Deep eutectic solvents as switchable solvents for highly efficient liquid–liquid microextraction of phenolic antioxidant: Easily tracking the original TBHQ in edible oils

•Tracking the original TBHQ content after oil storage is realized with common RP-HPLC method.•Switchable DESs are used for selectively extracting TBHQ from edible oils.•TQ can be reduced to TBHQ with assistance of sesamol-based DES.•This DES based VALLME method can be conducted at room temperature.•This DES based VALLME pretreatment needs only 5 min.