A: Infrared Absorption 197M.

B: 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.

Test solution: 5 mg per mL in dioxane.

Standard solutions— Dissolve an accurately weighed quantity of USP Mometasone Furoate RS, and dilute quantitatively with dichloromethane to obtain a solution containing 10 mg per mL. Dilute portions of this solution with dichloromethane to obtain Standard solutions A, B, C, D, and E containing 0.5 (5%), 0.2 (2%), 0.1 (1%), 0.02 (0.2%), and 0.01 (0.1%) mg per mL, respectively.

Test solution— Prepare a solution of Mometasone Furoate in dichloromethane containing 10 mg per mL.

Procedure— Separately apply 40 µL of the Test solution, and Standard solutions A, B, C, D, and E to a thin-layer chromatographic plate (see Chromatography 621) coated with a 0.25-mm layer of chromatographic silica gel. Develop the chromatogram in a chamber, previously equilibrated with a 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 air-dry. Examine the plate under short-wavelength UV light. Compare the intensities of any secondary spots observed in the chromatogram of the Test solution with those of the principal spots in the chromatogram of the Standard solutions: no secondary spot from the chromatogram of the Test solution is larger or more intense than the principal spot obtained from Standard solution C, and the sum of the intensities of the secondary spots obtained from the Test solution is not more than 2.0%.

Mobile phase— Prepare a filtered and degassed mixture of methanol and water (65:35). Make adjustments if necessary (see System Suitability under Chromatography 621).

Diluting solution— Prepare a solution consisting of a mixture of methanol, water, and acetic acid (65:35:0.2).

Internal standard solution— Transfer about 40 mg of beclomethasone dipropionate to a 100-mL volumetric flask, dilute with Diluting solution to volume, and mix.

Standard preparation— Dissolve an accurately weighed quantity of USP Mometasone Furoate RS in methanol, and dilute quantitatively, and stepwise if necessary, with Diluting solution to obtain a solution having a known concentration of about 0.1 mg per mL. Pipet equal amounts of this solution and the Internal standard solution, and dilute quantitatively, and stepwise if necessary, with Diluting solution to obtain a solution having a known concentration of about 0.02 mg per mL for mometasone furoate and 0.08 mg per mL for beclomethasone dipropionate.

Assay preparation— Dissolve an accurately weighed quantity of Mometasone Furoate in methanol, and dilute quantitatively, and stepwise if necessary, with Diluting solution to obtain a solution having a concentration of about 0.1 mg per mL. Pipet 10.0 mL of this solution and 10.0 mL of the Internal standard solution into a 50-mL volumetric flask, dilute with Diluting solution to volume, and mix.

Chromatographic system (see Chromatography 621)—The liquid chromatograph is equipped with a 254-nm detector and a 4.6-mm × 25-cm column that contains packing L7. The flow rate is about 1.7 mL per minute. Chromatograph the Standard preparation, and record the peak responses as directed under Procedure: the relative retention times are about 1.6 for beclomethasone dipropionate and 1.0 for mometasone furoate, the resolution, R, between the mometasone furoate and beclomethasone dipropionate peaks is not less than 4.0, the tailing factor for the mometasone furoate peak is not more than 1.8, and the relative standard deviation for replicate injections is not more than 2.0%.

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 C27H30Cl2O6 in the portion of Mometasone Furoate 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.