Ionic Liquid‐Based Polarity‐Adjustable Deep Eutectic Solvent Extraction Followed by High‐Performance Liquid Chromatography‐Diode‐Array Detection for the Determination of Liposoluble Anthraquinones in Salvia miltiorrhiza Bge. Root

ABSTRACT A simple, green, and efficient ultrasound‐assisted deep eutectic solvents (DESs) extraction followed by high‐performance liquid chromatography‐diode array detector was established to detect four liposoluble anthraquinones in Salvia miltiorrhiza Bge. root. In this study, a series of polarity‐adjustable DESs were prepared using n‐hexanol and tetrabutylammonium chloride, and their structure, density, viscosity, pH, and thermal stability were determined. The conditions for extraction were optimized through single‐factor experiments and response surface methodology. The kinetic and thermodynamic properties associated with the ultrasound‐assisted extraction of anthraquinones were investigated. The results showed that the standard curves for anthraquinones showed excellent linearity from 0.018 to 150 µg mL−1 (r > 0.9998). The detection and quantification limits varied from 5.04 to 5.60 ng mL−1 and 16.81 to 18.67 ng mL−1, respectively. The recoveries were measured as 84.1%–95.1%, and the relative standard deviations were not exceeded 4.6%.