Developing Analytical Methods to Support Duplicate-Diet Human Exposure Measurements. Jeffrey N. Morgan, Maurice R. Berry, and Linda S. Sheldon, U.S. Environmental Protection Agency, National Exposure Research Laboratory, 26 W. Martin Luther King Dr., Cincinnati, OH 45268; and Research Triangle Institute, Analytical and Chemical Sciences, P.O. Box 12194, Research Triangle Park, NC 27709
Historically, analytical methods for determination of environmental contaminants in foods have been developed in support of regulatory programs and are specific in food items or food groups. While considerable methods development effort has been devoted to pesticides, many classes of environmental contaminants of interest to USEPA, such as PAHs and VOCs, have received relatively little attention. In addition, most of the available methods for contaminants in foods have been developed, tested and validated for relatively few analytes and food items. Method performance for composited duplicate-diet samples, as collected in USEPA residential-based exposure monitoring programs, is largely unknown. In response to monitoring program needs, NERL-Cincinnati has initiated an analytical methods development program for both organic and inorganic contaminants in composite foods.
At the outset of this method development program, a manual of proposed analytical methods for determination of target compounds of interest to both the AHS and NHEXAS exposure monitoring programs (primarily pesticides and metals) was compiled from published methods in the literature. The most promising extraction, clean-up and detection techniques for pesticides, PAHs, and metals from this manual of proposed methods were then subjected to a single-laboratory validation. Some of these methods have also progressed through a second laboratory validation and an extension of the manual to include methods for additional compounds such as VOCs is currently in progress.
To date this method development program has been primarily conducted under EPA contracts and will continue to be contracted out for the short term, with ongoing projects in development of isotope dilution techniques for determination of VOCs and ICP-MS methods for metals. However, an in-house method development program is also being initiated with plans to explore issues such as applicability of new analytical technologies to determination of contaminants in composite foods, development of food materials to use as quality control samples in dietary exposure monitoring studies, development of reference materials for foods, and applicability of screening techniques, such as immunoassay, to dietary monitoring programs.