Medium: pH 7.5 simulated intestinal fluid TS (without the enzyme); 900 mL.

Apparatus 1: 100 rpm.

Time: 30 minutes.

Procedure— Determine the amount of C19H20N2O2 dissolved by employing UV absorption at the wavelength of maximum absorbance at about 264 nm on filtered portions of the solution under test, suitably diluted, if necessary, with Dissolution Medium, using a suitable spectrophotometer, 1-cm cells, and Dissolution Medium as the blank, in comparison with a solution of known concentration of USP Phenylbutazone RS in the same Medium.

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

Procedure for content uniformity— Transfer 1 Tablet to a 100-mL volumetric flask, add 60 mL of methanol, and shake by mechanical means for about 20 minutes or until the tablet is completely disintegrated. Dilute with methanol to volume, and mix. Filter a portion of mixture, discarding the first 10 mL of the filtrate. Dilute an accurately measured portion of the filtrate with sodium hydroxide solution (1 in 2500) to obtain a solution containing about 10 µg per mL. Prepare a solution of USP Phenylbutazone RS in methanol having a known concentration of about 1 mg per mL. Quantitatively dilute a portion of this solution with sodium hydroxide solution (1 in 2500) to obtain a Standard solution having a final known concentration of about 10 µg per mL. Concomitantly determine the absorbances of the solution from the Tablet and the Standard solution at the wavelength of maximum absorbance at about 264 nm, with a suitable spectrophotometer, using sodium hydroxide solution (1 in 2500) as the blank. Calculate the quantity, in mg, of C19H20N2O2 in the Tablet by the formula: in which T is the labeled quantity, in mg, of phenylbutazone in the Tablet; C is the concentration, in µg per mL, of USP Phenylbutazone RS in the Standard solution; D is 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 AU and AS are the absorbances of the solution from the Tablet and the Standard solution, respectively.

(Official January 1, 2007)

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

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

Procedure— Proceed as directed for Procedure in the Assay under Phenylbutazone. Calculate the quantity, in mg, of phenylbutazone (C19H20N2O2) in the portion of Tablets taken by the formula: in which C is the concentration, in mg per mL, of USP Phenylbutazone RS in the Standard preparation; and RU and RS are the ratios of the peak response of the phenylbutazone to that of the internal standard for the Assay preparation and the Standard preparation, respectively.