» Tolnaftate Cream 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 10 mL of the next-to-final chloroform solution prepared in the Assay 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.
Assay Transfer a portion of Cream, equivalent to about 10 mg of tolnaftate and accurately weighed, to a 250-mL separator containing about 75 mL of chloroform. Wash the chloroform solution successively with two 25-mL portions of 0.1 N sodium hydroxide, two 25-mL portions of 0.1 N hydrochloric acid, and 25 mL of water. Filter the chloroform layer through a chloroform-washed cotton pledget into a 100-mL volumetric flask. Add chloroform to volume, and mix. [noteReserve a 10-mL portion of this solution for the Identification test.] Dilute 5.0 mL of the solution with chloroform to 50.0 mL, and mix. Dissolve an accurately weighed quantity of USP Tolnaftate RS in chloroform, and dilute quantitatively and stepwise with chloroform to obtain a Standard solution having a known concentration of about 10 µg per mL. Concomitantly determine the absorbances of both solutions in 1-cm cells at the wavelength of maximum absorbance at about 258 nm, with a suitable spectrophotometer, using chloroform as the blank. Calculate the quantity, in mg, of C19H17NOS in the portion of Cream taken by the formula:
C(AU / AS)in which C is the concentration, in µg per mL, of USP Tolnaftate RS in the Standard solution, and AU and AS are the absorbances of the solution from the Cream and the Standard solution, respectively.
Auxiliary Information Please check for your question in the FAQs before contacting USP.
USP32NF27 Page 3772