A: The retention time of the major peak in the chromatogram of the Assay preparationcorresponds to that in the chromatogram of the Standard preparation,as obtained in the Assay.

B: Triturate an amount of the contents of the Capsules,equivalent to about 50mg of acetaminophen,with 50mLof methanol,and filter:the clear filtrate (test solution)responds to the Thin-layer Chromatographic Identification Test á201ñ,a solvent system consisting of a mixture of methylene chloride and methanol (4:1)being used.

Medium: water;900mL.

Apparatus 2: 50rpm.

Time: 45minutes.

Procedure— Determine the amount of C8H9NO2dissolved from UVabsorption at the wavelength of maximum absorbance at about 249nm on filtered portions of the solution under test,suitably diluted with Dissolution Medium,if necessary,in comparison with a Standard solution having a known concentration of USP Acetaminophen RSin the same Medium.

Tolerances— Not less than 75%(Q)of the labeled amount of C8H9NO2is dissolved in 45minutes.

Mobile phase— Prepare a suitable degassed mixture of water and methanol (3:1).Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Standard preparation— Dissolve an accurately weighed quantity of USP Acetaminophen RSin Mobile phaseto obtain a solution having a known concentration of about 0.01mg per mL.

Assay preparation— Weigh the contents of not fewer than 20Capsules,and calculate the average weight of the contents of each Capsule.Mix the combined contents of the Capsules,and transfer an accurately weighed portion,equivalent to about 100mg of acetaminophen,to a 200-mLvolumetric flask.Add about 100mLof Mobile phase,and shake by mechanical means for 10minutes.Dilute with Mobile phaseto volume,and mix.Transfer 5.0mLof this solution to a 250-mLvolumetric flask,dilute with Mobile phaseto volume,and mix.Pass a portion of this solution through a filter having a 0.5-µm or finer porosity,discarding the first 10mLof the filtrate.Use the clear filtrate as the Assay preparation.

Chromatographic system— The liquid chromatograph is equipped with a 243-nm detector and a 3.9-mm ×30-cm column that contains packing L1.The flow rate is about 1.5mLper minute.Chromatograph the Standard preparation,and record the responses as directed for Procedure:the column efficiency is not less than 1000theoretical plates;the tailing factor 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 major peaks.Calculate the quantity,in mg,of acetaminophen (C8H9NO2)in the portion of Capsules taken by the formula: in which Cis the concentration,in mg per mL,of USP Acetaminophen RSin the Standard preparation;and rUand rSare the acetaminophen peak responses obtained from the Assay preparationand the Standard preparation,respectively.