Solution A, Solution B, Mobile phase, System suitability solution, Standard preparation, and Chromatographic system— Proceed as directed in the Assay under Amcinonide, except to use a 240-nm detector.

Assay preparation— Dissolve an accurately weighed quantity of Ointment in a suitable volume of a mixture of acetonitrile and chloroform (4:1) by heating in a hot water bath, cooling, and adjusting quantitatively with the same solvent mixture to obtain a solution having a concentration of about 0.2 mg of amcinonide per mL. Cool to room temperature, dilute with acetonitrile to volume, and filter. Transfer 5 mL of this solution to a 50-mL volumetric flask, dilute with Solution B to volume, and mix.

Procedure— Separately inject equal volumes (about 10 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 amcinonide (C28H35FO7) in the portion of Ointment taken by the formula: in which C is the concentration, in mg per mL, of USP Amcinonide RS in the Standard preparation; and rU and rS are the peak responses obtained from the Assay preparation and the Standard preparation, respectively.