AWWA WQTC71464

Bromate is commonly formed from the ozonation of bromide in drinking water and is determined to be a human carcinogen. Currently, bromate is regulated in drinking water at 10 ug/L. U.S. Environmental Protection Agency (USEPA) Methods 300.1 B, 317.0, and 326.0 are approved by the USEPA for compliance monitoring. High concentrations of common anions, such as chloride, sulfate, and carbonate, can produce poor bromate peak shapes and lower recoveries. This often requires the analyst to either dilute the sample which raises the minimum reporting limit (MRL) or pretreat the sample offline prior to analysis. Pretreatment of samples requires increased time and cost for each analysis. Therefore, the objective of this project was to develop a method that eliminates high concentrations of matrix ions and minimizes interferences. This paper describes two new USEPA pending methods using two-dimensional (2D) ion chromatographic (IC). In the first dimension, a large loop is injected on a 4-mm high capacity ion exchange column to separate bromate from matrix anions. Bromate is selectively removed using automated valve switching onto a concentrator column. In the second dimension, Bromate is separated a second time using a 2-mm anion exchange column followed by quantitation after suppressed conductivity detection. This strategy allows the ability to inject large sample volumes, focus bromate partially resolved in the first dimension onto a concentrator column and separate it on a second, higher resolution column. It also combines two different column chemistries to enhance selectivity and reduce the possibility of false positives and eliminates the need for second column confirmation. This method also improves upon USEPA Method 314.0 and 314.1 for the determination of perchlorate in drinking water, even in the presence of high salt matrices (>1,000 mg/L for Cl^-, SO₄ and NO₃). The new method results in a 4-fold signal enhancement, which yields a lower detection limit (0.016 µg/L). Includes abstract only.