Radioactive materials compounds

Other compounds which may be found in crude oil are metals such as vanadium, nickel, copper, zinc and iron, but these are usually of little consequence. Vanadium, if present, is often distilled from the feed stock of catalytic cracking processes, since it may spoil catalysis. The treatment of emulsion sludges by bio-treatment may lead to the concentration of metals and radioactive material, causing subsequent disposal problems. 

Fluorine, which does not occur freely in nature except for trace amounts in radioactive materials, is widely found in combination with other elements, accounting for ca 0.065 wt % of the earth s cmst (4). The most important natural source of fluorine for industrial purposes is the mineral fluorspar [14542-23-5] CaF2, which contains about 49% fluorine. Detailed annual reports regarding the worldwide production and reserves of this mineral are available (5). A more complete discussion of the various sources of fluorine-containing minerals is given elsewhere (see Fluorine compounds, inorganic). 

Generally, labeled compounds are prepared by procedures which introduce the radionuchde at a late stage of the synthesis. This allows for maximum radiochemical yields, and reduces the handling time of radioactive material. When dealing with short half-life isotopes, a primary consideration is the time required to conduct synthetic procedures and purification methods. 

Radioactivity associated with Re can be detected only by using sophisticated laboratory equipment because of the low energy of the emitted P-particles. This radioactivity poses no health or safety ha2atds. Samples of the metal and its compounds ate not labeled as radioactive, and typical precautions associated with radioactive materials ate not taken during use and handling of the element or its compounds. 

Many fluorinations by electropositive fluorine reagents produce a-fluoro carbonyl compounds as the final result An extensive review exists on the preparation of a-fiuorocarbonyl compounds [101 Also, electropositive reagents are used widely in the preparation of F-labeled radioactive materials required in positron etmssion tomography for biomedical research Excellent reviews are available on fluonne-18 labeling [//, 72]. 

When specifically labelled compounds are required, direct chemical synthesis may be necessary. The standard techniques of preparative chemistry are used, suitably modified for small-scale work with radioactive materials. The starting material is tritium gas which can be obtained at greater than 98% isotopic abundance. Tritiated water can be made either by catalytic oxidation over palladium or by reduction of a metal oxide ... 

Table 2. Synthesis by recoil methods a partial list of radioactive organometallic compounds, other than the starting material, synthesized by recoil methods...

It is important to note that since the amounts of radioactive material produced are so extremely small (some 10 % of the total is typical) it is usually necessary to add macro quantities—10-100 mg—of each compound expected to be present, in order to effect a good separation and to measure the chemical yield of the carrier. The yield measured is the radioactivity in each separated chemical species as a fraction of the total radioactivity in the sample, corrected to 100% chemical yield of each respective carrier. The term retention is commonly used to refer to the yield of the parent compound. This term has the disadvantage, however, of implying that the radioactive atom remained in the same molecule. Since it often appears that the molecule is only later reconstituted, the terms yield and parent yield are to be preferred. 

Because exposure to radiation is a health risk, the administration of radioactive isotopes must be monitored and controlled carefully. Isotopes that emit alpha or beta particles are not used for Imaging, because these radiations cause substantial tissue damage. Specificity for a target organ is essential so that the amount of radioactive material can be kept as low as possible. In addition, an Isotope for medical Imaging must have a decay rate that is slow enough to allow time to make and administer the tracer compound, yet fast enough rid the body of radioactivity in as short a time as possible. 

Chemicals. Purified, P Cj-labelled alachlor (specific activity = 17 mCi/mM), butylate (specific activity = 2.54 mCi/mM) and metolachlor (specific activity = 4.5 mCi/mM) were used in the leaching, adsorption, and diffusion studies. The radiopurity of these compounds was greater than 95% as determined by thin-layer chromatography. All other studies were conducted using analytical grade, non-radioactive material (purity 5 95%). 

For many of the analytical techniques discussed below, it is necessary to have a source of X-rays. There are three ways in which X-rays can be produced in an X-ray tube, by using a radioactive source, or by the use of synchrotron radiation (see Section 12.6). Radioactive sources consist of a radioactive element or compound which spontaneously produces X-rays of fixed energy, depending on the decay process characteristic of the radioactive material (see Section 10.3). Nuclear processes such as electron capture can result in X-ray (or y ray) emission. Thus many radioactive isotopes produce electromagnetic radiation in the X-ray region of the spectrum, for example 3He, 241Am, and 57Co. These sources tend to produce pure X-ray spectra (without the continuous radiation), but are of low intensity. They can be used as a source in portable X-ray devices, but can be hazardous to handle because they cannot be switched off. In contrast, synchrotron radiation provides an... 

The first method is quicker, but the filtration entailed in this reaction presents a hazard because of the danger of inhalation. If it is desired to employ volatile radioactive materials, e.g. to introduce 32P into the molecule, the second method is recommended. Further, the first method involves some danger because of the pressure developed in an enclosed reaction vessel containing ethyl chloride. It is considered essential that operations with the more volatile radioactive compounds (up to b.p. 150°/760 mm.) should be carried out in a completely enclosed system. This is possible with the second method, and the extra time of operation involves a decrease in the radioactivity of only 15 per cent compared with the first method.4... 

The most widely used technique for the separation of large quantities of radioactive material is that of solvent extraction. The principle of the method is that ideally the partition coefficient of a compound between two solvents does not depend on concentration in a given set of conditions. This was shown in an early paper of Graham and Sea-borg (35) who demonstrated that the partition coefficients of gallium and cobalt chlorides between ether and aqueous hydrochloric acid were the same for concentrations of lCTli molar (i. e. no added carrier) as for 1-6xl0 s molar. 

