Iodine Topical Solution
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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)
1 DEFINITION
Iodine Topical Solution contains NLT 1.8 g and NMT 2.2 g of iodine (I) and NLT 2.1 g and NMT 2.6 g of sodium iodide (NaI) in each 100 mL.
Iodine 20 g
Sodium Iodide 24 g
Purified Water, a sufficient quantity to make 1000 mL
Dissolve Iodine and Sodium Iodide in 50 mL of Purified Water, then add sufficient Purified Water to bring to final volume.
2 IDENTIFICATION
A.
Analysis: Add 1 drop to a mixture of 1 mL of starch TS and 9 mL of water.
Acceptance criteria: A deep blue color is produced.
B. Identification Tests—General 〈191〉, Iodide
Sample: Evaporate a few milliliters on a steam bath to dryness.
Acceptance criteria: The residue meets the requirements of the test for Iodide.
C. Sodium:
The Sample obtained in Identification B imparts an intense yellow color to a nonluminous flame.
3 ASSAY
Iodine
Sample: 10.0 mL
Titrimetric system
Mode: Direct titration
Titrant: 0.1 N sodium thiosulfate VS
Endpoint detection: Visual
Analysis: Transfer the Sample into a glass-stoppered 500-mL flask, and dilute with 10 mL of water. Titrate with Titrant, adding 3 mL of starch TS as the endpoint is approached. Each milliliter of Titrant is equivalent to 12.69 mg of iodine (I).
Acceptance criteria: 1.8–2.2 g in 100 mL of Topical Solution
Sodium Iodide
Sample: 10.0 mL
Titrimetric system
Mode: Direct titration
Titrant: 0.05 M potassium iodate VS
Endpoint detection: Visual
Analysis: Transfer the Sample into a glass-stoppered 500-mL flask, add 30 mL of water and 50 mL of hydrochloric acid, cool to room temperature, and titrate with Titrant until the dark brown solution that is produced becomes pale brown. Add 1 mL of amaranth TS, and continue the titration slowly until the red color just changes to yellow. The difference in volume, in milliliters, between the Titrant used and half the volume of 0.1 N sodium thiosulfate VS used in the Assay for Iodine, multiplied by 14.99, represents the number of milligrams of sodium iodide (NaI) in the portion of Topical Solution taken.
Acceptance criteria: 2.1–2.6 g in 100 mL of Topical Solution
4 ADDITIONAL REQUIREMENTS
Packaging and Storage: Package in tight, light-resistant containers. Store at a temperature not exceeding 35°.
