Centrifugation free and air-assisted liquid-liquid microextraction based on deep eutectic solvent for determination of rare ginsenosides in Kang'ai injection

A simple, effective and convenient enrichment method coupled with high performance liquid chromatography (HPLC) was established for the analysis of rare ginsenosides in Kang'ai (KA) injection. Air assisted liquid-liquid microextraction was used in this work for the first time to determine the rare ginsenosides in KA injection. Deep eutectic solvent (DES) and tetrahydrofuran (THF) were specially selected as a novel green extraction solvent and an emulsified solvent, respectively. To remove the DES droplets, Fe3O4 nanoparticles were used. Therefore, centrifugation was free in this work, which can increase the efficiency of analysis procedure. Moreover, Fe3O4 nanoparticles were reusable. To achieve better extraction efficiency and enrichment factor, the experimental conditions have been optimized, including type and volume of DES and emulsified solvent, amount of Fe3O4 nanoparticles and inorganic salt, and pH value. Under the optimum extraction condition, the validation parameters show the limits of detection (LODs) are in the range from 10.2 ng/mL to 137.8 ng/mL and the limits of quantity (LOQs) are in the range from 55.5 ng/mL to 428.5 ng/mL. The recoveries of analytes range from 91.3% to 106.7% with the relative standard deviations (RSDs) ranging from 1.2% to 4.5%. The recommended approach was utilized to acquire the information of constituents in KA injection. Moreover, the results in this research could provide a study basis for further study of KA injection.