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 Ointment,equivalent to about 3mg of mometasone furoate,to a 50-mLscrew-capped centrifuge tube.Pipet 5.0mLof methanol into the tube,and attach the cap.Heat in a steam bath until the ointment completely melts,and shake vigorously until the ointment resolidifies.Place in an ice-water bath for 10minutes.Centrifuge,and filter a portion of the supernatant.Extract 1mLof the filtrate with 1mLof hexane;the lower phase obtained is the test solution.Apply 10µLof the test solution and 10µLof a Standard solution of USP Mometasone Furoate RSin methanol containing 0.6mg per mLto a suitable thin-layer chromatographic plate (see Chromatography á621ñ)coated with a 0.25-mm layer of chromatographic silica gel mixture.Allow the spots to dry,and develop the chromatogram in methanol until the solvent front has moved 2cm from the origin.Remove the plate from the developing chamber and air-dry.Develop the chromatogram in a second solvent system consisting of a mixture of chloroform and ethyl acetate (3:1),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 spots to air-dry.Examine the plate under short-wavelength UVlight:the RFvalue of the principal spot obtained from the test solution corresponds to that obtained from the Standard solution.

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 Ointment,equivalent to 1.0mg of mometasone furoate,to a 50-mLscrew-capped centrifuge tube.Pipet 10.0mLof Internal standard solutionand 10.0mLof Diluting solutioninto the tube,and attach the cap.Heat in an 85water bath until the ointment completely melts,and shake vigorously by hand until the ointment resolidifies.Repeat heating and shaking two more times.Place the tube in an ice-methanol bath for 10minutes.Centrifuge to obtain a clear supernatant,and transfer 10.0mLof the supernatant into a 25-mLvolumetric 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 Ointment 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.