A Miniaturized Sample Preparation Method for the Determination of Vitamins A and E in Food Products

A new analytical approach to the simultaneous identification and quantification of vitamins A and E in three representative matrices (Parmesan, spinach, and almonds) was developed. The analyses were based on high-performance liquid chromatography with UV-VIS/DAD detection. The procedure was optimized by a significant reduction in the weight of the tested products and quantities of reagents added during the saponification and extraction stages. A full method validation study was performed for retinol at two concentration levels (LOQ and 200 × LOQ), which showed satisfactory results, with recoveries ranging from 98.8 to 110.1%, and an average CV of 8.9%. Linearity was tested in the range of 1-500 µg/mL and showed the coefficient of determination R² = 0.999. The satisfactory recovery and precision parameters were achieved for α-tocopherol (LOQ and 500 × LOQ) in the range of 70.6-143.2%, with a mean CV equal to 6.5%. The observed linearity for this analyte in the concentration range of 1.06-532.0 µg/mL was R² = 0.999. The average extended uncertainties were estimated, using a top-down approach of 15.9% and 17.6% for vitamin E and A, respectively. Finally, the method was successfully applied to determine vitamins in 15 commercial samples.