Iodine chromatographic techniques

Sauer and Fitzgerald [9] have described thin layer chromatographic technique for the identification of water-borne petroleum oils. Aromatic and polar compounds are removed from the sample by liquid-liquid extraction with acidified methanol, the extract is chromatographed on a silica gel thin layer plate, and the separated components are detected by their fluorescence under long- and short-wave ultraviolet light. Unsaturated non-fluorescing compounds are detected by iodine staining. 

Shah, M., Kannamkumarath, S. S., Caruso, J. A., Wuilloud, R. G. Iodine speciation studies in commercially available seaweed by coupling different chromatographic techniques with UV and ICP-MS detection. J Anal At Spectrom 2005, 20, 176-182. 

Electrochemical techniques are inexpensive, but their limited specificity requires elimination of possible interference in the determination of even moderately low iodine levels in foodstuffs. They are well-suited for the detection of iodine species separated by chromatographic techniques. 

Chromatographic techniques are a well-established tool for iodine speciation when coupled with other detection methods. 

The most commonly used methods for speciation analysis of iodine in tissues and food are chromatographic techniques, such as anion exchange, size exclusion and reverse-phase chromatography, coupled with ICP-MS detection. 

Ion chromatography has been successfully applied to the quantitative analysis of ions in many diverse types of industrial and environmental samples. The technique has also been valuable for microelemental analysis, e.g. for the determination of sulphur, chlorine, bromine, phosphorus and iodine as heteroatoms in solid samples. Combustion in a Schoniger oxygen flask (Section 3.31 )is a widely used method of degrading such samples, the products of combustion being absorbed in solution as anionic or cationic forms, and the solution then directly injected into the ion chromatograph. 

For both polymerization and rubber processing it is important to know the type and amount of unsaturation. In this connection IR spectroscopy is perhaps the most useful technique, although it requires a preliminary evaluation of band absorptivities by means of suitable standards, analyzed by an independent technique. A number of methods are available to analyze these standards NMR spectroscopy, the iodine-monochloride method, gas-chromatographic analysis of pyrolysis products, materials balance determination, etc.12 Provided the termo-nomer content of the standard is not too low, the most useful technique is NMR, based on the ratio between the signal from all saturated protons (generally with chemical shifts of 2S from TMS) and the signal from olefinic protons, observed at lower fields (45-5.5 5). 

With the development of analytical techniques, new methods for iodine determination in biological materials and foodstuffs became available. These newer techniques mostly involve nuclear analytical methods and various types of spectrometric, chromatographic, and electrochemical techniques. 

Of the spectrometric techniques, ICP-MS is well-established and very frequently used for reliable determination of total iodine at very low levels, especially if ICP-IDMS is employed. Coupling of ICP-MS with chromatographic separation procedures is especially useful for the determination of iodine speciation in foodstuffs. 

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