THE COLORIMETRIC DETERMINATION OF EPHEDRINE WITH PERIODIC ACID

The colorimetric method for the determination of ephedrine and its preparations with periodic acid is reported. Ephedrine hydrochloride is oxidized with periodate at a pH about 7.2, buffered with phosphate, the acetaldehyde thus produced is separated from the reaction mixture by aeration and absorbtion in concentrated sulfuric acid, to which p-hydroxy biphenyl being added after aeration. The optical density of the bluishviolet color formed is compared with a standard graph using an electrophotometer. In the method specified, samples containing 0.005—0.05 mg ephedrine hydrochloride can be determined with an accuracy within ±5%. Factors which affect the color are studied. Lactose and glycerin give no interference. Data and details for using the method to determine ephedrine in fluid-extract and tablets are also given.