Automated pesticide residue analysis and screening

Abstract

In the United States, with probably the most intense and diversified agriculture in the world, there are registered for permitted use more than 900 chemical compounds¹ in more than 60,000 pesticidal formulations (Freeman 1965). In this country uses of these materials on more than 2,500 crop items (Kirk 1964) and other foodstuffs are regulated by joint considerations of the U. S. Food and Drug Administration (F.D.A.) and the U.S. Department of Agriculture (U.S.D.A.) (Harris and Cummings 1964), with assignments of tolerances or permitted residue values for amounts of particular chemicals to be legally acceptable on and in particular raw agricultural commodities at time of sale or consumption. These values may range from an actual zero to more than 100 parts per million (p.p.m.), depending in large measure upon the pharmacology and toxicology of the candidate chemical. Until recently and in broadest terms “zero” as interpreted by regulatory agencies could mean either numerical tolerance denied, because of probable hazard to be associated with the projected use, or a number less than unity predicated upon residue analytical capabilities and credulity at the moment. For certain pesticide chemicals which were of widespread application on certain major crops or products, and which were also of pharmacological concern, as residue analytical methodology improved in minimum detectability, and in reliability, some “zero” and other tolerance values have been lowered with certain commodities (e.g., milk) to accommodate a new analytical capability; present tolerances often reflect residues that could remain at harvest. This completely unsatisfactory dynamic tolerance situation has existed particularly with several of those pesticides which contain organically bound halogens, such as dieldrin, endrin, and heptachlor. It has also been involved both legally and morally with numerous chemicals previously registered by the U.S.D.A., and with F.D.A. concurrence, on a “no-residue” basis (Harris and Cummings 1964): at the time the “no-residue” registration was granted finite residues were not demonstrable yet subsequendly analytical detection of persisting residues was made possible by improvements in methodology, usually through exploitation of modern analytical instrumentation, and the original specific registration was revoked.

Presented in part at the September 1965 Technicon symposium “Automation in Analytical Chemistry,” New York, N. Y.