Medium: water;900mL.

Apparatus 1: 100rpm.

Time: 60minutes.

Mobile phase and Chromatographic system—Proceed as directed in the Assay.

Standard preparation— Prepare a solution in water containing about 0.0011Amg of USP Acetaminophen RS,0.0011AJmg of USP Dichloralphenazone RS,and 0.0011AJ¢mg of USP Isometheptene Mucate RSper mL,Abeing the labeled amount,in mg,of acetaminophen per Capsule,Jbeing the ratio of the labeled amount,in mg,of dichloralphenazone to the labeled amount,in mg,of acetaminophen per Capsule,and J¢being the ratio of the labeled amount,in mg,of isometheptene mucate to the labeled amount,in mg,of acetaminophen per Capsule,and filter.

Test preparation— Filter about 20mLof the solution under test through a glass fiber filter,discarding the first 15mLof the filtrate.

Procedure— Proceed as directed for Procedurein the Assayexcept to inject 100µL,instead of 10µL.Calculate the quantity,in mg,of acetaminophen (C8H9NO2),dichloralphenazone (C15H18Cl6N2O5),and isometheptene mucate [(C9H19N)2·C6H10O8]dissolved 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 responses of the corresponding analyte peaks obtained from the Test preparationand the Standard preparation,respectively.

Tolerances— Not less than 65%(Q)of the labeled amounts of isometheptene mucate [(C9H19N)2·C6H10O8],dichloralphenazone (C15H18Cl6N2O5),and acetaminophen (C8H9NO2)are dissolved after 60minutes.

Mobile phase— Prepare a mixture of 0.07Mmonobasic potassium phosphate,acetonitrile,0.007Msodium 1-decanesulfonate,and diethylamine (750:250:25:15).Adjust with phosphoric acid to a pHof 3.5.Filter and degas before use.Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Chromatographic test solution— Empty the contents of 1Capsule into a 100-mLvolumetric flask,add about 80mLof water,and swirl to dissolve.Dilute with water to volume,and mix.Pass a portion of this solution through a glass-fiber filter,discarding the first 5mLof the filtrate.[NOTE—Prepare this solution and chromatograph it as directed under Chromatographic system before preparing the Standard preparation and the Assay preparation.]

Standard preparation— Prepare a solution having known concentrations of about 3.25mg of USP Acetaminophen RS,3.25Jmg of USP Dichloralphenazone RS,and 3.25J¢mg of USP Isometheptene Mucate RSper mL,Jbeing the ratio of the labeled amount,in mg,of dichloralphenazone to the labeled amount,in mg,of acetaminophen per Capsule,and J¢being the ratio of the labeled amount,in mg,of isometheptene mucate to the labeled amount,in mg,of acetaminophen per Capsule.

Assay preparation— Transfer 20Capsules,accurately counted,to a 2000-mLvolumetric flask,add about 1900mLof water,and heat on a steam bath until the Capsules disintegrate.While still warm,shake by mechanical means for 15minutes,sonicate for 15minutes,and allow to cool to ambient temperature.Dilute with water to volume,and mix.Pass a portion of this mixture through a glass-fiber filter,discarding the first 5mLof the filtrate.

Chromatographic system(see Chromatography á621ñ)— The liquid chromatograph is equipped with a variable wavelength detector and a 4.6-mm ×25-cm column that contains 5-µm packing L7.The flow rate is about 1mLper minute.Chromatograph 10µLof the Chromatographic test solution,and record the chromatogram to confirm that all three analytes are detected and recorded acceptable levels of sensitivity.The wavelength and sensitivity settings are at 280nm and 3.0absorbance units full-scale until the acetaminophen peak has been recorded,then at 243nm and 0.5absorbance units full-scale until the dichloralphenazone peak has been recorded,and then at 190nm and 0.5absorbance units full-scale until the isometheptene mucate peak has been recorded.Chromatograph the Standard preparation,and record the peak responses as directed for Procedure:the relative standard deviation for replicate injections determined from each analyte peak 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 major peaks.Calculate the quantity,in mg,of acetaminophen (C8H9NO2),dichloralphenazone (C15H18Cl6N2O5),and isometheptene mucate [(C9H19N)2·C6H10O8)]in the portion of Capsules 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 responses of the corresponding analyte peaks obtained from the Assay preparationand the Standard preparation,respectively.