Iodine
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Tóm tắt nội dung
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 contains NLT 99.8% and NMT 100.5% of I.
2 IDENTIFICATION
A.
Solutions (1 in 1000) in chloroform and in carbon disulde have a violet color.
B.
Analysis: To a saturated solution add starch–potassium iodide TS.
Acceptance criteria: A blue color is produced. When the mixture is boiled, the color vanishes but reappears as the mixture cools, unless it has been subjected to prolonged boiling.
3 ASSAY
Procedure
Sample: 500 mg of powdered Iodine
Analysis: Place the Sample in a tared, glass-stoppered ask, insert the stopper, and add 1 g of potassium iodide dissolved in 5 mL of water. Dilute with water to 50 mL, add 1 mL of 3 N hydrochloric acid, and titrate with 0.1 N sodium thiosulfate VS, adding 3 mL of starch TS as the endpoint is approached. Each mL of 0.1 N sodium thiosulfate is equivalent to 12.69 mg of Iodine (I).
Acceptance criteria: 99.8%–100.5%
4 IMPURITIES
Limit of Chloride or Bromide
Sample solution: Triturate 250 mg of nely powdered Iodine with 10 mL of water, and lter the solution.
Analysis: To the Sample solution add, dropwise, sulfurous acid (free from chloride), previously diluted with several volumes of water, until the iodine color just disappears. Add 5 mL of 6 N ammonium hydroxide, followed by 5 mL of silver nitrate TS in small portions. Filter, and acidify the ltrate with nitric acid.
Acceptance criteria: The resulting liquid is not more turbid than a control made with the same quantities of the same reagents to which 0.10 mL of 0.020 N hydrochloric acid has been added, the sulfurous acid being omitted (0.028% as chloride).
Limit of Nonvolatile Residue
Analysis: Place 5.0 g in a tared porcelain dish, heat on a steam bath until the iodine has been driven off, and dry at 105° for 1 h.
Acceptance criteria: NMT 0.05% of the residue remains.
5 ADDITIONAL REQUIREMENTS
Packaging and Storage: Preserve in tight containers.
