A: Infrared Absorption 197M.

B: Prepare a Test preparation by dissolving 40 mg of Clemastine Fumarate in 2.0 mL of dilute alcohol (8 in 10) with slight warming. Similarly prepare a Standard preparation by dissolving 50 mg of fumaric acid in 10.0 mL of dilute alcohol (8 in 10). Separately apply 5-µL portions of the Test preparation and the Standard preparation to a suitable thin-layer chromatographic plate (see Chromatography 621) coated with a 0.25-mm layer of chromatographic silica gel mixture, and dry the spots with the aid of a current of air. Develop the chromatogram in a solvent system consisting of a mixture of diisopropyl ether, formic acid, and water (70:25:5) until the solvent front has moved about three-fourths of the length of the plate. Remove the plate from the developing chamber, mark the solvent front, dry at 100 for 30 minutes, cool, and spray the plate with 0.1 M potassium permanganate. Dry briefly with the aid of a current of warm air, and examine the chromatogram: the principal spot obtained from the Test preparation corresponds in RF value, color, and intensity to that obtained from the Standard preparation.

Test solution: 10 mg per mL, in methanol.

Spray reagent— Dissolve 850 mg of bismuth subnitrate in a mixture of 10 mL of glacial acetic acid and 40 mL of water, and mix (Solution A). Dissolve 8 g of potassium iodide in 20 mL of water (Solution B). Mix 5.0 of Solution A, 5.0 mL of Solution B, and 20 mL of glacial acetic acid in a 100-mL volumetric flask, dilute with water to volume, and mix.

Standard preparation— Dissolve a suitable quantity of USP Clemastine Fumarate RS in a mixture of chloroform and methanol (1:1) to obtain a solution having a known concentration of 20 mg per mL. Dilute portions of this solution quantitatively with the mixture of chloroform and methanol (1:1) to prepare 5 Comparison solutions having known concentrations of 0.10, 0.08, 0.06, 0.04, and 0.02 mg per mL, respectively (0.5%, 0.4%, 0.3%, 0.2%, and 0.1% of the Standard preparation, respectively).

Test preparation— Dissolve 100 mg of Clemastine Fumarate in 5.0 mL of a mixture of chloroform and methanol (1:1), and mix.

Procedure— Separately apply 5-µL portions of the Standard preparation, each of the 5 Comparison solutions, and the Test preparation to a suitable thin-layer chromatographic plate (see Chromatography 621) coated with a 0.25-mm layer of chromatographic silica gel mixture. Allow the spots to dry, and develop the chromatogram in a solvent system consisting of a mixture of chloroform, methanol, and ammonium hydroxide (90:10:1) until the solvent front has moved about three-fourths of the length of the plate. Remove the plate from the developing chamber, mark the solvent front, and dry the plate at room temperature with the aid of a current of air. Locate the spots on the plate by spraying first with Spray reagent, then with 3% hydrogen peroxide: the principal spot obtained from the Test preparation corresponds in RF value, color, and intensity to that obtained from the Standard preparation; the sum of the intensities of any secondary spots, if present in the chromatogram from the Test preparation, corresponds to not more than 1.0%; and the intensities of any secondary spots do not exceed 0.5% of that of the principal spot in the chromatogram from the Standard preparation on the basis of comparison with spots obtained from the Comparison solutions.