Tolnaftate Topical Powder
» Tolnaftate Topical Powder contains not less than 90.0 percent and not more than 110.0 percent of the labeled amount of C19H17NOS.
Packaging and storage— Preserve in tight containers.
Identification— Evaporate the 5-mL portion of the methanol solution, reserved from the Assay preparation, on a steam bath just to dryness, and dissolve the residue in 1 mL of alcohol. Using this as the test solution, proceed as directed in Identification test C under Tolnaftate: the specified result is observed.
Minimum fill 755: meets the requirements.
Mobile phase— Prepare a filtered and degassed mixture of acetonitrile and water (2:1). Make adjustments if necessary (see System Suitability under Chromatography 621).
Internal standard solution— Dissolve progesterone in methanol to obtain a solution containing about 1 mg per mL.
Standard preparation— Dissolve an accurately weighed quantity of USP Tolnaftate RS in methanol to obtain a solution having a known concentration of about 0.22 mg per mL. Transfer 20.0 mL of this solution to a 50-mL volumetric flask, add 5.0 mL of Internal standard solution, dilute with methanol to volume, and mix to obtain a solution having a known concentration of about 0.088 mg of USP Tolnaftate RS per mL.
Assay preparation— Transfer an accurately weighed quantity of Topical Powder, equivalent to about 5 mg of tolnaftate, to a screw-capped, 50-mL centrifuge tube. Add 25.0 mL of methanol, place the cap on the tube, rotate on a rotating device for 10 minutes, and centrifuge at about 2000 rpm for 5 minutes. Pass the supernatant through a 0.45-µm porosity filter, and transfer 20.0 mL of the filtrate to a 50-mL volumetric flask, retaining the remaining portion of the filtrate (about 5 mL) for the Identification test. Add 5.0 mL of Internal standard solution to the volumetric flask, dilute with methanol to volume, and mix.
Chromatographic system (see Chromatography 621)—The liquid chromatograph is equipped with a 254-nm detector and a 4-mm × 30-cm column that contains 10-µm packing L1. The flow rate is about 1 mL per minute. Chromatograph the Standard preparation, and record the peak responses as directed for Procedure: the resolution, R, between the analyte and internal standard peaks is not less than 3.0, and the relative standard deviation for replicate injections is not more than 3.0%.
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. The relative retention times are about 0.7 for progesterone and 1.0 for tolnaftate. Calculate the quantity, in mg, of C19H17NOS in the portion of Powder taken by the formula:
62.5C(RU / RS)
in which C is the concentration, in mg per mL, of USP Tolnaftate RS in the Standard preparation, and RU and RS are the peak response ratios obtained from the Assay preparation and the Standard preparation, respectively.
Auxiliary Information— Please check for your question in the FAQs before contacting USP.
Topic/Question Contact Expert Committee
Monograph Behnam Davani, Ph.D., M.B.A.
Senior Scientist
(MDAA05) Monograph Development-Antivirals and Antimicrobials
Reference Standards Lili Wang, Technical Services Scientist
USP32–NF27 Page 3772
Chromatographic Column—
Chromatographic columns text is not derived from, and not part of, USP 32 or NF 27.