Test solution: a mixture of methylene chloride and methanol (2:1).

Standard solutions: a mixture of methylene chloride and methanol (2:1).

Adsorbent: a 0.25-mm layer of chromatographic silica gel.

Eluant: a mixture of chloroform,tetrahydrofuran,cyclohexane,and ammonium hydroxide (18:18:13:1).

Visualization: 22.

Phosphate buffer— Dissolve 2.18g of monobasic potassium phosphate and 4.18g of dibasic potassium phosphate in 900mLof water,dilute with water to 1000mL,and mix.

Mobile phase— Prepare a filtered and degassed mixture of methanol and Phosphate buffer(3:1),making adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Standard preparation— Dissolve an accurately weighed quantity of USP Butoconazole Nitrate RSin Mobile phase,and quantitatively dilute with Mobile phaseto obtain a solution having a known concentration of about 0.2mg per mL.

Assay preparation— Transfer about 20mg of Butoconazole Nitrate,accurately weighed,to a 100-mLvolumetric flask,and dissolve in Mobile phase.Dilute with Mobile phaseto volume,mix,and filter.

Chromatographic system (see Chromatography á621ñ)—The liquid chromatograph is equipped with a 229-nm detector and a 4.6-mm ×25-cm column that contains packing L1and is maintained at 40.The flow rate is about 2mLper 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 2800theoretical plates;the tailing factor for the analyte peak is not more than 1.5;and the relative standard deviation for replicate injections is not more than 1.5%.

Procedure— Separately inject equal volumes (about 10µL)of the Standard preparationand the Assay preparationinto the chromatograph,record the chromatograms,and measure the responses for the major peaks.Calculate the quantity,in mg,of C19H17Cl3N2S·HNO3in the portion of Butoconazole Nitrate taken by the formula: in which Cis the concentration,in mg per mL,of USP Butoconazole Nitrate RSin the Standard preparation;and rUand rSare the peak responses obtained from the Assay preparationand the Standard preparation,respectively.