Gas chromatography radio

Buchtela, K., Grass, F., MUller, G. Radio gas-chromatography of metal chelates. I. Chro-matogr. 103, 141 (1975)... 

Product analyses carried out by radio gas chromatography and liquid scintillation counti. Standard deviation of data ca. 10%. 

Sample Analysis. For analysis via radio gas chromatography the irradiated sample mixture was quantitatively transferred into a greaseless injection loop by means of a 1-L mercury Toepler pump. The chromatography column consisted of 150 ft of 0.25-in. o.d. stainless steel beverage tubing packed with 30 wt % of the crotonic acid ester of H(CF2)8CH20H coated upon 30/40 ASTM mesh Chromosorb PA solid support. The column was operated at 273 K with a helium carrier gas flow rate of 25 cm min" (NTP). 

Fig. 1.8 Catalytic activities of the isoprenyl diphosphate synthases PalDSl, PaIDS4, PaIDS5, and PaIDS6 after heterologous expression in colL Products were measured by radio-gas chromatography (plotted in Bequcrcl, upper four panels) and identified by co-injection of non-radioactive terpenc standards, detected via a thermal conductivity detector (plotted as detector response, bottom panel). The main products after acid hydrolysis are listed G, geraniol F, farnesol and GG, geranylgeraniol. Bacteria containing only the expression vector without an isoprenyl diphosphate synthase sequence show ed no enzyme activity (top panel).

For the purification of tritiated compounds, radio-thin layer chromatography or radio-high performance liquid chromatography are frequently used, whilst radio-gas chromatography has its uses when the compounds are highly volatile.In addition, radio-size exclusion chromatography I I has been developed for tritiated macromolecules. 

Isotopically labelled fatty acids and the lipids derived from them are used in studies of reaction mechanism (e.g. hydrogenation) and of lipid biosynthesis and metabolism. Compounds containing radioactive isotopes ( H, are studied by liquid-scintillation counting or radio gas chromatography. Non-radio-active labels are studied by mass spectrometry or by NMR spectroscopy. 

A rather different approach has been used by the present authors. Rather than rely simply on analyses of product distributions, a radiotracer approach using [ F] (ti/2 = 110 min emitter) and [ Cl] (ti/2 = 3 X 10 year P emitter) has been employed to determine the quantities and labilities of halogen deposited on a prefluorinated chromia surface by direct radiochemical counting of the catalyst. By using radio gas chromatography, the distribution of a [ F] or [ C] label in the product mixtures has been obtained. 

Finally it should be mentioned that the bile acid nature of a peak can be made likely from isotope studies in vivo using simultaneous mass and isotope (i C or less preferably H) determination with radio-gas chromatography. The radioactivity detector, however, requires fairly high specific activities and one may have to collect the compound for conventional isotope determination. 

The gap between autoclave wall and fuel element had a thickness of 1 or 2 mm, respectively. The experiments were performed at 22 or 55 C brine temperature. A gas plenum with a pressure gauge for continues measuring was located above the autoclave. Gas samples were taken with an attachable gas sampling tube to analyse the gas composition by gas chromatography and radio gas chromatography. 

Labelling experiments were carried out on young olive plant one year aged. Microdroplets of the radioactive solution (specific radioactivity 1,94GBq/ mmole) were deposited on the surface of the first leaf from the top. Leaves were harvested after different times of incubation (2,4,6,12,24 and 48 h) and rinsed with distilled water. Lipids were extracted in chloroform -methanol (1 2, v v) then separated by thin layer chromatography. The obtained fatty acids were analysed by radio gas chromatography. Details of the methods have been given elsewhere (6). 

Methods used for isolation of the 15 000 x g particulate fraction from homogenates of the developing seeds, incubation of these fractions with [1- C] oleoyl-CoA or [2- C]malonyl-CoA in the presence of Mg , CoASH, NADH and/or NADPH, isolation of the very long chain monounsaturated fatty acids, and the analysis of their methyl esters by radio gas chromatography were essentially as described before [4,7]. In several experiments, the total lipids were extracted from the... 

Tsalas, S., Bachmann, K., Heinlein, G. The application of non-analytical radio gas-chromatography for the determination of adsorption enthalpies and entropies of inorganic bromides. Radiochim. Acta 29, 217—221 (1981)... 

The technique of using thermalized F atoms for the study of fluorine atom reactions has proven very useful with unsaturated hydrocarbons and halocarbons, providing data on mechanisms, relative rate constants and factors controlling such reactions. The characteristic difficulties of macroscopic fluorine chemistry are often avoided at tracer levels, and analysis by radio gas chromatography can be quite straightforward. However, e3q>eriments at pressures below 0.1 atmosphere are restively difficult, and most of the usual analytical methods are inapplicable at product mole fractions <10 °. 

The safflower (Carthamus tinctorius L.) seeds were grown for one week in total darkness and transferred into light. Cotyledons b ame greening and changed to leaves. Etioplasts were converted to chloroplasts. After 48 hours of illumination 50 nmoles of [1- C] linoleate (lOmCi/mM) were applied on the surface of cotyledons. After different times, cotyledons were removed and fractionated by differential centrifugation. The lipids of different pellets (chloroplasts 3000 x g, mitochondrial fraction 20.000 x g, microsomal fraction 100.000 x g) were analyzed by thin layer chromatography and their fatty acid methyl esters by radio gas chromatography. 

To analyze the molecular species of Pip, chromatographic spots, scraped from the plate, were incubated with 10 ll of acid phosphatase (Boehrmger, Germany, 60 U/ il) in citrate buffer (100 mM, pH 5.8) at 37°C in a final volume of 0.5 ml. The PI molecular species derived from Pip were analyzed by combining radio-HPLC and radio gas-chromatography of labelled fatty acid methyl esters, as previously described [1]. 

As an example of one experiment, 0.2 xl of sodium [l- C]acetate containing 440,000 cpm (counts per minute) was incubated with the ejaculatory bulbs at pH 6.8 in phosphate buffer. The products were extracted with hexane and subjected to radio-gas chromatography. The total label recovered was 54,000 cpm, but most of this was in fatty acids, 1162 cpm were recovered in the heptadecenone peak (2.15% of recovered label, 0.26% of applied label) and 625 cpm in tridecanone (1.15% of recovered label, 0.14% of applied label). The experiments effectively proved the site of biosynthesis and showed the compounds were being synthesized from acetate units. 

---