Highly efficient separation of isomeric epoxy fatty acids by micellar electrokinetic chromatography

A capillary electrophoresis (CE) method has been developed for simple and d irect separation of cis- and trans-12,13-epoxy-9(Z)-octadecenoic acid and 9 ,10-epoxy-12(Z)-octadecenoic acid isomers. Separation was performed in mice llar electrokinetic capillary chromatography (MEKC) using a buffer consisti ng of 25 mM berate (pH 9.20), 10 mM sodium dodecyl sulfate (SDS) and 10% v/ v acetonitrile. The key variables, concentrations of SDS and organic modifi er, were optimized by the application of a factorial experimental design. T he use of a low micellar concentration, just above critical micelle concent ration (CMC), in a background electrolyte containing an organic modifier no t only made it possible to dissolve and separate highly hydrophobic fatty a cid isomers, but also resulted In improved separation efficiency and select ivity. Separation efficiency up to 4 x 10(5) theoretical plates/m was achie ved under an optimized condition. Also investigated were the influence of t emperature on separation and the effect of organic modifier concentration o n the dynamic exchange of the analytes between micelles and the bulk of the buffer solution. Direct UV was;applied for detection of the fatty acids.