Effective Sample Preparation of Polyphenols in Wine Using Deep Eutectic Solvent‐based Dispersive Liquid–Liquid Microextraction HPLC‐UV Determination

Abstract

Polyphenols are phytochemicals that exist in grapes and are beneficial to human health. In this study, resveratrol, oxyresveratrol, and piceatannol in wine were extracted by deep eutectic solvent dispersive liquid–liquid microextraction (DES‐DLLME), and a method was established for quantifying these polyphenols by high‐performance liquid chromatography‐UV/Vis (HPLC‐UV/Vis). Several parameters pertaining to sample extraction, clean‐up, and concentration were optimized and verified with central composite design (CCD) using Design Expert 11. The optimized sample preparation parameters are as follows: the DES extraction solvent, tributylmethylammonium chloride/decanoic acid (1:3 M ratio); basic solvent, 1.3 mL of 5% potassium bicarbonate; volume of acetic anhydride, 250 μL; derivatization time, 5 min; dispersive solvent, methanol; ratio of extraction and dispersive solvents, 1:5.5; and salt, 1.0 g. Chromatographic separation by HPLC/UV–Vis was performed on an ACME C18 (4.6 mm id × 150 mm length, 5 μm particle size) column in gradient elution mode using water and 70% methanol. Under the established extraction and HPLC‐UV conditions, the limit of detection (LOD) and limit of quantitation (LOQ) of the three analytes in spiked samples ranged from 1.69 to 2.53 μg/L and 5.64 to 8.42 μg/L, respectively. Recovery studies were performed in low, medium, and high concentration ranges to establish a calibration curve, and the accuracy and precision in the working range were 95.1–108.0% and 1.3–6.7 RSD%, respectively. The calibration curves for quantitative analysis were obtained in the concentration ranges 5.6–56.4, 8.3–82.6, and 8.4–84.2 μg/L, with correlation coefficients (r2) ranging from 0.9947 to 0.9967. The proposed method was applied to the determination of polyphenols in wine samples.