In-syringe chitosan-assisted dispersive micro-solid phase extraction for the determination of anthraquinones in rhubarb-based oral liquids using high performance liquid chromatography

Abstract

A novel in-syringe chitosan-assisted dispersive micro-solid phase extraction method was established for the determination of anthraquinones in three kinds of traditional Chinese medicinal oral liquids containing rhubarb. Some parameters, including the concentration and molecular weight of chitosan, extraction time, pH of the solution, and the type and volume of eluent, affecting the extraction recovery were evaluated. Under the optimum conditions, i.e. 0.6 μg mL⁻¹ chitosan (M_r 3000), extraction time 2 min, pH 5.0, and 800 μL of methanol as the eluent for the extraction of emodin, chrysophanol and physcion from 10 mL of the sample solution, the extraction yield reached the highest value. A good linearity was obtained for the three anthraquinones (R² > 0.9983). The limit of quantitation was in the range of 1.8–3.0 ng mL⁻¹ and the relative standard deviations for intra- and inter-day precision were less than 4.68% and 5.36%, respectively. The method was successfully applied towards the determination of the content of the three anthraquinones in Huangzhihua oral liquid, Children's heat-clearing oral liquid, and Magnolia exhaust mixture. Satisfactory recoveries for the three anthraquinones were in the range of 85.9–120.3%. In this study, the use of chitosan as a sorbent material is reported for the first time for in-syringe dispersive micro-solid phase extraction combined with HPLC/UV to analyze anthraquinones in rhubarb-based oral liquids.