When using the instrument for the first time, please use the standard sample for operation measurement. After the sample measurement is accurate (error within ± 5%), other water sample measurement work can be carried out.
Operation process
Turn on the power supply of the host, press the program key → press the OK key → select CODL pre-, CODM pre-or CODH pre- (select according to the concentration of the sample to be tested) → press the OK key to enter the zero-point calibration interface for preheating.
Turn on the power supply of the digester and select the COD digestion mode (165 ℃, 20min);
When the COD of the sample is 0-150mg/L (pre-CODL), take 2 low-range prefabricated reagent tubes. Blank: absorb 2mL of distilled water into a colorimetric tube;
Sample: Take 2 mL of sample in another colorimetric tube;
When the COD of the sample is 150-1500mg/L (pre-CODM), take 2 high-range prefabricated reagent tubes. Blank: absorb 2mL of distilled water in one colorimetric tube; sample: take 2mL of sample in another colorimetric tube;
When the COD of the sample is 1500-15000mg/L (pre-CODH), take 2 high-range prefabricated reagent tubes. Blank: absorb 2mL of distilled water in a colorimetric tube; sample: take 1.8mL of distilled water in another colorimetric tube, and then add 0.2mL of sample (or dilute the sample 10 times and add 2mL);
Cover the above test tube and shake it well (make sure the lid is tightened, the test tube is hot, be careful of scalding); when the digester beeps to alarm, place the blank and the sample in the heated digester, cover it with a protective cover, and press the confirm button to start digestion; when the digester beeps to alarm again, the digestion is completed, and each test tube is taken out and cooled to room temperature (it can be cooled naturally, or water cooled after 3-5min of natural cooling);
After the colorimetric tube is cooled to room temperature, wipe it clean. Under the corresponding item that has been preheated, put the blank into the instrument, press the zero key for zero point calibration, then put it into the sample tube, and press the measurement key for sample measurement. The value is the concentration value.
Precautions
Built-in working curve, can directly measure water samples;
During the measurement, the water sample can be roughly anticipated and diluted beyond the range for sampling and measurement;
When measuring/adding samples and reagents, the pipette should be measured head-on concave liquid;
Pipettes or pipette tips for sample/reagent removal should not be cross-used to prevent reagent contamination;
It is normal to have precipitation;
Make sure that the digestion tube cover is tightened before digestion;
Do not shake the digestion tube violently during wiping and measurement;
Make sure the water sample is colored before testing, but it must be clear before testing.
Blank digestion tube is inserted into the colorimetric slot for about 2-3 seconds, and then press "Confirm" after the reading is stable;
During sample measurement, it is normal for the data to fluctuate in a small range in a short period of time, and it is a phenomenon; (the average value is taken as the final result)
Description
The main interfering factor of COD measurement is chloride ion, and this reagent has its own anti-chlorine interference of 1000mg/L.
Samples cannot be placed for a period of time or repeated for test comparisons at different time periods.
The measurement data should be within the corresponding range. If not, the water sample can only be roughly judged. If accurate data is required, it should be selected
Low range or high range or diluted measurement, so that the measurement data within the corresponding range.
The colorimetric solution cannot be placed in the digestion tube for a long time, and the digestion tube and its experimental tools should be cleaned in time.
The water sample pretreatment process and the colorimetric process should be completed in a compact manner.
The solution after the colorimetry is completed cannot be poured at will, and should be collected uniformly for centralized treatment.
If the digestion tube is scratched, please replace it in time to avoid affecting the accuracy of the data.
