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DIRECT MERCURY ANALYSIS IN ENVIRONMENTAL SOLIDS BY ICPMS WITH ON-LINE SAMPLE ASHING AND MERCURY PRECONCENTRATION USING A DIRECT MERCURY ANALYZER
Citation:
Heithmar, E M., C G. Rosal, AND J V. Cizdziel. DIRECT MERCURY ANALYSIS IN ENVIRONMENTAL SOLIDS BY ICPMS WITH ON-LINE SAMPLE ASHING AND MERCURY PRECONCENTRATION USING A DIRECT MERCURY ANALYZER. Presented at Winter Conference on Plasma Spectrochemistry, Scottsdale, AZ, January 6-12, 2002.
Impact/Purpose:
The overall goals of the task are to apply NERL's core capability in advanced chemical science and technology for maximum benefit in estimating exposures of ecosystems and humans to chemical stressors and to identify emerging pollution concerns, in particular long-range airborne transport of contaminants. This task comprises several subtasks, each with individual objectives:
Subtask 1: screen exposures of National Park PRIMENet ecosystems to chemical stressors, identifying indications of exposure requiring further evaluation, and use these samples evaluate new analytical methods as replacements for standard methods in future assessments of ecosystem contaminant exposures.
Subtask 2: evaluate a new mercury analytical approach with superior performance on complex solid matrices such as biological tissues, and apply the approach to estimating exposure of ecosystems and humans to mercury.
Subtask 3: determine distribution patterns of chemical contaminants in the southern Sierra Nevada Range of California, investigate topographic and weather factors that may influence the distributions, and determine if a correlation exists between contaminant distributions and extirpation patterns of the mountain yellow-legged frog.
Subtask 4: provide analytical methods to measure a number of inorganic and organic arsenic species in a variety of environmental matrices, elucidate the environmental transformations undergone by organoarsenic animal-feed additives, and determine if the potential exists for substantially increased exposure of humans and aquatic organisms to arsenic.
Description:
Mercury is a persistent, mobile, and highly toxic pollutant. It's biogeochemistry is probably the most complex of any metal. For these reasons, the U.S. Environmental Protection Agency (EPA), through its Office of Research and Development (ORD), has developed a comprehensive research plan to study the exposure of humans and ecosystems to mercury and the risks associated with these exposures. ORD's National Exposure Research Laboratory is tasked with developing tools for determining mercury in all environmental media.
Environmental analysis of mercury is most often accomplished by generation of elemental mercury from an aqueous sample or digest, followed by determination by either atomic absorption or atomic fluorescence spectrometry. Conventional analysis of aqueous samples or digests by inductively coupled plasma mass spectrometry (ICPMS) is problematic because of the high ionization potential of the element, the low abundance of its isotopes, and memory effects from sorption in the sampling system. ICPMS combined with cold vapor generation has been used to increase sensitivity.
The determination of mercury in solid environmental samples, such as soil, sediment, dust, and biological tissue, is difficult. The element is generally present at ultratrace concentrations. Sometimes only milligram quantities of sample are available (e.g., in the analysis of human hair or muscle tissue from live organisms), resulting in very low absolute mass of mercury. Digestion methods required for conventional analysis further dilute the concentration of the element and introduce the potential of contamination.