Clotrimazole Topical Solution
» Clotrimazole Topical Solution is a solution of Clotrimazole in a suitable nonaqueous, hydrophilic solvent. It contains not less than 90.0 percent and not more than 115.0 percent of the labeled amount of clotrimazole (C22H17ClN2).
Packaging and storage Preserve in tight containers, at a temperature between 2 and 30.
USP Reference standards 11
USP Clotrimazole Related Compound A RS
Identification Transfer a volume of Topical Solution, equivalent to about 10 mg of clotrimazole, to a screw-capped, 50-mL centrifuge tube, and add 5 mL of dilute ammonium hydroxide (1 in 100) and 10 mL of chloroform. Shake vigorously, centrifuge to obtain a clear chloroform phase, and proceed as directed in the Identification test under Clotrimazole Cream.
Dibasic potassium phosphate solution and Mobile phase Prepare as directed in the Assay under Clotrimazole.
Internal standard solution Transfer about 66 mg of testosterone propionate to a 100-mL volumetric flask, dissolve in 75 mL of methanol, dilute with Dibasic potassium phosphate solution to volume, and mix.
Standard preparation Transfer about 50 mg of USP Clotrimazole RS to a 50-mL volumetric flask, add 5.0 mL of Internal standard solution, dilute with Mobile phase to volume, and mix.
Resolution solution Prepare a solution of USP Clotrimazole Related Compound A RS in methanol having a concentration of about 0.2 mg per mL. Transfer 12 mL of this solution to a 25-mL volumetric flask, add 4 mL of Dibasic potassium phosphate solution and 3 mL of Standard preparation, dilute with Mobile phase to volume, and mix.
Assay preparation Transfer an accurately measured volume of Topical Solution, equivalent to about 50 mg of clotrimazole, to a 50-mL volumetric flask, add 5.0 mL of Internal standard solution, dilute with Mobile phase to volume, and mix.
Chromatographic system (see Chromatography 621) The liquid chromatograph is equipped with a 254-nm detector and a 2.1-mm × 6-cm guard column that contains 10-µm packing L7 and a 3.9-mm × 30-cm analytical column that contains 10-µm packing L1. The flow rate is about 1 mL per minute. Chromatograph the Resolution solution, and record the peak responses as directed for Procedure: the relative retention times are about 0.9 for clotrimazole related compound A and 1.0 for clotrimazole; and the resolution, R, between clotrimazole related compound A and 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 1.0 for clotrimazole and 1.5 for testosterone propionate; and the relative standard deviation for replicate injections is not more than 2.0%.
Procedure Separately inject equal volumes (about 20 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 clotrimazole (C22H17ClN2) in each mL of Topical Solution taken by the formula:
50(C / V)(RU / RS)in which C is the concentration, in mg per mL, of USP Clotrimazole RS in the Standard preparation; V is the volume, in mL, of Topical Solution taken; and RU and RS are the peak response ratios of clotrimazole to testosterone propionate obtained from the Assay preparation and the Standard preparation, respectively.
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USP35NF30 Page 2744Pharmacopeial Forum: Volume No. 27(2) Page 2133