Medium: water;500mL.

Apparatus 1: 100rpm.

Time: 30minutes.

Procedure— Dilute filtered portions of the solutions under test with water to a concentration of about 25µg per mL.Transfer 5.0-mLportions to suitable tubes.Add 1mLof a saturated sodium carbonate solution and 2mLof sodium metaperiodate solution (2in 100)to each,mix,and allow to stand for 10minutes.Add 20.0mLof hexanes,shake for 30seconds,and allow the phases to separate.Measure the absorbances of the hexanes extract in 1-cm cells at the wavelength of maximum absorbance,at about 242nm,with a suitable spectrophotometer,using hexanes as the blank.Determine the amount of (C10H15NO)2·H2SO4dissolved by comparison with a similarly treated Standard solution having a known concentration of USP Ephedrine Sulfate RSin water.Remove the contents of 1Capsule as completely as possible,with the aid of a current of air,dissolve the empty capsule shell in the Medium,determine the absorbance at the same dilution and in the same manner as for the Capsules,and make any necessary corrections.

Tolerances— Not less than 80%(Q)of the labeled amount of (C10H15NO)2·H2SO4is dissolved in 30minutes.

Standard preparation— Weigh accurately about 25mg of USP Ephedrine Sulfate RS,transfer to a 50-mLvolumetric flask with the aid of 10mLof water,add methanol to volume,and mix.Dilute 5.0mLof this solution with water to 100.0mL.

Assay preparation— Weigh accurately the contents of not less than 20Capsules,and mix.Transfer an accurately weighed portion of the mixture,equivalent to about 25mg of ephedrine sulfate,to a glass-stoppered conical flask,and add by pipet 50mLof a 1in 5mixture of water in methanol.Shake by mechanical means for 10minutes,and filter.Dilute 5.0mLof the filtrate with water to 100.0mL.

Procedure— Transfer 5-mLportions of the Assay preparationand the Standard preparationto separate glass-stoppered,50-mLcentrifuge tubes.Add 1mLof saturated sodium carbonate solution and 2mLof sodium metaperiodate solution (1in 50)to each tube,mix,and allow to stand for 10minutes.Pipet 20mLof n-hexane into each tube,shake for 30seconds,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 242nm,with a suitable spectrophotometer,using n-hexane as the blank.Calculate the quantity,in mg,of (C10H15NO)2·H2SO4in the portion of Capsule contents taken by the formula: in which Cis the concentration,in µg per mL,of USP Ephedrine Sulfate RSin the Standard preparation,and AUand ASare the absorbances of the hexane extracts of the Assay preparationand the Standard preparation,respectively.