Experimental equipment and consumables
1 500ml beaker, 1 glass rod, 250ml 98% concentrated sulfuric acid (analytical pure or superior grade), 1 250ml brown reagent bottle (with COD catalyst), some distilled water, 1 250ml graduated cylinder, 100-1000μL pipette 1 piece, 1 piece of 1-5ml pipette (other standard measuring tools can also be used), several matching pipette heads, 1 test tube rack, several empty digestion colorimetric tubes (Φ16mm, 10ml), 1 set of COD powder reagent consumables
Preparation of COD powder reagent
COD capture agent: solid powder reagent, used directly.
CODLR reagent (0-150mg/L): Bottled solution, used directly.
CODHR reagent (100-15000mg/L): Bottled solution, used directly.
COD catalyst: solid powder reagent, put the whole bottle of powder in a 500ml beaker, use a glass rod to slightly crush the small powder, add 250ml of concentrated sulfuric acid, put it in a dark place to dissolve (dissolution is slow), after the powder is completely dissolved, stir Evenly, put it into a brown reagent bottle, and store it in the dark at room temperature for later use.
Detection method:
(To estimate the COD value of the water sample, follow the steps below for detection)
Wear protective equipment as required during operation, and avoid contact with skin and clothing.
Don’t throw away the discarded reagents and the residual liquid after detection. They should be disposed of properly and safely.
If the indicated value of the instrument is not within the range of the test range, it cannot be regarded as the final test result. If you have any questions, please consult the after-sales service.
① When the estimated COD value of the water sample is 0-150mg/L:
A. Turn on the Detector and the digestion instrument to preheat (the digestion instrument can be set to 165°C, and the temperature will be raised in advance for 20 minutes)
B. Take several empty digestion colorimetric tubes in the test tube rack
C. Blank sample: add 2ml of distilled water to the empty tube
D. Sample to be tested: Add 2ml of the water sample to be tested into the empty tube (if the water sample to be tested is uneven, please shake it well before sampling)
E. Add 1/2 flat scoop of COD capture agent into the blank sample tube and the sample tube to be tested
F. Add 0.5ml CODLR reagent (0-150mg/L) to the blank sample tube and the sample tube to be tested
G. Add 2.5ml of COD catalyst into the blank sample tube and the sample tube to be tested (add slowly, be careful of splashing), tighten the tube cap, pinch the tube cap upside down and shake well (the test tube is hot, be careful of burns)
H. Put the blank sample tube and the sample tube to be tested into the digestion instrument for digestion (165°C, 20min), please ensure that the tube cap is tightened before digestion
I. After the digestion is completed, shake the tube cover upside down by hand, and place the blank sample tube and the sample tube to be tested on the test tube rack to cool to room temperature
J. Select the COD powder (0-150mg/L) detection item on the Detector, and according to the operation prompts, do blank calibration first, and then measure the sample to be tested (before testing, please ensure that the insoluble matter in the blank sample tube and the sample tube to be tested is completely precipitated , the outer wall is clean and free from scratches)
K. Data direct reading and printing
② When the estimated COD value of the water sample is 100-1500mg/L:
A. Turn on the Detector and the digestion instrument to preheat (the digestion instrument can be set to 165°C, and the temperature will be raised in advance for 20 minutes)
B. Take several empty digestion colorimetric tubes in the test tube rack
C. Blank sample: add 2ml of distilled water to the empty tube
D. Sample to be tested: Add 2ml of the water sample to be tested into the empty tube (if the water sample to be tested is uneven, please shake it well before sampling)
E. Add 1/2 flat scoop of COD capture agent into the blank sample tube and the sample tube to be tested
F. Add 0.5ml CODHR reagent (100-15000mg/L) to the blank sample tube and the sample tube to be tested
G. Add 2.5ml of COD catalyst into the blank sample tube and the sample tube to be tested (add slowly, be careful of splashing), tighten the tube cap, pinch the tube cap upside down and shake well (the test tube is hot, be careful of burns)
H. Put the blank sample tube and the sample tube to be tested into the digestion instrument for digestion (165°C, 20min), please ensure that the tube cap is tightened before digestion
I. After the digestion is completed, shake the tube cover upside down by hand, and place the blank sample tube and the sample tube to be tested on the test tube rack to cool to room temperature
J. Select the test item of COD powder (100-1500mg/L) on the Tester, according to the operation prompts, do blank calibration first, and then test the sample to be tested (before testing, please ensure that the insoluble matter in the blank sample tube and the sample tube to be tested is completely precipitated , the outer wall is clean and free from scratches)
K. Data direct reading and printing
③ When the estimated COD value of the water sample is 1000-15000mg/L:
A. Turn on the Detector and the digestion instrument to preheat (the digestion instrument can be set to 165°C, and the temperature will be raised in advance for 20 minutes)
B. Take several empty digestion colorimetric tubes in the test tube rack
C. Blank sample: add 2ml of distilled water to the empty tube
D. Sample to be tested: Dilute the water sample to be tested 10 times, and add 2ml of the diluted sample to the empty tube (if the water sample to be tested is not uniform, please shake it well and take a sample)
E. Add 1/2 flat scoop of COD capture agent into the blank sample tube and the sample tube to be tested
F. Add 0.5ml CODHR reagent (100-15000mg/L) to the blank sample tube and the sample tube to be tested
G. Add 2.5ml of COD catalyst into the blank sample tube and the sample tube to be tested (add slowly, be careful of splashing), tighten the tube cap, pinch the tube cap upside down and shake well (the test tube is hot, be careful of burns)
H. Put the blank sample tube and the sample tube to be tested into the digestion instrument for digestion (165°C, 20min), please ensure that the tube cap is tightened before digestion
I. After the digestion is completed, shake the tube cover upside down by hand, and place the blank sample tube and the sample tube to be tested on the test tube rack to cool to room temperature
J. Select the COD powder (1000-15000mg/L) detection item on the Detector, and according to the operation prompts, do blank calibration first, and then measure the sample to be tested (before testing, please ensure that the insoluble matter in the blank sample tube and the sample tube to be tested is completely precipitated , the outer wall is clean and free from scratches)
K. Data direct reading and printing (the indicated value of the instrument is the final concentration of the water sample)
④ When the estimated COD value of the water sample is greater than 15000mg/L:
It is necessary to dilute the COD value of the water sample to 100-1500mg/L, and perform the test according to the test method ②, the concentration of the water sample = the instrument indication value × the dilution factor.
