Medium: water; 1000 mL.

Apparatus 1: 100 rpm.

Times and Tolerances: as specified in the Labeling; use Acceptance Table 2.

Solvent A , Mobile phase, Chromatographic system, and Procedure—Proceed as directed in Test 1 for Dissolution under Phenylpropanolamine Hydrochloride Extended-Release Capsules.

Solvent A— Dissolve 1.9 g of sodium 1-hexanesulfonate in 700 mL of water, add 50 mL of 1 M monobasic sodium phosphate and 20 mL of 0.25 N triethylammonium phosphate (prepared by mixing 500 mL of a solution containing 25.3 g of triethylamine and 500 mL of a solution containing 9.6 g of phosphoric acid), and mix. Dilute with water to 1 L, and mix.

Mobile phase— Prepare a filtered and degassed mixture of Solvent A and methanol (100:82). Make adjustments if necessary (see Chromatography 621).

Standard preparation— Dissolve an accurately weighed quantity of USP Phenylpropanolamine Hydrochloride RS in methanol, and quantitatively dilute with methanol to obtain a solution having a known concentration of about 375 µg per mL.

Assay preparation— Weigh and finely powder not fewer than 20 Tablets. Transfer an accurately weighed portion of the powder, equivalent to about 750 mg of phenylpropanolamine hydrochloride, to a 200-mL volumetric flask. Add about 150 mL of methanol and sonicate for about 10 minutes. Dilute with methanol to volume, and mix. Transfer 10.0 mL of this solution to a 100-mL volumetric flask, dilute with methanol to volume, and mix. Use a filtered portion of the solution.

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 1.5 mL per minute. Chromatograph the Standard preparation, and record the peak responses as directed for Procedure: the tailing factor for the analyte peak is not more than 2.5, and the relative standard deviation for replicate injections is not more than 2.0%.

Procedure— Inject an accurately measured volume (about 70 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 phenylpropanolamine hydrochloride (C9H13NO·HCl) in the portion of Tablets taken by the formula: in which C is the concentration, in µg per mL, of USP Phenylpropanolamine Hydrochloride RS; and rU and rS are the peak responses obtained from the Assay preparation and the Standard preparation, respectively.