A: The contents of Capsules respond to Identification test A under Phensuximide.

B: The retention time exhibited by phensuximide in the chromatogram of the Assay preparation corresponds to that of phensuximide in the chromatogram of the Standard preparation, as obtained in the Assay.

Medium: water; 900 mL.

Apparatus 1: 100 rpm.

Time: 120 minutes.

Procedure— Determine the amount of C11H11NO2 dissolved, employing the procedure set forth in the Assay, making any necessary modifications.

Tolerances— Not less than 75% (Q) of the labeled amount of C11H11NO2 is dissolved in 120 minutes.

(Official January 1, 2007)

Mobile phase— Prepare a filtered and degassed mixture of water and acetonitrile (55:45). Make adjustments if necessary (see System Suitability under Chromatography 621).

Standard preparation— Dissolve an accurately weighed quantity of USP Phensuximide RS in Mobile phase to obtain a solution having a known concentration of about 1 mg per mL.

Assay preparation— Place 10 Capsules in a 500-mL volumetric flask, and add 280 mL of water. Sonicate in a water bath at 40 to 50, with occasional shaking, until the Capsules have broken, and cool to room temperature. Dilute with acetonitrile to volume, mix, and filter. Transfer an accurately measured volume of this specimen solution, equivalent to about 50 mg of Phensuximide, to a 50-mL volumetric flask, dilute with Mobile phase to volume, and mix.

Chromatographic system (see Chromatography 621)—The liquid chromatograph is equipped with a 254-nm detector and a 3.9-mm × 30-cm column that contains packing L1. The flow rate is about 1 mL per minute. Chromatograph the Standard preparation, and record the peak responses as directed for Procedure: the column efficiency determined from the analyte peak is not less than 2100 theoretical plates, and the relative standard deviation for replicate injections is not more than 1.5%.

Procedure— Separately inject equal volumes (about 20 µL) of the Standard preparation and the Assay preparation into the chromatograph, record the chromatograms, and measure the responses for the major peaks. Calculate the quantity, in mg, of C11H11NO2 per Capsule taken by the formula: in which C is the concentration, in mg per mL, of USP Phensuximide RS in the Standard preparation, V is the volume, in mL, of specimen solution taken for the Assay preparation, and rU and rS are the phensuximide peak responses obtained from the Assay preparation and the Standard preparation, respectively.