The detailed use of cod detector method

Detection principle

    Generally, the cod detector is used to determine the concentration by spectrophotometry, which is detected by sampling, dosing, digestion and other processes. Its principle is to rapidly catalyze the oxidation-reduction reaction of the water sample added with the reagent through the constant temperature digestion instrument. The pollutants in the water sample are oxidized and CrO is reduced to Cr. The COD detector determines the concentration of Cr in the water sample by colorimetry, and then the system calculates the concentration of COD according to the obtained data.

preparation

1. Intelligent digestion instrument
2. Cod detector
3. Reagent for cod detection (different instruments from different manufacturers have different reagents, which should be prepared according to the instrument instructions)
4. 2 10ml colorimetric tubes

Operation steps of COD detector

1. Turn on the power switch, and enter the project page after the cod detector screen displays the power-on screen.
2. Select the COD to be detected by pressing the key or touch screen, and enter the detection item page.
3. Take 3ml of purified water and water sample to be measured into two colorimetric tubes respectively, then add 10 drops of CODcr reagent I into each tube, and then add 1ml of low-range CODcr reagent II into each tube with a pipette gun.
4. Use a pipette gun to add 5ml of CODcr reagent Ⅲ into each tube. Cover the colorimetric tube and mix well. Put two digestion tubes into a 165 ℃ digester for digestion for 15 minutes (it must be noted that 15 minutes will be counted from the temperature of 165 ℃ after adding the digestion tube).
5. After 15 minutes, take out two digestion tubes and cool them to room temperature. Wipe the water stains and fingerprints on the colorimetric tube with paper towel or soft cloth. hold
6. Put the colorimetric tube containing pure water into the sample tank base of COD detector. Put on the shading cover. Move the cursor to the zero calibration key, press the OK key to zero calibration, and automatically return to the current range after zero calibration.

7. Put the colorimetric tube containing the measured water sample into the sample tank seat of the COD detector. Put on the shading cover. Move the cursor to the detection position, press the OK key, wait for a few seconds, and the cod tester will display the final parameter value.

matters needing attention

1. The colorimetric tube cannot be directly touched by hand.
2. Remove bubbles in the solution before testing.
3. If there are scratches on the colorimetric tube, please replace it immediately.
4. The cod detector should be stored away from light after use.
5. Do a good job of personal protection during cod detection.
6. The water sample and reagent waste liquid shall be properly treated after the test.