A Rapid Hydrophilic Interaction Liquid Chromatographic Method for Simultaneous Determination of Three Ephedrine Alkaloids in Ephedra Herb and Its Preparations

A rapid hydrophilic interaction liquid chromatographic method has been developed and validated for simultaneous quantitative analysis of methylephedrine, ephedrine, and pseudoephedrine in Ephedra Herb and its preparations. The chromatographic method was performed using a mobile phase consisted of acetonitrile-ammonium acetate (pH 5.0; 0.195 M) (95:5, v/v), running at 1.5 mL min⁻¹ on a Pinnacle II Cyano column (5 µm, 150 × 4.6 mm) at 30°C. The detector wavelength was set at 208 nm. The chromatographic method was validated for specificity, linearity and range, limit of detection and quantification, precision, stability, repeatability, and accuracy. The main parameters were specificity (peak purity match factors were >980), linearity (r > 0.9996), intra- and inter-day precisions (RSD %, 0.48  ∼ 1.70, and RSD %, 0.81 ∼ 1.86, respectively), limit of detections and quantifications (29.49 and 98.31 ng mL⁻¹ for methylephedrine; 47.74 and 159.1 ng mL⁻¹ for ephedrine; 121.8 and 406.0 ng mL⁻¹ for pseudoephedrine). The standard addition recoveries were in the range of 86.84 ∼ 102.1% and the RSDs of them were <5.23% in samples. The main mechanism was discussed from properties of analytes and optimized process. The results indicated the developed method was rapid (8 min), sensitive, and accurate for simultaneous determination of the analytes in Ephedra Herb and its three preparations.