Experimental equipment and consumables
2 250ml beakers, 2 glass rods, 500ml 98% concentrated sulfuric acid (analytical pure or superior grade), 1 250ml brown reagent bottle (total nitrogen reagent 1), 1 500ml brown reagent bottle (total nitrogen reagent 3 ), some distilled water, two graduated cylinders above 100ml, one 100-1000μL pipette, one 1-5ml pipette (other standard measuring tools can also be used), several matching pipette heads, one test tube rack, empty Several digestion colorimetric tubes (Φ16mm, 10ml), 1 set of total nitrogen reagent consumables
Total nitrogen reagent preparation
Total Nitrogen Reagent 1: Bottled solution, pour the whole bottle of Total Nitrogen Reagent 1 concentrate into a 250ml beaker, add 100ml of distilled water and mix well, put it into a brown reagent bottle for later use.
Total Nitrogen Reagent II: Bottled solution, used directly.
Total nitrogen reagent 3 (prepared by yourself): Take 50ml of distilled water in a 500ml beaker, add 450ml of concentrated sulfuric acid along the wall of the beaker while stirring, and put it into a brown reagent bottle for later use.
Detection method
(To estimate the total nitrogen 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 total nitrogen value of the water sample is 0-25mg/L:
A. Turn on the Detector and the digestion instrument to preheat (the digestion instrument can be set to 120°C, and the temperature can be raised in advance for 30 minutes)
B. Take several empty digestion colorimetric tubes in the test tube rack
C. Blank sample: add 4ml distilled water to the empty tube
D. Sample to be tested: Add 4ml of the water sample to be tested into the empty tube (if the water sample to be tested is uneven, please shake it well and take a sample)
E. Add 2ml of total nitrogen reagent 1 to the blank sample tube and the sample tube to be tested, tighten the cap of the tube, and shake it upside down
F. Put the blank sample tube and the sample tube to be tested into the digestion instrument for digestion (120°C, 30min). Please ensure that the tube cap is tightened before digestion
G. After the digestion is completed, shake the tube cap 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
H. Add 1ml of total nitrogen reagent 2 into the blank sample tube and the sample tube to be tested, tighten the cap of the tube, and shake it upside down
I. Take another empty colorimetric tube, first add 5ml total nitrogen reagent 3, then take 1ml blank sample digestion solution and add it to the test tube
J. Take another empty colorimetric tube, first add 5ml of total nitrogen reagent 3, then take 1ml of the sample digestion solution to be tested and add it to the test tube
K. Tighten the tube cap, shake it upside down, and let it stand for 10 minutes for color development
L. Select the total nitrogen-EPA (0-25mg/L) detection item on the Detector, according to the operation prompts, do blank calibration first, and then measure the sample to be tested (before testing, please ensure that there is no insoluble in the blank sample tube and the sample tube to be tested) objects, the outer wall is clean and free from scratches)
M. Data direct reading and printing
② When the estimated total nitrogen value of the water sample is 25-250mg/L:
A. Turn on the Detector and the digestion instrument to preheat (the digestion instrument can be set to 120°C, and the temperature can be raised in advance for 30 minutes)
B. Take several empty digestion colorimetric tubes in the test tube rack
C. Blank sample: add 4ml distilled water to the empty tube
D. Sample to be tested: Dilute the water sample to be tested 10 times, and add 4ml 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 2ml of total nitrogen reagent 1 to the blank sample tube and the sample tube to be tested, tighten the cap of the tube, and shake it upside down
F. Put the blank sample tube and the sample tube to be tested into the digestion instrument for digestion (120°C, 30min). Please ensure that the tube cap is tightened before digestion
G. After the digestion is completed, shake the tube cap 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
H. Add 1ml of total nitrogen reagent 2 into the blank sample tube and the sample tube to be tested, tighten the cap of the tube, and shake it upside down
I. Take another empty colorimetric tube, first add 5ml total nitrogen reagent 3, then take 1ml blank sample digestion solution and add it to the test tube
J. Take another empty colorimetric tube, first add 5ml of total nitrogen reagent 3, then take 1ml of the sample digestion solution to be tested and add it to the test tube
K. Tighten the tube cap, shake it upside down, and let it stand for 10 minutes for color development
L. Select the total nitrogen-EPA (25-250mg/L) detection item on the Detector, according to the operation prompts, do blank calibration first, and then measure the sample to be tested (before testing, please ensure that there is no insoluble in the blank sample tube and the sample tube to be tested) objects, the outer wall is clean and free from scratches)
M. Data direct reading and printing
③ When the estimated total nitrogen value of the water sample is greater than 250mg/L:
The total nitrogen value of the water sample needs to be diluted to 0-25mg/L, and the test is carried out according to the test method ①. The concentration of the water sample = the indicated value of the instrument × the dilution factor.
