Medium: water;900mL.Add 1.0mLof Internal standard solutionto each vessel.

Apparatus 2: 50rpm.

Time: 45minutes.

Mobile phase— Prepare a filtered and degassed mixture of methanol and water (60:40),making adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Internal standard solution— Prepare a solution in methanol of testosterone having a final concentration of about 0.5mg per mL.

Standard solution— Prepare a solution of USP Betamethasone RS,in methanol,having an accurately known concentration of about 0.5mg per mL.Pipet 1mLof this solution and 1mLof the Internal standard solutioninto a container,and quantitatively dilute with water to 900mL.

Chromatographic system(see Chromatography á621ñ)— The liquid chromatograph is equipped with a 254-nm detector and a 3.9-mm ×30-cm column that contains packing L1.The flow rate is about 2mLper minute.Chromatograph replicate injections of the Standard solution,and record the peak responses as directed for Procedure:the resolution,R,between betamethasone and testosterone is not less than 1.5;and the relative standard deviation for replicate injections is not more than 3.0%.

Procedure— Separately inject equal volumes (about 200µL)of the Standard solutionand filtered portions of the solution under test into the chromatograph,record the chromatograms,and measure the responses for the major peaks.The relative retention times are about 0.5for betamethasone and 1.0for testosterone.Calculate the quantity of C22H29FO5dissolved in comparison with the Standard solution,similarly chromatographed.

Tolerances— Not less than 75%(Q)of the labeled amount of C22H29FO5is dissolved in 45minutes.

Procedure for content uniformity—

Mobile phase— Prepare a filtered and degassed mixture of water and acetonitrile (2:1).Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Internal standard solution— Transfer about 25mg of beclomethasone to a 200-mLvolumetric flask,add methanol to volume,and mix.

Standard preparation— Dissolve an accurately weighed quantity of USP Betamethasone RSin methanol,and dilute quantitatively and stepwise,if necessary,with methanol to obtain a solution having a known concentration of about 0.1mg per mL.Mix equal volumes,accurately measured,of this solution and the Internal standard solutionto obtain a Standard preparationhaving a final known concentration of about 0.05mg of USP Betamethasone RSper mL.

Assay preparation— Weigh and finely powder not fewer than 20Tablets.Transfer an accurately weighed portion of the powder,equivalent to about 0.5mg of betamethasone,to a 125-mLseparator.Add 25mLof water,and shake by mechanical means for about 15minutes.Add 5.0mLof Internal standard solution.Extract with four 25-mLportions of chloroform.Filter the chloroform extracts through about 4g of chloroform-washed anhydrous sodium sulfate,collecting the extracts in a 150-mLbeaker.Evaporate the extracts on a steam bath with the aid of a stream of nitrogen to dryness,taking care to avoid overheating.Dissolve the residue in 2mLof methanol,and transfer to a 10-mLvolumetric flask.Rinse the beaker with small portions of methanol,transferring the rinses to the same flask.Dilute with methanol to volume,and mix.

Chromatographic system(see Chromatography á621ñ)— The liquid chromatograph is equipped with a 254-nm detector and a 4-mm ×30-cm column that contains packing L1.The flow rate is about 1.2mLper minute.Chromatograph the Standard preparation,and record the peak heights as directed for Procedure:the resolution,R,between the analyte and internal standard peaks is not less than 1.7;and the relative standard deviation for replicate injections is not more than 2.0%.

Procedure— Separately inject equal volumes (about 10µL)of the Standard preparationand the Assay preparationinto the chromatograph,record the chromatograms,and measure the heights of the major peaks.The relative retention times are about 1.4for beclomethasone and 1.0for betamethasone.Calculate the quantity,in mg,of betamethasone (C22H29FO5)in the portion of Tablets taken by the formula: in which Cis the concentration,in mg per mL,of USP Betamethasone RSin the Standard preparation;and RUand RSare the peak height ratios obtained from the Assay preparationand the Standard preparation,respectively.