A: Powder a number of Tablets,equivalent to about 100mg of metaproterenol sulfate,add 10mLof water,stir for about 3minutes,and centrifuge.Use the clear solution so obtained as the Test solution.Dissolve a suitable quantity of USP Metaproterenol Sulfate RSin water to obtain a Standard solution having a concentration of 10mg per mL.Apply separate 10-µLportions of the Test solutionand the Standard solution to a thin-layer chromatographic plate (see Chromatography á621ñ)coated with a 0.25-mm layer of chromatographic silica gel mixture.Proceed as directed in Identificationtest Aunder Metaproterenol Sulfate Inhalation Solution,beginning with “Allow the spots to dry”:the RFvalue of the principal spot obtained from the Test solutioncorresponds to that obtained from the Standard solution.

B: Mix a quantity of powdered Tablets,equivalent to about 20mg of metaproterenol sulfate,with 5mLof water,and filter:the filtrate responds to the tests for Sulfate á191ñ.

C: The chromatogram of the Assay preparationobtained as directed in the Assayexhibits a major peak for metaproterenol,the retention time of which corresponds to that exhibited in the chromatogram of the Standard preparationobtained as directed in the Assay.

Medium: water;500mL.

Apparatus 2: 50rpm.

Time: 30minutes.

Procedure— Determine the amount of (C11H17NO3)2·H2SO4dissolved from UVabsorbances at the wavelength of maximum absorbance at about 276nm of filtered portions of the solution under test,suitably diluted with Dissolution Medium,if necessary,in comparison with a Standard solution having a known concentration of USP Metaproterenol Sulfate RSin the same Medium.

Tolerances— Not less than 70%(Q)of the labeled amount of (C11H17NO3)2·H2SO4is dissolved in 30minutes.

Mobile phase,Standard preparation,and Chromatographic system— Prepare as directed in the Assayunder Metaproterenol Sulfate.

Assay preparation— Transfer 20Tablets to a 500-mLconical flask.Add an accurately measured volume of 0.01Nhydrochloric acid sufficient to yield a solution containing about 2mg of metaproterenol sulfate per mL,shake by mechanical means for 30minutes,and filter.Use the filtrate so obtained as the Assay preparation.

Procedure— Proceed as directed for Procedurein the Assayunder Metaproterenol Sulfate.Calculate the quantity,in mg,of metaproterenol sulfate [(C11H17NO3)2·H2SO4]in each Tablet taken by the formula: in which Vis the volume,in mL,of 0.01Nhydrochloric acid added;and C,rU,and rSare as defined therein.