Medium: simulated gastric fluid TS, prepared without pepsin; 900 mL.

Apparatus 1: 50 rpm.

Time: 45 minutes.

Procedure— Determine the amount of C15H13N3O4S dissolved from UV absorbances at the wavelength of maximum absorbance at about 333 nm of suitably filtered portions of the solution under test, suitably diluted with Dissolution Medium, if necessary, in comparison with a Standard solution having a known concentration of USP Piroxicam RS in the same medium. [NOTE—Use a suitable filter that does not adsorb piroxicam. To prepare the Standard solution, dissolve a suitable, accurately weighed quantity of USP Piroxicam RS in methanol to obtain a stock solution having a known concentration of about 0.5 mg per mL prior to dilution with Dissolution Medium.]

Tolerances— Not less than 75% (Q) of the labeled amount of C15H13N3O4S is dissolved in 45 minutes.

(Official January 1, 2007)

Buffer, Mobile phase, Standard preparation, and Chromatographic system— Prepare as directed in the Assay under Piroxicam.

Assay preparation— Transfer, as completely as possible, the contents of not less than 20 Capsules to a suitable tared container, and determine the average weight per capsule. Mix the combined contents, and transfer an accurately weighed portion, equivalent to about 50 mg of piroxicam, to a 100-mL volumetric flask. Add about 70 mL of 0.01 N methanolic hydrochloric acid, and shake by mechanical means for 30 minutes. Dilute with 0.01 N methanolic hydrochloric acid to volume, and mix. Centrifuge a portion of this mixture to obtain a clear solution. Transfer 10.0 mL of the solution so obtained to a 100-mL volumetric flask, add about 50 mL of 0.01 N methanolic hydrochloric acid and 20.0 mL of water, dilute with 0.01 N methanolic hydrochloric acid to volume, and mix.

Procedure— Proceed as directed for Procedure in the Assay under Piroxicam. Calculate the quantity, in mg, of C15H13N3O4S in the portion of the contents of Capsules taken by the formula: in which C is the concentration, in mg per mL, of USP Piroxicam RS in the Standard preparation, and rU and rS are the peak responses obtained from the Assay preparation and the Standard preparation, respectively.