Identification—
Evaporate 25 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.
Assay—
Pipet into a separator a volume of Topical Solution, equivalent to about 10 mg of tolnaftate, add 50 mL of chloroform, and extract with 50 mL of 0.1 N sodium hydroxide. Filter the chloroform layer through a chloroform-washed cotton pledget into a 250-mL volumetric flask, and extract the aqueous layer with two 45-mL portions of chloroform, filtering each portion into the flask. Add chloroform to volume, and mix.
[NOTE—Reserve a 25-mL portion of this solution for the
Identification test.
] Dilute 25.0 mL of the solution with chloroform to 100.0 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 C
19H
17NOS in each mL of Topical Solution taken by the formula:
(C / V)(AU / AS),
in which
C is the concentration, in µg per mL, of
USP Tolnaftate RS in the Standard solution,
V is the volume, in mL, of Topical Solution taken, and
AU and
AS are the absorbances of the solution from the Topical Solution and the Standard solution, respectively.
467
:
meets the requirements.