Gentian Violet contains not less than 96.0 percent and not more than 100.5 percent of gentian violet (C25H30ClN3), calculated on the anhydrous basis.
Chromatographic Purity: 96-101%
Water: Not more than 7.5%.
Residue on ignition: Not more than 1.5%.
Alcohol-insoluble substances— Not more than 1.0% of insoluble residue remains.
Arsenic— The limit is 0.001%.
Lead—The limit is 0.003%.
Zinc— Not more than 0.05%.
Gentian Violet USP
C25H30ClN3 407.98
Methanaminium, N-[4-[bis[4-(dimethylamino)phenyl]methylene]-2,5-cyclohexadien-1-ylidene]-Nmethyl-,chloride.
C. I. Basic violet 3.
[4-[Bis[p-(dimethylamino)phenyl]methylene]-2,5-cyclohexadien-1-ylidene]dimethylammonium chloride [548-62-9].
Gentian Violet contains not less than 96.0 percent and not more than 100.5 percent of gentian violet (C25H30ClN3), calculated on the anhydrous basis.
Identification—
A: Sprinkle about 1 mg on 1 mL of sulfuric acid: it dissolves in the acid with an orange or brown red color. When this solution is
diluted cautiously with water, the color changes to brown, then to green, and finally to blue.
B: Dissolve about 20 mg in 10 mL of water, and add 5 drops of
hydrochloric acid. To 5 mL of this solution add tannic acid TS drop wise: a deep blue precipitate is formed.
C: To the remainder of the solution prepared for
Identification test B add about 500 mg of zinc dust, and warm the mixture: rapid de-colorization occurs. Place a drop of the decolorized solution adjacent to a drop of
6 N ammonium hydroxide on a filter paper: a blue color is produced at the zone of contact.
Water: not more than 7.5%.
Residue on ignition: not more than 1.5%.
Alcohol-insoluble substances— Boil 1.0 g, accurately weighed, with 50 mL of alcohol under a reflux condenser for 15 minutes, filter through a tarred filtering
crucible, wash the residue on the filter with hot alcohol until the last washing is not colored violet, and dry the crucible at 105 for 1 hour: not more than 1.0% of
insoluble residue remains.
Arsenic— The limit is 0.001%.
Lead—The limit is 0.003%.
Zinc—
Zinc standard stock solution— Transfer about 1 g of zinc, accurately weighed, to a 1000-mL volumetric flask, add 50 mL of nitric acid, and mix to dissolve. Dilute with
water to volume, and mix.
Standard preparation— Dilute the Zinc standard stock solution with water to obtain a Standard preparation containing 0.50 Ag of zinc per mL.
Test preparation— Weigh accurately 0.50 g of Gentian Violet in a suitable tarred crucible. Place in a low-temperature plasma ashing apparatus, and ash until a constant
weight is attained. Pipette 10 mL of 6 N nitric acid into the crucible, and heat to dissolve the ash. Transfer the solution to a 500-mL volumetric flask, dilute with
water to volume, and mix. Prepare a reagent blank.
Procedure— Concomitantly determine the absorbance of the Standard preparation, the Test preparation, and the reagent blank at the zinc emission line at 213.9 nm, with
a suitable atomic absorption spectrophotometer (see Spectrophotometry and Light-Scattering 851 ) equipped with a zinc lamp and an air–acetylene flame, using water as
the blank. The absorbance of the Test preparation, corrected for that of the reagent blank, is not greater than the absorbance of the Standard preparation, similarly
corrected (0.05%).
Chromatographic purity— Dissolve 10 mg in 10 mL of methanol to obtain the Test solution. Transfer 1.0 mL of Test solution to a 100-mL volumetric flask, dilute
with methanol to volume, and mix (Diluted test solution). Apply 5 AL each of the Test solution and the Diluted test solution to a suitable thin-layer chromatographic
plate (see Chromatography 621 ) coated with a 0.25-mm layer of octadecylsilanized chromatographic silica gel. Allow the spots to dry, and develop the chromatogram in
a suitable chromatographic chamber with a solvent system consisting of the upper layer separated from a well-shaken mixture of water, butyl alcohol, and glacial acetic
acid (100:80:20), until the solvent front has moved about three-fourths of the length of the plate. Remove the plate from the chamber, allow the solvent to evaporate,
and visually locate the spots on the plate: the Test solution exhibits a principal spot and not more than one secondary spot which, if present in the chromatogram from
the Test solution, is not more intense than the principal spot obtained from the Diluted test solution (1.0%).
Assay— Transfer about 400 mg of Gentian Violet, accurately weighed, to a 300-mL conical flask, add 25 mL of water and 10 mL of hydrochloric acid, displace the air in
the flask with carbon dioxide, and pass a stream of carbon dioxide through the flask during the assay. Add 50.0 mL of 0.1 N titanium trichloride VS, heat to boiling,
and boil gently for 10 minutes, swirling the liquid occasionally. Cool the solution, add 5 mL of ammonium thiocyanate solution (1 in 10), and titrate with 0.1 N ferric
ammonium sulfate VS until a faint red color is produced. Perform a blank determination (see Residual Titrations 541 ). Each mL of 0.1 N titanium trichloride is
equivalent to 20.40 mg of C25H30ClN3.
