A: The retention time of the rimantadine peak in the chromatogram of the Assay preparationcorresponds 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 5Tablets.Transfer a portion of the powder,equivalent to 100mg of rimantadine hydrochloride,to a 10-mLcentrifuge tube,add 2mLof 1Nsodium hydroxide,and mix.Add 2mLof chloroform,and mix on a vortex mixer for 1minute.Allow the layers to separate,and use the organic layer as the test solution.Separately apply 10µLof the test solution and 10µLof a Standard solution of USP Rimantadine Hydrochloride RS,similarly prepared,to a suitable thin-layer chromatographic plate (see Chromatography á621ñ)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 105for 30minutes.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 3Nhydrochloric acid (1:1),for about 90minutes.Remove the plate,and allow it to air-dry for 60minutes.Prepare a spray reagent as follows.Dissolve 160mg of o-tolidine in 30mLof glacial acetic acid,dilute with water to 500mL,add 1g of potassium iodide,and mix until the potassium iodide is dissolved.Locate the spots on the plate by spraying with the spray reagent:the RFvalue 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;900mL.

Apparatus 2: 50rpm.

Time: 30minutes.

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 30minutes.

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

Assay preparation— Weigh and finely powder not fewer than 20Tablets.Transfer an accurately weighed portion of the powder,equivalent to about 40mg of rimantadine hydrochloride,to a 50-mLcentrifuge tube,add 15mLof 1Nsodium hydroxide,and mix.Add 25.0mLof Internal standard solution,and shake by mechanical means for about 15minutes.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 2µL)of the Standard preparationand the Assay preparationinto 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 Cis the concentration,in mg per mL,of USP Rimantadine Hydrochloride RSin the Standard preparation;and RUand RSare the ratios of the rimantadine peak response to the n-eicosane peak response obtained from the Assay preparationand the Standard preparation,respectively.