Tritium, characterization

DifficultSepa.ra.tions, Difficult separations, characterized by separation factors in the range 0.95 to 1.05, are frequentiy expensive because these involve high operating costs. Such processes can be made economically feasible by reducing the solvent recovery load (260) this approach is effective, for example, in the separation of m- and -cresol, Hnoleic and abietic components of tall oil (qv), and the production of heavy water (see Deuteriumand TRITIUM, deuterium). 

There should be specific, saturable binding to the receptor, accompanied by pharmacological characteristics appropriate to the functional effects, demonstrable using a radioactive, eg, tritium or iodine-125, ligand to label the receptor. Radioligand binding assays (1,6) have become a significant means by which to identify and characterize receptors and enzymes (see Immunoassays Radioactive tracers). Isolation of the receptor or expression of the receptor in another cell, eg, an oocyte can be used to confirm the existence of a discrete entity. 

The triatomic hydrogen molecule ion H3+ was first detected by J. J. Thomson in gas discharges and later fully characterized by mass spectrometry its relative atomic mass, 3.0235, clearly distinguishes it from HD (3.0219) and from tritium... 

Fritz, R. and Fritz, J., 1991, Characterizing Shallow Aquifers UsingTritium and 14C Periodic Sampling Based on Tritium Half-Life Applied Geochemistry, Vol. 6, pp. 17-33. 

Cheney et al. (1995) analyzed steroids by coupling an HPLC purification step with GC/MS. The steroids were initially characterized by their HPLC retention times compared with the retention times of tritium-labeled recovery standards. Next, the nemosteroids were characterized by their GC retention times. Finally, they were identified by their unique fragmentation spectra following derivatization with heptafluorobutyric anhydride or methoxyamine hydrochloride. For structmal identification, the mass spectra were compared to appropriate reference standards. This approach is highly specific, and its sensitivity is increased by the use of SIM. The detection limit for measuring allopregnanolone achieved in the 1995 study was 0.63 pmol (0.2 ng) starting from 100-300 mg of brain tissue. 

P xcept for tritium, carbon-14, and the long lived rare gases, the radio-active atoms produced by a nuclear detonation are accounted for completely within a population of radioactive particles. The nature of the particle population and the manner in which the individual radionuclides are distributed within it will vary with the conditions under which the detonation occurred. Characterization of the radioactive particle population requires ... 

After equilibration with fumarase, the mixture of fumarate and malate is analyzed for 3H. If tritium is originally present in the pro-3S position, the equilibration will not remove it (150 plus 152). On the other hand, tritium in the pro-3R position will be lost to the water by way of 153. To facilitate the analysis, [14C]acetate is added initially and the 3H I4C ratio is determined on the malate produced by malate synthase, before and after incubation with fumarase. The tritium content of the incubation water is also determined. The % retention of 3H in the fumarase reaction is given the symbol, F [127]. In detailed analyses, it has been shown that chirally pure (7 (-acetate is characterized by F = 79 and (S (-acetate by F= 21 [129]. The F value actually depends on four factors ... 

Various preparations of antisera to atropine have been reported. A racemic hemisuccinate ester was prepared and conjugated to bovine serum albumin by the carbodiimide technique. Antisera formed to the original immunogen selectively bound the R isomer (34), but a later antiserum prepared by this approach was reported to bind both R and S forms with "equal efficiency" (35). R, S-atropine was treated with diazotized p-amino-benzoic acid, and the resulting compound (which was not further characterized) was used for conjugation to bovine serum albumin by means of a carbodiimide-mediated reaction. Antisera resulting from use of this material were quite selective for the R isomer, with a cross-reaction of only about 2% for the S isomer (36). Virtanen et al. followed this procedure with S-atropine. Their antiserum bound equally to S- and R,S-atropine, as measured by displacement of tritium-labeled R,S-atropine (37). In another study (31), both racemic atropine and the S isomer were coupled to human serum albumin by the technique of Wurtzburger et al. (36), Antisera were obtained that were selective for both the R and S isomers (33). 

CIS-H4 and trans-P-mcthyl styrene 85 oxides have been tritium labelled also and used for biochemical characterization of the various forms of epoxide hydrolase. 

A nuclear species (nuclide) is characterized by its atomic number Z (that is, the nuclear charge in units of e, or the number of protons in the nucleus) and its mass number A (the sum of the number of protons plus the number of neutrons in the nucleus). We denote an atom that contains such a nuclide with the symbol zX, where X is the chemical symbol for the element. The atomic number Z is sometimes omitted because it is implied by the chemical symbol for the element. Thus, JH (or H) is a hydrogen atom and (or C) is a carbon atom with a nucleus that contains six protons and six neutrons. Isotopes are nuclides of the same chemical species (that is, they have the same Z), but with different mass numbers A, and therefore different numbers of neutrons in the nucleus. The nuclear species of hydrogen, deuterium, and tritium, represented by JH, jH, and jH, respectively, are all members of the family of isotopes that belong to the element hydrogen. 

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