A: Infrared Absorption 197K.

B: Ultraviolet Absorption 197U—

Mobile phase— Prepare a filtered and degassed mixture of 0.2 M ammonium acetate, methanol, and acetonitrile (38:32:30). Make adjustments if necessary (see System Suitability under Chromatography 621).

Resolution solution— Dissolve accurately weighed quantities of USP Miconazole Nitrate RS and USP Econazole Nitrate RS in Mobile phase to obtain a solution having known concentrations of about 25 µg of each per mL.

Test solution— Transfer 100 mg of Miconazole Nitrate to a 10-mL volumetric flask, add Mobile phase to volume, and mix.

Diluted test solution— Dilute an accurately measured volume of the Test solution quantitatively, and stepwise if necessary, with Mobile phase to obtain a solution containing 25 µg of miconazole nitrate per mL.

Chromatographic system (see Chromatography 621)— The liquid chromatograph is equipped with a 235-nm detector and a 4.6-mm × 10-cm column that contains 3-µm packing L1. The flow rate is about 2 mL per minute. Chromatograph the Resolution solution, and record the peak responses as directed for Procedure: the relative retention times are about 0.5 for econazole and 1.0 for miconazole; the resolution, R, between econazole and miconazole is not less than 10; and the relative standard deviation for replicate injections is not more than 2.0%.

Procedure— Separately inject equal volumes (about 10 µL) of the Test solution and Diluted test solution into the chromatograph, record the chromatograms for a time that is 1.2 times the retention time of the main peak, and measure the responses of all peaks, excluding the peak representing nitrate ion and any peak producing a response less than 0.2 times the response of the main peak. The response of any individual peak, other than the main peak in the chromatogram of the Test solution, is not greater than that of the main peak in the chromatogram of the Diluted test solution (0.25%), and the sum of the responses of all peaks, other than the main peak in the chromatogram of the Test solution, is not greater than twice the response of the main peak in the chromatogram of the Diluted test solution (0.5%).