Analysis of tetramethylpyrazine in Ephedrae herba by gas chromatography-mass spectrometry and high-performance liquid chromatography.

A simple and reliable HPLC method was developed for the determination of 2,3,5,6-tetramethylpyrazine (TMP) in Ephedrae herba. Further identification of TMP was achieved using GC-MS. The mobile phase used was methanol-water-35% acetic acid (35:65:0.5, v/v/v) at a flow-rate of 0.8 ml/min. The detection wavelength was set at 290 nm. The linear range of the peak area calibration curve of TMP was 2.64-264 mg/l (r=0.9987) and the recovery for TMP in Ephedrae herba extracts was 101.1-106.9%. The relative standard deviations of retention time and peak area were 0.18 and 1.5% (n=6), respectively. The detection limit of TMP was 0.03 mg/l. The contents of TMP in Ephedrae herba could easily be determined within 10 min.