Gas chromatography chiral

When the desired hydrogen uptake had been achieved, the vessel was opened, catalyst separated by filtration, and the reaction solution analysed by chiral gas chromatography (column Cydex B, 50 m, SGE Ltd). Analysis gave conversion and enantiomeric excess Enantiomeric excess is defined as IR - SI /(R+S). 

Initially, progress in this area was hampered by the lack of suitable analytical methods for chiral hydrocarbons. Early studies relied on optical rotation to determine enantiomeric excess (ee) values, but with the development of chiral gas chromatography (GC) and high-performance liquid chromatography (HPLC) columns, chromatographic methods have become more common. 

The reaction was diluted with TBME (100 mL) and stirred for 30 min. The phases were separated and once more TBME (100 mL) was added to the aqueous phase. The mixture was stirred for 10 min. The organic phases were combined and dried over Na2S04. Evaporation of the solvent yielded the cmde (5)-3-Hydroxytetrahydrothiophene-3-carbonitrile (10.26 g, 80 %) as shghtly yellow oil with 91 % ee measured by chiral gas chromatography (GC) after TMS-protection (ChirasU-Dex, 120 °C isotherm 11.9 min (5), 12.1 min (/ )). 

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). 

Leal, W. S Shi, X., Liang, D., Schal, C. and Meinwald, J. (1995). Application of chiral gas chromatography with electroantennographic detection to the determination of the stereochemistry of a cockroach sex pheromone. Proceedings of the National Academy of Sciences, USA 92 1033-1037. 

The purity of the ethyl glycidate prepared according to this procedure was >97% as measured by gas chromatography (BP5 capillary column from SGE). The enantiomeric purity was greater than 99% ee as determined by chiral gas chromatography on a 50-m CYDEX-B capillary column (0-cyclodextrin stationary... 

An attractive method for the determination of the enantiomeric excess of substrates and products resulting from the enzyme-catalyzed kinetic resolution of secondary alcohols is chiral gas chromatography (GC).48,49 This sensitive method is quick, simple to carry out and unaffected by the presence of impurities in the analyzed sample, therefore, isolation and purification of the analyzed sample is not required. Very small sample size is required for the analysis hence, reactions can be done on small scale. 

The enantioselective synthesis of phthalide 227 (the (3 )-isomer), and other substituted phthalides, and the determination of their absolute configuration has been reported <2005CH218>. In a different approach to the same compounds, 2-alkylbenzoic acids were fed to microorganisms known to affect asymmetric hydroxylation. Lactonization of the resulting alcohols yielded the phthalides, used as scents in cosmetics and soaps <1997JPP10243794>. There is sufficient interest in these optically pure compounds for a chiral gas chromatography (GC) stationary phase to have been developed to quantify stereoisomeric mixtures. A silylated /3-CD was employed... 

MoUer, K. Huhnerfuss, H. Rimkus, G., On the diversity of enzymatic degradation pathways of a-hexachlorocyclohexane as determined by chiral gas chromatography J. High Resol. Chro-matogr. 1993, 16, 672-673. 

Benschop and De Jong, 1988). In the case of toxicokinetic studies, it is important to differentiate between the two isomers because it is essential to know which isomer is stiU present in the circulation. Chiral gas chromatography can fulfill this requirement for G-agents like sarin and soman. Soman has two asymmetric atoms, phosphorus and carbon in the pinacolyl group. Therefore, the compound consists of four different stereoisomers. 

Adulteration of the oil with racemic, synthetic linalool may be detected using chiral gas chromatography, as studies showed the natural enantiomeric ratio of linalool to be as follows (R)-(-)-linalool (11-15%) (S)-(-H)-linalool (85-89%) [80]. 

