New reversed-phase liquid chromatographic method to detect aflatoxins in food and feed with cyclodextrins as fluorescence enhancers added to the eluent

The effect of succynil–β-cyclodextrin (β-CD–Su), dimethyl-β-cyclodextrin (DIMEB) and β-cyclodextrin (β-CD) on the fluorescence of aflatoxins B1, B2, G1, G2 and M1 (AFB1, AFB2, AFG1, AFG2 and AFM1) was studied: β-CD–Su promoted the largest fluorescence enhancement for AFB1 and AFM1 while DIMEB showed better results for AFG1. On the basis of the fluorescence enhancement, a new RP-HPLC method for detecting aflatoxins B1, B2, G1, G2 and M1 was developed using cyclodextrins directly dissolved in the LC eluent. Aflatoxins B1, B2, G1 and G2 were resolved using a MICRA NPS ODS-1 column using methanol–water as mobile phase to which 6×10−3 M β-CD–Su or β-CD were added. Chromatographic responses of AFB1 and AFG1 achieved using β-CD dissolved in the mobile phase were enhanced, respectively, 8 and 12 times, and 10 and 15 times with β-CD–Su. Detection limits lower than 0.3 μg/kg were achieved for all the four aflatoxins. Aflatoxin M1 was analysed using a Spherisorb S3 ODS-2 Narrow Bore column and methanol–water as mobile phase with added 2×10−3 M β-CD–Su. An area enhancement of 1.5 was detected for the toxin and the detection limit achieved under these analytical conditions was lower than 0.0005 μg/kg. Both methods were statistically validated showing a linear response for all the aflatoxins tested (R2≥0.99), and applied to the analysis of spiked and naturally contaminated food samples.