Medium: pH6.8phosphate buffer (see under Buffer Solutionsin the section Reagents,Indicators,and Solutions);900mL.

Apparatus 1: 100rpm.

Time: 45minutes.

Procedure— Determine the amount of C23H20N2O3Sdissolved from UVabsorbances at the wavelength of maximum absorbance at about 259nm of filtered portions of the solution under test,suitably diluted with Dissolution Medium,in comparison with a Standard solution having a known concentration of USP Sulfinpyrazone RSin the same Medium.

Tolerances— Not less than 75%(Q)of the labeled amount of C23H20N2O3Sis dissolved in 45minutes.

Acetonitrileand tetrahydrofuran mixture— Prepare a mixture of acetonitrile and tetrahydrofuran (4:1).

Mobile phase— Prepare a degassed and filtered solution of dilute phosphoric acid (3in 1000)and Acetonitrile and tetrahydrofuran mixture(65:35).

Internal standard solution— Prepare a solution of Benzoic Acid in acetonitrile having a concentration of about 2mg per mL.

Standard preparation— Transfer about 100mg,accurately weighed,of USP Sulfinpyrazone RSto a 200-mLvolumetric flask,add 100mLof acetonitrile,mix,add 10.0mLof Internal standard solution,dilute with acetonitrile to volume,and mix.Filter,discarding the first 5mLof the filtrate.

Assay preparation— Remove as completely as possible,and weigh,the contents of not less than 20Capsules,and mix.Transfer an accurately weighed portion of the powder,equivalent to about 100mg of sulfinpyrazone,to a 200-mLvolumetric flask,add 100mLof acetonitrile,mix,add 10.0mLof Internal standard solution,dilute with acetonitrile to volume,and mix.Filter,discarding the first 5mLof the filtrate.

Chromatographic system (see Chromatography á621ñ)—The liquid chromatograph is equipped with a 235-nm detector and a 4.6-mm ×10-cm column that contains packing L1.The flow rate is about 3mLper minute.Chromatograph the Standard preparation,and record the peak responses as directed under Procedure:the relative retention times are about 0.2for benzoic acid and 1.0for sulfinpyrazone;the resolution,R,between benzoic acid and sulfinpyrazone is not less than 13;and the relative standard deviation is not more than 2.0%.

Procedure— Separately inject equal volumes (about 10µL)of the Standard preparationand the Assay preparationinto the chromatograph,record the chromatograms,and measure the responses for the major peaks.The resolution,R,between benzoic acid and sulfinpyrazone is not less than 13.Calculate the quantity,in mg,of C23H20N2O3Sin the portion of Capsule contents taken by the formula: in which Cis the concentration,in mg per mL,of USP Sulfinpyrazone RSin the Standard preparation,and RUand RSare the relative peak response ratios obtained from the Assay preparationand the Standard preparation,respectively.