Test solution: 20mg,undried,per mL,in chloroform.

Mobile phaseand Chromatographic system— Prepare as directed in the Assay.

Test solution— Dissolve an accurately weighed quantity of Diflorasone Diacetate in water-saturated chloroform to obtain a solution having a concentration of about 6mg per mL.

Procedure— Inject a volume (about 10µL)of theTest solution into the chromatograph,record the chromatogram for a period equal to 5times the retention time of the major peak,and measure the areas of all the peaks.Calculate the percentage of each impurity in the portion of Diflorasone Diacetate taken by the formula: in which riis the peak area for each impurity;and rsis the sum of the areas of all the peaks:not more than 1.0%of any individual impurity is found;and not more than 2.0%of total impurities is found.

Mobile phase— Prepare a solution containing a mixture of water-saturatedn-butyl chloride,water-saturated methylene chloride,glacial acetic acid,and tetrahydrofuran (350:125:15:10).Make adjustments if necessary (seeSystem Suitability underChromatography á621ñ).

Internal standard solution— Using water-saturated chloroform,prepare a solution of isoflupredone acetate containing about 0.04mg per mL.

Standard preparation— Dissolve an accurately weighed quantity of USP Diflorasone Diacetate RSinInternal standard solution to obtain a solution having a known concentration of about 33µg per mL.

Assay preparation— Transfer about 15mg of Diflorasone Diacetate,accurately weighed,to a 500-mLvolumetric flask.AddInternal standard solution to volume,and mix.

Chromatographic system(see Chromatography á621ñ)— The liquid chromatograph is equipped with a 254-nm detector and a 4.6-mm ×10-cm column that contains 3-µm packing L3.The flow rate is about 2.5mLper minute.Chromatograph theStandard preparation,and record the peak areas as directed forProcedure:the resolution,R,between the analyte and internal standard peaks is not less than 12;and the relative standard deviation for not less than four replicate injections is not more than 2.0%.

Procedure— Separately inject equal volumes (about 10µL)of theStandard preparation and theAssay preparation into the chromatograph,record the chromatograms,and measure the areas for the major peaks.The relative retention times are about 1.0for diflorasone diacetate and 2.4for the internal standard.Calculate the quantity,in mg,of C26H32F2O7in the portion of Diflorasone Diacetate taken by the formula: in which Cis the concentration,in µg per mL,of USP Diflorasone Diacetate RSin theStandard preparation;and RUand RSare the ratios of the peak areas for diflorasone diacetate and the internal standard areas obtained from theAssay preparation and theStandard preparation,respectively.