A: Infrared Absorption 197K.

B: A solution of it responds to the ferrous sulfate-sulfuric acid test for Nitrate 191.

Test solution— Prepare a solution of it, in a mixture of dichloromethane and methanol (2:1), having an accurately known concentration of 20 mg per mL.

Standard solutions— Dissolve USP Sulconazole Nitrate RS in a mixture of dichloromethane and methanol (2:1), and dilute quantitatively with the same mixture to obtain separate solutions having accurately known concentrations of 0.02, 0.1, 0.2, and 0.4 mg per mL, respectively.

Eluant: a mixture of methylene chloride, cyclohexane, and diethylamine (50:45:5).

Visualization: 22.

Mobile phase— Dissolve 1.9 g of sodium 1-pentanesulfonate in 300 mL of water, add 700 mL of methanol, and mix. Adjust with 2 N sulfuric acid to an apparent pH of 3.8 ± 0.1, filter, and degas. Make adjustments if necessary (see System Suitability under Chromatography 621).

Standard preparation— Dissolve an accurately weighed quantity of USP Sulconazole Nitrate RS in Mobile phase, and dilute quantitatively, and stepwise if necessary, with Mobile phase to obtain a solution having a known concentration of about 0.2 mg per mL.

Assay preparation— Transfer about 20 mg of Sulconazole Nitrate, accurately weighed, to a 100-mL volumetric flask, dissolve in Mobile phase, dilute with Mobile phase to volume, and mix.

Chromatographic system (see Chromatography 621)—The liquid chromatograph is equipped with a 230-nm detector and a 4.6-mm × 25-cm column that contains packing L1 and is maintained at 40 ± 1.0. The flow rate is about 2 mL per minute. Chromatograph the Standard preparation, and record the peak responses as directed for Procedure: the column efficiency determined from the analyte peak is not less than 1500 theoretical plates, the tailing factor for the sulconazole nitrate peak is not more than 2.3, and the relative standard deviation for replicate injections is not more than 1.5%.

Procedure— Separately inject equal volumes (about 10 µL) of the Standard preparation and the Assay preparation into the chromatograph, record the chromatograms, and measure the responses for the major peaks. Calculate the quantity, in mg, of C18H15Cl3N2S·HNO3 in the portion of Sulconazole Nitrate taken by the formula: in which C is the concentration, in mg per mL, of USP Sulconazole Nitrate RS in the Standard preparation, and rU and rS are the peak responses obtained from the Assay preparation and the Standard preparation, respectively.