Simultaneous determination of alizarin and rubimaillin in Rubia cordifolia by ultrasound-assisted ionic liquid-reversed phase liquid chromatography.

Four kinds of ionic liquids were adopted to analyze the content of rubimaillin and alizarin in Rubia cordifolia roots with ultrasonic-assisted extraction coupled with HPLC. The chromatographic column, Purospher star RP-C18 (4.6 mm x 250 mm, 5 microm), was used. Methanol and 0.4% acetic acid-water as mobile phase with flow rate at 0.85 mL min(-1), gradient elution, detection wavelength at 250 nm, chromatographic column temperature was controlled at room temperature. The result showed that rubimaillin and alizarin had the highest extraction yield when the [ HMIM] PF6methanol solution concentration of 0.6 mol x L(-1) as extraction solvent and the conditions were solid-liquid ratio of 1:80 (g x mL(-1)). Under the optimal extraction conditions, the content of alizarin from 0.01 to 0.04 microg showed a good linearity (r = 0.9999), the average recovery was 97.12%, the content of rubimaillin from 0.41 to 1.35 microg showed a good linearity (r = 0.9999), the average recovery was 98.10%. This experiment adopted environmentally friendly reagent as extraction solvent, the extraction efficiency was improved, and the environmental pollution caused by organic solvent was avoided, the harm of human body aslo was reduced. This method was simple and reliable, its repeatability was also very good, which had an important significance in the study of traditional Chinese medicine active ingredient extraction methods.