The configuration of CODMn reagent requires fresh distilled water, preferably redistilled water or ultra-pure water, but not deionized water. Because deionized water contains traces of resin extracts and resin disintegrating particles, it is not suitable for the preparation of organic substance analysis test solution. Ion exchange treatment can remove most of the salts, alkalis, and free acids in raw water, but it cannot completely remove organic matter. If the CODMn test solution is configured with deionized water containing organic matter, the background value of the CODMn analyzer will be high when making water samples, which affects the determination of sample water.
The sodium oxalate, potassium permanganate, and other solutions should be replaced regularly. Sodium oxalate is unstable and will fail after a long time. To determine whether sodium oxalate is invalid, you can see whether there are flocculent sediments in the sodium oxalate solution; or whether the monitoring value is too small, and repeated zero calibration is invalid,
V0 is greater than VI. Sodium oxalate and potassium permanganate solutions are generally replaced at the same time. Reagent bottles must use brown bottles or black bottle covers on the outside of the bottles to slow down the changes of the reagents.
Each time the reagents are changed, the reaction chamber and corresponding piping need to be cleaned with new reagents, and then the calibration is performed again to make the instrument run under the new blank value. Otherwise, the instrument defaults to the blank value before reagent replacement when analyzing water samples, which affects the analysis results.
All reagents should be sealed as much as possible, potassium permanganate is easily reduced, and sodium oxalate is easily oxidized. Exposing them to the air will accelerate the change of reagent quality, which will affect the monitoring results.
for permanganate index analysis: The analyzer for determining the permanganate index is the French Seres2000 type CODMn automatic monitor, which has high technical content and precise instrument components. It uses the peristaltic pump
for accurate titration and has high stability. And accuracy, at present many water stations use COMDn for this product. The permanganate index refers to the amount of potassium permanganate used as an oxidizing agent in an acidic or alkaline medium when processing water samples, expressed in mg / L of oxygen. The measurement result is related to the acidity of the solution, the concentration of potassium permanganate, heating temperature, and time. The permanganate index is often used as a comprehensive indicator of the degree of contamination of surface water bodies with organic matter and reducing inorganic substances.