Stability of Bromate

This method allows determination of bromate at coneentration levels from 4 to 50 ag/L, with divergenee between results obtained with both IC/CD (referenee method) and methylene blue methods lower than 20 %. The high level of interferenee from hypoehlorite ions has been demonstrated but it ean be overeome by pre-treating samples with hydroxylamine hydrochloride. Such pre-treatment should be adapted to the matrix analysed on site (Ingrand et al, 2002). 

With reference to bromate determination, there have been few published flow injection (FI) studies. Gordon et al. (1994) described a spectrophotometric procedure based on the oxidation of chlorpromazine (CLP). A low limit of quantitation (0.8 ug/L) was realized but the method was susceptible to interference by cations and other co-oxidants. 

Previous sections of this chapter discussed the details of newly developed analytical methodologies and strategies for bromate separation and trace quantification. This confirms the current vast interest of the analytical community in bromate determination as a result of ongoing regulatory requirements. The acceptance of such methods depends mainly on the analytical performance as related to accuracy and precision. However, despite all analytical efforts, very little work has been done to investigate the stability of bromate species between sampling and analysis in different water matrices. Studies of bromate stability in water matrices should be carried out before any analytical methodology can be approved. 

In this respect the European Corrrmissiorr set up a project on Development of Laboratory and Field Methods for Determination of Bromate in Drinking Water 

Bromate stability was studied in two different dimensions. The first was related to direct evaluation of bromate stability in different water matrices. The second was devoted to stability of bromate species mobilized on activated alumina micro-columns with a view to developing a field sampling methodology from bromate in waters. 

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Flow Injection - Spectrophotometrie Detection Stability of Bromate... 

Stability of Bromate Speeies Immobilized on Alumina Microcolumns Interlaboratory Exercise for Bromate Determination... 

Guinamant et al, 2000 Ingrand et al, 2002). This project devised diiFerent woric packages including stability of bromate in waters, followed by an inter-laboratory comparison exercise to evaluate and validate the developed methods. 

In this study, the stability of bromate in water samples with different matrix constituents was investigated. Water samples ranged from soft to hard and were spiked with 1 mg/L bromide, 0.5 mg/L chlorite and 0.5 mg/L chlorate. These levels are considered to be higher than those normally observed in waters for these three anionic species. Each sample was also spiked with 2.5, 10 and 25 pg/L of bromate. Fiuthermore, a 5 pg/L of bromate standard in deionized water was also prepared. Brown glass bottles capped with polypropylene tops and PTFE inserts were used as sample containers. Samples were stored in the dark at 4 °C. Tables 2.5 and 2.6 summarize matrix constituents of each sample, preservation method spike levels and results of analyses. The results clearly demonstrate that for the two high and low total hardness waters tested, samples containing 2.5 to 25 pg/L bromate were stable for at least 20 days and that the addition of 50 mg/L ethylenediamine (EDA) preservative did not affect the results, as illustrated in Table 2.6. The results also confirm that 5 pg/L bromate standard made up in deionized water had the same stability over this period. 

The high total hardness stability tests were extended to more than 100 days and bromate results using the FI-ICP-MS method eonfirmed the stability of bromate over this period. Similarly the presence of 50 mg/L EDA preservative showed no effect on bromate stability. High total hardness water samples were further re-analysed after a period of 100 days and bromate content was found to be stable. 

Stability of Bromate Species Immobilized on Alumina Microcolumns... 

Thompson, K. C. 1999 Report on the stability of bromate in potable waters and on the interlaboratory trial to test various bromate analysis methods for potable waters. Contract No SMT4-CT-97-2-2134, December. (CR258). 

The stability of the halate(I) ion decreases, as expected, from C10 to 10 and only the chlorate(I) ion can be considered reasonably stable even in aqueous solution. Solid sodium bromate(I). NaBrO (with five or seven molecules of water of crystallisation) can be obtained, but on standing or warming it disproportionates ... 

Bancroft and Gesser [870] conclude that kinetic factors are predominant in determining whether decomposition of a metal bromate yields residual bromide or oxide. The thermal stabilities of the lanthanide bromates [877] and iodates [877,878] decrease with increase in cationic charge density, presumably as a consequence of increased anionic polarization. Other reports in the literature concern the reactions of bromates of Ag, Ni and Zn [870] and iodates of Cd, Co, Mn, Hg, Zn [871], Co and Ni [872], Ag [864], Cu [867], Fe [879], Pb [880] andTl [874]. 

