Micellar Electrokinetic Capillary Chromatography of Methylated Flavone Aglycones

Thirty four flavone aglycones isolated from herbs and spices were analysed by MECC on fused silica capillaries with sodium borate buffers and SDS micelles. Addition of organic solvents was necessary to improve the separation. However, when methanol was used, either as a sample solvent or as a constituent of the buffer, the most hydrophobic flavones appeared as double or triple peaks in the electropherograms. These double peaks disappeared when acetonitrile was used instead of methanol. The best separation was obtained with buffers containing acetonitrile when samples were dissolved in the same running buffer. In the separation of these flavones, in addition to the hydrophobic interaction with micelles, the ionization of phenolic hydroxyls and the borate complexation had some effect in the migration order of the molecules. A correlation between the migration order in MECC and the elution order previously reported for reversed-phase HPLC analyses was generally observed.