Two epidemiology studies have examined mortality among thorium workers neither found significant excess mortality. The standard mortality ratio (SMR) for all causes of death in a cohort of 3039 male workers in a thorium processing plant was 1.05 in comparison to United States white males (Polednak et al. 1983). The estimated radiation levels to the workers for inhalation intake ranged from 0.003-0.192 nCi/m (0.001-0.007 Bq/m ) for a period of 1-33 years. No evidence of overt industrial disease was found in a cohort of 84 workers at a thorium refinery exposed to <0.045-450 nCi/m (<0.002-0.02 Bq/m ) for <1-20 years (Albert et al. 1955). In both studies, the workers were exposed to other toxic compounds (uranium dust) as well as other radioactive materials (thoron, uranium daughters, thorium daughters, cerium). 

VAC TRAX is an ex situ thermal desorption process that separates contaminants such as volatile organic compounds (VOCs), semivolatile organic compounds (SVOCs), polychlorinated biphenyls (PCBs), and radioactive materials from soils, sludges, and solid trash. This process can be applied to mixed and unmixed waste streams. Because the nitrogen atmosphere in which the process occurs is inert, no combustion of organic material takes place. 

Sediments in the Mississippi River were accidentally contaminated with a low-level radioactive waste material that leaked from a nuclear power plant on the river. Pore water concentrations of radioactive compounds were measured following the spill and found to be 10 g/m over a 2-mm depth. The water contamination was 30% radioactive cesium ( Cs), with a half-life of 30 years, and 70% radioactive cobalt ( °Co), with a half-life of 6 years. Objections by the local residents are preventing clean-up efforts because some professor at the local state university convinced them that dredging the sediments and placing them in a disposal facility downstream would expose the residents to still more radioactivity. The state has decided that the sediments should be capped with 10 cm of clay and needs a quick estimate of the diffusion of radioactive material through the clay cap (Figure E2.8.1). If the drinking water limit (10 g/m ) is reached at mid-depth in the cap, the state will increase its thickness. Will this occur ... 

In a technique known as medical imaging, tracers are used in medicine for the diagnosis of internal disorders. Small amounts of a radioactive material, such as sodium iodide, Nal, which contains the radioactive isotope iodine-131, are administered to a patient and traced through the body with a radiation detector. The result, shown in Figure 4.11, is an image that shows how the material is distributed in the body. This technique works because the path the tracer material takes is influenced only by its physical and chemical properties, not by its radioactivity. The tracer may be introduced alone or along with some other chemical, known as a carrier compound, that helps target the isotope to a particular type of tissue in the body. 

All radioactive materials should be stored in well-labeled, glass containers. The label must include your name, the type of isotope, the radioactive compound, the total amount of radioactivity, the specific activity, and the date of measurement. 

Treatment of Com. Ten microliters of an 80% acetone solution, containing 100 fig. of C14-gibberellin, was applied with a micropipet near the middle of the upper surface of the first leaf, followed by 10 fjl. of 0.1% Tween 20 and 50% ethyl alcohol in order to increase absorption of the radioactive material. The drop of solution was kept from running down by means of lanolin paste. Four normal and four dwarf com plants were thus treated, while untreated plants were kept as controls. The same number of dwarf plants was treated with 0.05 fic. of C14-5-aminotriazole in order to compare the pattern of translocation of gibberellin with that of a compound whose movement has been studied previously (4). The treated plants and controls were then placed in the growth chamber, and one or two specimens were harvested at the end of 1, 2, and 7 days, freeze-dried, and autoradiographed. 

Interesting chemical and structural phenomena can occur when radioactive materials are stored in the solid state Extensive studies have been made of both the chemical and physical status of progeny species that result from the a or 3" decay of actinide ions in several different compounds The samples have been both initially pure actinide compounds—halides, oxides, etc.—and actinides incorporated into other non-radioactive host materials, for example lanthanide halides. In general, the oxidation state of the actinide progeny is controlled by the oxidation state of its parent (a result of heredity). The structure of the progeny compound seems to be controlled by its host (a result of environment). These conclusions are drawn from solid state absorption spectral studies, and where possible, from x-ray diffraction studies of multi-microgram sized samples. 

Radioactive compounds have been used for radiotherapy and diagnosis in various diseases. Radioactive material is available as a sealed radioactive source. Unsealed sources are usually liquid, particulate, or gaseous. Utmost care is taken in the preparation, handling, and disposal of these radioactive materials, which are very hazardous. 

This paper is the only one in the liquid chromatography portion of this symposium which will attempt to deal with chromatography specifically from the viewpoint of the pesticide metabolism chemist. A residue analyst knows what compound he must analyze for, and develops his method with the properties of that substance in mind. On the other hand, the pesticide metabolism chemist has a different problem. At the conclusion of the treatment, exposure, and harvest phases of a radiolabeled metabolism study, he divides his material into appropriate samples, and extracts each sample with selected solvents to obtain the radioactive materials in soluble form. Typically these extracts consist of low levels (ppm) of carbon-14 labeled metabolites in a complicated mixture of normal natural products from the plant, animal, or soil source. The identity of each metabolite is unknown, and each must be isolated from the natural background and from other labeled metabolites in sufficient quantity and in adequate purity for identification studies, usually by mass spectrometry. The situation is rather like looking for the proverbial "needle in the haystack" when one does not know the size, shape,or composition of the needle, or even how many needles there are in the stack. At this point a separation technique must be selected with certain important requirements in mind. 

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