Separation and determination of ephedrine alkaloids and tetramethylpyrazine in Ephedra sinica Stapf by gas chromatography-mass spectrometry.

A simple, sensitive, and reliable method using gas chromatography (GC)-mass spectrometry (MS) is developed for the simultaneous determination of ephedrine alkaloids and 2,3,5,6-tetramethylpyrazine (TMP) in Ephedra sinica Stapf. The sample is extracted with ethyl ether and submitted to GC-MS for identification and quantitation without derivatization. The column used for GC is an HP-5 (30.0 m x 250 microm x 0.25 microm, 5% phenyl methyl siloxane), and the carrier gas is helium. The detection limits for ephedrine, pseudoephedrine, and TMP are 0.4 ng 0.7 ng, and 0.02 ng (signal-to-noise ratio of 3), respectively. The reproducibility of the total procedure is proved to be acceptable (RSD < 2%), and the recoveries are above 93%.