A: The retention times of the major peaks in the chromatograms of the Assay preparationscorrespond to those in the chromatograms of the Standard preparations,as obtained in the Assay for acetaminophenand the Assay for codeine phosphate,respectively,under Acetaminophen and Codeine Phosphate Oral Solution.

B: Using the Oral Suspension,proceed as directed for Identificationtest Bunder Acetaminophen and Codeine Phosphate Oral Solution:the indicated results are obtained.

Add the following:

For Oral Suspension Packaged In Single-Unit Containers: meets the requirements.

Add the following:

For Oral Suspension Packaged In Multiple-Unit Containers: meets the requirements.USP28

Mobile phase— Dissolve 4.9g of monobasic potassium phosphate in 900mLof water,adjust with phosphoric acid to a pHof 3.9,add 216mg of sodium 1-octanesulfonate,and mix.Add 100mLof acetonitrile,mix,filter,and degas.Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Diluent— Prepare a mixture of 0.01Nsodium hydroxide and methanol (70:30).

Codeine phosphate standard stock solution— Prepare a solution of USP Codeine Phosphate RS,accurately weighed,in Diluenthaving a known concentration of about 0.5mg per mL.

Standard stock preparation— Transfer an accurately weighed quantity of about 5Jmg of USP Acetaminophen RS,Jbeing the ratio of the labeled amount,in mg,of acetaminophen to the labeled amount,in mg,of codeine phosphate hemihydrate,and 10.0mLof Codeine phosphate standard stock solutionto a 100-mLvolumetric flask,dissolve in and dilute with Diluentto volume,and mix.

Standard preparation— Transfer 10.0mLof Standard stock preparationto a 50-mLvolumetric flask,dilute with Mobile phaseto volume,and mix.This solution contains about 0.01mg of USP Codeine Phosphate RSand 0.01Jmg of USP Acetaminophen RSper mL.

Assay preparation— Transfer an accurately measured volume of well-mixed Oral Suspension,equivalent to about 50mg of acetaminophen,to a 100-mLvolumetric flask.Add 50mLof Diluent,and mix by mechanical means for 30minutes.Dilute with Diluentto volume,and mix.[NOTE—Foaming may be minimized by adding a few drops of acetonitrile before diluting with Diluent to volume.]Centrifuge a portion of this mixture,and transfer 10.0mLof the clear supernatant to a 50-mLvolumetric flask,dilute with Mobile phaseto volume,and mix.

Resolution solution— Prepare a solution in Diluentcontaining about 0.02mg of sodium benzoate and 0.03mg of methylparaben per mL.Transfer 10.0mLof this solution and 10.0mLof Standard stock preparationto a 50-mLvolumetric flask,dilute with Mobile phaseto volume,and mix.

Chromatographic system(see Chromatography á621ñ)— The liquid chromatograph is equipped with a 220-nm detector and a 4.6-mm ×15-cm column that contains 5-µm packing L11.The flow rate is about 2mLper minute.Chromatograph the Resolution solution,and measure the peak responses as directed for Procedure:the relative retention times are about 0.25for acetaminophen,0.5for benzoate,1.0for codeine,and 1.3for methylparaben;and the resolution,R,between each pair of adjacent peaks is not less than 2.Chromatograph the Standard preparation,and record the peak responses as directed for Procedure:the tailing factor for each analyte peak is not more than 2,the peak efficiency is not less than 500theoretical plates,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 responses for the major peaks.Calculate the quantity,in mg,of acetaminophen (C8H9NO2)in each mLof the Oral Suspension taken by the formula: in which Cis the concentration,in mg per mL,of USP Acetaminophen RSin the Standard preparation;Vis the volume,in mL,of Oral Suspension taken;and rUand rSare the acetaminophen peak responses obtained from the Assay preparationand the Standard preparation,respectively.Calculate the quantity,in mg,of codeine phosphate hemihydrate (C18H21NO3·H3PO4·½H2O)in each mLof the Oral Suspension taken by the formula: in which 406.37and 397.37are the molecular weights of codeine phosphate hemihydrate and anhydrous codeine phosphate,respectively;Cis the concentration,in mg per mL,of USP Codeine Phosphate RSin the Standard preparation;Vis the volume,in mL,of Oral Suspension taken;and rUand rSare the codeine peak responses obtained from the Assay preparationand the Standard preparation,respectively.