for oral suspension packaged in single-unit containers: meets the requirements.

for oral suspension packaged in multiple-unit containers: meets the requirements.

Diethylamine phosphate buffer, Diluent, Mobile phase, Standard preparation, and Chromatographic system— Proceed as directed in the Assay under Propoxyphene Napsylate Tablets.

Assay preparation— Transfer an accurately weighed quantity of the well-mixed Oral Suspension, equivalent to about 50 mg of propoxyphene napsylate monohydrate, to a 100-mL volumetric flask. Dissolve in and dilute with a solution of acetonitrile in water (2 in 5) to volume, and mix. Further dilute 10.0 mL of the resulting solution to 50 mL with the solution of acetonitrile in water (2 in 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 areas for the propoxyphene peaks. Calculate the quantity, in mg, of propoxyphene napsylate (C22H29NO2·C10H8O3S·H2O) in each mL of the Oral Suspension taken by the formula: in which 565.72 and 547.72 are the molecular weights of propoxyphene napsylate and anhydrous propoxyphene napsylate, respectively; C is the concentration, in mg per mL, of anhydrous USP Propoxyphene Napsylate RS in the Standard preparation; D is the density, in g per mL, of the Oral Suspension; WU is the weight, in g, of the Oral Suspension taken; and rU and rS are the peak responses obtained from the Assay preparation and the Standard preparation, respectively.