Nonradioactive iodine

Figure 17.6 a. Radioactive iodine molecules in the solid in the flask on the right are separated from nonradioactive iodine in the flask on the left. Note the readings on the radiation monitors, b. After the stopcock has been open for a time, the radiation monitors show that radioactive molecules are in both flasks. The particles must have moved back and forth between the flasks and between the solid and the gaseous phases. 

Problem 10.56. One of the products of radiation fallout from atmospheric bomb testing or nuclear accidents as at Chernobyl is iodine-131. People living in a region where iodine-131 was known to have been deposited were encouraged to use salt enriched with nonradioactive iodine-127. What was the basis of this treatment ... 

Arts. It was expected that the thyroid gland could not discriminate between iodine-127 and iodine-131. The rate of iodine uptake by the thyroid is dependent upon the iodine concentration. By flooding the body with the nonradioactive iodine, the body s concentration of iodine-131 would be significantly diluted, and its rate of uptake sharply reduced compared to the uptake of iodine-127. 

The thyroid gland, a small organ located in the neck near the Adam s apple, uses iodine to produce thyroid hormones. The thyroid gland cannot distinguish between radioactive iodine and stable (nonradioactive) iodine. If 1-131 were released into the atmosphere, people could ingest it in food products, milk, or water, or breathe it in. The thyroid gland would then absorb the 1-131 and gel a dose of radiation from it, increasing the risk for thyroid cancer or other thyroid... 

When potassium iodide is taken in the recommended doses, it floods the thyroid with nonradioactive iodine, preventing the thyroid from absorbing the cancer-causing radioactive iodine, which is then excreted in the urine. 

The use of radioactivity in diagnosis usually involves a radiotracer, a radioactive nuclide attached to a compound or introduced into a mixture in order to track the movanent of the compound or mixture within the body. Tracers are useful in the diagnosis of disease because of two main factors (1) the sensitivity with which radioactivity can be detected, and (2) the identical chemical behavior of a radioactive nucleus and its nonradioactive counterpart. For example, the thyroid gland naturally concentrates iodine. When a patient is given small amounts of iodine-131 (a radioactive isotope of iodine), the radioactive iodine accumulates in the thyroid, just as nonradioactive iodine does. However, the radioactive iodine emits radiation, which can then be detected with great sensitivity and used to measure the rate of iodine uptake by the thyroid, and thus to image the gland. 

Explain the difference between iodine 123 and 131 in both the nuclear arrangement of protons and neutrons and the difference in the break-down of the nucleus. The usual nonradioactive isotope of iodine is I 127. If 131 iodine gives off one beta particle what new element is formed ... 

Radioactive isotopes have the same chemical properties as the nonradioactive isotopes of the same element. Because they undergo the same chemical reactions, radioactive atoms are often used as tracers to determine what ordinary atoms are doing. For example, to detect problems in the human thyroid gland, physicians often presCTibe iodine that includes a tiny fraction of 53 , a radioactive isotope of iodine. The body should utilize all the iodine in the thyroid gland. With a Geiger counter, the physician can follow the path of the radioactive isotope. If the radioactive iodine is not absorbed by the thyroid, then the regular iodine has not been absorbed either, and the physician has confirmed that a certain problem exists. 

The dynamic nature of chemical equilibrium can be illustrated by placing equal masses of iodine crystals in two interconnected flasks, as shown in Figure 18-4a. The crystals in the flask on the left contain iodine molecules made up entirely of the nonradioactive isotope 1-127. The crystals in the flask on the right contain iodine molecules made up of the radioactive isotope 1-131. The Geiger counters indicate the radioactivity within each flask. 

Use (Nonradioactive.) Preparation of heavy water to moderate nuclear reactors. (Radioactive.) Tracers in biochemical, metallurgical, and medical research in geochemical and archeological research (14C) irradiation source for polymerization, sterilization, etc. therapeutic agents in various diseases (iodine, sodium, gold, etc.) electric power generation. 

The radioactive isotope of an element chosen for tracer studies has exactly the same chemical behavior as any other isotope of the same element. For example, iodine-127, the most abundant nonradioactive isotope of iodine, tends to concentrate in the th)rroid gland. Both radioactive iodine-131 and iodine-125 behave in the same way and are used to study the th)rroid. The rate of uptake of the radioactive isotope gives valuable information regarding underactivity or overactivity (hy-poactive or h)rperactive th)rroid). 

The use of K1 serves as an important remedy to protect from radioiodine exposure under nuclear accident conditions. In principle, under normal circumstances, excess iodine decreases sodium—iodide symporter (NIS) on the thyroid cell surface, thereby inhibiting further access for iodine into the thyroid. Excess iodide administration at the appropriate time decreases thyroid radioactive iodine uptake (RAIU) by increasing the amount of nonradioactive... 

Radiochemical methods of analysis can be grouped according to whether one measures radioactivity present in the sample or employs some means of introducing radioactivity into an otherwise nonradioactive sample in order to analyze for some component. An example of the first type is the determination of radioactive in rock samples. The second type is exemplified by using labeled KPO3 (I denoting a radioisotope of iodine) to determine the concentration of SO2 in air by the radiorelease method. This chapter will deal with the use of radioactivity to analyze otherwise nonradioactive substances. 

The number of the iodine atoms incorporated per protein heavily influences its binding ability. The greater the ratio of molecules of iodine atoms to molecules of protein in the reaction mixture the more iodine is incorporated into the protein, and the less immune reactivity and biological activity of the iodized protein. The stoichiometric relation of the reactants in the iodination mixture is an important factor too much iodine and the protein is dead. It is advisable to perform the reaction first with Todine (nonradioactive) and to check the iodized species, especially the simply iodized compoimd, for biological effects. 

B Label the cross-linker radioactively (radioactive cross-linkers are available in retail, e.g., H-HSAB or I-Denny-Jaffe reagent from NEN, or other, such as NHS-ASA or SASD, are easy to iodinate). Treat the radioactive cross-linker with an excess of nonradioactive ligand. Separate the radioactive PAL from unchanged ligand. 

Iodine—A nonmetallic solid element there are both radioactive and nonradioactive isotopes of iodine. 

The administration of stable iodine (nonradioactive) can be very effective against radioactive iodine intake, which tends to concentrate in the thyroid gland. Figure 9.3 shows the variation of the protection factor as a function of the time at which the stable iodine was... 

In two separate beakers, you prepare saturated solutions of Pbl2 in contact with the solid. One beaker contains only natural iodine atoms with nonradioactive isotopes. The other beaker contains radioactive iodide ion, Some of the solution, but no solid, containing the radioactive iodide ion is now added to the beaker containing nonradioactive iodide ion. Both solutions are saturated, so the amount of solid in this beaker remains constant. Yet after a time the solid lead iodide, which was originally nonradioactive, becomes radioactive. This is evidence for a dynamic equilibrium, in which radioactive iodide ions in the solution substitute for nonradioactive iodide ions in the solid. 

Radioactive isotopes are identified by writing the mass number after the element s name or symbol. Thus, in this example, the isotope is called iodine-131 or 1-131. Table 16.1 compares some stable, nonradioactive isotopes with some radioactive isotopes. 

For organic mass spectrometry, only a few elements with noticeable isotope patterns are important, while in inorganic mass spectrometry there are many isotope patterns of metals, some of them very complex. From Table 3.7 it can be seen that the elements carbon, sulfur, chlorine, bromine and silicon consist of naturally occurring stable, nonradioactive isotopes. The elements fluorine, phosphorus and iodine are among the few monoisotopic elements in the periodic table (Rosman and Taylor, 1998). 

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