Determination of the total glucosinolate content in rapeseed seeds by liquid chromatography: comparative study between the rapid isocratic and the reference gradient methods by a ring test

Isocratic liquid chromatography (LC) on cyanopropyl bonded silica column is an alternative method to gradient IC on octadecyl bonded silica column involved in the standardized method for total glucosinolotes (GSL) analysis in rapeseed seeds. Its advantages consist in more simple apparatus and eluent, and a shorter analysis duration. In the aim of a next standardization of isocratic LC, the performances of both methods ore compared on three rapeseed samples during a ring-test including six laboratories. Statistical treatment or the results according to ISO 5725 shows, with a risk level of 5%, the equivalency of both methods to determine total GSL content in rapeseed seeds. The elution mode appears to have no significant effect on results in opposite to the internal standard when its purity is not well-known.