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HJ 636-2012: Water quality - Determination of total nitrogen - Alkaline potassium persulfate digestion UV spectrophotometric method
HJ 636-2012
Water quality.Determination of total nitrogen.Alkaline potassium persulfate digestion UV spectrophotometric method
People's Republic of China National Environmental Protection Standards
Replacing GB 11894-89
Determination of Water Quality Total Nitrogen
Alkaline potassium persulfate digestion - UV spectrophotometric method
Water quality-Determination of total nitrogen-Alkaline
potassium persulfate digestion UV spectrophotometric method
(Release)
Issued on.2012-02-29
2012-06-01 implementation
Issued by the Ministry of Environmental Protection
Table of Contents
Preface II
1. Scope .1
2 Normative references .1
3 Terms and definitions
4 principle of the method .1
5 and eliminate interference 1
6 Reagents and materials 1
7 2 instruments and equipment
8 Sample 2
Analysis Step 9 .3
10 Results Calculation and representation .. 3
11 precision and accuracy ..4
12 Quality Assurance and Quality Control 4
13 Note ..4
Appendix A (informative) of sodium hydroxide and potassium persulfate nitrogen content determination 6
Foreword
To implement the "People's Republic of China Environmental Protection Law" and "People's Republic of China Water Pollution Prevention Law" to protect the environment,
Protection of human health, specifications determination of total nitrogen in water, the development of this standard.
This standard specifies the determination of surface water, groundwater, industrial wastewater and domestic sewage in total nitrogen - Alkaline potassium persulfate digestion purple
Outside spectrophotometry.
This standard is the "Water quality Determination of total nitrogen - Alkaline potassium persulfate digestion - UV spectrophotometric method" (GB 11894-89)
Amendments.
This standard was first published in 1989, the original standard was drafted by the Shanghai Environmental Monitoring Center, this is the first time to repair
Order. The main content of the amendments are as follows.
- Expanding the scope of the standard;
- Added sodium hydroxide and potassium persulfate nitrogen content requirements and nitrogen content determination method;
- Increased quality assurance and quality control provisions;
- Add a note terms.
From the date of implementation of this standard, the former State Environmental Protection Agency December 25, 1989 approved the national environmental protection published
Support Standard "Water quality Determination of total nitrogen - Alkaline potassium persulfate digestion - UV spectrophotometric method" (GB 11894-89) abolished.
Appendix A of this standard is an informative annex.
This standard is developed by the Ministry of Environmental Protection Science, Technology organization.
Drafting of this standard. Dalian Municipal Environmental Monitoring Center.
The standard verification. Tianjin Environmental Monitoring Center, the Liaoning Provincial Environmental Monitoring Experiment Center, Shenyang Environmental Monitoring
Heart Station, Anshan Municipal Environmental Monitoring Center Station, Jinzhou Municipal Environmental Monitoring Center Station and Yingkou Municipal Environmental Monitoring Center.
This standard MEP February 29, 2012 for approval.
This standard since June 1, 2012 implementation.
The standard explanation by the Ministry of Environmental Protection.
Water quality Determination of total nitrogen - Alkaline potassium persulfate digestion - UV spectrophotometric method
1 Scope
This standard specifies the determination of total nitrogen in water alkaline potassium persulfate digestion - UV spectrophotometric method.
This standard applies to surface water, groundwater, industrial wastewater and domestic sewage in the determination of total nitrogen.
When the sample volume is 10ml, the detection limit of this method is 0.05mg/L, measured in the range of 0.20 ~ 7.00mg/L.
2 Normative references
This standard refers to the contents of the following documents or the terms. For undated references, the effective version suitable
For this standard.
HJ/T 91 surface water and wastewater monitoring technical specifications
HJ/T 164 groundwater environmental monitoring technical specifications
3 Terms and Definitions
The following terms and definitions apply to this standard.
TN total nitrogen (TN)
Refers to the conditions specified in this standard can be measured by the sum of N samples dissolved nitrogen and suspended solids, including nitrite
Salts of nitrogen, nitrate nitrogen, inorganic salts, dissolved ammonia and most organic nitrogen compounds nitrogen.
4 principle of the method
At 120 ~ 124 ℃, Alkaline solution of nitrogen in the sample is converted to nitrate nitrogen compounds, using purple
Outside spectrophotometry at the wavelength of 220nm and 275nm, respectively, measured absorbance A220 and A275, according to formula (1) Calculation
Corrected absorbance A, total nitrogen (with N) content and the corrected absorbance A is proportional.
A = A220-2A275 (1)
5 and elimination of interference
5.1 When the above iodine ion content relative to 2.2 times the total nitrogen content, relative to the bromine ion content of more than 3.4 times the total nitrogen content of
When, on the determination of interference.
