Medium: pH5.8phosphate buffer (see Buffer Solutionsin the section Reagents,Indicators,and Solutions);900mL.

Apparatus 2: 50rpm.

Time: 45minutes.

Mobile phase— Proceed as directed in the Assay.

Standard solution— Prepare a solution in Dissolution Mediumhaving known concentrations of about L/900mg of USP Pseudoephedrine Hydrochloride RSand LJ/900mg of USP Acetaminophen RSper mL,in which Lis the labeled quantity,in mg,of pseudoephedrine hydrochloride in each Tablet;and Jis the ratio of the labeled quantity,in mg,of acetaminophen to the labeled quantity,in mg,of pseudoephedrine hydrochloride in each Tablet.

Test solution— Use a filtered portion of the solution under test.

Chromatographic system— Proceed as directed in the Assay,except to inject the Standard solution.

Procedure— Separately inject equal volumes (about 20µL)of the Standard solutionand the Test solutioninto the chromatograph,record the chromatograms,and measure the responses for the acetaminophen and pseudoephedrine peaks.Calculate the quantity,in mg,of acetaminophen (C8H9NO2)and pseudoephedrine hydrochloride (C10H15NO·HCl)dissolved by the formula: in which Cis the concentration,in mg per mL,of the appropriate USP Reference Standard in the Standard solution;and rUand rSare the peak responses of the corresponding analyte obtained from the Test solutionand the Standard solution,respectively.

Tolerances— Not less than 75%(Q)of the labeled amounts of C8H9NO2and C10H15NO·HCl is dissolved in 45minutes.

FOR TABLETS LABELED AS CHEWABLE—

Diluent— Prepare a mixture of water and acetonitrile (90:10).

Mobile phase— Prepare a solution of 0.005Methanesulfonic acid and 0.05Mmonobasic potassium phosphate.Prepare a filtered and degassed mixture of this solution and acetonitrile (900:100),and adjust with 5Nsodium hydroxide or 1Nhydrochloric acid to a pHof 4.6.Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Pseudoephedrine hydrochloride stock standard solution— Quantitatively dissolve an accurately weighed quantity of USP Pseudoephedrine Hydrochloride RSin Diluentto obtain a solution having a known concentration of about 0.6mg per mL.

Standard preparation— Transfer about 6Jmg of USP Acetaminophen RS,accurately weighed,to a 100-mLvolumetric flask,Jbeing the ratio of the labeled quantity,in mg,of acetaminophen to the labeled quantity,in mg,of pseudoephedrine hydrochloride in each Tablet.Add 2.0mLof 1Nhydrochloric acid and about 20mLof Diluent,and mix to dissolve.Add 10.0mLof Pseudoephedrine hydrochloride stock standard solution,dilute with Diluentto volume,and mix.This solution contains about 0.06Jmg of USP Acetaminophen RSand 0.06mg of USP Pseudoephedrine Hydrochloride RSper mL.

Assay preparation— Weigh and finely powder not fewer than 20Tablets.Transfer an accurately weighed portion of the powder,equivalent to about 30mg of pseudoephedrine hydrochloride,to a 500-mLvolumetric flask,add 10.0mLof 1Nhydrochloric acid and about 100mLof Diluent,and sonicate for 30minutes,with occasional shaking.Allow to cool,dilute with Diluentto volume,and mix.Pass a portion of this solution through a glass fiber filter,and use the filtrate as the Assay preparation.

Chromatographic system (see Chromatography á621ñ)— The liquid chromatograph is equipped with a 214-nm detector and a 4.6-mm ×25-cm column containing base-deactivated or end-capped packing L1.The flow rate is about 3mLper minute.Chromatograph the Standard preparation,and record the responses as directed for Procedure:the retention time for the acetaminophen peak is not less than 2minutes and the relative retention times are about 0.55for acetaminophen and 1.0for pseudoephedrine;the resolution R,between acetaminophen and pseudoephedrine is not less than 3.5;the tailing factor for the pseudoephedrine peak is not more than 2;and the relative standard deviation for replicate injections is not more than 2.0%.

Procedure— Separately inject equal volumes (about 10µL)of the Standard preparationand the Assay preparationinto the chromatograph,record the chromatograms,and measure the responses for the acetaminophen and pseudoephedrine peaks.Calculate the quantity,in mg,of acetaminophen (C8H9NO2)and pseudoephedrine hydrochloride (C10H15NO·HCl)in the portion of Tablets taken by the formula: in which Cis the concentration,in mg per mL,of the appropriate USP Reference Standard in the Standard preparation;and rUand rSare the peak responses for the corresponding analyte obtained from the Assay preparationand the Standard preparation,respectively.