» Clofazimine contains not less than 98.5 percent and not more than 101.5 percent of C27H22Cl2N4, calculated on the dried basis.
Packaging and storage Preserve in tight, light-resistant containers, at room temperature.
A: Infrared Absorption 197S: 5% solution in methylene chloride.
B: The RF value of the principal spot observed in the chromatogram of the Test preparation corresponds to that of Standard preparation A as obtained in the test for Chromatographic purity.
Loss on drying 731 Dry it at 105 for 3 hours: it loses not more than 0.5% of its weight.
Residue on ignition 281 not more than 0.1%.
Standard preparations Dissolve an accurately weighed quantity of USP Clofazimine RS in methylene chloride, and mix to obtain Standard preparation A having a known concentration of about 0.5 mg per mL. Dilute portions of Standard preparation A quantitatively with methylene chloride to obtain Standard preparations B and C having known concentrations of 0.25 and 0.1 mg per mL, respectively.
Test preparation Dissolve an accurately weighed quantity of Clofazimine in methylene chloride to obtain a solution having a known concentration of about 50 mg per mL.
Ammonia solution Pipet 1 mL of ammonium hydroxide into a 100-mL volumetric flask, dilute with water to volume, and mix. [notePrepare this solution fresh daily.]
Chromatographic plate Use a thin-layer chromatographic plate (see Chromatography 621) coated with a 0.25-mm layer of chromatographic silica gel mixture. Immediately before use, expose the plate to ammonia vapors for 30 minutes by suspending the plate in a tank containing a shallow layer of approximately 25 mL of Ammonia solution. [notePrevent the plate from coming into contact with the liquid.]
Procedure Separately apply 5 µL of the Test preparation and 5 µL of each Standard preparation to the Chromatographic plate. Allow the spots to dry, and develop the chromatogram in a solvent system consisting of a mixture of methylene chloride and n-propyl alcohol (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 air-dry. Examine the plate under short-wavelength UV light, and compare the intensities of any secondary spots observed in the chromatogram of the Test preparation with those of the principal spots in the chromatograms of the Standard preparations: no secondary spot from the chromatogram of the Test preparation is larger or more intense than the principal spot obtained from Standard preparation A (1.0%), and the sum of the intensities of the secondary spots obtained from the Test preparation corresponds to not more than 2.0%.
Assay Dissolve about 300 mg of Clofazimine, accurately weighed, in 5 mL of chloroform, with the aid of heat if necessary. Add 20 mL of acetone and 5 mL of glacial acetic acid, and titrate with 0.1 N perchloric acid VS in glacial acetic acid, determining the endpoint potentiometrically, using a glass electrode and a calomel electrode with a saturated solution of potassium chloride as the bridge fluid and agar gel as the bridge. Perform a blank determination, and make any necessary correction. Each mL of 0.1 N perchloric acid is equivalent to 47.34 mg of C27H22Cl2N4.
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USP32NF27 Page 1980