Packaging and storage—
Preserve in tight, light-resistant, non-metallic containers.
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 limits 61—
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 C
13H
6Cl
6O
2 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.
