Theoretical principles for the indirect determination of the total glucosinolate content in rapeseed and meal quantifying the sulphur concentration via X-ray fluorescence (X-RF method)

The introduction of double low oilseed rape cultivars into common crop production will require the development of methods for a precise, rapid and simple determination of the total glucosinolate content in rapeseed. Recent methods are often inappropriate for plant breeding work, and also for the trade and oil mills in separating parcels of seed according to their glucosinolate contents. In contrast to the methods commonly used (chromatography, enzymic and colorimetric tests) an indirect method is described here which is based on the very close correlation between the total sulphur and glucosinolate content in rapeseed. The sulphur content of the samples can be determined precisely and non-destructively by means of X-ray fluorescence spectroscopy (X-RF). This new method, which is suitable for rapeseed and meal, requires simple preparation of the seed samples by grinding and compressing. The whole analytical procedure (sample preparation and measurement) takes 2-4 min. If necessary, moist seed samples can be quickly dried by microwave heating, because the method does not require intact glucosinolates. The steps of the X-RF method are fairly insensitive to errors. The method shows an excellent repeatability (r = 1.9 μmol g^?1) and reproducibility (R = 3.8 μmol g^?1). The results obtained with this X-RF method correlate closely with the conventional reference methods (r² = 96-99%).