A: The retention time of the major peak in the chromatogram of the Assay preparation corresponds 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 2 mg of mometasone furoate, to a 50-mL centrifuge tube. Add 10 mL of water. Extract the aqueous solution with 20 mL of 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 1 mg per mL. Prepare a Standard solution of USP Mometasone Furoate RS having the same concentration as the test solution. The test solution so obtained responds to the Thin-layer Chromatographic Identification Test 201, a mixture of chloroform and ethyl acetate (3:1) being used as the developing solvent and 20 µL each of test solution and Standard solution being applied to the thin-layer chromatographic plate.

(Official January 1, 2007)

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

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

Procedure— Separately inject equal volumes (about 20 µL) of the Standard preparation and the Assay preparation into 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 C is the concentration, in mg per mL, of USP Mometasone Furoate RS in the Standard preparation, and RU and RS are the ratios of the mometasone furoate peak to the internal standard peak obtained from the Assay preparation and the Standard preparation, respectively.