[Determination of six Ephedra alkaloids in Chinese Ephedra (Ma Huang) by gas chromatography].

Six Ephedra alkaloids, namely ephedrine, pseudoephedrine, norephedrine, norpseudoephedrine, methylephedrine and methylpseudoephedrine, in 12 species of Chinese Ephedra were successfully separated and determined by gas chromatography with the highly specific and sensitive nitrogen phosphorus detector (GC/NPD). The column used (HP-5) had a cross linked 5% phenylmethylsilicone phase. Diphenylamine was used as the internal standard to check the reproducibility of the extraction yields of the alkaloids, the stability of the detector response and to quantify the alkaloids. The contents of the six alkaloids were calculated according to their regression equations. The way for the preparation of crude drug samples was improved, the diethyl ether extract of the alkalized crude sample was directly analysed by GC. The method is simple, rapid and sensitive. The results are in agreement with those of the HPLC method.