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

B: [Caution—Avoid contact with o-tolidine when performing this test, and conduct the test in a well-ventilated hood. ] Weigh and finely powder not fewer than 5 Tablets. Transfer a portion of the powder, equivalent to 100 mg of rimantadine hydrochloride, to a 10-mL centrifuge tube, add 2 mL of 1 N sodium hydroxide, and mix. Add 2 mL of chloroform, and mix on a vortex mixer for 1 minute. Allow the layers to separate, and use the organic layer as the test solution. Separately apply 10 µL of the test solution and 10 µL of a Standard solution of USP Rimantadine Hydrochloride RS, similarly prepared, to a suitable thin-layer chromatographic plate (see Chromatography 621) coated with a 0.25-mm layer of chromatographic silica gel. Place the plate in a low-actinic glass chromatographic chamber, and develop the chromatogram in a solvent system consisting of a mixture of ethyl acetate, methanol, and ammonium hydroxide (80:10:4) until the solvent front has moved about three-fourths of the length of the plate. Remove the plate from the chamber, dry it in a stream of hot air, and then heat in an oven at 105 for 30 minutes. Allow the plate to cool to room temperature. Place the dried plate in an atmosphere of chlorine, prepared from a mixture of 1.5% potassium permanganate solution and 3 N hydrochloric acid (1:1), for about 90 minutes. Remove the plate, and allow it to air-dry for 60 minutes. Prepare a spray reagent as follows. Dissolve 160 mg of o-tolidine in 30 mL of glacial acetic acid, dilute with water to 500 mL, add 1 g of potassium iodide, and mix until the potassium iodide is dissolved. Locate the spots on the plate by spraying with the spray reagent: the RF value of the principal spot in the chromatogram of the test solution corresponds to that of the principal spot obtained from the Standard solution.

Medium: water; 900 mL.

Apparatus 2: 50 rpm.

Time: 30 minutes.

Procedure— Determine the amount of C12H21N·HCl dissolved, employing the procedure set forth in the Assay.

Tolerances— Not less than 80% (Q) of the labeled amount of C12H21N·HCl is dissolved in 30 minutes.

(Official January 1, 2007)

Internal standard solution, Standard preparation, and Chromatographic system— Proceed as directed in the Assay under Rimantadine Hydrochloride.

Assay preparation— Weigh and finely powder not fewer than 20 Tablets. Transfer an accurately weighed portion of the powder, equivalent to about 40 mg of rimantadine hydrochloride, to a 50-mL centrifuge tube, add 15 mL of 1 N sodium hydroxide, and mix. Add 25.0 mL of Internal standard solution, and shake by mechanical means for about 15 minutes. Allow the layers to separate, and filter a portion of the top hexane layer through anhydrous sodium sulfate. Use the clear filtrate as the Assay preparation.

Procedure— Separately inject equal volumes (about 2 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 rimantadine hydrochloride (C12H21N·HCl) in the portion of Tablets taken by the formula: in which C is the concentration, in mg per mL, of USP Rimantadine Hydrochloride RS in the Standard preparation; and RU and RS are the ratios of the rimantadine peak response to the n-eicosane peak response obtained from the Assay preparation and the Standard preparation, respectively.