Quantification of the level of fat‐soluble vitamins in feed based on the novel microemulsion electrokinetic chromatography ( MEEKC ) method

BACKGROUND Simultaneous quantification of liposoluble vitamins is not a new area of interest, since these compounds co‐determine the nutritional quality of food and feed, a field widely explored in the human and animal diet. However, the development of appropriate methods is still a matter of concern, especially when the vitamin composition is highly complex, as is the case with feed designated for laboratory animals, representing a higher health and microbiological status . RESULTS A method combining microemulsion electrokinetic chromatography ( MEEKC ) with liquid–liquid extraction was developed for the determination of four fat‐soluble vitamins in animal feed. A separation medium consisting of 25 mmol L −1 phosphate buffer ( pH 2.5), 2‐propanol, 1‐butanol, sodium dodecyl sulfate and octane allowed the simultaneous determination of vitamins A, D, E and K within a reasonable time of 25 min. The polarity of the separation voltage was reversed in view of the strongly suppressed electro‐osmotic flow, and the applied voltage was set at 12 kV . The fat‐soluble vitamins were separated in the order of decreasing hydrophobicity . CONCLUSION It was proved that the proposed MEEKC method was sufficiently specific and sensitive for screening fat‐soluble vitamins in animal feed samples after their sterilization. © 2013 Society of Chemical Industry