| HIRANUMA APPLICATION DATA | Automatic Titrator | Data No. | B7 | Nov. 2,2018 |
| Drugs and Medicines | Available iodine in mouthwash (Povidone-iodine) |
1. Abstract
Determination method of available iodine in mouthwash containing povidone-iodine which is described in Japanese Pharmacopoeia is introduced here.
Dispense the sample and dilute it with DI water. Redox titration with sodium thiosulfate is performed based on the following formula (1).
| I₂ ＋ 2Na₂S₂O₃ → 2NaI ＋ Na₂S₄O₆ | ・・・(1) |
2. Configuration of instruments and Reagents
| (1) | Configuration of instruments | ||
| Main unit | : | Hiranuma Automatic Titrator COM series | |
| Electrodes | : | Platinum electrode PT-301 | |
| : | Reference electrode RE-201Z *The following electrode is also useable instead of the above electrode. ・PR-701BZ (Platinum reference electrode) ・Combination of PT-301 (Platinum electrode ) and GR-501BZ (Glass-reference electrode) |
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| (2) | Reagent | ||
| Titrant | : | 0.1 mol/L Sodium thiosulfate standard solution | |
3. Measurement procedure
| (1) | Dispense 5 mL of sample with volumetric pipette into a 100 mL beaker. |
| (2) | Add about 40 mL of DI water. |
| (3) | Immerse the electrode and titrate with 0.1 mol/L sodium thiosulfate standard solution. |
4. Measurement conditions and results
Examples of titration conditions
Measurement results
| Number of Measurement |
Size (mL) |
Titrant volume (mL) |
Available iodine (mg/mL) |
|---|---|---|---|
| 1 | 5 | 2.970 | 7.568 |
| 2 | 5 | 2.971 | 7.571 |
| 3 | 5 | 2.974 | 7.578 |
| Average | 7.57 mg/mL | ||
| Standard deviation | 0.005 mg/mL | ||
| Coefficient of variation | 0.07 % | ||
Examples of titration curve
5. Note
The determination method of available iodine in povidone-iodine which is described in Japanese Pharmacopoeia readily causes individual error because the endpoint is judged by our eyes using starch indicator. The end point detection by potentiometric titration using a platinum electrode described in this report allows to measure with less individual error.
Keywords: Available iodine, Mouthwash, Povidone-iodine, Redox titration, Platinum electrode
*Some measurement would not be possible depending on optional configuration of system.
