitive gas chromatographic determination of cyanide. Anal. Chem. 46, 924-5. 

Burnett, M.G., Swoboda, P.A.T. (1962) A simple method for the calibration of sensitive gas chromatographic detectors. Anal. Chem. 34, 1162-1163. 

A sensitive gas-chromatographic determination of selenium is possible as 5-chlor-or 5-nitro-piazselenol. These compounds are extractable into benzene or toluene for direct injection into a gas-chromatograph with BCD or TCD After treatment of steel samples with diluted mixtures of equal volumes of hydrochloric and nitric acids in the presence of perchloric acid, the selenium is completely converted into the quadrivalent state. Large amounts of Fe(III) are masked with phosphoric acid. In pure sulfuric acid ultramicro amounts of selenium are converted into seleneous acid with a bromine-bromide redox buffer solution For high-purity... 

The experimental scheme for anaerobic decomposition is shown in Fig. 5-4. Exactly 1.5 g of each substrate was added to a modified 1 litre Sohngen flask and autoclaved at 120°C and 15 psi to ensure sterility, after which each flask was filled to capacity with a sterile inorganic nutrient medium and pH adjusted. Next 50 ml of a heterogeneous innoculum prepared from muds from a local lake was injected into each flask as "inoculates", while 50 ml. of sterile nutrient medium was used for control samples. Headspace C1-C4 hydrocarbons were measured prior to incubation to provide baseline concentrations. Minimum detection limits were 3 ppb on a volume basis using a high-sensitivity gas chromatograph equipped with a flame ionisation detector. Samples were incubated at 25°C and 36°C over a five week period. 

During the 1970s the ECD became firmly established as the most sensitive gas chromatographic detector for some compounds. The kinetic model was described in terms of a numerical solution of the differential equations. This was assisted by the development of the constant current mode of measuring the response and the development of Ni-63 sources for the detector. The purification of the carrier gas and the further development of capillary columns improved the operation of the ECD. In addition, chemical reactions were used to make derivatives with a greater sensitivity in the ECD. Other ion molecule reactions were used to improve the sensitivity of... 

A. Tangerman, Highly sensitive gas chromatographic analysis of ethanol in whole blood, serum, urine, and fecal supernatants by the direct injection method, Clin. Chem., 43, 1003-1009 (1997). 

For measuring at low concentrations, the derivatisation of the extracted organotin compound with sodium tetraethylborate is an established procedure to make a more sensitive gas chromatographic analysis possible. Derivatisation can be combined with the extraction as prescribed in the German method but can also be carried out after the extraction. Selective detection is possible using GC-MS. For organo-metallic compounds atomic emission or atomic absorption detection is not only very sensitive, but very selective. The steps necessary for the chromatographic separation and detection are described in ISO/CD 17353 (2001). Application of this well-described method for soil samples does not mean that the difficulties with the extraction have been overcome. 

Chemical microanalysis is normally carried out in two stages first, the quantitative chemical conversion of the sample into simple products, and second, the quantitative determination of these products with the use of an appropriate technique. Elemental analysis produces a simple mixture of gaseous and volatile products, which can be quickly and effectively broken down into individual components to which a highly accurate and sensitive gas chromatographic (GC) detector can be applied. 

O Hara, D. and Singh, H. B., Sensitive gas chromatographic detection of acetaldehyde and acetone using a reduction gas detector, Atmos. Environ., 22, 2613-2615, 1988. 

Headspace Technique. One of the most recent methods of flavor analysis which evolved with the development of sensitive gas chromatographic instrumentation is the headspace technique. Withycombe et al (19), gave an excellent description of headspace analysis. In this procedure volatiles in gaseous state that are in equilibrium over the food are analyzed. 

Pharmacokinetic data related to the volatile anesthetics are sparse, perhaps because of onerous analytical challenges. Recently, a number of sensitive gas chromatographic assays have been published that may enhance our knowledge of the pharmacokinetics of these chiral drugs. 

A Sensitive Gas Chromatographic Technique for Quantification of Urinary Tryptamine... 

Sensitive Gas Chromatographic Method for the Determination in Plasma of FM 24, 1-(2-Exo-bicyclo[2,2,1]-hept-2-ylphenoxy)-3-[(1-methyl-ethyl) amino] -2-propanol, a New 3-Adrenoceptor Blocking Agent J. Chromatogr. 183(1) 99-103 (1980) ... 

A Sensitive Gas Chromatographic Method for the Determination of Pentachloro-phenol in Human Blood J. Chromatogr. 38(4) 467-472 (1968) ... 

Sensitive Gas Chromatographic Method for the Determination in Blood and Urine of SL 75212 [4-(2-Cyclo-propylmethoxyethyl)-l-phenoxy-3-isopropylaminopropane-2-ol], a New Adrenoceptor Blocking Agent J, Chromatogr. 176(1) 134-139 (1979) CA 91 168084h... 

Breimer, D. D., and Van Rossum, J, M. Rapid and Sensitive Gas Chromatographic Determination of Hexobarbital in Plasma of Man Using a Nitrogen Detector... 

Rapid and Sensitive Gas Chromatographic Determination of Underivatized Theophylline in Plasma and Saliva... 

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