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: Prepare a test solution of the Cream in acetonitrile containing 0.2 mg per mL of mometasone furoate. Prepare a Standard solution of USP Mometasone Furoate RS in acetonitrile 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.

Mobile phase— Proceed as directed under the Assay for Mometasone Furoate.

Internal standard solution— Dissolve a suitable quantity of beclomethasone dipropionate in acetonitrile to obtain a solution containing about 0.53 mg per mL.

Standard preparation— Dissolve an accurately weighed quantity of USP Mometasone Furoate RS in acetonitrile, and dilute quantitatively, and stepwise if necessary, with acetonitrile to obtain a solution having a known concentration of about 0.136 mg per mL. Pipet equal amounts of this solution and the Internal standard solution, and dilute quantitatively, and stepwise if necessary, with acetonitrile to obtain a solution having known concentrations of about 0.027 mg of mometasone furoate and 0.106 mg of beclomethasone dipropionate per mL.

Assay preparation— Transfer an accurately weighed portion of Cream, equivalent to about 2.0 mg of mometasone furoate, to a 50-mL screw-capped centrifuge tube. Pipet 15.0 mL of Internal standard solution and 15.0 mL of acetonitrile into the tube, and attach the cap. Heat in an 85 water bath until the cream completely melts, and shake by hand for 2 minutes. Repeat the heating and shaking. Place the tube in an ice-methanol bath for 10 minutes. Centrifuge to obtain a clear supernatant, and transfer 10.0 mL of the supernatant layer into a 25-mL volumetric flask. Dilute with acetonitrile to volume, and mix.

Chromatographic system (see Chromatography 621)—Proceed as directed in the Assay under Mometasone Furoate.

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 Cream 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.