Aflatoxin evaluation in ready-to-eat brazil nuts using reversed-phase liquid chromatography and post-column derivatisation

Abstract

A high-performance liquid chromatography-fluorescence (HPLC-FD) method for aflatoxin quantification in brazil nuts was developed. Samples of brazil nuts collected in Brazilian markets were extracted with methanol:water and cleaned using an immunoaffinity column. Aflatoxins were eluted with methanol and a post-column derivatisation was performed with bromine, using a Kobra Cell system. The optimised method for total aflatoxins was sensitive, with detection and quantification limits of 0.05 and 0.25 μg kg–1, respectively. The method was accurate, with recovery values of 87.6%; 85.3% and 85.0% for 0.5, 5.0 and 14.6 μg kg–1 spiked levels, respectively. It was shown that the method was applicable to brazil nuts. From a total of 95 brazil nut samples analysed from 21 São Paulo supermarket samples and 51 Manaus and 23 Belém street markets samples, 37.9% showed detectable levels of aflatoxins and three exceeded the recommended Codex Alimentarius limit of 10 μg kg–1 for ready-to-eat brazil nuts.