Radioiodine than iodide

Preparation of radioiodine in chemical forms other than iodide... 

In search of alternatives to Chloramine-T, Morrison (1980) demonstrated that lactoperoxidase from bovine milk was particularly effective for iodide oxidation and the radioiodination of proteins. The single strand polypeptide lactoperoxidase has a molecular weight of approximately 78 kD. The structure of lactoperoxidase contains a prosthetic heme group which is covalently linked to the protein at the active site of the enzyme. In the presence of minute quantities of hydrogen peroxide, lactoperoxidase oxidizes and binds radioiodide to proteins in the reaction mixture. The pH optimum of iodide oxidation by lactoperoxidase is 4-8.5 with an optimum at pH 5. The reaction is extremely rapid, allowing reaction times of less than 1 min. This provides very mild conditions and denaturation of proteins is low. Yields of up to 85% can be obtained and the method is widely used for labeling proteins and hormones. Lactoperoxidase may itself... 

The Food and Drug Administration has recommended that potassium iodide tablets be administered for projected thyroid doses greater than 25 rem. Ingestion of potassium iodide (KI) tablets reduces the dose to the thyroid caused by the intake of radioiodine. It must be understood, however, that use of the thyroid-blocking agent potassium iodide (KI) is not an adequate substitute for prompt evacuation or sheltering by the general population near a... 

To be effective, potassium iodide must be taken just before or shortly after exposure to radioiodine (within 1 to 2 hr). Thus, to be potentially effective, it must be readily available. Taking the recommended dosage of potassium iodide (130 mg) just before or at the time of exposure could block more than 90% of radioactive iodine uptake by the thyroid as indicated in Figure 5.4-2. If taken approximately 3 to 4 hr after acute exposure, only about 20% blocking would occur in some persons. Note that a small percentage of people could react adversely to potassium iodide, but the risk of a severe reaction is very small. 

Curie quantities of fission-produced iodine have been purified by adsorption on platinum (64). The Irradiated target, enriched uranium alloyed with aluminum, was dissolved In aqueous sodium hydroxide. The solution was acidified with sulfuric acid and sparged with air which was then passed through a sodium hydroxide scrubber. The scrubber solution, which now contained the radioiodine In the form of iodide, was acidified with sulfuric acid and the radioiodide was permitted to be adsorbed on a specially prepared platinum felt (directions for preparation of the felt not given). The iodine was removed from the felt by washing with dilute sodium hydroxide solution. Chemical yields were 65-75% and decontamination factors were greater than 10 for removal of other fission products. The original solution contained about 250 curies of radioiodine. 

In the procedure utilizing ion exchange, the sample solution was first subjected to the usual redox treatment to insure exchange, with the iodine ultimately being converted to iodide. The solution was then passed through a cation exchange resin of the phenol-sulfonic acid type and then iodide was adsorbed on preformed silver iodide. The recovery of radioiodine was greater than 97%. 

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