Determination of Aflatoxins B1, B2, G1, and G2 in Olive Oil, Peanut Oil, and Sesame Oil Using Immunoaffinity Column Cleanup, Postcolumn Derivatization, and Liquid Chromatography/Fluorescence Detection: Collaborative Study

The accuracy, repeatability, and reproducibility characteristics of a method using immunoaffinity column (IAC) cleanup with postcolumn derivatization and LC with a fluorescence detector (FLD) for determination of aflatoxins (AFs; sum of AFs B-1, B-2, G(1), and G(2)) in olive oil, peanut oil, and sesame oil have been established in a collaborative study involving 15 laboratories from six countries. Blind duplicate samples of blank, spiked at levels ranging from 0.25 to 20.0 mu g/kg for AF, were analyzed. A naturally contaminated peanut oil sample was also included. Test samples were extracted with methanol-water (55 + 45, v/v). After shaking and centrifuging, the lower layer was filtered, diluted with water, and filtered through glass microfiber filter paper. The filtrate was then passed through an IAC, and the toxins were eluted with methanol. The toxins were then subjected to RPLC-FLD analysis after postcolumn derivatization. Average recoveries of AFs from olive oil, peanut oil, and sesame oil ranged from 84 to 92% (at spiking levels ranging from 2.0 to 20.0 mu g/kg); of AFB(1) from 86 to 93% (at spiking levels ranging from 1.0 to 10.0 mu g/kg); of AFB(2) from 89 to 95% (at spiking levels ranging from 0.25 to 2.5 mu g/kg); of AFG(1) from 85 to 97% (at spiking levels ranging from 0.5 to 5.0 mu g/kg); and of AFG(2) from 76 to 85% (at spiking levels ranging from 0.25 to 2.5 mu g/kg). RSDs for within-laboratory repeatability (RSDr) ranged from 3.4 to 10.2% for AF, from 3.5 to 10.9% for AFB(1), from 3.2 to 9.5% for AFB(2), from 6.5 to 14.9% for AFG(1), and from 4.8 to 14.2% for AFG(2). RSDs for between-laboratory reproducibility (RSDR) ranged from 6.1 to 14.5% for AF, from 7.5 to 15.4% for AFB(1), from 7.1 to 14.6% for AFB(2), from 10.8 to 18.1% for AFG(1), and from 7.6 to 23.7% for AFG(2). Horwitz ratio values were <= 2 for the analytes in the three matrixes.