DETERMINATION OF MYCOTOXINS IN BROWN RICE BY HIGH PERFORMANCE LIQUID CHROMATOGRAPHY-TANDEM MASS SPECTROMETRY

Abstract

QuEChERS sample preparation was optimized and validated by ultra high performance liquid chromatography-tandem mass spectrometry method for determination of nine mycotoxins in brown rice: aflatoxin B1, aflatoxin B2, aflatoxin G1, aflatoxin G2, fumonisin B1, fumonisin B2, deoxynivalenol, ochratoxin A and zearalenone. The following suitable QuEChERS conditions were obtained using the solvent extraction of 1.0 g of the brown rice with 5.0 mL of acetonitrile containing 10% acetic acid in presence of four salts (2.0 g of anh. MgSO4, 0.50 g of NaCl, 0.50 g of sodium citrate tribasic dehydrate and 0.25 g sodium citrate dibasic sesquihydrate), and followed by the dispersive-solid phase extraction cleaning up step using mixed sorbents of octadecylsilane (50 mg), primary and secondary amine (25 mg) and silica (25 mg). This developed method allows to determine mycotoxins in trace levels below maximum limits of the EU regulation, with our method detection limits of 1.4-25 µg/kg. Using blank brown rice spiked with mycotoxins at known concentrations, acceptable accuracy and precision for quantitative analysis were obtained with the recoveries in a range of 81-101% and relative standard deviation of 5-19% for 5.0-1,000 µg/kg. Six out of fourteen real samples of brown rice were found to be contaminated with at least one of these mycotoxins, 2.49-5.41 µg/kg of fumonisin B1, 4.33±0.04 µg/kg of fumonisin B2 and 6.10-14.88 µg/kg of zearalenone.