A: Place a portion of Capsule contents, equivalent to about 250 mg of mefenamic acid, in a 250-mL volumetric flask, add about 100 mL of a mixture of chloroform and methanol (3:1), and shake vigorously. Dilute with a mixture of chloroform and methanol (3:1) to volume, mix, and filter: the filtrate so obtained responds to the Thin-layer Chromatographic Identification Test 201, a solvent system consisting of a mixture of chloroform, ethyl acetate, and glacial acetic acid (75:25:1) and the Ordinary Impurities 466 visualization technique 17 being used.

B: The retention time of the major peak in the chromatogram of the Assay preparation corresponds to that of the Standard preparation, obtained as directed in the Assay.

0.05 M Tris buffer— Dissolve 60.5 g of tris(hydroxymethyl)aminomethane in 6 L of water, and dilute with water to 10 L. Adjust with phosphoric acid to a pH of 9.0 ± 0.05. To a second container, transfer about 6 liters of this solution, add 100 g of sodium lauryl sulfate, and mix to dissolve the solid material. Transfer this solution back into the first container, and mix.

Medium: 0.05 M Tris buffer; 900 mL.

Apparatus 1: 100 rpm.

Time: 45 minutes.

Procedure— Determine the amount of C15H15NO2 dissolved, employing the procedure set forth in the Assay, making any necessary volumetric adjustments.

Tolerances— Not less than 75% (Q) of the labeled amount of C15H15NO2 is dissolved in 45 minutes.

(Official January 1, 2007)

Mobile phase, Standard preparation, and Chromatographic system— Proceed as directed in the Assay under Mefenamic Acid.

Assay preparation— Remove, as completely as possible, the contents of not fewer than 20 Capsules. Weigh the contents, and determine the average weight per capsule. Mix the combined contents, and transfer an accurately weighed quantity of the powder, equivalent to about 100 mg of mefenamic acid, to a 500-mL volumetric flask. Add 10.0 mL of tetrahydrofuran, and sonicate for about 5 minutes with occasional mixing. Dilute with Mobile phase to volume, mix, and filter.

Procedure— Proceed as directed for Procedure in the Assay under Mefenamic Acid. Calculate the quantity, in mg, of C15H15NO2 in the portion of Capsules taken by the formula: in which the terms are as defined therein.