Medium: pH 5.8 phosphate buffer (see Buffer Solutions in the section Reagents, Indicators, and Solutions); 900 mL.

Apparatus 2: 50 rpm.

Time: 45 minutes.

Mobile phase— Proceed as directed in the Assay.

Standard solution— Prepare a solution in Dissolution Medium having known concentrations of about L/900 mg of USP Pseudoephedrine Hydrochloride RS and LJ/900 mg of USP Acetaminophen RS per mL, in which L is the labeled quantity, in mg, of pseudoephedrine hydrochloride in each Tablet; and J is 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 20 µL) of the Standard solution and the Test solution into 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 C is the concentration, in mg per mL, of the appropriate USP Reference Standard in the Standard solution; and rU and rS are the peak responses of the corresponding analyte obtained from the Test solution and the Standard solution, respectively.

Tolerances— Not less than 75% (Q) of the labeled amounts of C8H9NO2 and C10H15NO·HCl is dissolved in 45 minutes.

FOR TABLETS LABELED AS CHEWABLE—

(Official January 1, 2007)

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

Mobile phase— Prepare a solution of 0.005 M ethanesulfonic acid and 0.05 M monobasic potassium phosphate. Prepare a filtered and degassed mixture of this solution and acetonitrile (900:100), and adjust with 5 N sodium hydroxide or 1 N hydrochloric acid to a pH of 4.6. Make adjustments if necessary (see System Suitability under Chromatography 621).

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

Standard preparation— Transfer about 6J mg of USP Acetaminophen RS, accurately weighed, to a 100-mL volumetric flask, J being the ratio of the labeled quantity, in mg, of acetaminophen to the labeled quantity, in mg, of pseudoephedrine hydrochloride in each Tablet. Add 2.0 mL of 1 N hydrochloric acid and about 20 mL of Diluent, and mix to dissolve. Add 10.0 mL of Pseudoephedrine hydrochloride stock standard solution, dilute with Diluent to volume, and mix. This solution contains about 0.06J mg of USP Acetaminophen RS and 0.06 mg of USP Pseudoephedrine Hydrochloride RS per mL.

Assay preparation— Weigh and finely powder not fewer than 20 Tablets. Transfer an accurately weighed portion of the powder, equivalent to about 30 mg of pseudoephedrine hydrochloride, to a 500-mL volumetric flask, add 10.0 mL of 1 N hydrochloric acid and about 100 mL of Diluent, and sonicate for 30 minutes, with occasional shaking. Allow to cool, dilute with Diluent to 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 621)— 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 3 mL per minute. Chromatograph the Standard preparation, and record the responses as directed for Procedure: the retention time for the acetaminophen peak is not less than 2 minutes and the relative retention times are about 0.55 for acetaminophen and 1.0 for 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 10 µL) of the Standard preparation and the Assay preparation into 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 C is the concentration, in mg per mL, of the appropriate USP Reference Standard in the Standard preparation; and rU and rS are the peak responses for the corresponding analyte obtained from the Assay preparation and the Standard preparation, respectively.