Analytical Method: Analytical Quality Assurance, Standard for Chlorine Dioxide

Reagents:

Cat.No. 102404 Potassium iodate, volumetric standard
Cat.No. 105043 Potassium iodide for analysis
Cat.No. 109072 Sulfuric acid 0.5 mol/L
Cat.No. 109136 Sodium hydroxide solution 2 mol/L
Cat.No. 116754 Water for analysis

Preparation of a KlO₃ Stock Solution:

Dissolve 1.005 g of KlO₃ in 250 mL of distilled water in a calibrated or conformity-checked 1000-mL volumetric flask. Subsequently make up to the mark with distilled water.

Preparation of a KlO₃/Kl Standard Solution:

Transfer 10.5 mL of the KlO₃ stock solution to a calibrated or conformity-checked 1000-mL volumetric flask, add approx. 1.0 g of Kl and make up to the mark with distilled water. 1 mL of this solution is equivalent to 0.020 mg of chlorine dioxide.

Preparation of the Chlorine Dioxide Standard Solution:

Pipette 10 mL KlO₃/Kl standard solution into a calibrated or conformity-checked 100-mL volumetric flask, add
2.0 mL of H₂SO₄ 0.5 mol/L, leave to stand for 1 min, and then add NaOH 2 mol/L dropwise (approx. 1 mL) until the solution just loses its color. Subsequently make up the solution to the mark with distilled water. The concentration of the solution is 2.00 mg/L chlorine dioxide.

Stability:

The KlO₃ stock solution remains stable for 4 weeks when stored in a cool place. The KlO₃/Kl standard solution can be used for 5 hours when stored in a cool place. The dilute chlorine dioxide standard solution is not stable and must be used immediately.