Grantee Research Project Results
1999 Progress Report: Development of a New, Simple, Innovative Procedure for the Analysis of Bromate and Other Oxy-Halides at Sub-ppb Levels in Drinking Water
EPA Grant Number: R825952Title: Development of a New, Simple, Innovative Procedure for the Analysis of Bromate and Other Oxy-Halides at Sub-ppb Levels in Drinking Water
Investigators: Weinberg, Howard S.
Current Investigators: Weinberg, Howard S. , Singer, Philip C.
Institution: University of North Carolina at Chapel Hill
EPA Project Officer: Hahn, Intaek
Project Period: September 1, 1997 through August 31, 1999 (Extended to December 31, 2000)
Project Period Covered by this Report: September 1, 1998 through August 31, 1999
Project Amount: $198,460
RFA: Drinking Water (1997) RFA Text | Recipients Lists
Research Category: Water , Drinking Water
Objective:
This project is evaluating a relatively simple methodology to provide the tools for assessing exposure to bromate in drinking water that has previously been impeded by the lack of sensitivity of existing methodologies. This analytical methodology will provide the water quality monitoring community with the ability, using existing analytical equipment with simple add-on accessories, to fulfill the goals of the Information Collection Rule and criteria for future drinking water regulations by easily achieving the required sensitivity in oxyhalide analysis.
A relatively unconventional approach to the analysis of chemical components of drinking water is employed. Ion chromatographic (IC) separation, with no pretreatment followed by a post-column reaction to produce tribromide (Br3-) from bromate, is applied to the analysis of a variety of aqueous samples. The tribromide ion is detected by ultraviolet (UV) absorbance at 267 nm. This method is very sensitive for bromate with a limit of quantitation of 0.2 µg/L, and also is very selective. Common anions typically separated by IC exhibit no interference, even at the levels normally found in drinking water. The method also has been optimized for similar sensitive quantitation for the oxyhalides iodate and chlorite. With the use of recently available higher capacity chromatographic columns, we predict even lower detection levels. The methodology is being applied to a wide variety of drinking waters throughout the United States including those disinfected by water utilities as well as those produced commercially and bottled.
Progress Summary:
We have optimized the methodology for the analysis of iodate, chlorite, and bromate at sub-ppb levels of detection in a variety of aquatic matrices including drinking waters from a number of treatment processes and synthetically produced solutions. The latter involved a series of controlled experiments employing a synthetic aquatic matrix containing a mixture of anions together with reconstituted natural organic matter as a source of organic carbon, all dissolved in deionized water. Ozonation of this water at varying ozone to total organic carbon (TOC) doses, different levels of alkalinity, pH, and bromide provided an opportunity to investigate correlations between bromate (at sub-ppb levels) and transferred ozone dose in these waters. Furthermore, the analytical method has been applied in practice to the determination of bromate in a pilot ozonation plant treating a surface water with low-level bromide (<50 µg/L) at a variety of ozone to TOC doses. The results of quality controlled analysis of these samples indicate the applicability of this analytical method to the determination of sub-ppb levels of bromate that are indeed likely to be found in ozonated waters that contain low bromide. Our next steps are to further simplify the methodology, share split sampling with the Environmental Protection Agency (EPA)?Cincinnati to compare and validate different methods, and begin a comprehensive survey of U.S. drinking waters containing low levels of bromide.
The project's accomplishments include:
- Optimized Post-Column Reaction. The optimized conditions were arrived at by holding one parameter constant while varying the others and measuring the response of a 150 mL sample injection of a 5 µg/L solution of bromate. These conditions were subsequently used during application of this method.
- Quantitation Limits. The limits of sensitivity of this method were assessed by determining quantitation limits both statistically by the method detection limit (MDL) and practically by the practical quantitation limit (PQL) for all three oxyhalides. These results indicate sub-ppb detection for all three components in laboratory-grade water with no other components present and a range of linearity with high linear regression coefficients for each of the oxyhalides in the range from PQL to 10 µg/L. The chromatography confirms that the method permits rapid separation of these oxyhalides and produces peaks clearly discernible from baseline noise at all levels in this calibration range.
- Application to Analysis of Drinking Water. Local tap water was analyzed as collected and after boiling a sample in a precleaned vessel on a hot plate, the latter to determine if consumed boiled water offered an enhanced oxyhalide exposure route. Replicate samples of each were spiked with 0.5 µg/L of each analyte. The results of these analyses indicate that although bromate does not appear to be produced as a result of chlorination in this water, iodate is found (1.5 µg/L) and increases slightly as a result of boiling. The presence of low-level iodide either in the raw water or introduced with one of the treatment chemicals is likely to contribute to the formation of iodo-halogenated disinfection by-products resulting from chlorine, an area which largely has been ignored by the drinking water community. Bottled water analysis suggests that the source water contained bromide and had undergone some form of oxidation (possibly ozonation) prior to bottling to achieve such a high bromate level (13.1 µg/L), assuming that indeed the water was collected from a natural spring as suggested on the bottle's label.
- Analysis of Synthetic Waters. Experiments were carried out to explore the impact of varying water quality on method integrity. Provided the ion exchange column capacity was not exceeded, method sensitivity and reproducibility were not impacted except for the case where reconstituted natural organic matter was employed. Although bromate spike recovery was about 95 percent, the chromatographic peak shape was somewhat different from those previously observed. This type of water represents an extreme natural aquatic matrix and was for illustrative purposes only. However, oxyhalide PQL values did not appear to be compromised. Consequently, we can reasonably extrapolate the effectiveness of this method towards sensitive bromate analysis in all drinking waters.
Future Activities:
We currently are attempting to increase method sensitivity further through the use of higher capacity anion exchange columns, after which a large nationwide survey of drinking waters will be conducted that represents a wide cross-section of different treatment processes and water quality. In addition, we will compare this current methodology to other low-level bromate approaches, both in-house and through sample splitting with EPA research laboratories.
Journal Articles on this Report : 1 Displayed | Download in RIS Format
Other project views: | All 4 publications | 2 publications in selected types | All 2 journal articles |
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Type | Citation | ||
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Weinberg HS, Yamada H, Joyce RJ. New, sensitive and selective method for determining sub-μg/l levels of bromate in drinking water. Journal of Chromatography A 1998;804(1-2):137-142. |
R825952 (1998) R825952 (1999) R825952 (2000) R825952 (Final) |
Exit Exit |
Supplemental Keywords:
drinking water, exposure, bromate, oxyhalides, risk, analytical methods., RFA, Scientific Discipline, Water, Environmental Chemistry, Drinking Water, Environmental Engineering, monitoring, public water systems, oxy-halides, animal model, disinfection byproducts (DPBs), treatment, bromate formation, brominated DPBs, carcinogenicity, chlorine-based disinfection, anion chromatographic resolution, tribromide ion, DBP risk management, water quality, drinking water contaminants, regulationsRelevant Websites:
http://www.unc.edu/~weinberg/hswrsrchFrame.html#Development
http://www.unc.edu/~weinberg/Discussion-Forum/WelcomePage.html
Progress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.