Temperature-assisted ionic liquid dispersive liquid-liquid microextraction combined with high performance liquid chromatography for the determination of anthraquinones in Radix et Rhizoma Rhei samples.

In this article, a novel method termed as temperature-assisted ionic liquid dispersive liquid-liquid microextraction (TA IL-DLLME) combining high performance liquid chromatography with diode array detection (HPLC-DAD) was developed for the determination of anthraquinones in Radix et Rhizoma Rhei samples. The ionic liquid (1-hexyl-3-methylimidazolium hexafluorophosphate) was used to replace volatile organic solvent as an extraction solvent for the extraction of anthraquinones (aloe-emodin, rhein, emodin, chrysophanol and physcion) from Radix et Rhizoma Rhei. Several important parameters influencing the extraction efficiency of TA IL-DLLME such as the type and volume of extraction solvent and disperser solvent, sample pH, extraction time, extraction temperature, centrifugation time as well as salting-out effects were optimized. Under the optimal conditions, the spiked recovery for each analyte was in the range of 95.2-108.5%. The precisions of the proposed method were varied from 1.1% to 4.4% (RSD). All the analytes exhibited good linearity with correlation coefficients (r(2)) ranging from 0.9986 to 0.9996. The limits of detection for all target analytes were ranged from 0.50 to 2.02 microg L(-1) (S/N=3). The experimental results indicated that the proposed method was successfully applied to the analysis of anthraquinones in Radix et Rhizoma Rhei.