A: Infrared Absorption á197Kñ.

B: Heat a 1in 50mixture of it with acetic acid,filter,and add 2mLof ammonium oxalate TSto the filtrate:a white precipitate,which is soluble in 3Nhydrochloric acid,is formed.

Solution A— Prepare a filtered and degassed mixture of water and acetic acid (98:2).

Solution B— Prepare a filtered and degassed mixture of acetonitrile and acetic acid (98:2).

Mobile phase— Use variable mixtures of Solution Aand Solution Bas directed for Chromatographic system.Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Diluent: a mixture of water and acetonitrile (1:1).

System suitability solution— Dissolve accurately weighed quantities of 3-phenoxybenzoic acid and USP Fenoprofen Calcium RSin Diluentto obtain a solution containing about 0.02mg of each per mL.

Standard solution— Dissolve an accurately weighed quantity of USP Fenoprofen Calcium RSin Diluentto obtain a solution having a known concentration of about 0.02mg per mL.

Test solution— Transfer about 200mg of Fenoprofen Calcium,accurately weighed,to a 100-mLvolumetric flask,dissolve in and dilute with Diluentto volume,and mix.

Chromatographic system(see Chromatography á621ñ)— The liquid chromatograph is equipped with a 270-nm detector and a 4.6-mm ×25-cm column that contains 5-µm packing L7.The flow rate is 1.5mLper minute.The chromatograph is programmed as follows. Chromatograph the System suitability solution,and record the peak responses as directed for Procedure:the relative retention times are about 0.89for 3-phenoxybenzoic acid and 1.0for fenoprofen;the resolution,R,between 3-phenoxybenzoic acid and fenoprofen is not less than 9.0;and the tailing factor for the fenoprofen peak is not more than 2.0.Chromatograph the Standard solution,and record the peak responses as directed for Procedure:the tailing factor for the fenoprofen peak is not more than 2.0;and the relative standard deviation for replicate injections is not more than 2.0%.

Procedure— Separately inject equal volumes (about 20µL)of the Standard solutionand the Test solutioninto the chromatograph,record the chromatograms,and measure the peak responses.Calculate the percentage of each impurity in the portion of Fenoprofen Calcium taken by the formula: in which Cis the concentration,in mg per mL,of USP Fenoprofen Calcium RSin the Standard solution;Wis the quantity,in mg,of Fenoprofen Calcium taken to prepare the Test solution;riis the response for each impurity peak obtained from the Test solution;and rSis the response of the fenoprofen peak obtained from the Standard solution:not more than 0.5%of any individual impurity is found;and not more than 2.0%of total impurities is found.

Solvent— Use dimethyl sulfoxide.

Test solution— Transfer about 750mg of Fenoprofen Calcium,accurately weighed,to a 50-mLvolumetric flask,dissolve in alcohol with the aid of heat,if necessary,cool,dilute with alcohol to volume,and mix.

Procedure— In a 150-mLbeaker,mix 70mLof water,2mLof sodium hydroxide solution (1in 10),and about 0.3g of hydroxy naphthol blue.Add about 1mLof the Test solution,and titrate to the blue endpoint with 0.05Medetate disodium.Transfer 10.0mLof the Test solutionto the solution so obtained,and titrate to the blue endpoint with 0.05Medetate disodium VS.Each mLof 0.05Medetate disodium is equivalent to 2.004mg of Ca:not less than 7.3%and not more than 8.0%of Ca,calculated on the anhydrous basis,is found.

Mobile phase— Prepare a suitable degassed mixture of acetonitrile,water,and phosphoric acid (50:49.6:0.4).Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Diluting solution— Prepare a mixture of methanol and water (700:300).

Resolution solution— Prepare a solution in Diluting solutioncontaining about 1mg of Fenoprofen Calcium and 1mg of gemfibrozil per mL.

Standard preparation— Transfer about 70mg of USP Fenoprofen Calcium RS,accurately weighed,to a 100-mLvolumetric flask,add 0.5mLof 0.5Nhydrochloric acid and 2mLof acetone,and dissolve by shaking.Dilute with Diluting solutionto volume,and mix.

Assay preparation— Transfer about 70mg of Fenoprofen Calcium,accurately weighed,to a 100-mLvolumetric flask,add 0.5mLof 0.5Nhydrochloric acid and 2mLof acetone,and dissolve by shaking.Dilute with Diluting solutionto volume,and mix.

Chromatographic system(seeChromatography á621ñ)— The liquid chromatograph is equipped with a 272-nm detector and a 4.6-mm ×15-cm column that contains 5-µm packing L7.The flow rate is about 2mLper minute.Chromatograph the Resolution solution,and record the peak responses as directed for Procedure:the relative retention times are about 0.5for fenoprofen and 1.0for gemfibrozil;the tailing factor for the fenoprofen peak is not more than 2;and the resolution,R,between the fenoprofen peak and the gemfibrozil peak is not less than 8.Chromatograph the Standard preparation,and record the peak responses as directed for Procedure:the column efficiency determined from the fenoprofen peak is not less than 3000theoretical plates;and the relative standard deviation for replicate injections is not more than 2.0%.

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 (C15H13O3)2Ca in the portion of Fenoprofen Calcium taken by the formula: in which Cis the concentration,in mg per mL,of anhydrous fenoprofen calcium in the Standard preparation,as determined from the concentration of USP Fenoprofen Calcium RS,corrected for moisture content by a titrimetric water determination;and rUand rSare the fenoprofen peak responses obtained from the Assay preparationand the Standard preparation,respectively.