Gentian Violet Cream
» Gentian Violet Cream is Gentian Violet in a suitable cream base. It contains, in each 100 g, not less than 1.20 g and not more than 1.60 g of gentian violet, calculated as hexamethylpararosaniline chloride (C25H30ClN3).
Packaging and storage— Preserve in collapsible tubes or other tight containers, and avoid exposure to excessive heat.
Identification—
A: Dissolve about 0.1 g in 5 mL of sulfuric acid: an orange or brown-red color is produced.
B: The visible absorption spectrum of a portion of the Assay preparation employed for measurement of absorbance in the Assay exhibits maxima at the same wavelengths as that of a similar solution of USP Gentian Violet RS, concomitantly measured.
Minimum fill 755: meets the requirements.
Assay
Standard preparation— Transfer an accurately weighed quantity of USP Gentian Violet RS, equivalent to about 13.5 mg of anhydrous gentian violet, to a 100-mL volumetric flask. Add 50 mL of hydrochloric acid, and mix until dissolved. Dilute with hydrochloric acid to volume, and mix. Pipet 5 mL of the solution into a 50-mL volumetric flask, add hydrochloric acid to volume, and mix.
Assay preparation— Transfer about 500 mg of Cream, accurately weighed, to a 100-mL volumetric flask. Add 15 mL of hydrochloric acid, warm in a water bath to disperse the cream thoroughly, cool, add hydrochloric acid to volume, and mix. Filter the mixture through a fine-porosity, sintered-glass filter. Pipet 2 mL of the solution into a 10-mL volumetric flask, add hydrochloric acid to volume, and mix.
Procedure— Concomitantly determine the absorbances of the Standard preparation and the Assay preparation in 1-cm cells at the wavelength of maximum absorbance at about 435 nm, with a suitable spectrophotometer, using hydrochloric acid as the blank. [note—Use quartz cells having tightly fitting covers to prevent corrosion caused by the hydrochloric acid.] Calculate the quantity, in mg, of C25H30ClN3 in the portion of Cream taken by the formula:
0.5C(AU / AS)
in which C is the concentration, in µg per mL, of USP Gentian Violet RS, calculated on the anhydrous basis, in the Standard preparation; and AU and AS are the absorbances of the Assay preparation and the Standard preparation, respectively.
Auxiliary Information— Please check for your question in the FAQs before contacting USP.
Topic/Question Contact Expert Committee
Monograph Behnam Davani, Ph.D., M.B.A.
Senior Scientist
1-301-816-8394
(MDAA05) Monograph Development-Antivirals and Antimicrobials
Reference Standards Lili Wang, Technical Services Scientist
1-301-816-8129
RSTech@usp.org
USP32–NF27 Page 2496