To a 20 mL flask was added 2.5 g of (R,S)-2-ethoxycarbonyl-3,6-dihydro-2H-pyran, followed by 7 mL of 0.2 M pH 7.5 phosphate buffer and 2 mL of Bacillus lentus protease-III solution (approximately 5% solution of the protein). The biphasic solution was stirred at room temperature (23 °C) using a magnetic stirrer. The pH was checked at 0.5 hour intervals and readjusted to 7.5 by the drop-wise addition of 1 N NaOH (approximately 7 mL were required over the complete reaction). The progress of the reaction was monitored by chiral gas chromatography. After 5 hours, the enantiomeric purity of the unreacted ester was >99% and the reaction was stopped by the addition of 10 mL of MTBE. The pH of the aqueous phase was adjusted to 8.5 and the mixture was transferred into a separatory funnel. The aqueous phase was extracted twice with 20 mL of MTBE and the combined organic layers were extracted once with saturated sodium bicarbonate (10 mL), followed by saturated sodium chloride solution (10 mL), and the organic... 

Determined by chiral gas chromatography (trifluoroacetyl derivative) or high-performance liquid chromatography (benzoyl derivative) analysis of the of the primary amine. 

When properly installed, the analytical system involving thermodesorption cold trap injection and two-dimensional chromatography can be used routinely for analysis of the stereoisomers of soman and sarin in blood and tissue samples at minimum detectable concentrations of 1 -5 pg of stereoisomer per ml blood or gram tissue. In recent toxicokinetic experiments in pigs, the analytical system comprised chiral gas chromatography on a Chirasil-L-Val column with splitless injection and detection... 

Standard reaction conditions. Catalysed reactions were conducted at 293 K in a Baskerville stainless steel reactor of volume 150 ml. 7.2 ml pyruvate ester (65 mmol) and alkaloid (0.17 mmol cinchonidine (50 mg) or 0.17 mmol quinuclidine (19 mg) or 0.17 mmol of each) were dissolved in 12.5 ml dichloromethane and added to the catalyst (250 mg) in the reactor. The reactor was operated at 30 bar in a constant pressure mode. Product analysis was by chiral gas chromatography to determine the enantiomeric excess (ee) and by GCMS to determine the masses of higher molecular weight products. 

Hydrogenations were conducted in a flow microreactor (i.d. 3 mm) constructed in glass and located in a tube furnace. The catalyst bed was supported by glass wool. The reactor temperature of 313 K was monitored by a thermocouple located inside the microreactor. Catalyst samples were pre-conditioned in a He flow (80 ml min" ) for 10 min followed by a 3 1 He H2 flow (80 ml min ) for a further 10 min. This He H2 mixture was then diverted through the saturator at 293 K to deliver methyl pyruvate vapour to the catalyst. The exit gas was analysed by chiral gas chromatography (25 m 3-Chirasil-dex). ee/%(i ) = 100([i -] - [5-])/([i -] + [S-])... 

Perfetti, T.A. and W.M. Coleman III Chiral-gas chromatography-selected ion monitoring-mass selective detection analysis of tobacco materials and tobacco smoke ... 

The first effective chiral stationary phase, as already referred to in chapter 1, utilized derivatized amino acids to provide chiral selectivity [7] and this was achieved as early as 1966. These types of stationary phases however, had very limited temperature stability and the optimum temperature for separation was often in excess of that at which the stationary phase was stable. The first relatively stable stationary phase, as already mentioned, was introduced by Bayer [6], who combined the derivatized optically active component of the stationary phase in a polysiloxane gum. Nevertheless, a number of small molecular weight materials were used as stationary phase in the early days of chiral gas chromatography. The first type introduced by Gil-Av are shown below. 

From the examples given, it is clear that, as a result of their natural volatility, the analysis of essential oils has become one of the major application areas for chiral gas chromatography. In fact, the problems of separating the enantiomers of the essential oils was one of the driving forces Aat stimulated the development of chiral gas chromatography. The successful resolution of enantiomers has been due, firstly, to the very high efficiencies available from open tubular columns and secondly, to the remarkable chiral selectivity and thermal stability offered by the cyclodextrin based stationary phases. 

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