Iodine Topical Solution
» Iodine Topical Solution contains, in each 100 mL, not less than 1.8 g and not more than 2.2 g of iodine (I), and not less than 2.1 g and not more than 2.6 g of sodium iodide (NaI).
Iodine 20 g
Sodium Iodide 24 g
Purified Water, a sufficient quantity, to make 1000 mL
Dissolve the Iodine and the Sodium Iodide in 50 mL of Purified Water, then add Purified Water to make 1000 mL.
Packaging and storage— Preserve in tight, light-resistant containers, at a temperature not exceeding 35.
Identification—
A: Add 1 drop to a mixture of 1 mL of starch TS and 9 mL of water: a deep blue color is produced.
B: Evaporate a few mL on a steam bath to dryness: the residue responds to the flame test for Sodium 191 and to the tests for Iodide 191.
Assay for iodine— Transfer 10.0 mL of Topical Solution into a glass-stoppered, 500-mL flask, and dilute with 10 mL of water. 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 I.
Assay for sodium iodide— Transfer 10.0 mL of Topical Solution to a glass-stoppered 500-mL flask, add 30 mL of water and 50 mL of hydrochloric acid, cool to room temperature, and titrate with 0.05 M potassium iodate VS 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 between the number of mL of 0.05 M potassium iodate used and half the number of mL of 0.1 N sodium thiosulfate used in the Assay for iodine, multiplied by 14.99, represents the number of mg of NaI in the volume of Topical Solution taken.
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 Scientific Liaison
1-301-816-8394
(SM12010) Monographs - Small Molecules 1
USP35–NF30 Page 3516