Quantitation of aflatoxins in walnut kernels by high-performance liquid chromatography with fluorescence detection

A total of 85 walnut samples collected between October 2012 and April 2013 in different provinces of Turkey were analysed for the presence of aflatoxins (AFs). The method involved methanol-water extraction, clean-up with immunoaffinity columns and a sensitive high-performance liquid chromatography coupled with fluorescence detection after post-column derivatisation. The method was validated for selectivity, linearity, trueness, precision, limit of detection and limit of quantification (LOQ), which met the performance criteria as set by EC regulation No. 401/2006. LOQs were 0.07, 0.04, 0.09 and 0.05 µg kg(-1) for AFB1, AFB2, AFG1 and AFG2, respectively. AFs were present in 9.4% of walnut samples (8/85) at total AFs levels ranging from 0.09 to 15.4 µg kg(-1). Only one of eight walnut samples exceeded the European Union limit of 2 and 4 µg kg(-1) for AFB1 and total AFs, respectively.