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DETERMINATION OF PERCHLORATE BY ION CHROMATOGRAPHY, SUPPRESSED CONDUCTIVITY AND MASS SPECTROMETRIC DETECTION USING AN OXYGEN-18 ENRICHED ISOTROPIC INTERNAL STANDARD
Hedrick, E J. AND D. J. Munch. DETERMINATION OF PERCHLORATE BY ION CHROMATOGRAPHY, SUPPRESSED CONDUCTIVITY AND MASS SPECTROMETRIC DETECTION USING AN OXYGEN-18 ENRICHED ISOTROPIC INTERNAL STANDARD. Presented at DoD Environmental Data Quality Workgroup/Intergovernmental Data Quality Task Force Perchlorate Testing Roundtable, Dallas, TX, October 22-23, 2003.
The goal of this project is to develop a method for the analysis of perchlorate in drinking water with a method detection limit between 0.02 and 0.1 ug/L (ppb) and a minimum reporting limit between 0.1 and 0.5 ug/L (ppb). [Note: this effort focuses on development of a sensitive and accurate method for laboratory analysis of perchlorate in drinking water: a related NERL task under the RARE program, 12505, focuses on development of a screening method for use with source waters.]
Perchlorate (ClO4 -) is a drinking water contaminant originating from the dissolution of the salts of ammonium, potassium, magnesium, or sodium in water. It is used primarily as an oxidant in solid propellant for rockets, missiles, pyrotechnics, as a component in air bag inflators, and in highway safety flares. Based on EPA Information Request Responses and occurrence monitoring, there have been 95 confirmed ClO4 - releases in 25 states and 230 users or manufacturers in 40 states. From accidental releases and improper disposal practices of the past, ClO4 - has become a contaminant in surface and ground waters where it is highly mobile and, due to its chemical stability, persists for decades. The primary human health effect is inhibition of iodide uptake by the thyroid gland. By disrupting thyroid hormone production, ClO4 - interferes with metabolism and can affect brain development in fetuses and children, leading to mental impairment. There is now a need for a method that can confirm and quantify ClO4 - at concentrations lower than what is achievable using ion chromatography with suppressed conductivity detection. Coupled with ion chromatographic separation, mass spectrometry is by far the most promising analytical tool available today for low-level identification and quantitation of ClO4 - in drinking water. In this work, sub-ppb quantitation of ClO4 - in drinking waters using ion chromatography electrospray ionization mass spectrometry (IC-ESI-MS) is demonstrated.
The primary mass of interest for ClO4 - is 99 based on the 75.77% relative abundance of the chlorine-35 isotope. Mass 101 is a secondary mass of interest based on the 24.23% abundance of chlorine-37. In this work we demonstrate the feasibility of using oxygen-18 enriched perchlorate as an internal standard. The greatest benefit of such an internal standard is for the improvement of accuracy in the determination of perchlorate in waters with high total dissolved solids such as sulfate, carbonate and chloride. In the event that ClO4 - is regulated in drinking water or that a second national occurrence survey is conducted, this research will lead to an inherently more specific and sensitive U.S. EPA method than is currently available.