Betadine Liquid 25655-41-8

Method name: Povidone-iodine - Determination of povidone-iodine - Potentiometric titration

Application scope: This method uses potentiometric titration to determine the content of iodine (I) in povidone-iodine. This method is suitable for the determination of iodine (I) in povidone-iodine. Method principle: Add water to the test sample and stir to dissolve it. According to the potentiometric titration method (Appendix Ⅶ A), titrate with sodium thiosulfate titration solution (0.1 mol/L). Each 1 mL of sodium thiosulfate titration solution (0.1 mol/L) is equivalent to 12.69 mg of I.

Reagents:

1. Water (freshly boiled and placed at room temperature)2. Sodium thiosulfate titration solution (0.1 mol/L)3. Anhydrous sodium carbonate4. Potassium iodide5. Standard potassium dichromate6. Starch indicator solution7. Dilute sulfuric acid.

Sample preparation

1. Sodium thiosulfate titrant (0.1 mol/L)

Preparation: Take 26 g of sodium thiosulfate and 0.20 g of anhydrous sodium carbonate, add an appropriate amount of freshly boiled cold water to dissolve into 1000 mL, shake well, and filter after leaving for 1 month.

Calibration: Take 0.15 g of standard potassium dichromate dried to constant weight at 120°C, accurately weigh, place in an iodine bottle, add 50 mL of water to dissolve, add 2.0 g of potassium iodide, shake gently to dissolve, add 40 mL of dilute sulfuric acid, shake well, seal, leave in the dark for 10 minutes, add 250 mL of water to dilute, titrate with this solution to the end point, add 3 mL of starch indicator solution, continue titrating until the blue disappears and bright green appears, and correct the titration result with a blank test. Each 1 mL of sodium thiosulfate titrant (0.1 mol/L) is equivalent to 4.903 mg of potassium dichromate. Calculate the concentration of this solution based on the consumption of this solution and the amount of potassium dichromate taken.

When the room temperature is above 25℃, the reaction solution and dilution water should be cooled to about 20℃.

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