Carriers, carbon-containing

The combustion of mixtures of hydrogen and air produces very few ions so that with only the carrier gas and hydrogen burning an essentially constant signal is obtained. When, however, carbon-containing compounds are present ionisation occurs and there is a large increase in the electrical conductivity of the flame. Because the sample is destroyed in the flame a stream-splitting device is employed when further examination of the eluate is necessary this device is inserted between the column and detector and allows the bulk of the sample to by-pass the detector. 

The composition of the carrier gas containing the nitrogen oxides is another very important factor in NO removal. The influence of oxygen content in N2/02/N0 mixtures on the conversion of NO was investigated [26-28], The addition of water vapor [26,27,29-32], carbon dioxide [26,32] and hydrocarbons [27-35] was studied as well. 

A carrier molecule containing four carbon atoms (the C4 unit) takes up a C2 unit (the activated acetic acid ), which is introduced into the cycle. The product is a six-carbon molecule (the C6 unit), citric acid, or its salt, citrate. CO2 is cleaved off in a cyclic process, so that a C5 unit is left this loses a further molecule of CO2 to give the C4 unit, oxalacetate. In the living cell, this process involves ten steps, which are catalysed by eight enzymes. However, the purpose of the TCA cycle is not the elimination of CO2, but the provision of reduction equivalents, i.e., of electrons, and... 

Dissolve the carrier protein (or another carrier that contains amine groups) in 0.1M sodium carbonate, 0.15 M NaCl, pH 8.5, at a concentration of 2mg/ml. 

At the end of considerations of heterogeneous supported catalysts, mention should be made of Ziegler-Natta catalysts for ethylene and propylene polymerisations supported on carbon-containing carriers, although there is rather scant information in the literature concerning this matter. 

The one-carbon carrier N, N -methylenetetrahydrofolate is derived from reactions of the one-carbon pool (Chapter 27). [The term one-carbon pool refers to all single-carbon-containing metabolites (e.g., -CH3, -CHO, NH=C-, etc.) that can be utilized in biosynthetic reactions such as formation of purine and pyrimidine.] These reactions include oxidation of glycine by glycine cleavage enzyme complex (glycine synthase) ... 

With the sample preparation method described earlier, the optimal amount of total carbon for AMS analysis is around l.Omg. When the total carbon level is far below that level, a precise amount of suitable carrier carbon is added. Petroleum-based tributyrin is often used as the carrier because it is a nonvolatile liquid, contains depleted levels of 14C and 3H, and its measurement is highly reproducible [18]. 

In a promising development of oxygen determination, Kirsten [106] carried out the pyrolytic determination of oxygen in organic compounds at 1020°C with the use of amorphous carbon containing 20% of nickel. An important feature of the method is the addition of chlorohydrocarbon vapour to the flow of carrier gas. Kirsten [106] found that the reactor, i.e., the quartz tube, is rapidly rendered inoperative if the temperature is increased above 1020°C. To obtain quantitative results, it is sufficient to evaporate 1-chloropentane at a rate of 18ql/h. At present the Kirsten method is applied to Carlo Erba instrumentation. 

Solid AMS samples use carrier carbon in LC fractions having low natural carbon. One microliter of tributyric acid (tributyrin) contains 615 p,g of carbon and is a suitable carrier additive. The compound can be purchased with between 9 and 35% natural biospheric carbon, apparently introduced by ingredient stocks obtained from natural lipids. A set of independently quantified background carrier samples taken with the UPLC trace shown in Figure 16.9 averaged 9.65 0.29% Modern, or an uncertainty of 0.18 amol on the 6 amol... 

This method is very reliable but suffers from the drawback that the lithium aluminum hydride contains carrier carbon that reduces the specific radioactivity. A solid phase technique has also been reported for the synthesis of [ C]methyl iodide (Sarkadi et al. 1997,1998). In an alternative method, that gives higher specific radioactivity, [ C] methane undergoes a free radical iodination in a circulating gas phase while the [ C] methyl iodide formed is continuously trapped on a solid phase to prevent further iodination (Larsen et al. 1997). 

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