A: Infrared Absorption á197Kñ—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 á201ñ,the test solution and the Standard solution being prepared at a concentration of 5mg per mLin acetone,chromatographic silica gel being used as the adsorbent,the solvent mixture being nitromethane,dichloromethane,and methanol (50:50:1),and UVlight being used to locate the spots.

Test solution: 10mg per mL,in methanol.

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

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

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

Chromatographic system (see Chromatography á621ñ)—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 9and 13minutes.Chromatograph the Standard preparation,and record the peak response as directed for Procedure:the column efficiency is not less than 3000theoretical plates,and the relative standard deviation for replicate injections is not more than 3.0%.

Procedure— Separately inject equal volumes (about 20µL)of the Standard preparationand the Assay preparationinto the chromatograph,record the chromatograms,and measure the responses for the major peaks.Calculate the quantity,in mg,of C24H30F2O6in the portion of Fluocinolone Acetonide taken by the formula: in which Cis the concentration,in mg per mL,of USP Fluocinolone Acetonide RSin the Standard preparation;and rUand rSare the peak responses obtained from the Assay preparationand the Standard preparation,respectively.