Carbon specific radioactivity

In order to lower the cost of the nuclear reaction, enriched water is recovered after trapping the F-fluoride ions on an ion exchange resin [54,55]. For this reason and also because of scarcity of enriched water, the exploration of different target strategies is still searched. In examples, a frozen [ 0]carbon dioxide gas target [56] and irradiation of 2-fluoroaniline by 30-40 MeV photons [ F(y,n) F] [57] was shown to be efficient. However, the specific radioactivity still remains very low. 

Irradiation of enriched water (>95 %) with protons (16 MeV) is the most common method used to produce no-carrier added [ F]fluoride. Fluorine being less ubiquitous than carbon, F-radiotracers can be obtained with very high specific radioactivities (50-500 GBq pmol ). The theoretically possible... 

Tritiated GAs of very high specific radioactivity have been prepared by catalytic reduction. The 1,2 double bond of GAq can be selectively reduced, using a partially poisoned palladium catalyst, to give [1,2-3h2]GA] (7 -,(75,76), although some reduction of the 16,17 double bond and the lactone also occurs (76). Introduction of 3h at sites other than carbon atoms 1 and 2 has also been found (76). [3h]GAI has been prepared from GAy by a similar method JT7). [3h]GA was converted... 

The importance of secondary-radiation effects may be seen from the decomposition of dextran-C sulfate containing about 20 D-glucose residues per molecule, observed by Bayly and Weigel. It had the relatively low specific radioactivity of 22.4 mC. per g.-atom of carbon (about 3 mC/ millimole of dextran sulfate). After three weeks in the freeze-dried form, it had charred and become a total loss. The decomposition was presumably attributable to a secondary-radiation effect arising from a prior liberation of sulfuric acid, which then released more sulfuric acid to destroy the material. 

The specific radioactivity of carbon dioxide was found to be higher than that of acrolein, but lower than the propene radioactivity. If carbon dioxide and acrolein were yielded by propene separately, the specific radioactivity of C02 would be identical to that of propene. 

Of course, the actual application of pertechnetate ions to corrosion inhibition of iron and carbon steels will obviously be a great problem because of the radioactivity of Tc, even in dilute solutions of TcO. A pertechnetate concentration of 5 10 M corresponds to a specific radioactivity of 84.15 pCi/l or 3.11 U/ Bq/1. Nevertheless, the corrosion inhibiting property of TcOj was proposed to be used in steam-generating nuclear reactors [42,43[-... 

Covalent protein binding studies require the use of radiolabeled compounds. H-tracers are often used because they are relatively easy to synthesize and are of high specific radioactivity. However, possibilities exist that the H-label may be lost if oxygenation of the test compound occurs directly on the carbons where the H-label is attached. As a consequence, observed binding values could be underestimated. tracers, on the contrary, are less likely to lose the label, and therefore are preferred. However, possibilities of losing a radiolabel should be considered for any given radiolabeled tracer. Therefore, evaluation of the loss of radiolabels needs to be performed before covalent... 

Gram scale radiolabeled syntheses of these three products were performed using a Mannich-like reaction in which phosphorous acid combines with Carbon-14 labeled formaldehyde and the particular amines required. The environmental application required several millicuries of carbon-14 radioactivity for each phosphonate at specific activities of several millicuries per millimole and high radiochemical purities. We were not successful in producing any of the final products shown in high yields but obtained mixtures containing significant amounts of what appeared to be all the possible intermediate incompletely phosphonated compounds. The separation properties of intermediates and final products were found to... 

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). 

The specific radioactivity of [ C]phosgene has been relative low, probably due to carrier carbon in the chlorine gas. 

C]ethyl iodide is synthesized with higher specific radioactivity and radiochemical purity from carbon monoxide by a palladium catalyzed reaction with methyl iodide followed by reduction and iodination (Eriksson and Langstrom 2001). 

The low reactivity and the low concentration of carbon monoxide in the environment make prerequisites for high levels of specific radioactivity. 

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