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.
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 C
19H
17NOSin 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.