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DETERMINATION OF ULTRATRACE CONCENTRATIONS OF AGRICULTURAL PESTICIDES IN WATER USING SOLID-PHASE EXTRACTION AND ANALYSIS BY GC/MS
Citation:
Momplaisir, G M., K E. Varner, E M. Heithmar, C G. Rosal, L A. Riddick, P. L. Ferguson, B. Gentry, D F. Bradford, AND N G. TallentHalsell. DETERMINATION OF ULTRATRACE CONCENTRATIONS OF AGRICULTURAL PESTICIDES IN WATER USING SOLID-PHASE EXTRACTION AND ANALYSIS BY GC/MS. Presented at Pittsburgh Conference on Analytical Chemistry and Applied Spectrometry, Orlando, FL, March 9-14, 2003.
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:
A comprehensive study of the distribution of airborne agricultural contaminants in the Southern Sierra Nevada has been initiated', due to the heavy pesticide use in a neighboring area: the San Joaquin Valley of California. Approximately forty commonly used agricultural pesticides in the San Joaquin Valley are to be measured in lake water at about 60 sites in the Southern Sierra Nevada. This paper describes the development of an extraction procedure for the isolation of pesticides from large volumes of water (up to 100 L).
Pesticide analytes are removed from the aqueous matrix by adsorption onto a solid phase sorbent, followed by sequential elution with organic solvents. The polymeric sorbent Nexus (Varian, Palo Alto, CA) offered more selectivity to the analytes than XAD and a silica-based material C,,. Also, when compared with the polymeric resin PPL, Nexus had a greater retention capacity. Recoveries of 80% or better were obtained for the majority of the compounds using the Nexus resin. Eight grams of sorbent were sufficient to displace the selected compounds from a I 00-L water sample with minimal loss of the most polar compound dimethoate.
The extracts were analyzed by conventional pulsed-splitless GC/MS or large-volume injection GC/MS (the subject of a companion paper at this conference). Because of the high organic contents of some lake water samples, a clean-up procedure was also developed. Preliminary data on the determination of agricultural contaminants in alpine lake waters of the Southern Sierra Nevada will be presented.