15.05.2018
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.