Dibasic potassium phosphate solution andMobile phase— Prepare as directed in the Assayunder Clotrimazole.

Internal standard solution— Transfer about 66mg of testosterone propionate to a 100-mLvolumetric flask,dissolve in 75mLof methanol,dilute with Dibasic potassium phosphate solutionto volume,and mix.

Standard preparation— Transfer about 50mg of USP Clotrimazole RSto a 50-mLvolumetric flask,add 5.0mLof Internal standard solution,dilute with Mobile phaseto volume,and mix.

Resolution solution— Prepare a solution of USP Clotrimazole Related Compound A RSin methanol having a concentration of about 0.2mg per mL.Transfer 12mLof this solution to a 25-mLvolumetric flask,add 4mLof Dibasic potassium phosphate solutionand 3mLof Standard preparation,dilute with Mobile phaseto volume,and mix.

Assay preparation— Transfer an accurately measured volume of Topical Solution,equivalent to about 50mg of clotrimazole,to a 50-mLvolumetric flask,add 5.0mLof Internal standard solution,dilute with Mobile phaseto volume,and mix.

Chromatographic system (see Chromatography á621ñ)— The liquid chromatograph is equipped with a 254-nm detector and a 2.1-mm ×6-cm guard column that contains 10-µm packing L7and a 3.9-mm ×30-cm analytical column that contains 10-µm packing L1.The flow rate is about 1mLper minute.Chromatograph the Resolution solution,and record the peak responses as directed for Procedure:the relative retention times are about 0.9for clotrimazole related compound Aand 1.0for clotrimazole;and the resolution,R,between clotrimazole related compound Aand clotrimazole is not less than 1.2.Chromatograph the Standard preparation,and record the peak responses as directed for Procedure:the relative retention times are about 1.0for clotrimazole and 1.5for testosterone propionate;and the relative standard deviation for replicate injections is not more than 2.0%.

Procedure— Separately inject equal volumes (about 20µL)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 clotrimazole (C22H17ClN2)in each mLof Topical Solution taken by the formula: in which Cis the concentration,in mg per mL,of USP Clotrimazole RSin the Standard preparation;Vis the volume,in mL,of Topical Solution taken;and RUand RSare the peak response ratios of clotrimazole to testosterone propionate obtained from the Assay preparationand the Standard preparation,respectively.