Tritium labelled organics

The production of tritium-labelled organic compounds was enormously facilitated by K. E. Wilz-bach s discovery in 1956 that tritium could be introduced merely by storing a compound under tritium gas for a few days or weeks the radiation induces exchange reactions between the hydrogen atoms in the compound and the tritium gas. The excess of gas is recovered for further use and the tritiated compound is purified chro-matographically. Another widely used method of... 

Phosphors for radio-activation are used as mixtures with a ji-radioactive compound (e.g., 3H, 14C, or 147Pm compounds) whose radiation effects continuous luminescence of the phosphor. Tritium-labeled organic binders are used for the production of luminous products and paints. Because of the high cost of tritium, the phosphors must have a high efficiency. 

Young, D. W. Stereospecific Synthesis of Tritium Labelled Organic Compounds using Chemical and Biological Methods, Vol. 4, p. 177, ibid. 1978... 

Helium-3 is now a readily available and inexpensive isotope. The presence of tritium and tritium-labeled organic compounds in commercial helium-3 is described by Lee and Rowland (1959) and a method of purification of the helium-3 is also outlined in this note. Typical gas-phase irradiations are carried out in 10-30 cc quartz (El-Sayed et al., 1958) or Pyrex 1720 (Lee et al., 1960a) ampoules containing 1-2 cc of He at S.T.P. and the organic compound at 20-200 mm Hg pressure. 

Early attempts to define phase contact by use of tritiated water and tritium-labeled organics were unsuccessful due to a variety of problems ranging from variations between vials to sample matrix, absolute efficiency measurement problems cind lack of recognition that phase contact variations Ccin occur over surprizingly small concentration ranges. In the method presented here, all of these common problems, with the exception of statistics and 48 hours spectrometer stability, are eliminated. 

Hot atom reactions have also been used to label organic compounds with T. Irradiation of helium-3 with neutrons according to the nuclear reaction produces very energetic tritium atoms that can displace ordinary hydrogen in organic compounds. This procedure is not very selective, and the labeling pattern must be determined to enable the tritiated product to be used effectively as a tracer (34). 

The incorporation of a chapter on deuteration in a steroid monograph is quite reasonable since development of a number of the most important deuteration reactions have actually had their impetus through steroid research. The field of steroid chemistry offers possibly the largest variety of deuteration reactions of any area of organic chemistry. Many of these deuteration techniques have also been used for tritium labeling, which is especially pertinent in view of the large demand for tritiated steroids as tracers in biological experiments. 

Tritium and Other Radionuclide Labeled Organic Compounds Incorporated in Genetic Material (1979)... 

Timmons (12) showed that the water in a never dried freshcut tree, when exchanged with a series of organic solvents could be replaced with radioactively tritium labeled MMA (hydrogen-3). After polymerization and the use of autoradiography the MMA was located in the cell wall structure. If the same wood was dried normally, and then treated in the usual manner with tritium labeled IWIA, the polymer was located exclusively in the capillaries and none was found in the cell walls. 

The metabolic pathways in plants and living organisms were studied by means of tritium-labeled morphine (508, 509). The use of unnaturally tritium-labeled codeine derivatives showed that P. somniferum is able to... 

The introduction or substitution of tritium into organic molecules is much easier than substitution and tritium-labelled compounds are eonsequently more easily prepared. Conversely, the label is also more readily lost This aspect is particularly important in biological experiments, as the loss of tritium is not due to the biological system, even though there is some uncertainty regarding the ability of biological systems to replace the tritium with hydrogen without modification of the chemical stmcture. 

This is generally the easiest and quickest method of tritium labelling. The unlabelled organic substance is heated with, for example, tritium-labelled water or acetic acid and a catalyst such as palladium or platinum. After removal of the excess solvent, labile tritium is removed by repeated equilibration with water or other appropriate solvents and the product purified by suitable methods. This results in labelling which is general but not, as a rale, uniform, and the precise determination of the labelhng is usuahy so laborious that it is not often attempted. The method is not apphcable to compoimds which are unstable under the conditions used, and it is not often possible to obtain a theoretical equilibrium concentration without excessive breakdown of the starting material. Purification... 

A 98% conversion efficiency has been achieved at 1.5 atmospheric pressure of CO2 and 10% excess of water, while the yield was 85% only when stoichiometric amounts of water and carbon dioxide were used. No isotopic fractionation has been noted when 5 to 10% excess of water has been used in the reaction in equation 5. Doubly labelled methane has been used in simultaneous analysis of and both in the atmosphere and in environmental carbon dioxide as well as in analysis of and H-labelled organic compounds. Proportional counters filled with methane possess very good counting properties and there is no need to add any inactive counting gas. and tritium-labelled methanes have also been produced" by pyrolysis of sodium acetate in molten sodium hydroxide (equation 6) ... 

In spite of the developments achieved in the preparation of samples labelled with tritium and carbon-14, however, no rapid combustion methods and suitable instruments have been available for the preparaticxi of multiple labelled organic substances containing other conbinatic is of soft beta omitting isotopes. On the other hand, the Improvenient of precision and automation as well as reduction of operational and maintenance costs seams also desirable. 

With this in view, automatic isotcpe analytical processes have been developed. Of these methods, the sample preparation techniques used for simultaneous determination of carbon-14/ tritium and carbon-14/sulfur-35 in dual labelled organic compounds and biological materials hy liquid scintillation counting are presented. For the determinaticai of carbon-14/sulfur-35 an iirproved versicai of a previously published method (Gacs et al., 1978a) is described. The principles of the procedures are shewn in Fig.l and Fig.2. 

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