Determination of ergosterol in canola (Brassica napus L.) by liquid chromatography

A sensitive and precise method is described to assay the oilseed canola (Brassica napus L.) for ergosterol, a fungal metabolite indicating spoilage. The ground seed is refluxed in methanol, and the methanol extract is saponified with potassium hydroxide. After addition of water, the mixture is partitioned into n-hexane. The n-hexane extract is dried, reconstituted, and applied to a silica solid-phase extraction cartridge, which is then washed with carbon tetrachloride, and eluted with acetone. The acetone eluate is acetylated, and the ergosterol determined as the acetate by liquid chromatography using a reverse-phase column and absorbency detection at 282 mn. Acetylation is necessary since an unidentified constituent of the matrix co-chromatographs with free ergosterol, and the ergosterol peak cannot otherwise be resolved. Using a 2-h acetylation at 60degreesC, recoveries of 10 and 25 ppm added ergosterol were 96.3% and 94.0%, respectively (n = 4, relative SD = 3.8% in each case). Results using a convenient overnight acetylation at 37degreesC were similar and not significantly different. The limit of detection was approximately 0.3 ppm. Crown Copyright (C) 2002 Published by Elsevier Science Ltd. All rights reserved.