Separation of divinyl ether fatty acid isomers by micellar electrokinetic chromatography

A micellar electrokinetic chromatography (MEKC) method has been developed f or the direct resolution of divinyl ether type of hydrophobic fatty acid is omers. The fatty acid isomers resolved include colneleic acid ICL), colnele nic acid (CLn), 14(Z)-etheroleic acid (14(Z)-EL), 14(Z)-etherolenic acid (1 4(Z)-Eln), 11(Z)-etheroleic acid (11(Z)-EL), 11(Z)-etherolenic acid (11(Z)- Eln), etheroleic acid (EL) and etherolenic acid (Eln). These fatty acid iso mers differ in number, position and spatial arrangement of the double bonds and the position of the ether oxygen. A central composite design was emplo yed for the optimization of the key variables of the separation, namely the concentrations of sodium dodecyl sulfate (SDS) and organic modifiers. The use of micelles combined with an organic modifier in the background electro lyte made it possible to dissolve and separate relatively hydrophobic fatty acid isomers, and to achieve high separation efficiency. Using heptakis-(2 ,3-dimethyl-6-sulfato)-beta -cyclodextrin (HDMS-beta -CD) as a buffer addit ive, complete separation of the examined eight divinyl ethers was achieved. Separation efficiencies up to 5 x 10(5) theoretical plates/m were achieved under optimized conditions. Direct UV was applied for detection of the fat ty acids. The results were compared with those obtained from high-performan ce liquid chromatography (HPLC) separation.