Microdetermination of the major individual isothiocyanates and oxazolidinethione in rapeseed

Abstract

Abstract A method has been developed for the quantitative determination of the major individual thioglucosides (as their aglycones) in rapeseed on a micro scale. The thioglucosides in the meal were hydrolyzed with myrosinase (B.C. 3.2.3.1, thioglucoside glucohydrolase), and the released aglycones were extracted with methylene chloride. The 3‐butenyl and 4‐pentenyl isothiocyanates were determined by gas‐liquid chromatography. The 5‐vinyl‐2‐oxazolidinethione was determined on an aliquot of the same extract by ultraviolet absorption. Five to 20 milligrams of seed or meal were used, and one operator could analyze 24 samples per day. The standard deviation was ŷ3% for the isothiocyanates and ŷ6% for the oxazolidinethione. The limit of detection was 0.1 mg per gram of meal for the isothiocyanates and 0.3 mg per gram of meal for the oxazolidinethione. Small amounts of phenylethyl isothiocyanate and two unidentified isothiocyanates were also found.