Determination of Nivalenol and Deoxynivalenol in Cereals by Electron-Capture Gas Chromatography

Abstract

Nivalenol (NIV) is an important Fusarium mycotoxin shown to occur naturally in grains from several countries. Extraction and cleanup procedures previously described for trichothecene analysis have been modified to give good recoveries of NIV from cereal products. The extraction solvent is methanol-water (7 + 3). The extract is treated with 10% aqueous ammonium sulfate solution and then a 10 mL aliquot is partitioned into ethyl acetate (160 mL) on a hydrophilic matrix. After evaporation, the sample extract is dissolved in methylene chloridemethanol (3 +1) for column chromatography on silica gel 60. The toxins are eluted with methylene chloride-methanol (9 + 1) following column washes with toluene and n-hexane. NIV and deoxynivalenol (DON) trimethylsilyl ethers are formed with Tri-Sil TBT and determined by gas chromatography on a 3% OV-3 packed column or DB-5 capillary column with electron-capture detection. The method has been evaluated for wheat, wheat flour, corn flour, rye flour, and barley. Recoveries averaged 89% for NTV and 106% for DON from ground cerealsand flours at a spiking level of 1 μ/g; 72% and 82%, respectively, from wheat spiked at 0.5 μ/g; and 90% and 100%, respectively, from cereals spiked at 0.2 μ/g. Heptafluorobutj rates are used for confirmation of identity; the problem of 2 derivative peaks forming with NTV on the OV-3 packed column has been overcome by using an SPB-5 or DB-5 capillary column which gave single peaks.