Determination of aflatoxin levels in peanut butter using HPLC and ELISA procedures: Inter-laboratory comparison.

Six laboratories analyzed portions of the same aqueous acetonitrile extracts of three peanut butters for aflatoxin concentrations by an HPLC procedure (using immunoaffinity column clean - up) and by an ELISA procedure. The extracts were from a nominal "blank" peanut butter, a peanut butter naturally contaminated with aflatoxins (mostly B1), and from a "blank" peanut butter to which equal amounts of aflatoxin B1, B2, G1; and G2 standards had been added. Similar results for the HPLC and ELISA procedures were obtained for the blank (means 2.8 and 4.0μg/kg, respectively) and naturally contaminated (means 26.0 and 25.9μg/kg, respectively) peanut butters. However, the result by ELISA (mean 16.7μg/kg) for the spiked peanut butter was much lower than that obtained by HPLC (mean 28.3 μg/kg).