Effect of Water Matrix on Bromate Stability

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. 

This study concluded that bromate concentrations are stable in hard waters for up to 100 days when stored in brown glass bottles in dark at 4°C. It was also 

Sample constituents Preservation technique Total hardness (mg/L CaCOj) Spiked bromate concentration (Pg/L) Analysis schedule (days) 

Spiked deionized water containing 1 mg/L bromide, 0.5 mg/L chlorite and 0.5 mg/L chlorate (added as KBr, NaClOj and KClOj) None 0 5 0,2, 10,20 

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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... 

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