A: 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.

B: Dilute a portion of Oral Solution with methanol to obtain a solution containing about 1 mg of acetaminophen per mL. This test solution responds to the Thin-Layer Chromatographic Identification Test 201, a solvent system consisting of a mixture of methylene chloride and methanol (4:1) being used.

for oral solution packaged in single-unit containers: meets the requirements.

for oral solution packaged in multiple-unit containers: meets the requirements.

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

Assay preparation— Transfer an accurately measured volume of Oral Solution, equivalent to about 500 mg of acetaminophen, to a 250-mL volumetric flask, dilute with Mobile phase to volume, and mix. Transfer 5.0 mL of this solution to a second 250-mL volumetric flask, dilute with Mobile phase to volume, and mix. Transfer 25.0 mL of this solution to a 100-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.

Procedure— Proceed as directed for Procedure in the Assay under Acetaminophen Capsules. Calculate the quantity, in mg, of acetaminophen (C8H9NO2) in each mL of the Oral Solution taken by the formula: 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 Solution taken; and rU and rS are the acetaminophen peak responses obtained from the Assay preparation and the Standard preparation, respectively.