PREPARATION TECHNIQUES OF SMALL SAMPLE SIZES FOR SULFUR AND INDIRECT TOTAL GLUCOSINOLATE ANALYSIS IN BRASSICA SEEDS BY X-RAY-FLUORESCENCE SPECTROSCOPY

Two new preparation techniques for Brassica seeds are introduced, whic h enable the determination of total sulphur concentrations and indirec tly the total glucosinolate concentrations in small sample sizes and s ingle seeds by means of X-ray fluorescence spectroscopy. Small sample sizes, down to 250 mg, are milled in peppermill type grinders and prep ared as thin layers in liquid cuvettes. Single seeds are embedded by m eans of a sulphur free glue based on acetylated glucose in wax tablets and cut into halves. Measurement and calibration for small sample siz es are in accordance with the rules for the original X-RF method. In c ase of single seeds the area of the cut surface need to be estimated a nd the collected S-Kalpha intensities corrected for the active fluores cent area of the standard reference materials.