A: Infrared Absorption 197K.

B: Ultraviolet Absorption 197U—

Solution: 800 µg per mL.

Medium: 0.1 N hydrochloric acid in methanol (1 in 10).

C: Shake 10 mg with 5 mL of water, and cool the resulting suspension in ice. Keeping the suspension cool, add 0.4 mL of potassium chloride solution (1 in 10), 0.1 mL of diphenylamine TS, and dropwise, with shaking, 5 mL of sulfuric acid: an intense blue color develops.

Standard preparation— Dissolve an accurately weighed quantity of USP Econazole Nitrate RS in methanol to obtain a solution containing 75 µg per mL.

Test preparation— Dissolve an accurately weighed quantity of Econazole Nitrate in methanol to obtain a solution containing 20 mg per mL.

Procedure— Apply separately 20 µL of the Test preparation and 20 µL of the Standard preparation to a suitable thin-layer chromatographic plate (see Chromatography 621) coated with a 0.25-mm layer of chromatographic silica gel. Allow the spots to dry, place the plate in a chromatographic chamber, and develop the chromatograms in a solvent system consisting of a mixture of 1,4-dioxane, toluene, and 13.5 M ammonium hydroxide (60:40:1) 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 in a current of air. Expose the plate to iodine vapors for 1 hour, and air-dry until the iodine has dissipated. Compare the intensities of any secondary spots observed in the chromatogram of the Test preparation with that of the principal spot in the chromatogram of the Standard preparation: no individual secondary spots in the chromatogram of the Test preparation are larger or more intense than the principal spot produced by the Standard preparation, corresponding to not more than 0.375%, and the total of all such secondary spots observed is not more than 2.0%.