High Performance Liquid Chromatographic Method for the Determination of Ochratoxins a and B in Foods

Abstract

A method is described for the determination of low levels of ochratoxins A and B in foods by high performance liquid chromatography (HPLC). Ochratoxins were extracted from samples with the methanol-1% sodium bicarbonate system. The extracts were transferred to ether after acidification with phosphoric acid, then the ether layer was washed with water, dried with anhydrous sodium sulfate and evaporated to dryness. The residue was dissolved in chloroform (saturated with 1% ammonia water) and applied to a silica gel column (15% water content). The column was washed with 40 ml of chloroform. Ochratoxins were eluted with 50 ml of benzene-glacial acetic acid (9:1). The eluate was washed with water, dried with anhydrous sodium sulfate and evaporated to dryness, then the residue was subjected to HPLC after being dissolved in acetonitrile. The recoveries of ochratoxins added to foods at levels of 20 and 100 ppb were in the range from 87% to 101% and the detection limit was 2. 5 ppb in samples. For chemical confirmation of ochratoxins A and B in samples, the methyl esters were prepared by heating at 100°C for 20 min with methanol-sulfuric acid. The identification limit was 2 ppb in samples. By using this method, 171 commercial samples were analyzed. Ochratoxin A was detected in rye flour at a trace level (<2. 5ppb)~20ppb. © 1984, Japanese Society for Food Hygiene and Safety. All rights reserved.