A: The retention time of the major peak in the chromatogram of the Assay preparationcorresponds to that of the Standard preparation,both relative to the internal standard,as obtained in the Assay.

B: Transfer a quantity of Topical Solution,equivalent to about 2mg of mometasone furoate,to a 50-mLcentrifuge tube.Add 10mLof water.Extract the aqueous solution with 20mLof chloroform.Remove the chloroform layer,dry over anhydrous sodium sulfate,and filter through a cotton pledget.Repeat the chloroform extraction and combine the dried extracts.Evaporate the chloroform solution to dryness on a steam bath under a stream of nitrogen.Allow the test specimen to cool to room temperature.Dissolve the residue in a mixture of chloroform and methanol (4:1)to obtain a test solution containing 1mg per mL.Prepare a Standard solution of USP Mometasone Furoate RShaving the same concentration as the test solution.The test solution so obtained responds to the Thin-layer Chromatographic Identification Test á201ñ,a mixture of chloroform and ethyl acetate (3:1)being used as the developing solvent and 20µLeach of test solution and Standard solution being applied to the thin-layer chromatographic plate.

Mobile phase ,Diluting solution,Internal standard solution,Standard preparation,and Chromatographic system—Proceed as directed in the Assayunder Mometasone Furoate.

Assay preparation— Transfer an accurately weighed portion of Topical Solution,equivalent to 1.0mg of mometasone furoate,to a 50-mLvolumetric flask.Pipet 10.0mLof Internal standard solutioninto the flask,dilute with Diluting solutionto volume,and mix.

Procedure— Separately inject equal volumes (about 20µL)of the Standard preparationand the Assay preparationinto the chromatograph,record the chromatograms,and measure the responses for the major peaks.Calculate the quantity,in mg,of mometasone furoate (C27H30Cl2O6)in the portion of Topical Solution taken by the formula: in which Cis the concentration,in mg per mL,of USP Mometasone Furoate RSin the Standard preparation,and RUand RSare the ratios of the mometasone furoate peak to the internal standard peak obtained from the Assay preparationand the Standard preparation,respectively.