title: [Use of extraction-frequency metric method for the determination of microquantities of ephedrine and its application in pharmaceutical analysis].
abstract: A new extraction--frequency metric 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 micrograms with a correlation coefficient of 0.999 and a detection limit of 0.02 micrograms. Methods for the assay of ephedrine hydrochloride tablet and nasal solution have been proposed.
authors.affiliation: Chemical Engineering Department, Hunan University, Changsha.
authors.forename: L H
authors.initials: LH
authors.lastname: Nie
authors.forename: X T
authors.initials: XT
authors.lastname: Zhang
authors.forename: S Z
authors.initials: SZ
authors.lastname: Yao
mesh_terms: D002623:Chemistry Techniques, Analytical / Q000379:methods; D004809:Ephedrine / Q000032:analysis*; D013607:Tablets
chemical_list: D013607:Tablets; D004809:Ephedrine