A:Infrared Absorption á197Mñ.

B: The retention time of the major peak in the chromatogram of the Assay preparationcorresponds to that in the chromatogram of the Standard preparation,as obtained in the Assay.

Mobile phaseand System suitability solution— Prepare as directed in the Assay.

Standard solution— Use the Standard preparation,prepared as directed in the Assay.

Test solution— Use the Assay preparation,prepared as directed in the Assay.

Detector sensitivity solution— Transfer 1.0mLof the Standard solutioninto a 100-mLvolumetric flask,dilute with a mixture of water and acetonitrile (4:1)to volume,and mix.Dilute quantitatively,and stepwise if necessary,with a mixture of water and acetonitrile (4:1)to obtain a solution having a known concentration of about 0.1µg per mL.

Chromatographic system (see Chromatography á621ñ)— The liquid chromatograph is equipped with a 240-nm detector and a 4.6-mm ×25-cm column that contains packing L1.The column temperature is maintained at 25±5.The flow rate is about 1.0mLper minute.Chromatograph the System suitability solution,and record the peak area responses as directed for Procedure:the relative retention times are about 1.4for o-flutamide and 1.0for flutamide;and the resolution,R,between flutamide and o-flutamide is not less than 6.0.Chromatograph the Detector sensitivity solution,and record the peak area responses as directed for Procedure:the relative standard deviation for replicate injections is not more than 10.0%for flutamide.

Procedure— Inject a volume (about 20µL)of the Test solutioninto the chromatograph,record the chromatogram,and measure the peak area responses.Calculate the percentage of each impurity in the portion of Flutamide taken by the formula: in which Fis the relative response factor of the impurities according to the table below;riis the peak area response for each impurity;and rsis the sum of the responses of all the peaks:the impurities meet the requirements tabulated below.

Mobile phase— Prepare a filtered and degassed mixture of water and acetonitrile (55:45).Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Standard preparation— Dissolve an accurately weighed quantity of USP Flutamide RSin 50mLof acetonitrile,and dilute quantitatively,and stepwise if necessary,with water to obtain a solution having a known concentration of about 0.2mg per mL.

System suitability solution— Transfer about 50mg of USPo-Flutamide RS,accurately weighed,to a 50-mLvolumetric flask,dissolve in 10mLof acetonitrile,dilute with water to volume,and mix.Transfer 1.0mLof this solution and 5.0mLof the Standard preparationinto a 100-mLvolumetric flask,dilute with a mixture of water and acetonitrile (4:1)to volume,and mix.

Assay preparation— Transfer about 50mg of Flutamide,previously dried and accurately weighed,to a 250-mLvolumetric flask.Add 50mLof acetonitrile,and sonicate until the Flutamide dissolves.Add 150mLof water,mix,and allow to warm to room temperature.Dilute with water to volume,and mix.

Chromatographic system(see Chromatography á621ñ)— The liquid chromatograph is equipped with a 240-nm detector and a 4.6-mm ×25-cm column that contains packing L1.The column temperature is maintained at 25±5.The flow rate is about 1.0mLper minute.Chromatograph the System suitability solution,and record the peak area responses as directed for Procedure:the relative retention times are about 1.4for o-flutamide and 1.0for flutamide;and the resolution,R,between flutamide and o-flutamide is not less than 6.0.Chromatograph the Standard preparation,and record the peak area responses as directed for Procedure:the tailing factor is not more than 2.0;and the relative standard deviation for replicate injections is not more than 1.5%.

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 C11H11F3N2O3in the portion of Flutamide taken by the formula: in which Cis the concentration,in mg per mL,of USP Flutamide RSin the Standard preparation;and rUand rSare the peak area responses obtained from the Assay preparationand the Standard preparation,respectively.