Field Analytical Method for Perchlorate

Perchlorate is a widely-used component of solid fuel, missile and rocket propellants, explosives and pyrotechnics. It has been shown to reduce iodide uptake into the thyroid gland. The EPA has found Perchlorate contamination in 18 states and believes contamination may exist in as many as 39 states. In early January 2005, the National Academy of sciences, in an EPA-sponsored study, recommended a reference dose (RfD) for human ingestion of 0.7 µg/kg/day, which suggests a maximum contaminant level (MCL) of 24.5 µg/l (ppb) or lower, while several states allow between 1 and 6 µg/L. Based upon this recommendation, there is a need for field monitoring of Perchlorate in ground and surface waters to test the effluent of remediation facilities and to determine soil cleanup levels. To provide a field analytical method, we have devised a technology that combines ion chromatography (IC) , similar to that use in EPA Method 314, with specific Perchlorate detection using a low detection limit ion selective electrode (ISE). Use of the Perchlorate ISE as the detector results in lower interference form common anions than is found using Method 314. For this method, we received a patent in 2004 (U.S. Patent no 6,736,958). This method simplified and improved Method 314, as the ISE replaced both the conductivity detector and the suppression Unit. It also improved the approach of measuring Perchlorate by ISE, because the presence of sufficiently high levels of competing ions, measured without separation, can yield false positive results. The innovation of this Phase I research is to simplify and standardize electrode construction by casting the electrode on thin-walled, porous tubing having defined free space. The objectives are to 1) cast electrodes on a selection of porous tubing, selecting one which provide optimum robustness and reproducibility; 2) optimize electrode response by selecting the ionophore, plasticizer and other ISE components; and 3) determine the selectivity obtained when using the perchlorate ISE as the detector for IC. Phase II will focus on optimizing calibration, developing analytical software, and field testing a prototype instrument. The resulting instrument will be suitable for field use, adaptable to batch analysis in the lab, and capable of remote sensing. Potential markets include DoD contractors, environmental engineers and testing labs, state and municipal water authorities and remediation firms.