Analysis of 5-vinyl-1,3-oxazolidine-2-thione in complex matrices at ppb level

Abstract

5-Vinyl-1,3-oxazolidine-2-thione (5-VOT) is a goitrogenic compound released by enzymatic degradation of progoitrin, the most important glucosinolate occurring in rapeseed meal. This paper describes an analytical method for determining the 5-VOT in complex matrices. The method proposed by Quinsac et al. [J. Assoc. Off. Anal. Chem., 75(3) (1992) 529] has been improved by modification of the extraction conditions and the purification steps. The extraction of 5-VOT is performed with hot acid buffer. The first purification step is achieved by solid-phase chromatography (C 18). The second purification step of 5-VOT is carried out by complexation with phenyl mercury acetate in cyclohexane and, afterwards, by decomplexation using an aqueous solution of sodium thiosulfate. These reactions move 5-VOT from an aqueous to an organic medium, and then back again to the aqueous phase. This procedure ensures a high purification efficiency. The precise quantification of 5-VOT is completed in 12 min by reverse-phase liquid chromatography (C 18), using an isocratic elution with an ultraviolet detector and with synthetic 4,4-dimethyl-1,3-oxazolidine-2-thione as internal standard. Using this modified method, 5-VOT can be determined in different matrices such as rapeseed meal, animal diets, muscle, several organs (thyroid, liver, kidney and lung) and biological fluids (plasma and milk). The quantification limit of 5-VOT in the sample is of 1 ppb (1 μg kg −1), the recovery rate of 5-VOT is about 90% and the repeatability is over 97%.