A: The retention times of the carbinoxamine maleate and dextromethorphan hydrobromide peaks in the chromatogram of the Assay preparationcorrespond to those in the chromatogram of the Standard preparation,as obtained in the Assay for carbinoxamine maleate and dextromethorphan hydrobromide.

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

Add the following:

FOR ORAL SOLUTION PACKAGED IN SINGLE-UNIT CONTAINERS: meets the requirements.USP28

Add the following:

FOR ORAL SOLUTION PACKAGED IN MULTIPLE-UNIT CONTAINERS: meets the requirements.USP28

pH5.5buffer— Dissolve about 4.4g of dibasic potassium phosphate in 1000mLof water.Adjust with phosphoric acid to a pHof 5.5.

Mobile phase— Prepare a filtered and degassed mixture of methanol and pH5.5buffer(60:40).Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Standard preparation— Dissolve accurately weighed quantities of USP Carbinoxamine Maleate RSand USP Dextromethorphan Hydrobromide RSin water,and dilute quantitatively,and stepwise if necessary,with water to obtain a solution having known concentrations of about 0.1mg per mLof carbinoxamine maleate and 0.3mg per mLof dextromethorphan hydrobromide.

Assay preparation— Transfer an accurately measured volume of Oral Solution to a volumetric flask,and dilute with water to volume to obtain a solution having concentrations of about 0.1mg per mLof carbinoxamine maleate and 0.3mg per mLof dextromethorphan hydrobromide,and mix.

Chromatographic system (see Chromatography á621ñ)— The liquid chromatograph is equipped with a 225-nm detector and a 4.6-mm ×25-cm column that contains packing L9.The flow rate is about 1.5mLper minute.Chromatograph the Standard preparation,and record the peak responses as directed for Procedure:the relative retention times are about 0.8for dextromethorphan and 1.0for carbinoxamine;the resolution,R,between carbinoxamine and dextromethorphan is not less than 3.0;the tailing factor for the dextromethorphan peak is not more than 2.0;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 analyte peaks.Calculate the quantities,in mg,of carbinoxamine maleate (C16H19ClN2O·C4H4O4)and dextromethorphan hydrobromide (C18H25NO·HBr)in each mLin the volume of Oral Solution taken by the formula: in which Cis the concentration,in mg per mL,of the appropriate Reference Standard in the Standard preparation;Vis the volume of Oral Solution taken;Dis the dilution factor used for the Assay preparation;and rUand rSare the peak responses for the appropriate analyte obtained from the Assay preparationand the Standard preparation,respectively.

pH5.5buffer and Mobile phase— Proceed as directed in the Assay for carbinoxamine maleate and dextromethorphan hydrobromide.

Standard preparation— Dissolve an accurately weighed quantity of USP Pseudoephedrine Hydrochloride RSin water,and dilute quantitatively,and stepwise if necessary,with water to obtain a solution having a known concentration of about of 1.2mg per mLof pseudoephedrine hydrochloride.

Assay preparation— Transfer an accurately measured volume of Oral Solution to a volumetric flask,dilute with water to volume to obtain a solution having a concentration of about 1.2mg per mLof pseudoephedrine hydrochloride,and mix.

Chromatographic system (see Chromatography á621ñ)— The liquid chromatograph is equipped with a 257-nm detector and a 4.6-mm ×25-cm column that contains packing L9.The flow rate is about 1.5mLper minute.Chromatograph the Standard preparation,and record the peak responses as directed for Procedure:the column efficiency is not less than 1000theoretical 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 analyte peaks.Calculate the quantity,in mg,of pseudoephedrine hydrochloride (C10H15NO·HCl)in each mLin the volume of Oral Solution taken by the formula: in which Cis the concentration,in mg per mL,of USP Pseudoephedrine Hydrochloride RSin the Standard preparation;Vis the volume of Oral Solution taken;Dis the dilution factor used for the Assay preparation;and rUand rSare the peak responses for pseudoephedrine hydrochloride obtained from the Assay preparationand the Standard preparation,respectively.