Beta-cyclodextrin post-column fluorescence enhancement of aflatoxins for reverse-phase liquid chromatographic...

beta-Cyclodextrin enhances the fluorescence of aflatoxins B1 and G1 in aqueous systems. This effect was utilized in developing a unique reverse-phase liquid chromatographic (LC) method for determination of aflatoxins B1, B2, G1, and G2 (B1 detection limit 1 ppb), without preparing derivatives of B1 and G1. The aflatoxins are dissolved in methanol or the mobile phase for injection onto the LC system. Using a mobile phase of methanol-beta-cyclodextrin (1 + 1), the aflatoxins are resolved on a C18 column. Fluorescence of the aflatoxins is enhanced by post-column introduction of an aqueous concentrated beta-cyclodextrin solution. All 4 aflatoxins elute within 10 min in the order G2, G1, B2, B1. Fluorescence responses for B1 and G1 standards were linear over the concentration range 0.5-10 ng, yielding correlation coefficients (r) of 0.9989 and 1.000, respectively. The average peak response ratio for G1:B1 for the mobile phase-enhancement solution described was 0.765 with a coefficient of variation (CV) of 0.98%. CVs were 6.2, 9.0, and 7.5% for multiple assays of aflatoxin B1 in 3 samples of naturally contaminated corn. For samples of corn spiked to a total B1 content of 8.3 ng/g, average B1 recovery was 90% (CV 11.7%).