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: Transfer a portion of Suppositories,equivalent to about 20mg of acetaminophen,to a beaker,add 20mLof methanol,and heat on a steam bath until melted.Remove the beaker from the steam bath,allow to cool with occasional stirring,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.

Mobile phase,Standard preparation,and Chromatographic system— Proceed as directed in the Assayunder Acetaminophen Capsules.

Assay preparation— Tare a small dish and a glass rod,place in the dish not fewer than 5Suppositories,heat gently on a steam bath until melted,then stir,cool while stirring,and weigh.Transfer an accurately weighed portion of the mass,equivalent to about 100mg of acetaminophen,to a separator,add 30mLof solvent hexane,and mix to dissolve.Add 30mLof water,shake gently,and allow the phases to separate.[NOTE—If an emulsion forms,allow sufficient time for it to separate.]Transfer the aqueous layer to a 200-mLvolumetric flask,wash the solvent hexane in the separator with three 30-mLportions of water,adding the washings to the volumetric flask,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.

Procedure— Proceed as directed for Procedurein the Assayunder Acetaminophen Capsules.Calculate the quantity,in mg,of acetaminophen (C8H9NO2)in each Suppository taken by the formula: in which Cis the concentration,in mg per mL,of USP Acetaminophen RSin the Standard preparation;Ais the average weight,in mg,of each Suppository taken;Wis the weight,in mg,of the Suppository mass taken;and rUand rSare the acetaminophen peak responses obtained from the Assay preparationand the Standard preparation,respectively.