Sources of iodine

Iodized Salt. Iodized table salt has been used to provide supplemental iodine to the U.S. population since 1924, when producers, in cooperation with the Michigan State Medical Society (24), began a voluntary program of salt iodization in Michigan that ultimately led to the elimination of iodine deficiency in the United States. More than 50% of the table salt sold in the United States is iodized. Potassium iodide in table salt at levels of 0.006% to 0.01% KI is one of two sources of iodine for food-grade salt approved by the U.S. Food and Dmg Administration. The other, cuprous iodide, is not used by U.S. salt producers. Iodine may be added to a food so that the daily intake does not exceed 225 p.g for adults and children over four years of age. Potassium iodide is unstable under conditions of extreme moisture and temperature, particularly in an acid environment. Sodium carbonate or sodium bicarbonate is added to increase alkalinity, and sodium thiosulfate or dextrose is added to stabilize potassium iodide. Without a stabilizer, potassium iodide is oxidized to iodine and lost by volatilization from the product. Potassium iodate, far more stable than potassium iodide, is widely used in other parts of the world, but is not approved for use in the United States. 

Occurrence. Iodine [7553-56-2] is widely distributed in the Hthosphere at low concentrations (about 0.3 ppm) (32). It is present in seawater at a concentration of 0.05 ppm (33). Certain marine plants concentrate iodine to higher levels than occur in the sea brine these plants have been used for their iodine content. A significant source of iodine is caUche deposits of the Atacama Desert, Chile. About 40% of the free world s iodine was produced in Japan from natural gas wells (34), but production from Atacama Desert caUche deposits is relatively inexpensive and on the increase. By 1992, Chile was the primary world producer. In the United States, underground brine is the sole commercial source of iodine (35). Such brine can be found in the northern Oklahoma oil fields originating in the Mississippian geological system (see Iodine and iodine compounds). 

Potassium iodide is added as a nutrient to prevent goiter, a thyroid problem caused by lack of iodine, and to prevent a form of mental retardation associated with iodine deficiency. A project started by the Michigan State Medical Society in 1924 promoted the addition of iodine to table salt, and by the mid-1950s three-quarters of U.S. households used only iodized salt. Potassium iodide makes up 0.06 percent to 0.01 percent of table salt by weight. Sometimes cuprous iodide—iodide of copper—is used instead as the source of iodine. 

Iodine is essential in the mammalian diet to produce the thyroid hormone thyroxine deficiency in humans causes goitre. Collectively, deficiencies of iodine, iron, zinc and vitamin A in humans are thought to be at least as widespread and debilitating as calorie deficiencies (Welch and Graham, 1999). The main source of iodine in soils is oceanic salts rather than parent rock, and so deficiency is most widespread in areas remote from the sea (Fuge, 1996). In principle deficiency is easily corrected with dairy supplements. However in practice this is not always feasible. Addition of iodate to irrigation water has successfully corrected widespread iodine deficiency in parts of China where the usual methods of supplementation had failed (Cao et al., 1994 Jiang et al 1997). However there is not much information on the behaviour of iodine in soil and water systems. 

Strontium iodide (Srl ) is made by treating strontium carbonate with hydrochloric acid. It is used as a medicinal source of iodine. 

Potassium iodide is found in seaweed. Some important appbcations of this compound involve its use in pharmaceuticals and as a source of iodine in food, especially in animal and poultry feed. Potassium iodide is added to table salt to provide iodine in human food. 

A normal rate of thyroid hormone synthesis depends on an adequate dietary intake of iodine. Iodine is naturally present in water and soil, although some soils contain very low amounts. As a result, seafood is a more reliable source of iodine than crop plants. Approximately 1.6 billion people in more than 100 countries live in areas where natural sources of dietary iodine intake are marginal or insufficient. A minimum of 60 j.g of elemental iodine is required each day for thyroid hormone synthesis, and at least 100 j.g/day is required to eliminate thyroid follicular cell hyperplasia and thyroid enlargement (i.e., iodine deficiency goiter). 

