You are here:
METHODS DEVELOPMENT FOR THE ANALYSIS OF CHIRAL PESTICIDES
Citation:
Ulrich, E M. METHODS DEVELOPMENT FOR THE ANALYSIS OF CHIRAL PESTICIDES. Presented at ORD/OPPTS Scientist to Scientist Seminar, Research Triangle Park, NC, October 1, 2003.
Impact/Purpose:
The goal of this task is to contribute to a better understanding of human exposure to pesticides, especially for small children by developing methods to characterize sources and pathways in and around the residential environment. We will support the science behind FQPA and assist the Office of Pesticide Programs (OPP) in the development of guidelines for the assessment of residential exposure to pesticides. Specific research objectives include: (i) to evaluate and develop methods for measuring pesticides in air using passive/diffusive samplers. Assess and refine devices for the collection of surface transferable pesticide residues and to establish transfer efficiencies; (ii) to develop and apply analytical methods for new and emerging pesticides using both gas and liquid chromatographic methods in support of the National Exposure Research Laboratory's (NERL) Human Exposure Measurement Project; and, (iii) to conduct pilot studies investigating chiral chromatographic methods.
Description:
Chiral compounds exist as a pair of nonsuperimposable mirror images called enantiomers. Enantiomers have identical physical-chemical properties, but their interactions with other chiral molecules, toxicity, biodegradation, and fate are often different. Many pharmaceutical compounds are comprised of enantiomers, furthermore 29% of 1700 surveyed agrochemicals and their degradates are chiral. With increased regulatory pressure, specific enantiomers are beginning to be treated as separate compounds. Single or enriched enantiomer formulations are becoming more prevalent, especially in Europe. The invention of chiral separation techniques significantly increased the development of methods for chiral compounds. The mechanism for enantiomer separation using derivatized cyclodextrin gas chromatography is not well understood, but is becoming a popular analytical tool. We will discuss the different types of columns, parameters affecting separation, and the peak fitting method for determining enantiomer fractions. Enantiomer fractions [EF = chromatographic peak area (+) enantiomer / sum of (+) and (-) areas] can be used to differentiate between types of degradation pathways, implicate sources of contamination, and give a more complete picture of environmental contamination for more accurate risk assessments. Currently at EPA, these techniques are being employed in human exposure projects like CTEPP, and ecological research projects in sediment, plants, and biota.
This work has been funded by the US EPA and USGS. It has been subjected to EPA review and approved for presentation. Mention of trade names of cmercial products does not constitute endorsement or recommendation for use.