STUDIES ON THE DETERMINATION OF CERTAIN MAJOR CONSTITUENTS OF PLANT DRUGS——Ⅱ.APPLICATION OF ION EXCHANGE METHODS IN THE DETERMINATION OF ALKALOIDS

It has been reported (8, 9, 10) that by boiling sulfonic acid type ion exchange resin with certain plant drugs, the alkaloids in the latter could be transferred quantitatively to the resin and could be determined subsequently. In this paper are reported the results obtained with ion exchange resins of sulfonic acid type and an ion exchange fabric of phosphoric acid type. Nine to ten kinds of plant drugs were studied in each case. Five of these, Areca catechu L., Fritillaria thunbergii Miq., Stemona tuberosa Lour., Sophora flavescens Ait. and Leonurus heterophyllus Sweet, could be determined by the ion exchange resins and four, namely, Atropa belladonna L., Areca catechu L., Leonurus heterophyllus Sweet and Coptis chinensis Franch, by the ion exchange fabric. Where the method worked, it was simple, rapid and gave the same results as those obtained with the pharmacopeiacal methods. Analytical Procedures: 1. Ion exchange resin: Place 0.1—6g of finely powdered sample, accurately weighed, in a flask, add 25—50 ml of water and 10g of sulfonic acid type cation exchange resin (H form), heat for 30—40 minutes in a boiling water bath. After cooling, remove the drug residue with water. Transfer the ion exchange resin to a suitable column, wash the resin with water and 95% ethanol, elute the alkaloids from the resin with 4N NH₄OH in 70% v/v methanol solution. Collect 100—300 ml of eluate and evaporate to remove methanol and ammonia. To the remaining liquid, add 50 ml of 0.6 N H₂SO₄ and titrate the alkaloids with 0.01 M silicotungstic acid. 2. Ion exchange fabric: Place 0.1—1g of finely powdered sample, accurately weighed, in a flask, add 25—50 ml of water and 1—2 g of phosphoric acid type ion exchange fabric, heat for half hour in a boiling water bath. Wash the ion exchange frabric with water, and shake or heat for 10 minutes with 50—100 ml of 0.6N H₂SO₄, then titrate the alkaloids with 0.01 M silicotungstic acid.