SEPARATION OF DESULPHOGLUCOSINOLATES BY MICELLAR ELECTROKINETIC CAPILLARY CHROMATOGRAPHY BASED ON A BILE-SALT

Micellar electrokinetic capillary chromatography (MECC) has been devel oped as a promising method for the determination of 40 desulphoglucosi nolates. A sodium cholate based MECC method was found to be efficient for the qualitative and quantitative analysis of desulphoglucosinolate s produced in an on-column, enzymatic step from the corresponding inta ct glucosinolates. Separation conditions and sensitivity of the method have been optimised with respect to different parameters, including c apillary types, where the 75-mu m I.D. capillary increased the sensiti vity 2.5 times over that of a 50-mu m capillary. With use of a high-se nsitivity optical cell assembly (Z-cell), the sensitivity was further increased ten times, resulting in detection of picogram amounts, or co ncentration levels corresponding to 10(-6)mu M. Repeatability with a 7 5-mu m capillary was good, with the relative standard deviation varyin g between 0.2% and 0.9% for relative migration times and for relative normalised areas between 1.0% and 3.0%. Linearity of the optimised met hod gave correlation coefficients between 0.99 and 0.9999 for the 50-m u m capillary and 0.99 and 0.9997 for the 75-mu m capillary. Separatio n efficiency expressed as number of theoretical plates (Nim) was in th e range of 250 000-300 000 for the 50-mu m capillary and 210 000-250 0 00 for the Z-cell. Limitations and possibilities of the MECC method he re presented are discussed with respect to analyses of glucosinolates occurring in a wide range of cruciferous seed, vegetative plant parts including cabbage varieties, feed and food.