From these measurements it appears that the stability of the compounds does not follow the expected order of chlorate < bromate < iodate. This behavior, however, cannot be regarded to be a characteristic property of ammonium halogenates only, because according to our experiments the same order of stability has been found in case of potassium halates. It is fairly difficult to propose a reliable reaction mechanism merely from kinetic data... 

Comparing the stability of the triammincs of silver halides, the chloride is more stable than the bromide, and the iodide cither does not exist or is very unstable. This is contrary to the usual observations in the ammines, where the stability of the ammine rises from chloride to iodide. In the case of the ammines of the oxy-halogen salts of silver the most unstable is the iodate, which is non-existent at ordinary pressure, then comes the bromate, and the most stable is the chlorate.3... 

Cystine, which contains a disulfide bond, is reported to be the most numerous and reactive amino acid present in hair keratin. Disulfide bonds in cystine are reduced by mercaptans and phosphines, and oxidized by perborates, bromates, and bleach. These reactions result in structural rearrangements within keratin which may affect the physiochemical properties of hair, since disulfide bonds in cystine contribute to the stability of hair. For example, hydrogen peroxide bleaching of hair is an oxidative process which occurs readily in an alkaline medium. This results in the formation of perhydroxy anions which have been proposed to react with cystine to form cysteic acid residues. The process of bleaching results in the loss of approximately 15% of the cystine bonds originally present in keratin and may explain the increased permeability of bleached hair to chemicals. - ... 

Electrode-Preparation and Aging. Electrode preparation procedures are given by Keston (14) and by Ives and Janz (II). Electrodes were prepared from a paste containing 90% silver oxide and 10% silver bromate placed on a platinum spiral and heated in a furnace for 7 min at 650°C. Janz and Taniguchi (12) have reviewed the preparation, reproducibility, and stability of this electrode. Taylor and Smith (13) found the equilibrium potential to be stable within 0.02 mV. Electrodes... 

The thermal stabilities of the lanthanide bromates and iodates [43] decrease with increase in cationic charge density, presumably as a consequence of increased anionic polarization. Metallic lead reacts [44] with K, Ca and Ba iodates to yield the iodites at about 700 K ... 

Acid by Potassium Bromate, Z. Phys. Chem. (Leipzig) 263, 410-412 (IIIC, D) Bar-Eli, K., Geiseler, W. Mixing and Relative Stabilities of Pumped Stationary States, 1981 J. Phys. Chem. 85 (23) 3461-3468... 

The oxoacids and their salts are very stable, in contrast to the lack of stability of the halogen oxides themselves. A large number of these acids exist at the representative oxidation states of the halogens, namely, +1, +3, +5, and +7. Even perbromic acid, HBr04, has been synthesized by fluorination of bromates. 

The previous section addressed the effect of water matrix on bromate stability. This section investigates the possibility of developing an alternative approach to sampling of bromate species in waters by employing columns of a selective packing material. This study was based on the development of an FI system with aluminamicrocolumns... 

It should be noted that chaos control can only be obtained if deterministic chaos is involved. In case of (i) chaotic laser (ii) diode (iii) hydrodynamic and magneto-elastic systems and (iv) more recently myocardial tissue, feedback algorithm has been successfully applied to stabilize periodic oscillations. Quite recently, in order to stabilize periodic behaviour in the chaotic regime of oscillatory B-Z reaction, Showalter [14] and co-workers (1998) applied proportional feedback mechanism. Feedback was applied to the system by perturbing the flow rate of cesium-bromate solutions in the reactor keeping the flow rate of malonic acid fixed in these experiments. This experimental arrangement helped the stabilization of periodic behaviour within the chaotic regime. 

In aquation of the cations [M(NH3)5Br] + (M = Cr or Co) in alcohol-water mixtures, solvent composition variation has much more effect on A.S than on iiH. This is attributed to solvation-shell ordering effects in the transition state. Enhancement of reactivity in the reaction of cobalt(ii) with chlorophyllic acid in methanol on addition of lithium nitrate is attributed to inhibition of transition-state solvation. The effective radius of a transition state can be guessed from the variation of rate constant with dielectric constant. This approach has been used for the bromide-bromate reaction. In contrast to this concentration of attention on the transition state, it may be noted that it is the stabilization of the reactant in relation to water structure that is thought to control the variation of the racemization rate of the ( + )-[Co(phen)3] + cation in t-butyl alcohol-water mixtures. ... 

Clarke, B. L. 1976. Stability of the Bromate-Cerium Malonic Acid Network. I. Theoretical Formulation, J. Chem. Phys. 64, 4165-4178. 

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