Performance of two immunochemical assays in the analysis of peanuts for aflatoxin at 37 field laboratories

A study was conducted to measure the precision of 2 rapid aflatoxin assay systems in use at 37 peanut buying points during the 1991 harvest season. Aflatoxin laboratories were established at the 37 buying points to analyze peanut samples from all incoming farmers' stock loads as part of a joint project sponsored by various segments of the U.S. peanut industry and the U.S. Department of Agriculture. Eighteen laboratories were equipped with Neogen's veratox FSP rapid assay system, whereas 19 laboratories used Vicam's Aflatest rapid assay system. To monitor the performance of the field laboratories during the project, 3 portions of each of six 27 kg samples of ground peanuts were sent to each laboratory for analysis over a period of 6 weeks. Aflatoxin concentrations ranged from 0 to 300 ng/g when eight 200 g subsamples of each sample were analyzed by liquid chromatography (LC). For the 5 samples contaminated with aflatoxin, relative standard deviations for repeatability (RSDr) for laboratories using veratox FSP ranged from 18.66 to 53.29%, and the relative standard deviations for reproducibility (RSDR) ranged from 22.79 to 59.29%. For laboratories using the Aflatest system, RSDr values ranged from 18.70 to 41.48%, and RSDR values ranged from 23.84 to 47.56%. Horwitz ratios < 2.0 were found for 4 of the 5 contaminated samples for both methods, indicating that the overall precision of the 2 methods used in the project was good. Mean aflatoxin concentrations, as determined with the rapid assay systems, were generally lower than those determined by LC, particularly for more highly contaminated samples.(ABSTRACT TRUNCATED AT 250 WORDS)