Determination of zearalenone in botanical dietary supplements, soybeans, grains, and grain products by immunoaffinity column cleanup and liquid chromatography: single-laboratory validation

The accuracy, repeatability, and reproducibility characteristics of a method for measuring levels of zearalenone (ZON) in botanical root products, soybeans, grains, and grain products were determined by an AOAC single-laboratory validation procedure. Replicates of 10 test portions of each powdered root product (black cohosh, ginger, ginseng), brown rice flour, brown rice grain, oat flour, rice bran, soybeans, and wheat flour at each spiking level (ZON at 0, 50, 100, and 200 microg/kg) were analyzed on 3 separate days. Test samples were extracted with methanol-water (75 + 25, v/v). The extracts were centrifuged or filtered, diluted with phosphate-buffered saline (PBS) containing 0.5% Tween 20, and filtered; the filtrates were applied to an immunoaffinity column containing antibodies specific for ZON. After the column was washed with methanol-PBS (15 + 85, v/v) containing 0.5% Tween 20 and then with water, the toxin was eluted from the column with methanol, and the eluate was diluted with water. The eluate containing the toxin was then subjected to RPLC with fluorescence detection. All commodities that were found to contain ZON at < 10 microg/kg were used for the recovery study. The average within-day and between-days recoveries of ZON added at levels of 50-200 microg/kg ranged from 82 to 88% and from 81 to 84%, respectively, for all test commodities. The total average of within- and between-day SD and RSDr values for all test commodities ranged from 2.5 to 7.3 microg/kg and from 4.6 to 6.2%, respectively. HorRat values were <1.3 for all matrixes examined. The tested method was found to be acceptable for the matrixes examined.