Micelle-mediated extraction and cloud-point preconcentration of osthole and imperatorin from Cnidium monnieri with analysis by high performance liquid chromatography.

A new method based on micelle-mediated extraction and cloud-point preconcentration was developed for the separation and determination of hydrophobic compounds osthole and imperatorin from Cnidium monnieri by high performance liquid chromatography with photodiode array detection. The non-ionic surfactant C(13)E(8) (Genapol X-080) was chosen as the extract solvent. Various experimental conditions were investigated to evaluate and optimize the extraction and preconcentration process. The chromatographic separation was accomplished on a Zorbax SB-C(18) analytical column (150 mm x 4.6mm i.d., 5 microm particle diameter) maintained at 30 degrees C and detected by UV absorption at 320 nm. The gradient elution was achieved with a mobile phase composed of 0.1% phosphoric acid and acetonitrile at a flow rate of 1.0 mL min(-1). Under the optimum conditions, the calibration curve for both analytes was linear in the range of 0.52-33.5 microg mL(-1) with the correlation coefficients greater than 0.9996. The intra-day and inter-day precision (RSD) is below 5.3% and the limits of detection (LOD) for the analytes are 93 and 124 ng mL(-1)(S/N=3). The proposed technique is a low cost, simple and sensitive method with high clean-up effect. Finally, the method was successfully applied to separate and determine osthole and imperatorin from C. monnieri, respectively.