A: Infrared Absorption 197K: previously dried at 105 for 3 hours.

B: Ultraviolet Absorption 197U—

Test solution: 10 mg per mL, in chloroform.

Mobile phase and Chromatographic system— Proceed as directed in the Assay.

Standard stock solution— Accurately weigh about 10 mg each of USP Propoxyphene Related Compound A RS and USP Propoxyphene Related Compound B RS into a 50-mL volumetric flask, dissolve using 2 mL of methanol, dilute with Mobile phase to volume, and mix.

Standard solution— Transfer 5.0 mL of the Standard stock solution to a 50-mL volumetric flask, dilute with Mobile phase to volume, and mix.

System suitability solution— Dissolve an accurately weighed quantity of USP Propoxyphene Napsylate RS in Standard solution, and dilute quantitatively, and stepwise if necessary, to obtain a solution having known concentrations of about 4.5 mg per mL of USP Propoxyphene Napsylate RS, about 0.02 mg per mL of USP Propoxyphene Related Compound A RS, and about 0.02 mg per mL of USP Propoxyphene Related Compound B RS.

Test solution— Use the Assay preparation.

Chromatographic system— Chromatograph the System suitability solution, and record the peak responses as directed for Procedure: the relative retention times are about 0.63 for propoxyphene related compound A, 0.78 for propoxyphene related compound B, and 1.0 for propoxyphene napsylate; the resolution, R, between propoxyphene related compound B and propoxyphene related compound A is not less than 2.0; and the relative standard deviation for replicate injections is not more than 2.0%.

Procedure— Separately inject equal volumes (about 50 µL) of the Standard solution and the Test solution into the chromatograph, record the chromatograms, and measure the peak responses. Calculate the quantity, in mg, of propoxyphene related compound A in the portion of Propoxyphene Napsylate taken by the formula: in which C is the concentration, in mg per mL, of USP Propoxyphene Related Compound A RS in the Standard solution; 491.67 and 319.88 are the molecular weights of propoxyphene related compound A napsylate and propoxyphene related compound A, respectively; and rU and rS are the propoxyphene related compound A peak responses obtained from the Test solution and the Standard solution, respectively: not more than 0.5% of propoxyphene related compound A napsylate is found. Calculate the quantity, in mg, of propoxyphene related compound B napsylate in the portion of Propoxyphene Napsylate taken by the formula: in which C is the concentration, in mg per mL, of USP Propoxyphene Related Compound B RS in the Standard solution; 533.71 and 325.45 are the molecular weights of propoxyphene related compound B napsylate and propoxyphene related compound B, respectively; and rU and rS are the propoxyphene related compound B peak responses obtained from the Test solution and the Standard solution, respectively. Not more than 0.6% of propoxyphene related compound B napsylate is found.

Solvent— Use dimethyl sulfoxide.

(Official January 1, 2007)

0.1 M Monobasic ammonium phosphate buffer, pH 6.3— Dissolve 11.5 g of monobasic ammonium phosphate and 1.0 mL of triethylamine in 1000 mL of water, adjust with 10% sodium hydroxide to a pH of 6.3 ± 0.05, and mix.

Mobile phase— Prepare a filtered and degassed mixture of methanol and 0.1 M Monobasic ammonium phosphate buffer, pH 6.3 (67:33). Make adjustments if necessary (see System Suitability under Chromatography 621).

Standard preparation— Dissolve an accurately weighed quantity of USP Propoxyphene Napsylate RS in Mobile phase to obtain a solution having a known concentration of about 5.0 mg per mL.

Assay preparation— Transfer about 250 mg of Propoxyphene Napsylate, accurately weighed, to a 50-mL volumetric flask, dissolve in and 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 1.5 mL per minute. Chromatograph the Standard preparation, and record the peak responses as directed for Procedure: the retention time of propoxyphene napsylate is about 9 minutes; the tailing factor for the propoxyphene napsylate peak is not more than 3.5; and the relative standard deviation for replicate injections is not more than 2.0%.

Procedure— Separately inject equal volumes (about 50 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 C22H29NO2 ·C10H8O3S in the portion of Propoxyphene Napsylate taken by the formula: in which C is the concentration, in mg per mL, of USP Propoxyphene Napsylate RS in the Standard preparation; and rU and rS are the peak responses obtained from the Assay preparation and the Standard preparation, respectively.