Analysis by gas-liquid chromatography

Haworth methylation of methyl /3-D-glucopyranoside and its 4-benzyl and 4-(tetrahydropyran-2-yl) ethers was investigated in connection with partial-methylation studies on cellulose.267 For the unsubstituted glycoside, the ratios of relative rate-constants k2 k3 k4 k were estimated to be 8 2 1 8, and, for the 4-ethers, it was found that ke> k2> k3 best agreements between calculated and experimental yields were found with the assumption that the rate constant for reaction at HO-3 is doubled when HO-2 is substituted. Later methylation studies,268 performed to low degrees of substitution, with analysis by gas-liquid chromatography, gave k2> k4> k3 for the reactivity... 

Srivastava, V.K., P.K. Srivastava, and U.K. Misra. 1985. Polycyclic aromatic hydrocarbons of coal fly ash analysis by gas-liquid chromatography using nematic liquid crystals. Jour. Toxicol. Environ. Health 15 333-337. 

Norbornadiene (from Koch-Light Ltd.) of purity greater than 99% was purified by distillation through a Normatron automatic still at a reflux ratio of 25 1. The fraction (60 vol%) boiling at 89.3 °C/998 mbar was collected [18] bp 89.5 °C/1013 mbar). Analysis by gas liquid chromatography (GLC) (Pye Unicam - with OVO-1 columns), showed one... 

Extraction Procedure. We modified the extraction procedure of Nelson et al (10). Brie acidified with 2 ml of 5% trichloracetic acid (TCA) was extracted 3 times with 20 ml of petroleum ether. The combined extracts were reduced to 5 ml in a rotating evaporator, returned to the separatory funnel, and combined with 60 ml each of acetonitrile and distilled water. The acetonitrile-water-insecticide mixture was extracted twice with 60 ml of petroleum ether and anhydrous Na2S04 was added to the combined 120 ml extract. The extract was evaporated just to dryness and the residue was dissolved in benzene for analysis by gas-liquid chromatography (GLC). Extraction efficiencies in spiked experiments were 73% (aldrin) and 83% (dieldrin). 

The material which collects in the receiver is distilled through a 15-cm. Vigreux column at atmospheric pressure. Methyl isocyanide, a colorless, vile-smelling liquid, is collected at 59-60° weight 57-61 g. (69-74%) (Note 6). Analysis by gas liquid chromatography indicates that the purity exceeds 99% (Note 7). 

Amina Acid Analysis by Gas-Liquid Chromatography, Recent Developments in,... 

At the end of two hours, the heating was discontinued and about 500 mL. of hot water was added to the mixture. The mixture was acidified with concentrated hydrochloric acid and was then extracted three times with about 250 mL. of benzene and the combined extract was washed with water. The benzene was removed by distillation and the solid product was dried in a vacuum oven and weighed. The yield was 106.9 g of 3,4,5-trimethoxybenzaldehyde, representing a yield of 99.3% of the theoretical. Analysis by gas-liquid chromatography (g.l.c.) showed a purity of 99.85% with syringaldehyde as the only detectable impurity. 

Tetrachloromethane and hexachloroethane in phosgene are determined following their extraction into tetrachloroethene. The phosgene is destroyed using aqueous sodium hydroxide, and the tetrachloroethene layer separated prior to analysis by gas-liquid chromatography. 

AT-alkanes are dominant constituents of natural hydrocarbons in the marine environment and their ease of analysis by gas—liquid chromatography explains that this class is relative well documented. 

Analysis by gas-liquid chromatography Actual values are lower ... 

Pearce R J, (1977) Ammo acid analysis by gas-liquid chromatography of N-heptafluorobutyryl isobutyl esters. Complete resolution using a support-coated tubular capillary column. / Chromatogr 136, 113-126... 

The analysis of volatile sulphur compounds is difficult as additional compounds may be formed if the sample is heated or exposed to light or oxygen. Headspace analysis by gas-liquid chromatography using a flame photometric detector is the most satisfactory technique although solvent extraction may be necessary for the less volatile compounds. The sulphur compounds which have been identified in beer are listed in Table 22.19. 

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