Spectrophotometric Determination of Chlorine Dioxide
Key words: spectrophotometry; chlorine dioxide (ClOâ‚‚); US analytical instrument; V-1200
This method describes a reliable and accurate procedure for the spectrophotometric determination of chlorine dioxide. The process involves the preparation of a standard stock solution, calibration curve development, and sample analysis. (1) **Preparation of Chlorine Dioxide Standard Stock Solution**: To prepare the stock solution, 300 mL of distilled water is placed in Flask A. One end of a glass tube is connected to an air compressor, while the other end is attached to Flask B, a high-strength borosilicate glass bottle equipped with three glass tubes. The first tube introduces air into the flask, the second connects to a dropping funnel, and the third allows gas to escape. Sodium chlorite (10 g) is dissolved in 750 mL of water and transferred into Flask B. A 20 mL portion of 10% sulfuric acid is added to the separating funnel. Flask C contains a saturated sodium chlorite solution, while Flask D, a 2 L borosilicate glass collection bottle, holds 1500 mL of water to absorb the generated ClOâ‚‚. The system is placed inside a fume hood for safety. Once the setup is complete, the air compressor is turned on, and 5 mL of sulfuric acid is added every 5 minutes. After the final addition, the airflow continues for an additional 30 minutes. The resulting yellow solution is collected in a brown bottle and stored at 4°C. The concentration should range between 250 mg/L and 600 mg/L. (2) **Preparation of Chlorine Dioxide Standard Solution**: Before use, a measured volume of the stock solution is diluted with double-distilled water to obtain a working concentration of 250 mg/L. (3) **Construction of the Calibration Curve**: A series of standard solutions are prepared by diluting the 250 mg/L solution to concentrations of 0, 10, 25, 50, 100, 150, 200, and 250 mg/L in 100 mL volumetric flasks. Each solution is measured for absorbance at 430 nm using distilled water as the blank. A linear regression is performed between the mass of ClOâ‚‚ (in mg) and the corresponding absorbance values, and a standard curve is plotted. (4) **Sample Analysis**: For sample measurement, the disinfectant solution or its diluent is analyzed directly. The absorbance at 430 nm is recorded, with distilled water as the reference. The concentration of ClOâ‚‚ in the sample is determined using the standard curve equation. (5) **Calculation**: The chlorine dioxide content (X) in mg/L is calculated using the formula: **X = Ï Ã— (Vâ‚ / Vâ‚‚)** Where: - Ï is the concentration obtained from the standard curve (mg/L), - Vâ‚ is the volume of the diluted disinfectant (mL), - Vâ‚‚ is the original volume of the disinfectant (mL). The method has a detection limit of 10 mg/L and a linear range from 10 mg/L to 250 mg/L. The average recovery rate is 103.3%, and the relative standard deviation is less than 10%. This technique is suitable for routine monitoring of chlorine dioxide in water treatment and disinfection applications. Key words: spectrophotometry; chlorine dioxide (ClOâ‚‚); US analytical instrument; V-1200Jiangsu Qilong Electronic Technology Co., Ltd. , https://www.qilongtouch.com