Ultrasonic-Assisted Liquid-Liquid Microextraction Based on Natural Deep Eutectic Solvent for the HPLC-UV Determination of Tert-Butylhydroquinone from Soybean Oils

A novel natural deep eutectic solvent (NADES) composed of choline chloride (ChCl) and sesamol was prepared for the first time and was successfully employed in ultrasonic-assisted liquid-liquid microextraction (UALLME) of tert-butylhydroquinone (TBHQ) from soybean oils in the present study. In a typical experiment, 400 μL NADES as extraction solvent was added to a sample containing 0.2 g soybean oil, and then ultrasonic-assisted extraction was applied. After centrifugation, NADES phase containing TBHQ was directly analyzed by reverse phase high-performance liquid chromatography-ultraviolet detector (HPLC-UV), and no phase inversion was involved, which can satisfy the rapid sample pretreatment process. Under optimized condition, TBHQ showed a linear calibration curve in the range of 5~500 mg/kg (r2 = 0.9999) and lower limit of detection (LOD) of 0.02 μg/mL. The recoveries were in the range of 93.4~108.8%, and the intra-day and inter-day precision were less than 2.3%. This method was successfully applied to the determination of TBHQ in ten soybean oil samples, in which the results were close to that for conventional liquid-liquid extraction with methanol as solvent. Moreover, this sesamol-based NADES exhibited good protection ability to TBHQ during the extraction process due to the original antioxidant activity of sesamol.