A Green Ultrasonic-Assisted Liquid-Liquid Microextraction Based on Deep Eutectic Solvent for the HPLC-UV Determination of TBHQ in Edible Oils

A green and inexpensive ultrasonic-assisted liquid-liquid microextraction (UALLME) technique based on deep eutectic solvents (DESs) was employed in the extraction and separation of tert-butylhydroquinone (TBHQ) from edible oils. In a typical experiment, 400 μL DES as extraction solvent was added to 3.0 mL sample solution containing 0.15 g edible oil, and then ultrasonic-assisted extraction was applied. After centrifugation, DES phase containing TBHQ was directly analyzed by reverse phase high-performance liquid chromatograph-ultraviolet detector (HPLC-UV) and no phase inversion was involved, which can simplify the sample pretreatment process. Under optimized condition, TBHQ showed a linear calibration curve in the range of 5∼500 mg/kg (r2 = 0.9998) and lower limit of detection (LOD) of 0.02 μg/mL. The recoveries were in the range of 98.5∼112%, and the intraday and inter-day precision were less than 3.2%. This method was successfully applied to the determination of TBHQ in 13 edible oil (e.g., soybean oil, blend oil) samples, which the result was close to that for conventional liquid-liquid extraction with methanol as solvent.