Medium: pH 7.0 phosphate buffer (see Buffer Solutions in the section Reagents, Indicators, and Solutions); 1000 mL.

Apparatus 1: 10-mesh basket; 100 rpm.

Time: 60 minutes.

Procedure— Filter 20 mL of the solution under test, and transfer 10.0 mL of the filtrate to a 100-mL volumetric flask. Dilute with Dissolution Medium to volume, and mix. Determine the absorbances of this solution and a Standard solution prepared from USP Fenoprofen Sodium RS, in the same medium having a known concentration of about 60 µg per mL at the wavelength of maximum absorbance at about 270 nm, using Dissolution Medium as the blank. Calculate the amount of C15H14O3 dissolved, in mg, by the formula: in which 242.28 is the molecular weight of fenoprofen; 264.26 is the molecular weight of anhydrous fenoprofen sodium; C is the concentration of anhydrous fenoprofen sodium in the Standard solution, as determined from the concentration of USP Fenoprofen Sodium RS corrected for moisture content by a titrimetric water determination; and AU and AS are the absorbances of the solutions obtained from the substance under test and the USP Reference Standard, respectively.

Tolerances— Not less than 75% (Q) of the labeled amount of C15H14O3 is dissolved in 60 minutes.

(Official January 1, 2007)

Mobile phase, Diluting solution, Resolution solution, Standard preparation, and Chromatographic system— Proceed as directed in the Assay under Fenoprofen Calcium.

Assay preparation— Weigh and finely powder not fewer than 20 Tablets. Transfer an accurately weighed portion of the powder, equivalent to about 6000 mg of fenoprofen, to a 250-mL volumetric flask, add 50 mL of 0.5 N hydrochloric acid, and sonicate for 10 minutes, shaking the solution occasionally. Dilute with acetone to volume, sonicate for 10 minutes, and stir for an additional 30 minutes. Transfer 5.0 mL of this solution to a 200-mL volumetric flask, dilute with Diluting solution to volume, and mix. Pass a portion of this solution through a suitable filter having a 0.5-µm or finer porosity, discarding the first 8 mL of the filtrate, and use the clear filtrate as the Assay preparation.

Procedure— Proceed as directed in the Assay under Fenoprofen Calcium. Calculate the quantity, in mg, of fenoprofen (C15H14O3) in the portion of Tablets taken by the formula: in which 484.55 is two times the molecular weight of fenoprofen; 522.61 is the molecular weight of fenoprofen calcium; and the other terms are as defined therein.