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Strategiesfor electrokinetic chromatography of fat-soluble vitamins

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Owing to the non-ionic nature of fat-soluble vitamins, separations by capillary electrophoresis (CE) have to be based on electrokinetic chromatography (EKC) where the vitamins interact with some type of charged pseudo-stationary phase in the separation medium. In general, most EKC is carried out as micellar electrokinetic chromatography (MEKC) with micelles as the pseudo-stationary phase. Fat-soluble vitamins may be separated by MEKC, but interactions with the micelles are in many cases strong resulting in long separation times. In addition, the most hydrophobic vitamins may precipitate inside the separation capillary. Both problems may be partially reduced utilizing organic modifiers in the separation medium, but micelle formation is gradually supressed as the organic modification is increased. Thus, from our point of view, MEKC is not very attractive for the rapid quality control of fat-soluble vitamins. In our laboratory, substantial attention has been focused on alternative pseudo-stationary phases. In this presentation, these efforts will be summarized on both separational and practical aspects. Most work has been carried out in 80 % acetonitrile and 20 % water utilizing tetraalkylammonium salts as the pseudostationary phase. With these systems, fat-soluble vitamins were separated in order of decreasing hydrofobicity prior to the electroosmotic flow. Thus, separations were completed within 5-10 minutes with an efficiency of 150.000 to 200.000 theoretical plates. In addition to tetraalkylammonium salts, several other pseudo-stationary phases have been evaluated including both positively and negatively charged compounds commercially available.

TidsskriftJournal de Pharmacie de Belgique
Udgave nummer3
Antal sider1
StatusUdgivet - 1 dec. 1998

ID: 231654731