Determination of Anthraquinones in Radix Polygoni Multiflori Praeparata by Liquid-phase Microextarction- High Performance Liquid Chromatography

OBJECTIVE To quantitatively analyze anthraquinones in Radix Polygoni Multiflori Praeparata by liquid-phase microextraction (LPME) coupled with high performance liquid chromatography. METHODS With a self-made LPME system, the optimal extraction conditions were as follows: polyvinylidene difluoride hollow fiber as solvent carrier, 1-octanol as extraction solvent, HCl concentration in the donor was 2 mmol·L-1, methanol content in the donor was 50%, the stirring rate was 1 800 r·min-1 and the extraction time was 60 min. After microextraction, the extract was dried in 80 ℃ water bath, dissolved with 60 μL methanol and then analyzed by HPLC at 434 nm. RESULTS Under the optimal conditions, detection limits of aloe-emodin, crysophanol rhein, physcion and emodin were 0.30, 0.25, 0.25, 0.30 and 0.35 μg·L-1, respectively. The average relative standard deviation (precision) ranged from 8.1% to 14.1%. The relative recoveries in Radix Polygoni Multiflori Praeparata ranged from 75.4% to 111.5%. The LPME enrichment factors of the five analytes were 21, 21, 36, 44 and 47 respectively. Emodin, physcion, trace rhein and crysophanol in Radix Polygoni Multiflori Praeparata were determined. CONCLUSION Liquid-phase microextraction is a pre-processing technique which is simple, quick, with high selectivity, high enrichment factor and little organic solvent consumption. It could be applied to simultaneous analysis of anthraquinones in Radix Polygoni Multiflori Praeparata.