COD prefabricated reagent simple operation process (0-15000mg/L)

Author: 同奥科技

Abstract: 本文介绍了COD（化学需氧量）测试的简易操作流程，包括预热、浓度预判和操作指南。测试前需预判水样的COD浓度，并选择相应的预制试剂：0-150mg/L使用CODL试剂，150-1500mg/L使用CODM试剂，1500-15000mg/L使用CODH试剂。浓度超出15000mg/L时需稀释水样。操作中需注意加盖摇匀时的烫伤防护、试剂管的专用性、移液工具的选择与校准等。还包括消解器的升温和消解过程的注意事项，以及样品管的要求。

Digestion device preheating:Turn on the power of the digester, select the COD digestion mode (165°C, 20min), press confirm (or start), and the digester will automatically heat up and preheat;

Concentration prediction:Before testing the water sample, the COD value of the water sample is first predicted, and the COD prereagent corresponding to the range is selected for operation, for example, predictionCOD concentration values between 0-150mg/L require the selection of pre-made reagents in the range of 0-150mg/L; If the predicted COD concentration value is 150-15000mg/L, it is selectedChoose pre-made reagents in the range of 150-15000mg/L.

Remark:The shielding ability of this reagent to chloride ions is: less than or equal to 1000mg/L. Beyond this concentration, dilute below 1000mg/L before proceeding.

1. When the predicted value is in the range of 0-150mg/L

Precast reagents in the range of 0-150mg/L are selected; Digestion time: 20min; Analytical procedure: CODL pre.

Simple operation process of COD precast reagent (0-15000mg/L) with Figure 1

2. When the predicted value is in the range of 150-1500mg/L

Choose pre-made reagents in the range of 150-15000mg/L; Digestion time: 20min; Analytical Procedure:CODM pre.

Simple operation process of COD precast reagent (0-15000mg/L) with Figure 2

3. When the predicted value is in the range of 1500-15000mg/L

Choose pre-made reagents in the range of 150-15000mg/L; Digestion time: 20min; Analytical procedure: CODH pre.

Simple operation process of COD precast reagent (0-15000mg/L) with Figure 3

4. When the predicted value exceeds 15000 mgL /L

The water sample needs to be diluted to the corresponding concentration value in sections 1-3 above, and then manipulated according to the corresponding range, and the determination result is multiplied by the dilution factor.

5. Test steps on the computer

Simple operation process of COD precast reagent (0-15000mg/L) with Figure 4

6. Precautions

◆ If there is COD, the treated water sample will show green, and the darker the color, the higher the concentration value of the water sample.

◆ After adding the water sample, the test tube will be hot, and when the cap is shaken, it is necessary to avoid scalding (you can wrap the cap with a wiping cloth), tighten the cap, and shake all the sediment at the bottom.

◆ Prefabricated reagent tubes of different ranges cannot be mixed, and the same range of reagents must be used for blanks and samples.

◆ Pay attention to cross-contamination, use different measuring utensils for different liquids (pay attention to changing the tip when using a pipette).

◆ Use a suitable pipette to take the liquid, do not use a 5mL pipette to remove 2mL and less liquid, less than or equal to 2mL of liquid, it is recommendedPipette 2 times with a 1mL pipette.

◆ When using a pipette, it is necessary to calibrate the pipette frequently (it is recommended to do so once a week), and pay attention to replacing the tip during use.

◆ The protective cover must be covered during the heating and digestion process of the digester. During the digestion process, beware of scalding, pay attention to the high temperature area of the digester.

◆ After the digestion tube is taken out from the digester, take one piece at a time, it is forbidden to take out multiple tubes at the same time, pay attention to the high temperature, and prohibit shaking.

◆ The cooling process can be natural cooling or water cooling, but the temperature must be below 120°C for water cooling.

◆ The digested COD sample tube must be clear and translucent (colored, but must not be turbid, no suspended solids, precipitated at the bottom, and shaken)

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