Povidone-iodine Drug Analysis

method name
Povidone iodine - determination of povidone iodine - potentiometric titration method
Application scope
This method uses potentiometric titration to determine the iodine (I) content in povidone-iodine.
This method is suitable for the determination of iodine (I) content in povidone-iodine.
Method principle
Add water and stir to dissolve the test sample. According to the potentiometric titration method (Appendix VII A), titrate with sodium thiosulfate titrant (0.1mol/L). Each 1mL of sodium thiosulfate titrant (0.1mol/L) is equivalent to 12.69 mg of I.
Reagents
1. Water (freshly boiled and brought to room temperature)
2. Sodium thiosulfate titrant (0.1mol/L)
3. Anhydrous sodium carbonate
4. Potassium iodide
5. Benchmark potassium dichromate
6. Starch indicator liquid
7. Dilute sulfuric acid
Sample preparation
1. Sodium thiosulfate titrant (0.1mol/L)
Preparation: Take 26g of sodium thiosulfate and 0.20g of anhydrous sodium carbonate, add an appropriate amount of newly boiled cold water to dissolve into 1000mL, shake well, let it sit for 1 month and then filter.
Calibration: Take 0.15g of the standard potassium dichromate dried to constant weight at 120°C, weigh it accurately, put it in an iodine bottle, add 50mL of water to dissolve, add 2.0g of potassium iodide, shake gently to dissolve, add 40mL of dilute sulfuric acid, Shake well, stopper tightly, place in dark place for 10 minutes, add 250mL of water to dilute, titrate with this solution to near end point, add 3mL of starch indicator solution, continue titration until blue disappears and becomes bright green, and use blank test for titration results Correction. Each 1mL of sodium thiosulfate titrant (0.1mol/L) is equivalent to 4.903mg 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°C, the reaction solution and dilution water should be cooled to about 20°C.
2. Starch indicator liquid
Take 0.5g of soluble starch, add 5mL of water and stir evenly, then slowly pour it into 100mL of boiling water, stir as you add, continue to boil for 2 minutes, let it cool, pour out the supernatant liquid, and you have it. This liquid should be prepared fresh before use.
3. Dilute sulfuric acid
Take 57mL of sulfuric acid and dilute it with water to 1000mL.
Operation steps: Take about 1g of this product, weigh it accurately, put it in a beaker, add 120mL of water, stir to dissolve, and titrate with sodium thiosulfate titrant (0.1mol/L) according to the potentiometric titration method (Appendix VII A). 1mL of sodium thiosulfate titrant (0.1mol/L) is equivalent to 12.69mg of I.
Note 1: "Precision weighing" means that the weighing should be accurate to one thousandth of the weighed weight, and "precision measuring" means that the accuracy of measuring the volume should comply with the national standards for pipettes of that volume. Accuracy requirements.
Note 2: "Moisture determination" uses the drying method. Take 2~5g of the test sample and spread it flatly in a flat weighing bottle that has been dried to constant weight. The thickness should not exceed 5mm. The loose test sample should not exceed 10mm. Weigh it accurately. Open the bottle cap and dry it at 100~105℃ for 5 hours. Cover the bottle cap, transfer it to a dryer, cool it for 30 minutes, weigh it accurately, dry it at the above temperature for 1 hour, cool it, and weigh it twice in a row. The difference in weighing does not exceed 5mg. Based on the weight loss, calculate the moisture content (%) in the test sample