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A novel method, HPLC-MS/MS was developed to qualitatively identify and quantitatively determine the 28 components including 19 diterpenoids, 6 phenolic acids and 3 flavonoids in Isodon rubescens, an important traditional Chinese medicine. The separation was performed on a C(18) column with linear gradient elution with 0.1% aqueous formic acid/methanol containing 0.1% formic acid at a flow rate of 0.7 mL/min. The identification and quantification of those analytes were achieved on a hybrid quadrupole linear ion trap mass spectrometer. Multiple-reaction monitoring scanning was employed for quantification with switching electrospray ion source polarity between positive and negative modes in a single run. Full validation of the method was carried out (linearity, precision, accuracy, LOD and LOQ). The results indicated that the method was simple, rapid, specific and reliable. The proposed method was successfully applied for the qualitative and quantitative analysis of 28 chemical compositions in 21 batches of natural and cultured I. rubescens samples from different sources which had great variation on the contents. The results demonstrated that the method was useful for standardization and differentiation of large numbers of similar samples.

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A normal-phase enantioselective high-performance liquid chromatographic method was developed for the enantiomeric resolution of naproxcinod, the most advanced cyclooxygenase-inhibiting nitric oxide donator of anti-inflammatory drugs designed for treatment of osteoarthritis. The enantiomers of naproxcinod were resolved on a Chiralpak AD-H (250 × 4.6 mm, 5 μm) column using a mobile phase system containing n-hexane and 2-propanol (95:5, v/v). The resolution between the enantiomers was found to be more than 2.0. The limit of detection and limit of quantitation of (R)-enantiomer were found to be 5 and 15 ng/mL, respectively, for 20 μL injection volume. The sample solution and mobile phase were found to be stable for at least 48 h. The final optimized method was successfully applied to separate (R)-enantiomer from naproxcinod and was proven to be reproducible and accurate for the quantitative determination of (R)-enantiomer in bulk drugs.

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A reversed-phase high-performance liquid chromatography method was established for the simultaneous determination of four major constituents, namely myricitrin, hyperin, quercitroside, and quercetin in Folium Rhododendri Micranthi. The optimal conditions of separation and detection were achieved on a C18 analytical column with a gradient mobile phase consisting of acetonitrile and 1% acetic acid at the flow rate of 1.0 mL/min, and detection wavelength was set at 355 nm. All calibration curves showed good linear regression (r > 0.9993) within test ranges. The reproducibility of relative standard deviations was less than 2.3%, and recovery of analytes was greater than 99.4%, respectively. The method was successfully applied to determine the contents of four compounds in Folium Rhododendri Micranthi. The results indicated that the contents of myricitrin, hyperin, quercitroside and quercetin in Folium Rhododendri Micranthi were 0.166%, 0.303%, 0.299%, and 0.053%, respectively.