USE OF EXTRACTION-FREQUENCYMETRIC METHOD FOR THE DETERMINATION OF MICROQUANTITIES OF EPHEDRINE AND ITS APPLICATION IN PHARMACEUTICAL ANALYSIS

A new extraction-frequencymetric method has been proposed for the determination of ephedrine, which can not be determined by the conventional extraction-weighing method due to its volatility. The method is based on extraction of the free alkaloid followed by measuring the frequency shift of a specially constructed ring- coated piezoelectric crystal at room temperature. The frequency shift is in linear relationship with the content of ephedrine hydrochloride over a range 0.05-1.2 μg with a correlation coefficient of 0.999 and a detection limit of 0.02μg. Methods for the assay of ephedrine hydrochloride tablet and nasal solution have been proposed.