Medium: water; 900 mL.

Apparatus 1: 100 rpm.

Time: 60 minutes.

pH 7.5 Phosphate buffer— Prepare a solution of 0.025 M monobasic potassium phosphate, and adjust to a pH of 7.5 by the addition of 1 N potassium hydroxide.

Mobile phase— Prepare a suitable degassed and filtered mixture of acetonitrile and pH 7.5 Phosphate buffer (65:35).

Chromatographic system (see Chromatography 621)—The liquid chromatograph is equipped with a 210-nm detector and a 4-mm × 15-cm column that contains packing L15. The flow rate is about 1.0 mL per minute. Chromatograph three replicate injections of the Standard solution, and record the peak responses as directed for Procedure: the relative standard deviation is not more than 3.0%.

Procedure— Separately inject equal volumes (about 50 µL) of the Standard solution and a filtered aliquot of the solution under test into the chromatograph, record the chromatograms, and measure the responses for the major peaks. Calculate the percentage of C12H17NO·C4H6O6 dissolved in comparison with a Standard solution of USP Phendimetrazine Tartrate RS, similarly prepared and chromatographed.

Tolerances— Not less than 70% (Q) of the labeled amount of C12H17NO·C4H6O6 is dissolved in 60 minutes.

(Official January 1, 2007)

Mobile phase, Diluent, Internal standard solution, Standard preparation, and Chromatographic system— Prepare as directed in the Assay under Phendimetrazine Tartrate Capsules.

Assay preparation— Weigh and finely powder not fewer than 20 Tablets. Transfer an accurately weighed portion of the powder, equivalent to about 35 mg of phendimetrazine tartrate, to a 50-mL volumetric flask, add 25 mL of Internal standard solution, and sonicate for about 15 minutes. Cool the solution to room temperature, dilute with Internal standard solution to volume, mix, and filter through a 0.45-µm membrane filter.

Procedure— Proceed as directed for Procedure in the Assay under Phendimetrazine Tartrate Capsules. Calculate the quantity, in mg, of C12H17NO·C4H6O6 in the portion of Tablets taken by the formula: in which C is the concentration, in mg per mL, of USP Phendimetrazine Tartrate RS in the Standard preparation, and RU and RS are the peak response ratios obtained from the Assay preparation and the Standard preparation, respectively.