A: Infrared Absorption 197K—If a difference appears, dissolve portions of both the test specimen and the USP Reference Standard in ethyl acetate, evaporate to dryness, and repeat the test on the residues.

B: It responds to the Thin-layer Chromatographic Identification Test 201, the test solution and the Standard solution being prepared at a concentration of 5 mg per mL in acetone, chromatographic silica gel being used as the adsorbent, the solvent mixture being nitromethane, dichloromethane, and methanol (50:50:1), and UV light being used to locate the spots.

Test solution: 10 mg per mL, in methanol.

Mobile phase— Prepare a suitable, degassed solution of water, acetonitrile, and tetrahydrofuran (77:13:10).

Standard preparation— Dissolve about 20 mg of USP Fluocinolone Acetonide RS, accurately weighed, in 23 mL of a mixture of acetonitrile and tetrahydrofuran (13:10), dilute with water to 100.0 mL, and mix.

Assay preparation— Transfer about 20 mg of Fluocinolone Acetonide, accurately weighed, to a 100-mL volumetric flask, dissolve in 23 mL of a mixture of acetonitrile and tetrahydrofuran (13:10), dilute with water to volume, and mix.

Chromatographic system (see Chromatography 621)—The liquid chromatograph is equipped with a 254-nm detector and a 4.5-mm × 10-cm column that contains packing L1. Adjust the flow rate so that the retention time for fluocinolone acetonide is between 9 and 13 minutes. Chromatograph the Standard preparation, and record the peak response as directed for Procedure: the column efficiency is not less than 3000 theoretical plates, and the relative standard deviation for replicate injections is not more than 3.0%.

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 C24H30F2O6 in the portion of Fluocinolone Acetonide taken by the formula: in which C is the concentration, in mg per mL, of USP Fluocinolone Acetonide RS in the Standard preparation; and rU and rS are the peak responses obtained from the Assay preparation and the Standard preparation, respectively.