[Determination of vitamin A, D and E in dishes by two-dimensional liquid chromatography]

To establish a method for the simultaneous determination of vitamins A, D and E in dishes by two-dimensional liquid chromatography.

The samples were saponified and extracted with a mixture of ethyl acetate and n-hexane(3∶2, V/V)under the protection of antioxidants, and determined by two-dimensional liquid chromatography. The baseline separation of retinol, α-tocopherol, β-tocopherol, γ-tocopherol, δ-tocopherol, and α-tocotrienols was achieved by using Alphasil pentafluorophenyl column(PFP, 150 mm×4.6 mm, 5 μm) as the one-dimensional column, and using water and methanol as mobile phases for gradient elution under the fluorescence detector. The separation detection of ergocalciferol and cholecalciferol from other impurities was achieved on the UV detector by Alphasil VC-C_(18) column(150 mm×4.6 mm, 3.5 μm) as the two-dimensional column.

The baseline separation detection of retinol, ergocalciferol, cholecalciferol and five tocopherols was achieved. The compounds were linearly correlated within the set range, and the correlation coefficients were >0.999. The recovery rate of the method was between 85.4% and 106.4%. The detection limit of all-trans retinol was 0.7 μg/100 g, and the limit of quantitation was 2.4 μg/100 g. The limits of detection and quantification of tocopherols ranged from 1.1 to 2.5 μg/100 g and 3.6 to 8.3 μg/100 g. The detection limit of ergocalciferol and cholecalciferol was 0.3 μg/100 g, and the limit of quantification was 1.0 μg/100 g. In the end, finished dishes such as dry fried hairtail, braised mushroom, steamed egg with soy sauce, sweet and sour ribs were repeatedly measured by this method for six times, and the relative standard deviation was less than 10%.

The method has the characteristics of simple operation, good repeatability, high accuracy and friendly to operators and ecological environment. It can realize the simultaneous typing detection of vitamins A, D and E in finished dishes.