DETERMINATION OF DEOXYNIVALENOL IN 1991 UNITED-STATES WINTER AND SPRING WHEAT BY HIGH-PERFORMANCE THIN-LAYER CHROMATOGRAPHY

A thin-layer chromatographic (TLC) method was modified for determinati on of deoxynivalenol (DON) in 1991 U.S. winter and spring wheat. After extraction with acetonitrile-water (84 + 16) and cleanup on a charcoa l-alumina-Celite (7 + 5 + 3) column, acetonitrile was used instead of ethyl acetate to transfer the concentrated extract containing DON. Aft er the extract was evaporated to dryness, the residue was dissolved in methanol and an aliquot was spotted on a high-performance TLC plate. After development with chloroform-acetone-2-propanol (8 + 1 + 1), the plates were sprayed with aluminum chloride solution and heated; DON wa s quantitated by fluorodensitometry. Average recoveries of DON added t o duplicate test portions of wheat at 200, 400, and 800 ng/g were 83, 82, and 72%, respectively. The detection limit was 40 ng/g. The method was applied to 81 test samples of spring and winter wheat. The wheat contained DON levels that ranged from nondetectable to 9330 ng/g (aver age 1570 ng/g). The results indicate that DON levels were higher in wh eat from Missouri, North Dakota, and Tennessee than in wheat from 7 ot her states. The identity of DON, which was isolated from 21 of the ext racts by preparatory TLC, was confirmed by gas chromatography/mass spe ctrometry in all 21 test samples.