A thiourea‐UV assay for total glucosinolate content in rapeseed meals

A rapid and sensitive method for the determination of the total glucosinolate content in rapeseed is described. The method is based on the specific UV absorbance of the thioureas and oxazolidine‐2‐thiones. Results obtained were confirmed by gas‐liquid chromatography. Recoveries varying from 94 to 103% were obtained for samples containing mixtures of isothiocyanate and oxazolidine‐2‐thione (a total of 0.25 to 0.78 mg per assay). The relative stadard deviation for rapeseed meals varied from 4 to 10% for the total glucosinolate content (expressed as 3‐butenylisothiocyanate) and depended on the size of sample taken. The relative standard deviation for oxazolidine‐2‐thione varied from 5 to 35% for the same meal. The lower limit of detection for rapeseed meal is of the order of 0.25 mg of 3‐butenylisothiocyanate per g.