Iodine species analyses

The first iodine species analyses in the containment atmosphere were carried out about 3 months after the accident. Their results ... 

Figure 12.2 Comparison of (a) UV absorbance detection at 225 nm and (b) ICP-MS detection ( I) for the analysis of iodine species in levothyroxine pharmaceutical tablets. Iodine species (1) inorganic iodine (2) T2 (3) TTAA2 (4) T3 (5) TTAA3 (6) T4 (7) TTAA4. The concentration of each iodine species was 200mgL . From Kannamkumarath, S. S., Wuilloud, R. G., Stalcup, A., Caruso, J. A., Patel, H., et al. Determination of levothyroxine and its degradation products in pharmaceutical tablets by HPLC-UV-ICP-MS. J. Anal. At. Spectrom. 2004, 19, 107-113. Reproduced by permission of The Royal Society of Chemistry...

Various analytical techniques for the determination of different levels of total iodine or iodine species in foodstuffs and related materials are presently available. They differ in principles, equipment needed, detection limits, reliability, i.e., accuracy and precision of results, the ease of performance, sample throughput, and analysis cost. The choice of the most appropriate method largely depends on the purpose of the analysis, e.g., whether it concerns routine monitoring and/or screening or whether delicate certification of a foodstuff reference material is to be carried out. Obviously, one of the decisive parameters is whether the method s detection limit is sufficiently low for the given purpose. For this reason, it appears useful to give the typical iodine levels in various foods to facilitate the choice of the appropriate method(s). Table 2.5 lists the average iodine content of foods (fresh and dry basis), which was adapted from the data reported by Koutras et al. (1985). 

The methods employed for the miscible displacement studies were similar to those used in previous experiments (Hu and Brusseau, 1998). We connected a high-performance liquid chromatography (HPLC) pump (Model 301 from Alltech Associates Inc., Deerfield, IL) to the column, and placed a three-way valve in-line to facilitate switching between treatment solutions. Several iodine species (iodide, iodate, and 4-iodoaniline) were used to study transport behavior. We also examined the transport of tritium and bromide, commonly used conservative tracers, so that we could compare their transport behavior with iodine species. For transport experiments of 4-iodoaniline, which is used as a representative refractory organic iodine species, the solution was allowed contact only with glass or stainless steel, to avoid potential interaction of organoiodine with plastics in the column system. Column effluents were collected with an automated fraction collector (Retriever 500, ISCO Inc., Lincoln, NE) for chemical analysis, as described below. 

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. 

Speciation analysis of iodine in human urine samples has also been carried out by ion chromatography (IC) combined with ICP-MS (Stark etai, 1997). Because of the possible interconversion of the iodine species, depending on the pH value, different eluent—column combinations were used for acidic or alkaline sample solutions. Iodide, iodate and several unidentified, presumably organo-iodine species could be separated and detected. 

Pre-separation neutron activation analysis was used to determine the contribution of iodide and iodate to the total iodine content of seawater (Hou et al. 2000). Iodine species were separated by means of an anion-exchange resin that preferentially retained the iodide. Iodate in the effluent was reduced to iodide and passed through another anion exchange column. Both firactions were analyzed by NAA. Urine and milk samples were also analyzed. 

Figure 10.36 Analysis of bromine and iodine species in a bottled water using IC-ICP/MS. Separator column lonPac ASM with guard column dimensions 250 mm x4 mm i.d. column temperature ambient eluent ...

Rate-determining steps leading to I(IV) and I(III) are postulated, with subsequent rapid reduction of intermediate iodine species. An induction period followed by oxidation of the [Fe(phen)3] complex is a feature of the reaction of that complex with bromate ions. The rates of the corresponding reactions with CI2 and affected by Cl", Br", or hydrogen ion. The oxidations occur via the one-electron transfer steps and an analysis of the data and those for other metal ion reductants has been made using a Marcus theory approach. The kinetics of the peroxodisulfate oxidation of two [Fe(II)(a-diimine)3] complexes have been investigated in binary aqueous-solvent mixtures.The rate data have been dissected into initial and transition state energies. Comparisons between the relative contributions to these parameters for redox and substitution reactions remain a topic of interest. 

The kinetics of the batch reaction between chlorine(III) and iodine species has now been documented. It is known that chloride ion accelerates the decomposition of Cl(III) in acid media. It is natural to speculate on the effect bromine species would have on Cl(III). Would the system Cl(III)-Br oscillate Would it "clock" What reaction would occur when Cl(III) and Br2 are mixed Would mechanistic analysis require postulation of BrC102 type intermediates To find out, we mixed Cl(III) with Br in flow and batch, and reacted Br2 (and Br3 ) with Cl(III) in batch. 

A negative effect found when working at low hquid flow rates is an increase in wash-out times, leading to a subsequent drop in sample throughput In order to mitigate this problem, new low inner volume spray chambers have been developed and their performance has been tested in ICP-MS. For a mini cyclonic spray chamber, called the Cinnabar, wash-out times were found to be significantly shortened with respect to a double pass spray chamber for the analysis of iodine species. Due to its simplicity and the small dispersion provided by this spray chamber, it has also been successfully applied as part of a CE-ICP-MS interface. Low inner volume single pass spray chambers have also been used in various ways as aerosol transport devices for ICP-MS, namely with the nebuliser directly connected to them, with an impact surface (i.e. bead) inside them and as part of a CE-ICP-MS interface. ... 

Buchberger et al. [104] carried out a selective determination of iodide in brine. The performance of a potentiometric method using an ion-selective electrode and of liquid chromatography coupled with ultraviolet detection at 230 nm were compared as methods for the determination of iodide in the presence of other iodide species. Satisfactory results were obtained from the potentiometric method provided the solution was first diluted tenfold with 5 M sodium nitrate, and external standards were used. Better reproducibility was, however, achieved with HPLC, provided precautions were taken to prevent reduction of iodine to iodide in the mobile phase, for which extraction of iodine with carbon tetrachloride prior to analysis was recommended. This was the pre-... 

Analysis by GC of the various organolead species present in gasoline requires special detectors because of the profusion of species with retention times near those of the organometaHic compounds. An old determination method consisted of scrubbing the separated species in iodine solution, foHowed by spectrophotometric determination of the complex with dithizone (2)133,134 (see also Table 2). 

The release of radioactive iodines from BWR circuits, first into the steam phase and then into the turbine hall, has also been considered thermodynamically (75). A re-analysis of some experimental data of Styrikovich et al (97), suggested that iodates were not, as had been tentatively proposed, likely to be present. Styrikovich s prediction of HIO as a principal species under BWR conditions was confirmed, but it was concluded that his experiments had not measured its steam/water partition coefficient. In view of the meagre experimental evidence, however, more work on this system is desirable. 

As an example of the application this work, Kapral [285] and Pagistas and Kapral [37] have considered the reaction rate between iodine atoms (or some other similar species) effectively distributed uniformly in solution. They compared their calculations with those of the diffusion equation analysis and with the molecular pair approach rather than compare rate coefficients, Kapral [285] compared the rate kernels (which are approximately the time derivatives of rate coefficients). Over long times, these kinetic theory and molecular pair rate kernels both reduce to the typical form of the Smoluckowski rate kernel. However, with parameters such as R — 0.43 nm and D = 6 x 10 9m2s 1, the time beyond which the rate kernels of kinetic theory and the Smoluchowski theory are in reasonably close agreement is 20 ps, a time much longer than the velocity... 

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