Dissolved carbon dioxide flotation–emulsification microextraction technique coupled with high‐performance liquid chromatography was developed for the separation and determination of fat‐soluble vitamins (A, D3, E and K3) in multivitamin pharmaceutical preparations. Dissolved carbon dioxide flotation was used to break up the emulsion of extraction solvent in water and to collect the extraction solvent on the surface of the aqueous sample in the narrowed capillary part of extraction cell. Carbon dioxide bubbles were generated in situ through the addition of 300 μL of concentrated hydrochloric acid into the alkaline sample solution at pH = 11.5 (1% w/v sodium carbonate) which was sonicated to intensify the carbon dioxide bubble generation. Several factors affecting the extraction process were optimized. Under the optimal conditions, the limits of detection were 0.11, 0.47, 0.20 and 0.35 μg L−1 for A, E, D3 and K3 vitamins in water samples, respectively. The inter‐day and intra‐day precision of the proposed method were evaluated in terms of the relative standard deviation and were < 10.5%.
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