Rapid method for the clean-up of extracts of cottonseed prior to aflatoxin determination by bi-directional HPTLC

Summary

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.