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Improved x-ray spectrometric method for determining glucosinolates

A. Pinkerton1, P.J. Randall1and R.J. Mailer2

1 CSIRO Division of Plant Industry, G.P.O. Box 1600, Canberra, A.C.T. 2601
NSW Agriculture, Agricultural Research Institute, Wagga Wagga, NSW 2650

Glucosinolates are the most detrimental components in oilseed rape; their breakdown products in the high protein meal after oil extraction can adversely affect animal growth. The Australian oilseeds industry has adopted the Canola standard, i.e. <30 pmol/g of four particular glucosinolates in meal. A rapid method for determining glucosinolates in seed and meal of rapeseed and other oilseed brassicas is essential for screening cultivars in breeding programs and for analysing batches delivered for crushing.


A recently developed X-ray fluorescence spectrometric (XRFS) method ( I) for determining oxidised S (S6+) and carbon bonded S (Sc) in plant material utilizes the small SK wavelength shift with change in chemical bonding (oxidation number). A glucosinolate molecule contains two S atoms, one S6+ and one Sc (Fig. I). Protein contains only Sc atoms. Analysis for S6+ provides an estimate of glucosinolate content (Fig. I ).

Figure 1. Principal S fractions in rapeseed.

Figure 2. Linear relationship between S6+ in rapeseed and total glucosinolates determined by glucose release (2).

Results and discussion

S6+ is highly linearly correlated with glucosinolate contents determined by chemical Methods (Fig. 2). Errors from inclusion of sulfate are small because sulfate, a small fraction of total S. is correlated with glucosinolates. The S6+ method is superior to an existing XRFS method (2) which uses total S because protein S. a large fraction of total S. is not correlated with glucosinolates.


4. Pinkerton. A.. Randall. P.J. and Norrish. K. 1991. Commun. Soil Sci. Plant Anal. 20. 1557-1574.

5. Mailer. R. and Wratten. N. 1985. Aust. J. Exp. Agric. 25. 932-8.

6. Wathelet. J.P., Wagstaffe, P.J. and Boenke. A. 1991. Report CD-NA-13339-EN-C. Office for Official Publications of the European Communities, Luxembourg.

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