Ultrasonic Solvent Extraction Followed by Dispersive Solid Phase Extraction (d-SPE) Cleanup for the Simultaneous Determination of Five Anthraquinones in Polygonum multiflorum by UHPLC-PDA

A rapid and effective ultra-high performance liquid chromatography (UHPLC) method was developed for the determination of five anthraquinones (emodin, physcion, aloe-emodin, rhein, and chrysophanol) in Polygonum multiflorum. The target compounds were ultrasonically extracted with 70% methanol, followed by dispersive solid-phase extraction (d-SPE) with HC-C18 and desorption with acetonitrile. The five anthraquinones were separated on an ACQUITY UPLC(®) HSS T3 column (2.1 × 100 mm, 1.8 μm) and detected by a photodiode array detector (PDA) at 254 nm. Under the optimized conditions, linear relationships were achieved in the range of 0.3~100 mg/L for emodin, 0.3~40 mg/L for physcion, 0.1~20 mg/L for aloe-emodin, and 0.05~20 mg/L for rhein and chrysophanol. The limits of detection of the five analytes ranged from 0.01 to 0.08 mg/L, and the recoveries were within the range of 82.8~118.4% with an RSD (n = 6) of 1.0~10.3%. The intra-day and inter-day precision (n = 5) of the five targets were in the range of 1.0~1.8% and 3.0~3.1%, respectively. Furthermore, this method was applied to analyses of Polygonum multiflorum samples collected from different regions in China with satisfactory results. All the results indicated that this method is suitable for the detection of five anthraquinones in Polygonum multiflorum.