Bromate analysis

Determination of Inorganic Oxyhalide Disinfection By-products in Drinking Water using Ion Chromatography with the Addition of a Postcolumn Reagent for Trace Bromate Analysis... 

Bromate has been classified as a human carcinogen by both the I/VRC (International Agency for the Research on Cancer) and the USEPA (United States Environmental Protection Agency) and is known to be toxic to fish and other aquatic life [11, 12]. Bromate could be produced in aquatic systems upon the oxidation of aqueous bromide. Controlled ozonation has been considered as an effective disinfectant tool in aquatic systems [13] but when sea water is subjected to ozonation, oxy-bromide ozonation by-products (OBP) are produced and these are important both in terms of their disinfection ability and also in relation to their potential toxicity. When seawater is oxidized, aqueous bromide (Br-) is initially converted to hypobro-mite (OBr ) which can then either be reduced back to bromide or oxidized further to bromate (Br03-) which is known to be toxic to fish and other aquatic life and classified as a human carcinogen. There has been thus a considerable interest in bromate analysis so that trace analysis of bromate in water has received considerable attention in recent years. 

These experiments demonstrated an important analytical feature, namely that bromate analysis cannot be performed directly for waters containing more than 50 mg/L of bicarbonate and 10 mg/L of chloride (which correspond to levels commonly found in natural waters), and that consequently a pre-treatment step is required. These results were confirmed by the analysis of natural river and mineral waters (Ingrand et al, 2002). 

Table 2.6 Average results of bromate analysis in different waters spiked at 0,2.5, 10 and 25 p.g/L Br03 and analysed at intervals of 0, 2, 10 and 20 days...

For bromate analysis, ethylenediamine (EDA) is added to the sample in order to convert any hypobromite present into the corresponding bromamines, thus preventing ongoing conversion to bromate. Bromate has been found to be stable in a range of drinking waters over three months using amber glass bottles either with or without EDA (Thompson, 1999). 

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 above results indicated that the highly sensitive detection of chlorate and iodinate can be achieved by using the techniques employed for bromate analysis. The sensitivity of chlorate and iodinate will be 90 and 111% of bromate. However, the A iax values of Cl2Br and l2Br are 10 and 30 nm lower than that of BrjBr". If Clg and 13 are the final products, a specific... 

Determination of inorganic oxyhalide disinfection by-products in drinking water using 1C with the addition of a postcolumn reagent for trace bromate analysis... 

However, it is not easy to select one postcolumn derivatization method for bromate analysis from the various... 

The second alternative for detecting traces of nitrite is the detection via the formation of triiodide, which will be discussed in more detail for bromate analysis in Section 10.1.2 [27]. It is described in a similar form by Mima and Hamada [28]. The reaction mechanism for nitrite is as follows ... 

Table 10.4 Summary of US EPA methods for bromate analysis based on ion chromatography techniques.

Figure 10.23 Schematic instrument setup for bromate analysis after preconcentration (according to ISO 15061).

As an alternative to conductivity detection, Diemer and Heumann [74], Seu-bert et al. [75-78], and Pergantis et al. [79] successfully employed inductively coupled plasma mass spectrometry (ICP-MS) as an elegant but costly detection method for trace bromate analysis. By adapting the chromatographic conditions to the requirements and possibilities of ICP-MS, minimum detection limits below lOOng/L can be achieved [75,76]. The most important changes include the increase of the anion-exchange capacity of the separator column and the... 

DeBorba, B. and Rohrer, J. (2005) Application Note No. 168 Determination of Trace Concentrations of Disinfection Byproduct Anions and Bromide in Drinking Water Using Reagent-Free Ion Chromatography Followed by Postcolumn Reagent of o-Dianisidine for Trace Bromate Analysis. Thermo Fisher Scientific, Sunnyvale, CA, USA. 

A300 IC Anion is also available in a 100 mm X 10 mm i. d. format (Star Ion A300 HC), which has a higher ion-exchange capacity due to the larger inner diameter of the column. According to the manufacturer, this column is particularly well-suited for trace bromate analysis in drinking water. 

A number of different ion chromatographic techniques exist for bromate analysis. In method 300.0 (Part B) [20], the U.S. EPA describes the separation of oxyhalides - chlorite, chlorate, and bromate in the presence of mineral acids on lonPac AS9-SC with suppressed conductivity detection. On this stationary phase, adequate separation between bromate and chloride is achieved with the standard eluant mixture of sodium carbonate and sodium bicarbonate if the chloride excess is less than 100-fold. Because in real-world samples the chloride content can easily be 50-100 mg/L, bromate quantification in the concentration range between 1 pg/L and 10 pg/L is impossible under standard conditions. Kuo et al. [21] improved the separation by treating the sample with a cation exchanger in the silver form, through which the chloride content is decreased to a value determined by the solubility of silver chloride in solution ( 0.4 mg/L chloride). 

As an alternative to conductivity detection, Heitkemper et al. [27] and Seubert et al. [28] successfully employed ICP-MS as a detection method for bromate analysis and achieved a minimum detection limit of 0.8 pg/L Regarding sample preparation, this detection method does not require a reduction of the chloride content prior to the ion chromatographic separation because of its high selectivity for brornine-containing compounds. However, this method is also not free of interferences. Tribromoacetic acid, for example, interferes and thus has to be removed completely prior to analysis. 

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