Transfer a volume of Oral Suspension, equivalent to about 240 mg of acetaminophen, to a separator, add 50 mL of ethyl acetate, and shake. Filter the ethyl acetate extract through a funnel containing glass wool and about 10 g of anhydrous sodium sulfate. Collect the filtrate in a beaker, and evaporate on a steam bath to dryness. Dry the residue in vacuum over silica gel: the crystals so obtained respond to Identification
Add the following:
Limit of 4-aminophenol
Prepare a mixture of water, methanol, and formic acid (425:75:2).
Prepare a filtered and degassed mixture of 0.01 M sodium butanesulfonate in Diluent.
Make adjustments if necessary (see System Suitability
under Chromatography 621 )
Dissolve an accurately weighed quantity of USP 4-Aminophenol RS
, and dilute quantitatively, and stepwise if necessary, with Mobile phase
to obtain a solution having a known concentration of about 24 µg per mL.
Transfer an accurately measured portion of Oral Suspension, equivalent to about 120 mg of acetaminophen, to a 25-mL volumetric flask, dissolve in and dilute with Mobile phase to volume, and mix.
Chromatographic system (see Chromatography 621)
The liquid chromatograph is equipped with a 272-nm detector and a 4.6-mm × 20-cm column that contains 10-µm packing L1. The flow rate is about 2.0 mL per minute. Chromatograph the Standard solution
and the Test solution,
and record the peak areas as directed for 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 areas for the major peaks: the peak area of 4-aminophenol obtained from the Test solution
is not greater than the corresponding peak area obtained from the Standard solution.USP29
Mobile phase, Standard preparation, and Chromatographic system
Proceed as directed in the Assay
under Acetaminophen Capsules
Transfer an accurately measured volume of Oral Suspension, previously well-shaken, equivalent to about 100 mg of acetaminophen, to a 200-mL volumetric flask, add about 100 mL of Mobile phase, and shake by mechanical means for 10 minutes. Dilute with Mobile phase to volume, and mix. Transfer 5.0 mL of this solution to a 250-mL volumetric flask, dilute with Mobile phase to volume, and mix. Pass a portion of this solution through a filter having a 0.5-µm or finer porosity, discarding the first 10 mL of the filtrate. Use the clear filtrate as the Assay preparation.
Proceed as directed for Procedure
in the Assay
under Acetaminophen Capsules
. Calculate the quantity, in mg, of acetaminophen (C8
) in each mL of the Oral Suspension taken by the formula:
10,000(C/V)(rU / rS)
in which C
is the concentration, in mg per mL, of USP Acetaminophen RS
in the Standard preparation; V
is the volume, in mL, of Oral Suspension taken; and rU
are the acetaminophen peak responses obtained from the Assay preparation
and the Standard preparation,