Rapid method for the clean-up of extracts of cottonseed prior to aflatoxin determination by bi-directional HPTLC
A PH non-polar bonded-phase clean-up procedure has been developed for determining aflatoxin concentrations in aqueous acetone extracts of cottonseed by bi-directional HPTLC. It involves the addition of lead acetate solution to the extract prior to its passage through the bonded-phase cartridge.
The accuracy and precision of the method have been evaluated for a range of aflatoxin concentrations between 4.7–806.1 μg/kg (B1), 2.8–419.8 μg/kg (B2), 5.1–820.3 μg/kg (G1) and 3.3–396.9 μg/kg (G2). The coefficients of variation varied between 0.8 and 12%, with mean recoveries between 83% and 99%. Correlation coefficients of 1.0 for each aflatoxin showed the closeness of fit of the weighted regression curves. Small systematic errors were detected for aflatoxins B1, B2 and G1 as the 95% confidence intervals of the regression intercepts failed to include the expected value of zero. The limits of detection were found to be between 1.1 μg/kg (B2 and G2) and 2.7 μg/kg (B1).
Comparison of the method with the first action AOAC method for cottonseed showed that the PH cartridge method recovered 80% more aflatoxin B1 and 52% more B2 from a sample naturally contaminated with aflatoxin. It was also more precise for aflatoxin B1 as well as being more rapid and cost effective.
Key WordsThin-layer chromatography Aflatoxin determination Cottonseed Salid phase extraction
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