Analysis gas chromatography

Assays are performed under isothermal conditions. The operating conditions for MegSi derivatives of samples and standard are as follows  

Flow of the carrier gas (nitrogen), 35ml/min column temperature 170, 210, 230 and 290 °C. Detector temperature (flame ionization), 300 °C, sample size, 0.3 il. In order to determine Kovats indices (I) of Me3Si derivatives, several mixtures of n-alkaline (C10-C24) are injected under the same operating conditions. The Kovats indices are a means of calibrating the columns. The gas holdup time is calculated by the Peterson and Hirsch method (1959), and (I) values are statistically calculated by the computer methods of Grobler and Balisz (1974). 

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Gas Chromatography Analysis. From a sensitivity standpoint, a comparable technique is a gas chromatographic (gc) technique using flame ioni2ation detection. This method has been used to quantify the trimethylsilyl ester derivative of biotin in agricultural premixes and pharmaceutical injectable preparations at detection limits of approximately 0.3 pg (94,95). 

Gas chromatography analysis was performed on a Hewlett Packard GC Model 5890 equipped with a flame ionization detector and automatic injector 7673A. 

Both recycled and non-recycled essential oils met the standards for specific gravity, angular rotation and refractive index of the Food Chemicals Codex [22] and United States Pharmacopeia [23] for cold-pressed lemon peel oil. Results of gas chromatography analysis show the same compounds and levels in both systems, specially for the oxygenated compounds as citral (neral and geranial). Therefore, recycling the aqueous discharges to the extractor does not cause undesirable modifications. 

Consider the quantitative gas chromatography analysis of alcohol-blended gasoline for ethyl alcohol by the internal standard method, using isopropyl alcohol as the internal standard. The peaks for these two substances are well resolved from each other and from other components. Assume there... 

The substrate (9 mmol), isopropyl butyrate (18 mmol) and toluene (9 mL) were then added and the Schlenk tube was inserted in an oil bath at 73 °C, which indicated the started of the reaction. The reaction mixture was stirred at 70 °C for 23 h at a pressure of 200 mbar. Small aliquots of reaction mixture were taken for gas chromatography analysis. For preparative purposes, the reaction mixture was concentrated, filtered, washed with toluene and concentrated in vacuo to yield the crude product. 

All aldehydes used in the experiment were freshly distilled or washed with aqueous NaHC03 solution to minimize the amount of free acid. Chiral HPLC was performed using a chiral OJ-H column (0.46 cm x 25 cm, Daicel industries) with a water 717 auto sampler and a UV-vis detector (254 nm). The eluting solvent used was different ratios of hexane and 2-propanol. Chiral gas chromatography analysis was performed in a Shimadzu auto sampler with cyclodextrins columns as chiral stationary phase (fused-silica capillary column, 30 m X 0.25 mm x 0.25 gm thickness, /3-Dex-120 and /3-Dex-325 from Supelco, USA) using He as a carrier gas (detector temperature 230 °C and injection temperature 220 °C). 

For gas chromatography analysis, samples were spiked with 2-methyl-naphthalene as an internal standard. Samples were analyzed using a Shimadzu GC-17A series gas chromatograph equipped with RTX-5 column, 15 m (length) 0.25 mm (i.d.) and 0.25 pm (film thickness). The initial column temperature was 70 °C and temperature was increased at 20 °C min 300 °C, and column temperature was held for 13 min. Retention times R naphthalene, 3.2 min 2-methyl-naphthalene, internal standard, 4.09 min 1-tetralone, 4.7 min menadione, 5.68 min 1-naphthol, 5.7 min 4-hydroxy-1-tetralone, 6.1 min and 2-methy 1-4-hydroxy-1-tetralone, 6.18,6.27,6.3 and 6.4 min. 

Gas chromatography analysis using a silicone gum column indicated the product to be 97% pure. 

Gas Chromatography Analysis of Water for Pesticides. All analyses for pesticides in water were done by gas chromatography. Solvents used for extraction were checked by gas chromatography for purity and interferences and all glassware used in the extraction was cleaned in a chromic acid/sulfuric acid mixture. Standards consisted of mixtures of various pesticides (actual commercial formulations) suspended or dissolved in water. These aqueous standards were extracted in the same manner as unknown solutions. The standard concentrations encompassed the concentration of unknowns to be determined. A standard curve normally consisted of a set of four pesticide concentrations. Blanks were run and an internal standard (eicosane) was used. The internal standard concentration was kept constant for all analyses. The conditions for GC analysis were guided by the pesticides expected in the water. For the more complex mixtures, such as those employed in the synthetic waste and those encountered in the field, a 6 ft., 3 percent SE-30 on GAS CHROM Q column sufficed. A typical chromatogram of a complex pesticide mixture is shown in Figure 2. ( )... 

Yields determined by gas chromatography analysis only. d Fifteen percent of this product is the dihydro derivative, that is, the acetal of 3-phenylpropanal. 

