Hexachlorophene Cleansing Emulsion
» Hexachlorophene Cleansing Emulsion is Hexachlorophene in a suitable aqueous vehicle. It contains not less than 90.0 percent and not more than 110.0 percent of the labeled amount of C13H6Cl6O2. It contains no coloring agents.
Packaging and storage— Preserve in tight, light-resistant, non-metallic containers.
USP Reference standards 11
USP Hexachlorophene RS Click to View Structure
Identification— Place a volume of Emulsion, equivalent to about 150 mg of hexachlorophene, in a glass-stoppered, 25-mL graduated cylinder, dilute with a mixture of equal volumes of chloroform and methanol to volume, mix, and allow to stand for about 5 minutes. Apply 10 µL of this solution and 10 µL of a solution of USP Hexachlorophene RS in the same chloroform and methanol mixture containing 6 mg per mL to a suitable thin-layer chromatographic plate (see Chromatography 621) coated with a 0.25-mm layer of silica gel. Develop the chromatogram in a solvent system consisting of a mixture of toluene and glacial acetic acid (9:1) until the solvent moves to about 10 cm above the point of application. Remove the plate, mark the solvent front and evaporate the solvent in a current of warm air. Spray the plate with dilute nitric acid (1 in 5), and warm on a hot plate until yellow spots appear: the RF value of the principal spot obtained from the solution under test corresponds to that obtained from the Standard solution.
Microbial enumeration tests 61 and Tests for specified microorganisms 62 It meets the requirements of the tests for absence of Staphylococcus aureus and Pseudomonas aeruginosa.
pH 791 Place 20 mL of the well-shaken Emulsion and 10 mL of water in a glass-stoppered, 50-mL graduated cylinder, mix, and determine the pH in a suitable pH meter, using a glass electrode and preferably a sleeve-type calomel electrode: the pH is between 5.0 and 6.0.
Assay—
Standard preparation— Weigh accurately about 50 mg of USP Hexachlorophene RS into a 50-mL volumetric flask, add 10 mL of methanol, shake until dissolved, add methanol to volume, and mix. Pipet 3 mL of this solution into a 100-mL volumetric flask, add 1 mL of dilute hydrochloric acid (1 in 10), add methanol to volume, and mix.
Assay preparation— Transfer an accurately weighed portion of Emulsion, equivalent to about 30 mg of hexachlorophene, to a 100-mL volumetric flask, add methanol to volume, and mix. Filter the solution through paper, taking adequate precautions to prevent evaporation. Pipet a 10-mL aliquot of the filtrate into a 100-mL volumetric flask, add 1 mL of dilute hydrochloric acid (1 in 10), and add methanol to volume.
Procedure— Concomitantly determine the absorbances of the Assay preparation and the Standard preparation in 1-cm cells at the wavelength of maximum absorbance at about 299 nm, with a suitable spectrophotometer, using a mixture of 99 volumes of methanol and 1 volume of hydrochloric acid as the blank. Calculate the quantity, in mg, of C13H6Cl6O2 in the portion of Emulsion taken by the formula:
C(AU / AS)
in which C is the concentration, in µg per mL, of USP Hexachlorophene RS in the Standard preparation; and AU and AS are the absorbances of the Assay preparation and the Standard preparation, respectively.
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62 Radhakrishna S Tirumalai, Ph.D.
Principal Scientific Liaison
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(GCM2010) General Chapters - Microbiology
USP35–NF30 Page 3409