RESUMEN
AIM: Determination of total alkaloids in Dendrobium nobile Lindl.METHODS: Dried materials were subjected to exhaustive extraction with ethanol: water (9:1,v/v) under reflux.Following filtration and condensation,the residue was dissolved in 3% hydrochloric acid and filtered.The solution was refined using a strongly acidic cation exchange resin column through sequential elution.After elution of deionized H2O,the eluent with 50% of alcoholic plus 5% of ammonia was collected until alkaloids were completely desorbed and evaporated under reduced pressure.The test sample was obtained.The test sample was dissolved in glacial acetic acid and titrated with perchloric acid titrand(0.1 mol/L) with automatic titrator.The herb should contain alkaloids,calculated as dendrobium(per 1ml of perchloric acid titrand is equivalent to 26.3 mg dendrobium).RESULTS: The results of three batches of material were 0.85% ,0.63% ,1.03% respectively.CONCLUSION: The method is convenient,fast,effective and reliable.Automatic potentiometric titration can be used for determination of alkaloids in Dendrobium nobile Lindl.