Simultaneous determination of four fat-soluble vitamins by microemulsion liquid chromatography

A novel system was developed for the rapid determination of fat-soluble vitamins A, D-2, D-3 and E with microemulsion liquid chromatography (MELC). The effects of operating parameters on the separation selectivity were investigated. The optimized microemulsion system consisted of 98% (v/v) of 50 g/L sodium dodecyl sulfate (SDS)-10% (w/w) n-butanol-1.0% (w/w) n-octane-84% water (w/w) and 2% (v/v) acetonitrile. The type and content of surfactant, the content of oil phase and the organic additive (acetonitrile) were found to play important roles in the separation of four fat-soluble vitamins. The four analytes were baseline separated within 20 min on a Venusil ASB C-18 column (150 mm x4.6 mm, 5 mu m) with a flow rate of 0. 7 mL/min and the detection wavelength of 265 nm at 40 degrees C. The relative standard derivations (RSDs, n = 5) of retention times and peak areas of the analytes were less than 2. 3% and 3. 0%, respectively. The linear ranges of vitamins A, D-2, D-3 and E were 22.0 - 88.0 mg/L, 20.2 - 81. 0 mg/L, 24.3 -97.2 mg/L and 125.0 -500.0 mg/L, with their correlation coefficients (r(2)) of 0. 999 6, 0. 999 4, 0. 999 8 and 0. 999 8, respectively. The detection limits (S/N = 3) were 0. 37, 0.34, 0.41 and 2. 12 mg/L, respectively. This method was successfully applied to the determination of commercial Vitamins with Minerals Tablets (21), and the results were satisfactory.