A Rapid and Sensitive Method for the Determination of Vitamin E and Carotenoids in Vegetables and Fruits Using Deep Eutectic Solvent-Based Dispersive Liquid-Liquid Microextraction

Conventional extraction techniques for fat-soluble nutrient analysis in foods may present certain limitations, including variable or limited efficiency, high solvent consumption, lengthy procedures, and potential environmental and health concerns. This study evaluates deep eutectic solvents (DESs) as a green and efficient alternative for extracting vitamin E and carotenoids from vegetables and fruits. Conductor-like screening model for real solvents (COSMO-RS) simulation and experimental screening identified the menthol-thymol (1:2) DES as optimal due to the balanced distribution of polar and nonpolar sites within its components. A novel dispersive liquid-liquid microextraction method based on this DES (DES-DLLME) was developed and integrated with HPLC for the simultaneous quantitation of vitamin E and carotenoids. The optimized method demonstrated excellent analytical performance with low detection limits (0.01-0.18 µg/mL), satisfactory recovery rates (80.04-111.95%), and high reproducibility (relative standard deviation, RSD < 16.83%). When applied to a range of Chinese food samples, the obtained nutrient profiles were largely consistent with USDA reference data, with observed variations likely due to factors such as geographic origin, cultivation practices, and post-harvest processing. This DES-based approach offers an efficient, reproducible, and environmentally friendly method for determining fat-soluble vitamins and carotenoids in complex food matrices, offering significant value for food quality assessment and nutritional research.