The Determination of Iodine Species in Environmental and Biological Samples

Iodine is found in organic forms in plants and animals and in inorganic forms in natural water samples. Methods of identification and quantitative determination for iodine species are decided by the types of compound and the matrices in which they occur. Iodine is an essential element and specific radioimmunoassay methods have been devised for physiologically important compounds (thyroxine and related compounds) in which it is found. In addition, marine plants and animals have provided a rich source of varied and unexpected organic iodine compounds that occur, along with other organic halogen compounds, as secondary metabolites. Natural waters, particularly marine waters contain iodine chiefly in the forms of iodide and iodate. Organic iodine compounds in biological samples have been identified by classical natural products chemical techniques following their isolation, and by modem spectroscopic methods. Routine analysis of such compounds can be done by gas chromatography (GC) and high performance liquid chromatography (HPLC). Analysis of inorganic iodine species in waters is carried out by catalytic, electrochemical and spectrometric methods and by GC; possibly HPLC inductively coupled-mass spectrometry (ICP-MS) might be the method of choice in the future.