5.2 water samples hexavalent chromium ions and trivalent iron ions interfere with the determination, may be added to a 5% hydroxylamine hydrochloride solution 1 ~ 2ml
eliminate.
6 Reagents and materials
Unless otherwise indicated, the use of line with national standards of analytical reagent analysis, test water-free ammonia (6.1).
6.1 No ammonia
Per liter of water was added 0.10ml of concentrated sulfuric acid distillation, collecting the distillate in a stoppered glass container. You can also use freshly prepared
Deionized water.
6.2 Sodium hydroxide (NaOH)
Nitrogen content should be less than 0.0005%, nitrogen content determination of sodium hydroxide in Appendix A.
6.3 potassium persulfate (K2S2O8)
Nitrogen content should be less than 0.0005% of potassium persulfate in determination of the amount of nitrogen in Appendix A.
6.4 potassium nitrate (KNO3). reference reagent or pure class distinctions.
At 105 ~ 110 ℃ drying 2h, cooled to room temperature in a desiccator.
6.5 of concentrated hydrochloric acid. ρ (HCl) = 1.19g/ml.
Concentrated sulfuric acid 6.6. ρ (H2SO4) = 1.84g/ml.
6.7 hydrochloric acid solution. 19.
6.8 sulfuric acid solution. 135.
6.9 Sodium hydroxide solution. ρ (NaOH) = 200g/L
Weigh 20.0g of sodium hydroxide (6.2) dissolved in a small amount of water and dilute to 100ml.
6.10 Sodium hydroxide solution. ρ (NaOH) = 20g/L
Amount of sodium hydroxide solution (6.9) 10.0ml, diluted with water to 100ml.
6.11 Alkaline potassium persulfate solution
Weigh 40.0g of potassium persulfate (6.3) was dissolved in 600ml of water (it can be placed in a water bath heated to 50 ℃ completely dissolved); the other
Weigh 15.0g of sodium hydroxide (6.2) dissolved in 300ml of water. After the sodium hydroxide solution was cooled to room temperature, mixing two
Kinds of solution volume to 1000ml, stored in a polyethylene bottle, can be stored for a week.
6.12 potassium nitrate standard stock solution. ρ (N) = 100mg/L
Weigh 0.7218g potassium nitrate (6.4) is dissolved in an appropriate amount of water, go to 1000ml volumetric flask, dilute to the mark with water, mix
uniform. 1 ~ 2ml of chloroform was added as a preservative, in 0 ~ 10 ℃ dark place, is stable for 6 months. It can also be purchased directly
Buy a commercially available certified reference solution.
6.13 potassium standard solution. ρ (N) = 10.0mg/L
10.00ml amount of potassium nitrate stock standard solution (6.12) to 100ml volumetric flask, dilute to the mark with water, mix,
Pro with the existing service.
7 instruments and equipment
7.1 UV spectrophotometer. a 10mm quartz cuvette.
7.2 Autoclave. maximum working pressure of not less than 1.1 ~ 1.4kg/cm2; maximum operating temperature of not less than 120 ~
124 ℃.
7.3 plug ground glass colorimetric tube. 25ml.
7.4 General Commonly used laboratory instruments and equipment.
8 samples
Sample collection and preservation 8.1
Referring HJ/T 91 and the relevant provisions of HJ/T 164 collected samples.
The collected samples were stored in polyethylene bottles good or hard glass bottles with concentrated sulfuric acid (6.6) adjusted to pH 1 to 2,
7d can be stored at room temperature. Store in a polyethylene bottle, -20 ℃ frozen, save for a month.
8.2 Preparation of the sample
Take appropriate samples were adjusted to pH 5-9 with sodium hydroxide solution (6.10) or sulfuric acid solution (6.8), to be tested.
9 analysis step
9.1 Draw a calibration curve
Measure 0.00,0.20,0.50,1.00,3.00 and 7.00ml of potassium nitrate standard solution (6.13), respectively, in 25ml
Stoppered ground glass colorimetric tube, which corresponds to the total nitrogen (as N) content were 0.00,2.00,5.00,10.0,30.0
And 70.0μg. Diluted with water to 10.00ml, then add 5.00ml Alkaline solution (6.11), plugged pipe plug, with
Gauze and wire lashing tight plug, prevent pop. Colorimetric tube was placed in the high-pressure steam sterilizer and heated to a top pressure valve blow off
Valve, heating was continued to 120 ℃ start time, maintaining the temperature between 120 ~ 124 ℃ 30min. Natural cooling, open valve deflated,
Remove the cover, remove the cuvette cooled to room temperature, hold the plug than the color of liquid in the tube and mix by inverting 2-3 times.
