Bromate determination

-Hakim R. Elwaer, PhUippe Quevauviller, K. Clive Thompson and Cameron W. McLeod 

1 Identification and Removal of the Main Interferences Interferenee during the pre-eoncentration step Examples of removal of major inorganic interfering anions Study of potential organic interference 

2 Sample Pre-treatment Automation Alternative Laboratory Methods 

2 Flow Injection - Spectrophotometrie Detection Stability of Bromate 

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

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Fig. 1. Trace bromate determination using matrix elimination and preconcentration. See text for details. Peaks 1, fluoride 1.0 mg/1 2, unknown 3, chlorite, 0.01 mg/1 4, bromate 0.005 mg/1 5, chloride, 200 mg/1 6, nitrite 0.1 mg/1 7, bromide, 0.01 mg/1 8, chlorate, 0.01 mg/l 9, nitrate, 10.0 mg/l 10, o-phosphate, 0.1 mg/l 11, sulfate, 200 mg/l. Sample B was pretreated with OnGuard II Ag, H cartridges. Samples also contained 200 mg/l bicarbonate.

P.W. Levy et al, Kinetics of Defect and Radiolytic Formation in Single Crystal Sodium Bromate Determined from Color Center Measurements , JPhysChem 76, 3751 (1972)... 

Flow injection (FI) provides a powerful approach to trace element analysis (Valcaicel and Luque de Castro, 1999 Sanz Medel, 1999). FI methodologies are realistic alternatives to ion chromatography and hence offer scope for extending and/or advancing analytical capabilities for bromate determination. 

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. 

The results obtained for the vast majority of the laboratories carrying out the ISO 15061 IC method were considered to be fit for the purpose. In addition to this method, five alternative methods suitable for trace bromate determinations were also considered, namely on-line IC-ICP-MS, simple on-line column chromatography ICP-MS, IC with chlorpromazine post-column reaction and colorimetric detection, and fluorescence quenching with Carbostyril (with pre-treatment), which are all capable of achieving a bromate detection limit below 1 xg/L. A field method with methylene blue and fluorescence quenching with Carbostyril without sample pretreatment did not lead to satisfactory results at this level of bromate concentrations. 

In the analysis of raw and drinking water components are of interest that are formed during the chlorination with for instance hypochlorite or chlorine dioxide and are physiologically active. Such components are amongst other bromate- and iodine-containing substances. After concentration of the sample bromate is determined with IC. The limit of the bromate determination is Ipgl. ... 

The interferences of chlorite create a significant problem during bromate determination. A number of procedures have been investigated for removing chlorite without adversely affecting bromate levels. Of these, the procedure that employs Fe(II) in acidic solution was found to be the most effective. The elimination of these intafaing compounds was the final step toward the development of EPA Method 317.0. ... 

Sensitivity for bromate determination has been improved by more than a factor of 10 through the use of a postcolumn derivatization reaction in which HI is generated in situ from K1 and reacts with bromate to form the triiodide anions (la ). In 2000, the U.S. EPA published Method 317.0, which uses postcolumn derivatization with o-dianisidine this reacts with the eluting bromate to form a chromophore, which is then measured with a UVA is detector. This method offers excellent limits of detection, below 1 p-g/L, for bromate, as well as for chlorite and chlorate. 

Hautman, D.P. Munch, D.J. Frehis, Ch. Wagner Pepich, B.V. Review of the methods of the U.S. environmental protection agency for the bromate determination and validation of Method 317.0 for disinfection byproduct anions and low-level bromate. J. Chromatogr. 2001, 920, 221-226. 

Thompson, K.C. Guinamant, Jl-. Ingrand, V. Elwaer, A.R. McLeod, D.C. Schmitz, F. Swaef, G. QueauviUer, P. Interlaboratory trial to determine the analytical state-of-the-art of bromate determination in drinking water. J. Environ. Monit. 2000, 2,416-422. 

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