Dichlorofluorescein,
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This article is compiled based on the United States Pharmacopeia (USP) – 2025 Edition
Issued and maintained by the United States Pharmacopeial Convention (USP)
C20H10CI2O5 401.20 CAS RN®: 76-54-0.-
[NOTE-This specification covers both the 4,5- and 2,7-isomers of dichlorofluorescein, either of which is suitable for the preparation of dichlorofluorescein TS.]
A weak orange-colored, crystalline powder. Sparingly soluble in water, soluble in alcohol and in solutions of alkali hydroxides.
Residue on Ignition (Reagent test): Ignite 200 mg with 5 drops of sulfuric acid: the residue weighs not more than 1 mg (0.5%).
Sensitiveness: Dissolve 100 mg in 60 mL of alcohol, add 2.5 mL of 0.1 N sodium hydroxide, and dilute with water to 100 mL. Add 1 mL of this solution to a solution of potassium iodide prepared by dissolving 100 mg of potassium iodide, previously dried at 105° to constant weight and accurately weighed, in 50 mL of water containing 1 mL of glacial acetic acid, and titrate with 0.1 N silver nitrate VS until the color of the precipitate changes from pale yellowish-orange to pink. The volume of 0.1 N silver nitrate consumed is not more than 0.10 mL greater than the calculated volume, the calculated volume being based upon the Kl content of the dried specimen as determined in the Assay under Potassium lodide (USP monograph).
