Identification—
Place a quantity of Topical Powder, equivalent to about 30 mg of clioquinol, in a glass-stoppered, 50-mL conical flask, add 20 mL of 1 N sulfuric acid, and shake for 5 minutes. Filter, transfer 5 mL of the filtrate to a glass-stoppered test tube, add 5 drops of
potassium dichromate TS and 2 mL of chloroform, and shake well: a red-violet color develops in the chloroform layer.
Assay—
Transfer an accurately weighed quantity of Topical Powder, equivalent to about 50 mg of clioquinol, to a 200-mL volumetric flask, add 100 mL of 3 N hydrochloric acid, and shake by mechanical means for 15 minutes. Dilute with 3 N hydrochloric acid to volume, and mix. Filter a portion of the solution, dilute 4.0 mL of the filtrate with 3 N hydrochloric acid to 200.0 mL, and mix. Concomitantly determine the absorbances of this solution and of a Standard solution of
USP Clioquinol RS in the same medium having a known concentration of about 5 µg per mL in 1-cm cells at the wavelength of maximum absorbance at about 267 nm, with a suitable spectrophotometer, using 3 N hydrochloric acid as the blank. Calculate the quantity, in mg, of C
9H
5ClINO in the portion of Topical Powder taken by the formula:
10C(AU / AS),
in which
C is the concentration, in µg per mL, of
USP Clioquinol RS in the Standard solution; and
AU and
AS are the absorbances of the solution from the Topical Powder and the Standard solution, respectively.
467
:
meets the requirements.