A: Infrared Absorption 197K—Use a portion of powdered Tablets.

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

Medium: simulated gastric fluid TS (without enzyme); 900 mL.

Apparatus 2: 50 rpm.

Times: 15 minutes, 1 hour, and 3 hours.

Procedure— Determine the amount of C8H9NO2 dissolved from UV absorbances at 243 nm, using a filtered portion of the solution under test in comparison with a Standard solution having a known concentration of USP Acetaminophen RS in the same Medium.

Tolerances— The percentages of the labeled amount of C8H9NO2 dissolved at the times specified conform to Acceptance Table 1.

FOR GELATIN-COATED TABLETS—

(Official January 1, 2007)

Mobile phase— Prepare a mixture of water and phosphoric acid (9:1). Combine 1 mL of this solution with a mixture of water and methanol (700:300). Filter and degas. Make adjustments if necessary (see System Suitability under Chromatography 621).

Standard preparation— Dissolve an accurately weighed quantity of USP Acetaminophen RS in methanol, and dilute quantitatively, and stepwise if necessary, with Mobile phase to obtain a solution having a known concentration of about 0.65 mg per mL.

Assay preparation— Transfer 10 Tablets into a 250-mL volumetric flask containing 50 mL of water and a magnetic stir bar. Stir at least 30 minutes or until the coating has dissolved. Add 150 mL of methanol, and stir for 45 minutes. Tablet cores should be disintegrated at least 15 minutes prior to ending the stirring. Remove the magnetic stir bar and rinse into the flask with methanol. Dilute with methanol to volume, mix well, and centrifuge. Transfer 5 mL of the clear supernatant to a 200-mL volumetric flask, dilute with Mobile phase to volume, and mix well.

Chromatographic system (see Chromatography 621)— The liquid chromatograph is equipped with a 295-nm detector and a 3.9-mm × 15-cm column that contains packing L1. The flow rate is about 2.0 mL per minute. Chromatograph the Standard preparation, and record the peak responses as directed for Procedure: the tailing factor is not more than 3.0, and the relative standard deviation for replicate injections is not more than 2.0%.

Procedure— Separately inject equal volumes (about 20 µL) of the Standard preparation and the Assay preparation into the chromatograph, record the chromatograms, and measure the responses for the major peaks. Calculate the quantity, in mg, of acetaminophen (C8H9NO2) in each Tablet taken by the formula: in which C is the concentration, in mg per mL, of USP Acetaminophen RS in the Standard preparation; and rU and rS are the acetaminophen peak responses obtained from the Assay preparation and the Standard preparation, respectively.