The submitters found that analysis of the undistilled aldehyde by gas chromatography indicated a purity of 98.6%. The analysis was conducted on a column packed with 16% LS-40 on Chromosorb P/AW at 100°. N.m.r. analysis indicated an isotopic purity of 97.9% (trace of impurity at 9.60 p.p.m. due to CHO, carbon tetrachloride solution, internal tetra-methylsilane as reference). If the crude aldimine is hydrolyzed, the aldehyde is obtained in 96% overall yield however, the purity is only 94% by gas chromatography analysis. The checkers found no detectable impurity by gas chromatography in the distilled aldehyde, and the n.m.r. spectrum indicated very high isotopic purity. 

The acid chloride or the acid may be purchased from Aldrich Chemical Company, Inc. The acid chloride must be pure (99% minimum by gas chromatography analysis) whether purchased or prepared. Purification was effected by recrystallization from Skellysolve B. 

The product, which is about 90% bicyclobutane and 10% cyclobutene, is sufficiently pure for most purposes. The purity of the product can be determined by gas chromatography analysis at room temperature, using a 275-cm.-long column containing 20% /3,/3 -oxydipropionitrile on Chromosorb W (45/60). The retention times are 2.7 and 3.8 minutes for cyclobutene and bicyclobutane, respectively. Bicyclobutane (b.p. 8°) can be stored temporarily in the gas storage bulb as a liquid in a dry ice-acetone bath or for longer periods of time in an ampoule, sealed under vacuum, and stored in a freezer. 

This procedure appears to be general for the preparation, without rearrangement, of lesser substituted olefins. 2-Methyl-cyclohexanone tosylhydrazone gives 3-methylcyclohexene (98% yield by gas chromatography analysis).8 Cholestan-6-one tosylhydrazone gives A6-cholestene (95% isolated yield), androstan-... 

B. Hydrogenolysis of the Phenolic Ether Biphenyl. To a solution of 10 g. (0.032 mole) of the product from Part A in 200 ml. of benzene is added 2 g. of 5% palladium-on-charcoal, and the mixture is shaken with hydrogen in a Parr apparatus at 40 p.s.i. and 35-40° for 8 hours (Note 3). The mixture is filtered, and the insoluble residue is washed with three 100-ml. portions of hot ethanol (Note 4). The filtrates are combined, and the solvent is removed by means of a rotary evaporator at 60° (12 mm.) to leave a solid residue. The product is dissolved in 100 ml. of benzene, and 100 ml. of 10% sodium hydroxide solution is added. The mixture is shaken, and the layers are separated. The aqueous layer is extracted with 100 ml. of benzene, and the original benzene layer is washed with 100 ml. of water (Note 5). The benzene solutions are combined and dried over magnesium sulfate. Removal of the benzene by distillation yields 4.0-4.7 g. (82-96%) of biphenyl as a white powder, m.p. 68-70° (Note 6). The infrared spectrum is identical with that of an authentic sample, and a purity of at least 99.5% was indicated by gas chromatography analysis. 

A. I. Meyers, W. Beverung, and G. Garcia-Munoz, J. Org. Chem., 29, 3427 (1964). The discrepancy between the work reported earlier and the present work regarding isomer distribution may be due to variations in catalyst activity. The present reduction mixture consists of four decalol isomers of which the cis-cis product represents 50-55% as determined by gas chromatography analysis on a 250-om. column containing 10% Carbowax 20M on Chromosorb P at 150-200°. 

This procedure represents a novel, convenient, and fairly general method for preparing y-aryl-/3-diketones. By this method the submitters have phenylated the dianion of 1-phenyl-1,3-butanedione (61%), 2,4-heptanedione (98%), 2,4-nonanedione (78%), 2,4-tridecanedione (53%), and 3,5-heptanedione (50%).6 Substituted diaryliodonium salts have also been used to produce l-(4-chlorophenyl)-2,4-pentadione (44%), 4-(4-methyl-phenyl)-l-phenyl-l,3-butanedione (44%), and l-(4-methyl-phenyl)-2,4-nonanedione (21%).6 Under these conditions no more than a trace, if any, of arylation at the a-position of the /3-diketones was observed by gas chromatography analysis. 

Gas chromatography analysis showed total consumption of starting ethyl... 

Gas chromatography analysis was done on a Perkin-Elmer model 800 unit using dual X 6 columns packed with silanized Chromasorb W (product of Johns-Manville) coated with 5% neopentylglycolsebecate and y2% phosphoric acid. The column temperature was programmed from 100° to 240° C. at 8°/imm during analysis. 

Gas chromatography—analysis of compounds that can be volatilized without being decomposed or chemically rearranged ... 

Robbins, L. A., Bethea, R. M., Wheelock, T. M. Single detector and fore column trap for series gas chromatography analysis. J. Chromatog. 13, 361 (1964). 

Estrada-Pena, A. and Dusbabek, F. (1993). Cuticular hydrocarbon gas chromatography analysis of Argas vulgaris, A. polonicus, and their hybrids. Exp. Appl. Acarol., 17, 365-376. 

The gas chromatography analysis (Hewlett Packard 5890 with Perkin Elmer ion trap detector) of the soluble coke fractions for different reaction... 

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