Three-component deep eutectic solvent for revered-phase air-assisted liquid–liquid microextraction for the determination of furanic compounds in transformer oil by HPLC-UV

Abstract

In this work, a revered-phase air-assisted liquid–liquid microextraction approach based on three-component deep eutectic solvent for pretreatment of petroleum oils was developed. The approach was utilized for the determination of furanic compounds in aged transformer oil by high-performance liquid chromatography with UV detection. The procedure assumed multiple aspiration of oil sample and deep eutectic solvent into a syringe and injection of the extraction mixture into an Eppendorf tube (11 instant extraction cycles). This process resulted in the formation of a cloudy solution, attributed to the dispersion of extraction solvent droplets into the oil sample. After centrifugation the obtained extract phase was introduced into a chromatographic system without additional purification and dilution. To establish the optimal microextraction procedure conditions, key parameters such as the extraction solvent composition, phase ratio and the number of extraction cycles were investigated. Cheap and available low viscosity deep eutectic solvent based on choline chloride, acetic acid and water provided the highest extraction recovery values (from 85 to 96 %). It was found, that acetic acid as precursor of extraction solvent acted key-role for maximum extraction recovery for all analytes. The phenomenon of the influence of hydroxyl groups in the structure of analytes on the extraction efficiency was revealed. Under optimal condition, the limits of detection were in the range from 3 to 6 μg L−1.