A: Transfer the finely ground contents of 1Tablet to a test tube,add 5mLof methanol,shake for 5minutes,and centrifuge.Use the clear supernatant as the test solution.Prepare a Standard solution in methanol containing,in each mL,about 20mg of USP Propoxyphene Napsylate RSand 130mg of USP Acetaminophen RS.Apply 10µLof the test solution on a line parallel to and about 2cm from the bottom edge of a 20-×5-cm thin-layer chromatographic plate (see Chromatography á621ñ)coated with chromatographic silica gel mixture,and apply 10µLof the Standard solution separately on the starting line.Place the plate in a developing chamber containing a mixture of chloroform,butyl acetate,and formic acid (50:50:20),and develop the chromatogram until the solvent front has moved about 15cm above the line of application.Remove the plate,allow to dry in a hood,and view under short-wavelength UVlight:the solution under test exhibits two principal spots having intensities and RFvalues identical to those of the two principal spots obtained from the Standard solution.

B: The retention time of the major peak for propoxyphene in the chromatogram of the Assay preparationcorresponds to that in the chromatogram of the Standard preparation,as obtained in the Assay for propoxyphene napsylate.

C: The retention time of the major peak for acetaminophen in the chromatogram of the Assay preparationcorresponds to that in the chromatogram of the Standard preparation,as obtained in the Assay for acetaminophen.

Medium: pH4.5acetate buffer,prepared as directed in the test for Dissolutionunder Propoxyphene Hydrochloride,Aspirin,and Caffeine Capsules;500mL.

Apparatus 1: 100rpm.

Time: 60minutes.

Diethylamine phosphate buffer,Mobile phase,and Chromatographic system— Proceed as directed in the Assayunder Propoxyphene Napsylate Tablets.

Standard solution— Transfer about 10mg of USP Propoxyphene Napsylate RSand about 10Jmg of USP Acetaminophen RS,both accurately weighed,to a 100-mLvolumetric flask,Jbeing the ratio of the labeled amount,in mg,of acetaminophen to the labeled amount,in mg,of propoxyphene napsylate in each Tablet.Dissolve in and dilute with Dissolution Mediumto volume,and mix.This solution contains about 0.1mg of USP Propoxyphene Napsylate RSand 0.1Jmg of USP Acetaminophen RSper mL.[NOTE—Retain a portion of this solution for use in preparing the Standard solutionwhen determining the amount of acetaminophen dissolved.]

Test solution andProcedure— Proceed as directed in the Dissolutiontest under Propoxyphene Napsylate Tablets.

Diethylamine phosphate buffer— Prepare as directed in the Assayunder Propoxyphene Napsylate Tablets.

Mobile phase,Chromatographic system,and Procedure— Proceed as directed in the Assay for acetaminophen.

Standard solution A— Transfer 10.0mLof the Standard solutionto a 100-mLvolumetric flask,dilute with Dissolution Mediumto volume,and mix.This solution contains about 0.01Jmg of USP Acetaminophen RSper mL.

Test solution A— Quantitatively dilute a filtered portion of the solution under test with Dissolution Mediumto obtain a solution having a concentration of about 0.01Jmg of acetaminophen per mL.

Tolerances— Not less than 75%(Q)of the labeled amounts of C22H29NO2·C10H8O3S·H2Oand C8H9NO2is dissolved in 60minutes.

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

Standard preparation— Transfer about 10mg of USP Propoxyphene Napsylate RSand about 10Jmg of USP Acetaminophen RS,both accurately weighed,to a 100-mLvolumetric flask,Jbeing the ratio of the labeled amount,in mg,of acetaminophen to the labeled amount,in mg,of propoxyphene napsylate in each Tablet.Dissolve in and dilute with Diluentto volume,and mix.This solution contains about 0.1mg of USP Propoxyphene Napsylate RSand 0.1Jmg of USP Acetaminophen RSper mL.[NOTE—Retain a portion of the Standard preparationfor use in the Assay for acetaminophen.]

Assay preparationand Procedure— Proceed as directed in the Assayunder Propoxyphene Napsylate Tablets.[NOTE—Retain a portion of the Assay preparationfor use in the Assay for acetaminophen.]

Diethylamine phosphate buffer— Prepare as directed in the Assayunder Propoxyphene Napsylate Tablets.

Mobile phase— Prepare a mixture of Diethylamine phosphate bufferand acetonitrile (4:1).Sonicate for 15minutes,and pass through a filter having a 0.5-µm or finer porosity.Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Standard preparation— Transfer 10.0mLof the Standard preparationprepared as directed in the Assay for propoxyphene napsylateto a 100-mLvolumetric flask,dilute with Mobile phaseto volume,and mix.This solution contains about 0.01Jmg of USP Acetaminophen RSper mL.

Assay preparation— Transfer 10.0mLof the Assay preparationprepared as directed in the Assay for propoxyphene napsylateto a 100-mLvolumetric flask,dilute with Mobile phaseto volume,and mix.

Chromatographic system(see Chromatography á621ñ)— The liquid chromatograph is equipped with a 245-nm detector and a 3.9-mm ×30-cm column containing packing L1.The flow rate is about 1mLper minute.Chromatograph the Standard preparation,and record the responses as directed for Procedure:the tailing factor is not more than 1.5;and the relative standard deviation for replicate injections is not more than 2.0%.

Procedure— Separately inject equal volumes (about 20µL)of the Standard preparationand the Assay preparationinto the chromatograph,record the chromatograms,and measure the areas for the acetaminophen peaks.Calculate the quantity,in mg,of acetaminophen (C8H9NO2)in the portion of Tablets taken by the formula: in which Cis the concentration,in mg per mL,of USP Acetaminophen RSin the Standard preparation;Dis the dilution factor used to prepare the Assay preparationin the Assay for propoxyphene napsylate;and rUand rSare the peak responses obtained from the Assay preparationand the Standard preparation,respectively.