Medium: pH7.5simulated intestinal fluid TS(without the enzyme);900mL.

Apparatus 1: 100rpm.

Time: 30minutes.

Procedure— Determine the amount of C19H20N2O2dissolved by employing UVabsorption at the wavelength of maximum absorbance at about 264nm on filtered portions of the solution under test,suitably diluted,if necessary,with Dissolution Medium,using a suitable spectrophotometer,1-cm cells,and Dissolution Mediumas the blank,in comparison with a solution of known concentration of USP Phenylbutazone RSin the same Medium.

Tolerances— Not less than 70%(Q)is dissolved in 30minutes.

Procedure for content uniformity— Transfer 1Tablet to a 100-mLvolumetric flask,add 60mLof methanol,and shake by mechanical means for about 20minutes or until the tablet is completely disintegrated.Dilute with methanol to volume,and mix.Filter a portion of mixture,discarding the first 10mLof the filtrate.Dilute an accurately measured portion of the filtrate with sodium hydroxide solution (1in 2500)to obtain a solution containing about 10µg per mL.Prepare a solution of USP Phenylbutazone RSin methanol having a known concentration of about 1mg per mL.Quantitatively dilute a portion of this solution with sodium hydroxide solution (1in 2500)to obtain a Standard solution having a final known concentration of about 10µg per mL.Concomitantly determine the absorbances of the solution from the Tablet and the Standard solution at the wavelength of maximum absorbance at about 264nm,with a suitable spectrophotometer,using sodium hydroxide solution (1in 2500)as the blank.Calculate the quantity,in mg,of C19H20N2O2in the Tablet by the formula: in which Tis the labeled quantity,in mg,of phenylbutazone in the Tablet;Cis the concentration,in µg per mL,of USP Phenylbutazone RSin the Standard solution;Dis the concentration,in µg per mL,of phenylbutazone in the solution from the Tablet based on the labeled quantity per Tablet and the extent of dilution;and AUand ASare the absorbances of the solution from the Tablet and the Standard solution,respectively.

Acetate buffer,Mobile phase,Internal standard solution,Standard preparation,and Chromatographic system— Proceed as directed in the Assayunder Phenylbutazone.

Assay preparation— Weigh and finely powder not fewer than 20Tablets.Accurately weigh a portion of the powder,equivalent to about 500mg of phenylbutazone,and transfer to a 250-mLvolumetric flask.Pipet 50mLof water into the flask,and shake by mechanical means for 15minutes.Add about 120mLof acetonitrile,and sonicate until insoluble material is dispersed into fine particles.Shake by mechanical means for 20minutes,dilute with acetonitrile to volume,and mix.Centrifuge a portion of this solution.Pipet 7mLof the solution into a 50-mLvolumetric flask,add 10.0mLof Internal standard solution,dilute with acetonitrile to volume,and mix.Pass a portion through a 0.5-µm filter,discarding the first few mLof the filtrate.[NOTE—Use this solution within 8hours of its preparation.]

Procedure— Proceed as directed for Procedurein the Assayunder Phenylbutazone.Calculate the quantity,in mg,of phenylbutazone (C19H20N2O2)in the portion of Tablets taken by the formula: in which Cis the concentration,in mg per mL,of USP Phenylbutazone RSin the Standard preparation;and RUand RSare the ratios of the peak response of the phenylbutazone to that of the internal standard for the Assay preparationand the Standard preparation,respectively.