Compound Clioquinol Topical Powder

This article is compiled based on the United States Pharmacopeia (USP) – 2025 Edition

Issued and maintained by the United States Pharmacopeial Convention (USP)

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1 DEFINITION

Compound Clioquinol Topical Powder contains NLT 22.5% and NMT 27.5% of clioquinol (C₉H₅ClINO).

Mix the Lactic Acid with Lactose. Then add Clioquinol and Zinc Stearate to the mixture, and mix.

2 IDENTIFICATION

A.

Sample: A quantity of Topical Powder equivalent to 30 mg of clioquinol

Analysis: Place the Sample in a glass-stoppered, 50-mL conical flask, add 20 mL of 1 N sulfuric acid, and shake for 5 min. Filter, and 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.

Acceptance criteria: A red-violet color develops in the chloroform layer.

3 ASSAY

3.1 PROCEDURE

Standard solution: 5 µg/mL of USP Clioquinol RS in 3 N hydrochloric acid

Sample solution: Transfer a quantity of Topical Powder equivalent to 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 min. Dilute with 3 N hydrochloric acid to volume. Filter a portion of the solution. Dilute 4.0 mL of the filtrate with 3 N hydrochloric acid to 200.0 mL, and mix.

Blank: 3 N hydrochloric acid

3.1.1 Instrumental conditions

Mode: UV

Analytical wavelength: 267 nm

Cell: 1 cm

3.1.2 Analysis

Samples: Standard solution and Sample solution

Determine the absorbances of the Standard solution and the Sample solution at the wavelength of maximum absorbance. Calculate the percentage of clioquinol (C₉H₅ClINO) in the portion of Topical Powder taken:

                Result = (A_U/A_S) x (C_S/C_U) × 100

A_U = absorbance of the Sample solution

A_S = absorbance of the Standard solution

C_S = concentration of clioquinol in the Standard solution (µg/mL)

C_U = nominal concentration of clioquinol in the Sample solution (µg/mL)

Acceptance criteria: 22.5%-27.5%

4 ADDITIONAL REQUIREMENTS

PACKAGING AND STORAGE: Package in well-closed, light-resistant containers.

USP REFERENCE STANDARDS (11)

USP Clioquinol RS