Tolnaftate Cream »Tolnaftate Cream contains not less than 90.0percent and not more than 110.0percent of the labeled amount of C19H17NOS. Packaging and storage— Preserve in tight containers. USP Reference standards á11ñ USP Tolnaftate RS. Identification— Evaporate 10mLof the next-to-final chloroform solution prepared in the Assayon a steam bath just to dryness,and dissolve the residue in 1mLof alcohol.Using this as the test solution,proceed as directed in Identificationtest Cunder Tolnaftate:the specified result is observed. Minimum fill á755ñ: meets the requirements. Assay— Transfer a portion of Cream,equivalent to about 10mg of tolnaftate and accurately weighed,to a 250-mLseparator containing about 75mLof chloroform.Wash the chloroform solution successively with two 25-mLportions of 0.1Nsodium hydroxide,two 25-mLportions of 0.1Nhydrochloric acid,and 25mLof water.Filter the chloroform layer through a chloroform-washed cotton pledget into a 100-mLvolumetric flask.Add chloroform to volume,and mix.[NOTE—Reserve a 10-mLportion of this solution for the Identificationtest.]Dilute 5.0mLof the solution with chloroform to 50.0mL,and mix.Dissolve an accurately weighed quantity of USP Tolnaftate RSin chloroform,and dilute quantitatively and stepwise with chloroform to obtain a Standard solution having a known concentration of about 10µg per mL.Concomitantly determine the absorbances of both solutions in 1-cm cells at the wavelength of maximum absorbance at about 258nm,with a suitable spectrophotometer,using chloroform as the blank.Calculate the quantity,in mg,of C19H17NOSin the portion of Cream taken by the formula: C(AU/AS), in which Cis the concentration,in µg per mL,of USP Tolnaftate RSin the Standard solution,and AUand ASare the absorbances of the solution from the Cream and the Standard solution,respectively. Auxiliary Information— Staff Liaison:Behnam Davani,Ph.D.,MBA,Senior Scientist Expert Committee:(PA7)Pharmaceutical Analysis 7 USP28–NF23Page 1951 Phone Number:1-301-816-8394