Note 1. If there during digestion cuvette nozzle or tube plugs rupture should be re-sampled and analyzed.
Each colorimetric tubes were added 1.0ml of hydrochloric acid solution (6.7), diluted to 25ml marking, stoppered mix. use
10mm quartz cuvette in the spectrophotometer, using water as a reference, were measured at 275nm and 220nm wavelength
Absorbance. Ab is the absorbance of the calibration zero concentration, other standard series corrected absorbance difference between As and Ar according to the formula (2),
(3) and (4) are calculated. In total nitrogen (in N) content (μg) as abscissa and ordinate value corresponding Ar,
Calibration curve.
Ab = Ab220-2Ab275 (2)
As = As220-2As275 (3)
Ar = As-Ab (4)
Where.
Ab - zero concentration (blank) was corrected absorbance;
Ab220 - zero concentration (blank) solution in absorbance at a wavelength of 220nm;
Ab275 - zero concentration (blank) solution at a wavelength of 275nm absorbance at;
As - corrected absorbance of standard solution;
As220 - standard solution to the absorbance at a wavelength of 220nm;
As275 - standard solution absorbance at a wavelength of 275nm at;
Ar - corrected absorbance zero standard solution concentration (blank) was corrected absorbance difference.
9.2 Determination
10.00ml weighed sample (8.2) in 25ml stoppered ground glass colorimetric tube, measured in accordance with step 9.1.
Note 2. When the amount of nitrogen in a sample of more than 70μg, can reduce the amount of sample and diluted with water to 10.00ml.
9.3 blank test
10.00ml with water instead of the sample according to step 9.2 was measured.
10 Results Calculation and representation
10.1 Calculation Results
Referring to equation (2) to (4) and the absorbance of the sample is calculated correcting the difference between the absorbance of the blank test correction Ar, the total sample
Nitrogen concentration ρ (mg/L) according to the formula (5) is calculated.
bV
faA × - =) (rρ (5)
Where.
ρ - Samples of total nitrogen (N to count) mass concentration, mg/L;
Ar - corrected absorbance of the sample and blank test correction absorbance difference;
a - intercept of the calibration curve;
b - the slope of the calibration curve;
V - sample volume, ml;
f - dilution.
10.2 The results are shown
When the measurement result is less than 1.00mg/L, reserved to two decimal places; when not less than 1.00mg/L, rounded to three
effective number.
11 precision and accuracy
11.1 Precision
6 Laboratory of total nitrogen concentration of 0.20,1.52 and 4.78mg/L unified sample were determined, laboratory
Within the relative standard deviation were. 4.1% ~ 13.8%, from 0.6% to 4.3%, from 0.8% to 3.4%; interlaboratory relative standard deviation
Respectively. 8.4%, 2.7%, 1.8%; repeatability limits were. 0.06mg/L, 0.14mg/L, 0.27mg/L; reproducibility limit
They were. 0.07mg/L, 0.17mg/L, 0.35mg/L.
11.2 Accuracy
6 laboratory TN concentrations were (1.52 ± 0.10) mg/L and (4.78 ± 0.34) mg/L of certified reference
Samples were measured relative errors were. 1.3% ~ 5.3%, from 0.2% to 4.2%; final value relative error (RE ± 2 RES)
Respectively. 2.6% ± 2.8%, 1.5% ± 3.2%.
12 Quality Assurance and Quality Control
The correlation coefficient r 12.1 calibration curve should be greater than or equal 0.999.
12.2 each batch of samples should at least make a blank test, corrected absorbance Ab blank test should be less than 0.030. Exceeding this value
Should check the test water, reagent (mainly sodium and potassium persulfate) purity, high-pressure vessels and steam sterilizer sewage
Stained health
10% of each batch of samples to be measured in parallel 12.3 at least double the sample, number of samples is less than 10 when measured at least a parallel double
kind. When the total nitrogen content of the sample ≤1.00mg/L, the measurement results of the relative deviation should be ≤10%; when the total nitrogen content of the sample> 1.00mg/L
When the measurement results relative deviation should be ≤5%. The measurement results parallel double the average of the sample reported.
12.4 each batch of samples to be measured a standard solution calibration curve point intermediate concentrations, the measured results of the calibration curve of the concentration point
The relative degree of error should be ≤10%. Otherwise, you must re-calibration curve.
12.5 each batch of samples should be tested at least 10% of the spiked samples, the number of samples is less than 10, should be measured at least one spiked sample
Products, and the recovery should be between 90% and 110%.
13 Notes
Some 13.1 nitrogenous organic compounds under assay conditions specified in this standard can not be fully converted to nitrate.
13.2 should be ...