Water quality detector-Steps to detect ozone content in water

  Generally, drinking water or natural water after ozone disinfection can be directly measured by potassium iodide-DPD on-site colorimetric method, and the range is 0.02mg/L-2.50mg/L. The main principle is that ozone in water can react with potassium iodide to form free iodine, and when the pH is 6.2-6.5, free iodine can react with N,N diethyl-p-phenylenediamine (DPD) to form a red compound, which can It selectively absorbs light with a wavelength of 520 nm. You can determine the concentration of ozone according to the degree of light absorption of the water sample.

  In addition, everyone should pay attention to the excessive iron and copper ions in the water will interfere with the final test results. We can add 0.1mL of disodium EDTA solution to the water sample to eliminate it. If the residual chlorine content in the water sample is too high, It will greatly affect the results and can be eliminated by adding 0.2 mL of glycine solution to the water sample.

Instruments and reagents used for testing

instrument

1. Spectrophotometer

2. Colorimetric bottle

reagent

1. Potassium iodide reagent tube

2. DPD reagent tube

3. Potassium iodide (KI)

4. Disodium EDTA solution

Weigh 4g of disodium EDTA and dissolve it in laboratory pure water, dilute to 1000mL with laboratory pure water, and mix well.

5. Glycine solution

Weigh 10g of glycine and dissolve it in laboratory pure water, dilute to 100mL with laboratory pure water and mix well.

6. Potassium iodate standard stock solution

Weigh 0.1486 g of high-grade pure potassium iodate pre-baked at 120 ℃-140 ℃ for 2 hours, dissolve with laboratory pure water, dilute to 100 mL, and mix well.

7. Potassium iodate standard solution

Accurately pipette 1.00mL of potassium iodate standard stock solution into a 100mL brown volumetric flask, add about 20mL of water, add about 1g of potassium iodide, 1 drop of 20% sulfuric acid solution, shake well, let stand for 2min, and then use laboratory pure water to make up , mix well. Prepared for temporary use. Potassium iodate solution with a concentration of 14.86 mg/L is equivalent to ozone with a concentration of 10.0 mg/L.

Check detailed steps

1. Pipette the water sample to be tested to the 10mL mark of the colorimetric bottle, wipe the outer wall of the colorimetric bottle, and place the colorimetric bottle in the colorimetric tank to lock.

2. Zero adjustment, carry out blank measurement, the instrument displays "0.00", indicating that the zero adjustment is completed.

3. Add a potassium iodide reagent to the colorimetric bottle, pipette the water sample to be tested to the scale line of the colorimetric bottle, add a DPD reagent, tighten the colorimetric bottle positioner, shake to dissolve the reagent, and wipe it clean The outer wall of the colorimetric bottle was placed in the colorimetric tank and locked, and placed for 3 minutes.

4. Carry out a concentration measurement. According to the built-in standard curve of the instrument, the value displayed on the instrument is the mass concentration of ozone in the water sample (unit, mg/L).