A: The retention times of the major peaks in the chromatogram of the Assay preparationcorrespond to those in the chromatogram of the Standard preparation,as obtained in the Assay.

B: Transfer a portion of Capsule contents,equivalent to about 12mg of codeine phosphate,to a separator,add 5mLof water,1mLof ammonium hydroxide,and 5mLof methylene chloride,shake for 1minute,and allow the layers to separate.Use the clear,lower layer as the test solution.Prepare a Standard solution of USP Acetaminophen RSand USP Codeine Phosphate RSin methanol containing 12mg of each per mL.Apply 10µLof each solution to a suitable thin-layer chromatographic plate (see Chromatography á621ñ)coated with a 0.25-mm layer of chromatographic silica gel mixture.Allow the spots to dry,and develop the chromatogram in a solvent system consisting of a mixture of methanol and ammonium hydroxide (49:1)until the solvent front has moved about three-fourths of the length of the plate.Remove the plate from the developing chamber,mark the solvent front,and allow the solvent to evaporate.Locate the spots on the plate by examination under short-wavelength UVlight:the RFvalues of the two principal spots obtained from the test solution correspond to those obtained from the Standard solution.

Medium: 0.01Nhydrochloric acid;900mL.

Apparatus 2: 50rpm.

Time: 30minutes.

Procedure— Determine the amounts of acetaminophen (C8H9NO2)and codeine phosphate hemihydrate (C18H21NO3·H3PO4·½H2O)dissolved by employing the procedure set forth in the Assay,except to use 0.01Nhydrochloric acid to prepare the Codeine phosphate standard stock solutionand to make any other necessary volumetric adjustments.

Tolerances— Not less than 75%(Q)of the labeled amounts of C8H9NO2and C18H21NO3·H3PO4·½H2Ois dissolved in 30minutes.

PROCEDURE FOR CONTENT UNIFORMITY—

Buffer solution,Mobile phase,Codeine phosphate standard stock solution,Standard preparation,and Chromatographic system— Prepare as directed in the Assayunder Acetaminophen and Codeine Phosphate Tablets.

Assay preparation— Remove as completely as possible the contents of not fewer than 20Capsules,weigh,and mix.Transfer an accurately weighed portion of the combined contents,equivalent to about 300mg of acetaminophen,to a 100-mLvolumetric flask,add about 75mLof Mobile phase,and sonicate for 10minutes.Dilute with Mobile phaseto volume,and mix.Transfer 5.0-mLof the resulting solution to a 50-mLvolumetric flask,dilute with Mobile phaseto volume,and mix.Pass a portion of this solution through a suitable 1-µm filter.

Procedure— Separately inject equal volumes (about 30µL)of the Standard preparationand the Assay preparationinto the chromatograph,record the chromatograms,and measure the peak responses.Calculate the quantity,in mg,of acetaminophen (C8H9NO2)in the portion of Capsules taken by the formula: in which Lis the labeled quantity,in mg,of acetaminophen in each Capsule;CAis the concentration,in mg per mL,of USP Acetaminophen RSin the Standard preparation;CUis the concentration,in mg per mL,of acetaminophen in the Assay preparation,based upon the labeled quantity per Capsule and the extent of dilution;and rUand rSare the peak responses obtained from the Assay preparationand the Standard preparation,respectively.Calculate the quantity,in mg,of codeine phosphate hemihydrate (C18H21NO3·H3PO4·½H2O)in the portion of Capsules taken by the formula: in which 406.37and 397.37are the molecular weights of codeine phosphate hemihydrate and anhydrous codeine phosphate,respectively;Lis the labeled quantity,in mg,of codeine phosphate hemihydrate in each Capsule;CCis the concentration,in mg per mL,of USP Codeine Phosphate RSin the Standard preparation;CUis the concentration,in mg per mL,of codeine phosphate hemihydrate in the Assay preparation,based upon the labeled quantity per Capsule and the extent of dilution;and the other terms are as defined herein.