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Analytical Methods for Drinking Water |  |
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Laboratory Studies Currently Being ConductedThe Technical Support Center (TSC) of the Office of Ground Water and Drinking Water (OGWDW) has had an on-site laboratory located in Cincinnati, Ohio since OGWDW was established in 1975. TSC has conducted most of the major EPA drinking water occurrence surveys performed by OGWDW. These surveys have provided the main occurrence databases that were used to support the development of the current drinking water regulations. In addition to this occurrence data gathering, the TSC laboratory has developed 19 chemical analytical methods for the OGWDW. Nine of the 15 methods found in "Methods for the Determination of Organic Compounds in Drinking Water, Supplement III" (EPA-600-R-95-131) and 7 of the 11 methods found in "Methods for the Determination of Organic and Inorganic Compounds in Drinking Water, Volume I" (EPA-815-R-00-014) were developed through TSC. As new methods are developed they will be posted on the Internet to allow laboratories an opportunity to test and evaluate their performance. To view recently developed methods go to "Analytical Methods Developed by the Office of Ground Water and Drinking Water." We also welcome your comments on both the new methods and on what new methods TSC should be looking at in the future. Please forward your comments to Munch.Dave@epa.gov. We will be regularly including information on current TSC chemistry and microbiology laboratory projects. The following projects are either currently underway or are scheduled to begin soon. CHEMISTRY New Method for the Analysis of Bromate Studies have been completed concerning the development of an analytical method that would further reduce the detection limit for bromate. The existing ion chromatograph (IC) plumbing configuration found in U.S.EPA Method 300.1 was slightly modified by adding a bromate selective and highly sensitive detection system employing a Post Column Reagent (PCR). In Method 300.1, the IC separates the various anionic constituents of a sample matrix (bromate, chloride, nitrate, sulfate, etc...) and employs conductivity as a means of detection. Conductivity works well for most anions but consequently it is non-specific and coeluting interferences can occur. By attaching a Post Column Reagent (PCR) system after the conductivity detector, bromate can be selectively and specifically identified in a complex matrix. The primary objective of this work was to further reduce the quantitation limit for bromate in drinking water using a simple, rugged, and reproducible methodology that is specific for bromate. This work has been peer reviewed and EPA Method 317.0 which is titled, "Determination of Inorganic Oxyhalide Disinfection By-products in Drinking Water Using Ion Chromatography with the Addition of a Postcolumn Reagent for Trace Bromate Analysis" has been published. Revision 2.0 of this method has recently been published. This revision provides additional technical notes concerning the purity of the post column reagents and approaches for improving sensitivity if impure reagents are used. Please contact us if you would like help getting this method running in your laboratory. Additional Analytical Methods Development
TSC is also seeking laboratories that are interested in peer reviewing new methods, performing second laboratory validations of new methods, or who may be interested in working with TSC on the development of new methods. If you are interested in helping in any of these areas, please contact David Munch at Munch.Dave@epa.gov. MICROBIOLOGY Aeromonas Methodology An analytical method (EPA Method 1605) for unregulated contaminant monitoring is being developed for enumeration of Aeromonas spp. in finished waters. This method is an adaptation of a method that was first described in 1987 by Havelaar, et al. The method is designed to be easy to use, but as definitive as possible using membrane filtration to determine Aeromonas density. A water sample is filtered through 0.45 um pore size membrane filter and the filter is placed on ampicillin-dextrin agar (ADA). This medium uses 10 ppm ampicillin for selection of Aeromonas, dextrin as a fermentable carbohydrate, and bromthymol blue as an indicator of acidity produced by the fermentation of dextrin. Yellow colonies are counted and can be further verified by subculturing some or all yellow colonies and testing for cytochrome c (oxidase test) and trehalose fermentation. The method is being evaluated to determine the percent of yellow colonies which confirm as positive for aeromonads by the oxidase and trehalose tests as well as the percent of non-target colonies which confirm as positive for aeromonads. The optimum incubation conditions have been evaluated. Time storage studies are currently being performed on 16 species of aeromonads. A peer review and multi-lab method validation will be completed before the method becomes final. Protozoa Performance Evaluation Program A laboratory performance evaluation program for Giardia and Cryptopsporidium drinking water methodology has been undertaken in response to a need expressed by utilites and laboratories. Live organisms are counted using flow cytometery and provided to laboratories in a water and sediment matrix once per quarter. Labs analyze the unknown samples using their standard method(s) and report the results to EPA. Individual results are provided to the laboratories along with a summary report. This is a voluntary program which provides the labs and their customers with an independent estimate of their performance. Currently, twenty labs are participating in the program. Human Caliciviruses Human caliciviruses may be responsible for a large fraction of outbreaks of waterborne gastroenteritis. The gasteroenteritis caused by human caliciviruses is moderate in severity, but it is self-limiting. The extent of waterborne calicivirus outbreaks is not known because there is no analytical method for monitoring these viruses. Enteric human caliciviruses cannot be cultured in cell culture, and therefore can only be detected with sufficient sensitivity in water by PCR analyses. PCR analyses in water concentrates are inhibited by the presence of natural substances such as humic materials. Preliminary work for detection of other viruses in water concentrates has indicated that immunomagnetic separation (IMS) can separate viruses from PCR inhibitors enough to increase the sensitivity of PCR assays by 10 to 100 fold. Human caliciviruses are a diverse group and the genotypes that cause outbreaks change over time. Therefore, to detect the full range of human caliciviruses, an analytical method must have broad specificity. TSC has begun a cooperative agreement with investigators at Baylor College of Medicine in Houston to develop a monoclonal antibody which reacts with most or all members of Norwalk-like genogroups I and II caliciviruses. These investigators believe that they can develop such a cross-reactive antibody based on virus capsid surface structure maps. This antibody will be used in an IMS format to separate these viruses from PCR inhibitors in water concentrates. This IMS could be used in conjunction with existing, or newly developed virus filters and detection methods for a calicivirus analytical method.
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