Standard solution— Transfer 2.0mLof 0.100Niodine VSto a 500-mLvolumetric flask,dilute with water to volume,and mix.

Procedure— Visually examine a portion of the Inhalation Solution (Test solution)in a suitable clear glass test tube against a white background:it is not pinkish,and it contains no precipitate.If any yellow color is observed in theTest solution,concomitantly determine the absorbances of theTest solution and theStandard solution in 1-cm cells with a suitable spectrophotometer set at 460nm:the absorbance of theTest solution does not exceed that of theStandard solution.

A: Apply 4µLof the Inhalation Solution and 4µLof an aqueous solution of USP Metaproterenol Sulfate RScontaining about 50mg per mLto a suitable thin-layer chromatographic plate (seeChromatography á621ñ)coated with a 0.25-mm layer of chromatographic silica gel mixture.Allow the spots to dry,and develop the chromatogram in a solvent system consisting of the upper layer of a freshly prepared mixture of butyl alcohol,water,and formic acid (50:25:7)until the solvent front has moved about three-fourths of the length of the plate.Remove the plate from the developing chamber,mark the solvent front,and allow the solvent to evaporate.Locate the spots on the plate by examination under short-wavelength UVlight:theRFvalue of the principal spot obtained from the Inhalation Solution corresponds to that obtained from theStandard solution.

B: The chromatogram of theAssay preparation obtained as directed in theAssay exhibits a major peak for metaproterenol,the retention time of which corresponds to that exhibited in the chromatogram of theStandard preparation obtained as directed in theAssay.

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

Assay preparation— Transfer an accurately measured volume of Inhalation Solution,equivalent to about 200mg of metaproterenol sulfate,to a 100-mLvolumetric flask,dilute with 0.01Nhydrochloric acid to volume,and mix.

Procedure— Proceed as directed forProcedure in theAssay underMetaproterenol Sulfate.Calculate the quantity,in mg,of metaproterenol sulfate [(C11H17NO3)2·H2SO4]in each mLof the Inhalation Solution taken by the formula: in whichVis the volume,in mL,of Inhalation Solution taken;andC,rU,andrSare as defined therein.