Goiter due to iodide deficiency is best managed by prophylactic administration of iodide. The optimal daily iodide intake is 150-200 meg. Iodized salt and iodate used as preservatives in flour and bread are excellent sources of iodine in the diet. In areas where it is difficult to introduce iodized salt or iodate preservatives, a solution of iodized poppy-seed oil has been administered intramuscularly to provide a long-term source of inorganic iodine. 

The mechanism for the reaction is believed to be as shown in Eq. 15.170 (start with CH3OH, lower right, and end with CHjCOOH, lower left).180 The reaction can be initiated with any rhodium salt, e.g., RhCl3, and a source of iodine, the two combining with CO to produce the active catalyst, IRItfCO y. The methyl iodide arises from the reaction of methanol and hydrogen iodide. Note that the catalytic loop involves oxidative addition, insertion, and reductive elimination, with a net production of acetic acid from the insertion of carbon monoxide into methanol. The rhodium shuttles between the +1 and +3 oxidation states. The cataylst is so efficient that the reaction will proceed at atmospheric pressure, although in practice the system is... 

Sea plants, particularly kelp found in the waters around California and the Bay of Biscay, have been a source of iodine. Because of pollution, the kelp beds ill California are no longer a major source. Iodine also is found in the petroleum oil well brine of California and, in small percentages, in sodium nitrate of Chile. Die latter was once the primary source of the clement. Brines now are the major source. 

The sodium iodate found as an impurity in Chile saltpeter was once the major source of iodine. 

Martino E, Aghini-Lombardi F, Mariotti S, Bartalena L, Braverman L, Pinchera A. Amiodarone a common source of iodine-induced thyrotoxicosis. Horm Res 1987 26(1 1) 158-71. 

Potassium iodide, which is used in unmeasured but excess amounts in iodo-metric titration, is the source of iodine for many types of reactions. It dissociates to iodide anion, which then reacts with the analyte to produce iodine. Hypochlorite reaction is shown below as an example. By measuring the amount of iodine released, the concentration of the analyte in the sample can be determined. 

The iodine content of a variety of foods in East Africa was measured by ICP-MS [276]. Samples were dried and homogenized prior to dissolution. Tellurium was used as an internal standard. Only saltwater fish were found to be a sufficient dietary source of iodine. 

With respect to iodine chemistry, the major sources of iodine are thought to be from macroalgal sources releasing organoiodine com-... 

Sodium iodate, NaI03.—The iodate is a constituent of Chile saltpetre or sodium nitrate, and remains in the mother-liquor after crystallization of the nitrate. It is an important source of iodine. The salt can be prepared by oxidizing sodium iodide with sodium peroxide6 or by the electrolytic method,7 and also by the interaction of sodium iodide and periodate.8 It forms white crystals. 

Sodium nitrate, NaN03.—Immense deposits of sodium nitrate are situated in Chile, hence the name Chile saltpetre. The local name is Caliche. The origin of the deposits is a matter of dispute.2 The crude product is contaminated with clay and sand, and is purified by crystallization from water. An important impurity is sodium iodate, a valuable source of iodine.8 Analyses have been given by Machattie 4 (I.) and Schulze5 (II.), the numbers expressing percentages ... 

Under a nitrogen atmosphere, even iodine azide undergoes addition to alkenes with a reversal of the regiochemistry, consistent with a radical pathway24,38 41. Furthermore, the solvent and the source of iodine azide affect the nature of the reagent and consequently the regio- and stereoselectivity of the addition14 16 42,43. 

Similarly, the source of iodine azide and other experimental factors influence both the regio-and stereoselectivity of the addition to 3-methylene-5a-androstane (7) and l-tm-butyl-4-methylenecyclohexane48. Regioselective, but not stereoselective, addition is achieved by working in acetonitrile in the presence of oxygen48. 

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