Conference on Applied Statistics in Agriculture

SAMPLING SCHEMES TO DETECT VERY LOW CONCENTRATIONS

Many mycotoxins and certain drug residues can be important at very low concentrations in feeds and foods. Government regulatory agencies establish maximum acceptance concentrations (Action Levels) to avoid proven effects of known toxins and provide Advisory Levels where effects are not yet well established. The Action Levels for the aflatoxins range from 5 to 300 ppb (ng/g) depending on the particular toxin and the intended use of the feed or food. Other naturally occurring mycotoxins, such as DON, zearalenones, and fumonisons, have advisory levels in the range of 1 to 5 ppm (j.A-g/g) . Chemotherapeutic agents in feeds must be measured in ppm or even ppb. Common acceptance sampling techniques can usually be used for liquids, flours, meals, etc. A problem arises, however, when the substance to be measured is concentrated in individual kernels of grain. In some cases, a single "hot II kernel contains enough toxin to contaminate thousands of clean kernels. The common sampling techniques for large lots (such as truck, barge or ship loads) can be unreliable at concentrations around the Action or Advisory Levels. The problem will continue to arise as modern testing instruments become more sensitive at lower concentrations. This paper will review some biases of current sampling procedures and discuss methods of changing the sizes of the types I and II errors.