Speciation iodine

Luther et al. [92] have described a procedure for the direct determination of iodide in seawater. By use of a cathodic stripping square-wave voltammetry, it is possible to determine low and sub-nanomolar levels of iodide in seawater, freshwater, and brackish water. Precision is typically 5% (la). The minimum detection limit is 0.1 - 0.2 nM (12 parts per trillion) at 180 sec deposition time. Data obtained on Atlantic Ocean samples show similar trends to previously reported iodine speciation data. This method is more sensitive than previous methods by 1-2 orders of magnitude. Triton X-100 added to the sample enhances the mercury electrode s sensitivity to iodine. 

Baker A. R., Tunnicliffe C., and Jickells T. D. (2001) Iodine speciation and deposition fluxes from the marine atmosphere. J. Geophys. Res. 106, 28743-28749. 

A. Wimschneider, K. G. Heumann, Iodine speciation in size fractionated atmospheric particles by isotope dilution mass spectrometry, Fresenius J. Anal. Chem., 353 (1995), 191-196. 

Although Garland and Curtis (41) found volatile I2 evolution when 03 was passed over seawater in batch reactors, they did not analyze the seawater for any change in iodine speciation. I2 and other interhalogen compounds, IX, should disproportionate to HOI in water. The first step in this thermal reaction does not lead to oxygen-atom transfer from 03 unless OH or H20 hydrolyzes I2 and IX. 

The applications of LC coupled to ICP-MS in iodine speciation have been reviewed elsewhere and some representative examples are presented in Table 12.2. " ... 

Table 12.2 Analytical applications of HPLC-ICP-MS for iodine speciation... 

Michalke, B., Schramel, P., Witte, H. Method developments for iodine speciation by reversed-phase liquid chromatography-ICP-mass spectrometry. Biol Trace Elem Res 2000, 78, 61-19. Michalke, B., Schramel, P., Witte, H. Iodine speciation in human serum by reversed-phase hquid chromatography-ICP-mass spectrometry. Biol Trace Elem Res 2000, 78, 81-91. 

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. 

The distribution of iodine speciation in seawater varies with depth and geographical location. 

Determination of iodine and iodine speciation in seawater is helpful in understanding the marine environment. 

Chromatographic methods are especially useful for iodine speciation when coupled with ICP-MS, electrochemical detection, or chemiluminescence detection. The total iodine can be determined following various ashing procedures with a moderately low detection limit. 

NAA provides a possibility of nondestructive performance of reliable determination of total iodine in foodstuffs and diets at very low levels. The lowest detection limit of all analytical techniques can be achieved if RNAA or PS-NAA is used. PS-NAA is also suitable for iodine speciation analysis. 

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. 

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

In the future, it is likely that more information about the iodine cycle in seawater will be obtained, together with progress in iodine speciation. 

In addition to measurement of the total iodine content, assessment of iodine speciation in soils is a major focus of this study. In the natural soil samples that we analyzed, iodine is mostly (nearly 90% of total iodine) present as organic species, among them appreciable amounts (about 50% for most soils) are nonlabile, i.e., extractable with 5% TMAH under elevated temperature (Table 10.6). In contrast, inorganic iodine becomes important (up to 50%) in sediments with low organic matter, however, organic species are still the dominant form of iodine. 

In addition to iodine speciation, the input concentration and contact time have an effect on iodine sorption and transport behavior. Because the sorption of both I (especially) and IO3 are related to the presence and magnitude of soil components that possess positively charged surfaces, and since positively charged surface sites are fim-ited, the extent of sorption will probably be affected by the input concentration. Positively charged adsorption sites may exist on the edges of 2 1 clays (such as smectite and iUite), on Al- and Fe-oxide surfaces, and on 1 1 clays (such as kaolinite). The number of sorption sites in variable-charge minerals is influenced by ionic strength, solution... 

Amperometric detection of iodide after chromotographic separation has proven a sensitive method to study stable iodine, while accelerator mass spectrometry is the method of choice for analyzing 1. However, further development of sensitive and specific analytical methods for different iodine species in complex matrices is warranted. Multiple and integrated approaches are needed to tackle complex issues surrounding iodine speciation. 

Examination of iodine speciation, with due attention to potential interconversion among species, is essential when interpreting the environmental behavior of iodine. Conflicting reports of iodine cycfing in the environment could be due to the lack of understanding of iodine speciation and theit disparate envitonmental behavior. 

Iodine Speciation in the Liquid Phase of Soil Yamaguchi et al. (2006) further investigated iodine sorption behavior in relation to by determining the speciation of the element in Japanese paddy field soils subject to oxic and anoxic conditions brought about by irrigation management. These workers observed the disappearance of added lOj from anoxic soils as 1 concentrations in soil solution increased, i.e., the transformation from oxic to anoxic... 

Under anoxic (low soil conditions, e.g., after flooding, the release of iodine into the liquid phase increases due to reduced sorption induced by changes in soil geochemistry and iodine speciation. 

Iodine Speciation in Foodstuffs, Tissues, and Environmental Samples Iodine Species and Analytical Method... 

Michalke and Schramel (1999) reported a method of CE coupled to ICP-MS for the speciation analysis of iodine. A buffer comprising phosphate (pH 2.3), NaOH, sodium dodecyl sulfate (SDS) and borate (pH 8.3) for stacking was employed for the separation of iodide, iodate, T4 and T3. The separated four iodine species were subsequently detected during a pressure-driven detection step (basehne-separated) at 19.5, 29.1, 36.6 and 42.2 s. The detection fimits were determined at 0.08 p,g I/l (iodide), 0.3 p.g I/l (iodate), 3.5 p.g I/l (T4) and 2.5 p,g I/l (T3). This method has been appfied for iodine speciation in human serum and urine. The serum from a healthy person contained iodide (13p.g I/l), T4 (6lp,g I/l) and T3 (7.5p.g I/l), whereas the serum from a thyroid-operated person lacked T3. 

Sanandez and Szpunar (1999) determined iodine species in milk and infant formulas using SEC-ICP-MS. Iodine species were quantitatively eluted with 30 mM Tris buffer within 40 minutes and detected by ICP MS with a detection limit of 1 rg/l (as I). A systematic study of iodine speciation in milk samples of different animals (cow, goat), humans of different geographic origin (several European... 

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