Identification—
Place 2 g of the Cream in a 150-mL beaker, add 50 mL of chloroform and 15 g of anhydrous sodium sulfate, and stir with a glass rod to dissolve the specimen. Filter the solution, and clarify the filtrate, if necessary, by the further addition of anhydrous sodium sulfate and a second filtration. Evaporate the filtrate to dryness, and dissolve the residue in chloroform to obtain a solution containing about 100 µg of amcinonide per mL. Apply 25 µL of this solution, and 25 µL of a solution of
USP Amcinonide RS in chloroform containing 100 µg per mL, on a line parallel to and about 3 cm from the bottom edge of a thin-layer chromatographic plate (see
Chromatography 
621
) coated with a 0.25-mm layer of chromatographic silica gel. Place the plate in a developing chamber containing and equilibrated with ether. Develop the chromatogram until the solvent front has moved about 12 cm above the line of application. Remove the plate, allow the solvent to evaporate, and locate the spots on the plate by viewing under short-wavelength UV light: the intensity and the
RF value of the principal spot obtained from the solution under test are similar to those of the spot obtained from the Standard solution.
Assay—
Solution A, Solution B, Mobile phase, System suitability solution, Standard preparation, and Chromatographic system—
Proceed as directed in the
Assay under
Amcinonide.
Assay preparation—
Transfer an accurately weighed quantity of Cream, equivalent to about 10 mg of Amcinonide, to a 50-mL volumetric flask, add 5 mL of Solution B and 15 mL of acetonitrile, and heat over a steam bath until dissolved. Add 20 mL of Solution B while hot, cool to room temperature, dilute with Solution B to volume, and refrigerate for 30 minutes. Vigorously shake the solution to disperse the mixture, and filter while cold. 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. Record the chromatograms, and measure the responses for the major peaks. Calculate the quantity, in mg, of amcinonide (C
28H
35FO
7) in the portion of Cream taken by the formula:
500C(rU / rS),
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.
