(Official January 1, 2007)

Standard preparation— Weigh accurately about 26 mg of USP Ephedrine Sulfate RS, transfer to a 50-mL volumetric flask with the aid of 10 mL of water, add methanol to volume, and mix. Pipet 5 mL of the resulting solution into a 100-mL volumetric flask, dilute with water to volume, and mix.

Assay preparation— Transfer an accurately measured volume of Nasal Solution, equivalent to about 26 mg of ephedrine sulfate, to a 50-mL volumetric flask, dilute with a 1 in 5 mixture of water in methanol to volume, and mix. Pipet 5 mL of the resulting solution into a 100-mL volumetric flask, dilute with water to volume, and mix.

Procedure— Transfer 5-mL portions of the Assay preparation and the Standard preparation to separate glass-stoppered, 50-mL centrifuge tubes. Add 1 mL of saturated sodium carbonate solution and 2 mL of sodium metaperiodate solution (1 in 50) to each tube, mix, and allow to stand for 10 minutes. Pipet 20 mL of n-hexane into each tube, shake for 30 seconds, and allow the phases to separate. Concomitantly determine the absorbances of the n-hexane extracts in 1-cm cells at the wavelength of maximum absorbance at about 242 nm, with a suitable spectrophotometer, using n-hexane as the blank. Calculate the quantity, in mg, of (C10H15NO)2·H2SO4 in each mL of the Nasal Solution taken by the formula: in which V is the volume, in mL, of Nasal Solution taken, C is the concentration, in µg per mL, of USP Ephedrine Sulfate RS in the Standard preparation, and AU and AS are the absorbances of the hexane extracts of the Assay preparation and the Standard preparation, respectively.