Dibasic potassium phosphate solution and Mobile phase— Prepare as directed in the Assay under Clotrimazole.

Internal standard solution, Standard preparation, Resolution solution, and Chromatographic system— Prepare as directed in the Assay under Clotrimazole Topical Solution.

Assay preparation— Weigh and finely powder not fewer than 10 Vaginal Inserts. Transfer an accurately weighed portion of the powder, equivalent to about 100 mg of clotrimazole, to a 50-mL, screw-capped centrifuge tube, add 10.0 mL of Internal standard solution and 15 mL of Mobile phase, rotate for 15 minutes, and centrifuge for 10 minutes. Using a suitable syringe, transfer the supernatant to a 100-mL volumetric flask. Rinse the syringe with 25 mL of Mobile phase, adding the rinsings to the centrifuge tube. Rotate the centrifuge tube for 15 minutes, and centrifuge for 10 minutes. Using a suitable syringe, transfer the supernatant to the 100-mL volumetric flask. Rinse the syringe with 25 mL of Mobile phase, and add the washings to the 100-mL volumetric flask. Dilute with Mobile phase to volume, and mix.

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 the portion of Vaginal Inserts taken by the formula: in which C is the concentration, in mg per mL, of USP Clotrimazole RS in the Standard preparation; and RU and RS are the peak response ratios of clotrimazole to testosterone propionate obtained from the Assay preparation and the Standard preparation, respectively.