» Desoximetasone Gel contains not less than 90.0 percent and not more than 110.0 percent of the labeled amount of C22H29FO4.
Packaging and storage Preserve in collapsible tubes, at controlled room temperature.
USP Reference standards 11
Identification Transfer an amount of Gel, equivalent to 100 µg of desoximetasone, to a 15-mL centrifuge tube. Add 3 mL of acetonitrile, sonicate for approximately 1 minute, centrifuge, and transfer the clear supernatant to another 15-mL centrifuge tube. Evaporate the solution under nitrogen at a temperature between 35 and 45 to dryness. Dissolve the residue in 100 µL of methanol, using a sonicator. Streak separately the entire test solution and 100 µL of a Standard solution of USP Desoximetasone RS in methanol containing 1 mg per mL on a thin-layer chromatographic plate (see Chromatography 621) coated with a 0.25-mm layer of chromatographic silica gel mixture and an area of preadsorbent material on which specimens are applied. Allow the streaks to dry, and develop the chromatogram in a saturated chamber containing a mixture of acetone and chloroform (1:1). Allow the solvent front to move not less than 10 cm beyond the origin. After drying, examine the plate under UV light at 254 nm: the RF value of the principal spot obtained in the chromatogram of the test solution corresponds to that of the Standard solution.
Minimum fill 755: meets the requirements.
Alcohol content Transfer about 2.5 g of Gel, accurately weighed, to a 50-mL volumetric flask. Dissolve in methanol, dilute with methanol to volume, and mix. Determine the alcohol content of the specimen thus prepared by the Method IIGas-Liquid Chromatographic Method (see Alcohol Determination 611), using isopropyl alcohol as the internal standard and using methanol in place of water as the solvent: between 18.0% and 24.0% (w/w) of C2H5OH is found.
Mobile phase Prepare a suitable filtered and degassed solution of methanol, water, and glacial acetic acid (65:35:1). Adjust the ratio, if necessary, so that the retention time of desoximetasone is about 8 minutes.
Standard preparation Using an accurately weighed quantity of USP Desoximetasone RS, prepare a solution in methanol containing 0.5 mg per mL. Dilute an accurately measured volume of this solution with methanolic calcium chloride dihydrate solution (1.5 in 100) to obtain a Standard preparation having a known concentration of about 0.025 mg per mL.
Assay preparation Transfer an accurately weighed quantity of Gel, equivalent to about 1.25 mg of desoximetasone, to a 50-mL volumetric flask, add approximately 40 mL of methanolic calcium chloride dihydrate solution (1.5 in 100), and sonicate to disperse the gel. Dilute with the same solution to volume, mix, and centrifuge. Use the clear supernatant.
Chromatographic system (see Chromatography 621)The liquid chromatograph is equipped with a 254-nm detector and a 3.9-mm × 30-cm column that contains packing L1. The flow rate is about 1.5 mL per minute. Chromatograph five replicate injections of the Standard preparation, and record the peak responses as directed for Procedure: the relative standard deviation is not more than 2.0%.
Procedure Separately inject equal volumes (about 10 µL) of the Standard preparation and the Assay preparation into the chromatograph by means of a sampling valve, record the chromatograms, and measure the responses for the major peaks. Calculate the quantity, in mg, of C22H29FO4 in the portion of Gel taken by the formula:
50C(rU / rS)in which C is the concentration, in mg per mL, of USP Desoximetasone RS in the Standard preparation; and rU and rS are the peak responses of desoximetasone obtained from the Assay preparation and the Standard preparation, respectively.
Auxiliary Information Please check for your question in the FAQs before contacting USP.
USP35NF30 Page 2833