Ascorbic acid and choline chloride: A new natural deep eutectic solvent for extracting tert-butylhydroquinone antioxidant

A novel natural deep eutectic solvent (NADES) based on choline chloride and ascorbic acid (vitamin C) was synthesized for the first time. This NADES is green since choline chloride and vitamin C are frequently used food additives. And ultrasonic-assisted liquid-liquid microextraction technique was employed using this NADES for the extraction tert-butylhydroquinone from edible oils, which was coupled with the HPLC-UV analysis. The experimental conditions of liquid-liquid microextraction were optimized, and a near 100% extraction efficiency was obtained. The liquid-liquid microextraction combined HPLC-UV method for the determination of tert-butylhydroquinone showed good recovery (i.e., 96.1-109%) and precision (i.e., the relative standard deviation for intra-day and inter-day precision were 1.8% and 2.9%, respectively), as well as a lower limit of detection (i.e., 0.02 mg/kg). This method was successfully applied in the determination of tert-butylhydroquinone in 12 kinds of edible oils, and the results were close to those of conventional liquid-liquid extraction with methanol. Importantly, this novel NADES (choline chloride + vitamin C) exhibited an excellent protection ability for tert-butylhydroquinone during the extraction process, which indicated that this NADES could be used as an excellent extraction medium for easily oxidized compounds in complicated samples.