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HJ 717-2014: Soil quality. Determination of total nitrogen. Modified Kjeldahlmethod
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Soil quality. Determination of total nitrogen. Modified Kjeldahlmethod
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HJ 717-2014
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Basic data | Standard ID | HJ 717-2014 (HJ717-2014) | | Description (Translated English) | Soil quality. Determination of total nitrogen. Modified Kjeldahlmethod | | Sector / Industry | Environmental Protection Industry Standard | | Classification of Chinese Standard | Z18 | | Word Count Estimation | 11,126 | | Date of Issue | 11/27/2014 | | Date of Implementation | 1/1/2015 | | Quoted Standard | HJ 537; HJ 613; HJ/T 166 | | Regulation (derived from) | Ministry of Environmental Protection Notice 2014 No. 77 | | Issuing agency(ies) | Ministry of Ecology and Environment | | Summary | This Standard specifies the determination of total nitrogen content in soil samples Kjeldahl method. This Standard applies to the determination of total nitrogen in the soil. When the sample volume is lg time, this standard method detection limit of 48mg/ | HJ 717-2014: Soil quality. Determination of total nitrogen. Modified Kjeldahlmethod---This is a DRAFT version for illustration, not a final translation. Full copy of true-PDF in English version (including equations, symbols, images, flow-chart, tables, and figures etc.) will be manually/carefully translated upon your order.
Soil quality.Determination of total nitrogen.Modified Kjeldahlmethod
People's Republic of China National Environmental Protection Standards
Soil quality - Determination of total nitrogen Kjeldahl method
Soil quality - Determination of total nitrogen - Modified Kjeldahl
method
(release
draft)
Issued on.2014-11-27
2015-01-01 implementation
Ministry of Environmental Protection issued
i Table of Contents
Preface ii
1. Scope .1
2 Normative references .1
3 Terms and definitions
4 principle of the method .1
5 Reagents and materials 1
6 .2 equipment
Sample 3 7
Analysis Step 8 .3
9 Results Calculation and representation .4
10 precision and accuracy .5
11 Quality assurance and quality control .. 5
12 waste disposal .5
Appendix A (informative) precision and accuracy ..6
Foreword
To implement the "People's Republic of China Environmental Protection Law", protecting the environment, safeguarding human health and regulating the determination of total nitrogen in soil,
Development of this standard.
This standard specifies the determination of total nitrogen in soil samples Kjeldahl method.
This standard is the first release.
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. Tianjin Environmental Monitoring Center.
The standard verification unit. State Key Lab of odor pollution control environmental protection, scientific research and monitoring by the Ministry of Agriculture, Environmental Protection, Tianjin River
Eastern Environmental Monitoring Station, Tianjin Tanggu District Environmental Monitoring Station, Tianjin Dongli District, Tianjin, Hebei District environmental monitoring and environmental monitoring stations.
This standard is approved by the Ministry of Environmental Protection November 27, 2014.
This standard since January 1, 2015 implementation.
The standard explanation by the Ministry of Environmental Protection.
1 Soil quality - Determination of total nitrogen Kjeldahl method
WARNING. The reagents used in this method has a certain corrosive, the operation should avoid direct contact with these chemicals,
Sample digestion process should be carried out in a fume hood; thermal contact with organic perchlorate explosive, so decomposed solution must be cooled
Perchloric acid was added.
1 Scope
This standard specifies the determination of total nitrogen in soil samples Kjeldahl method.
This standard applies to the determination of total nitrogen in the soil.
When the sample volume is 1g, the present standard method detection limit of 48 mg/kg.
2 Normative references
This standard refers to the contents of the following documents or the terms. For undated references, the effective version applies to this standard.
HJ 537 Water quality - Determination of ammonia distillation - and titration
HJ 613 Determination of dry matter and soil moisture weight method
HJ/T 166 soil environmental monitoring technical specifications
3 Terms and Definitions
The following terms and definitions apply to this standard.
TN total nitrogen
The sum of the nitrogen content of the sample under the conditions specified in this standard can be measured, including organic nitrogen (such as proteins, amino acids, nucleic acids,
Urea, etc.), nitrate, nitrite and ammonium nitrogen, but also including some linked nitrogen, nitrogen-containing azo compounds and azide.
4 principle of the method
Total nitrogen in soil under the action of sodium thiosulfate, concentrated sulfuric acid, perchloric acid and the catalyst, the oxidation-reduction reaction is completely converted to ammonium
nitrogen. Alkalized solution after digestion distilled ammonia is absorbed by boric acid titration with a standard solution of hydrochloric acid, according to the amount of standard solution of hydrochloric acid to calculate
Total nitrogen content of the soil.
5 Reagents and materials
The reagents used in this standard, unless otherwise indicated, the use of chemical reagents analytical line with national standards of analysis, test water-free ammonia
(5.1).
5.1 No ammonia
Per liter of water was added 0.10 ml of concentrated sulfuric acid (5.2) distillation, collecting the distillate in a stoppered glass container, it can also be used to freshly prepared
Deionized water.
5.2 Concentrated sulfuric acid. ρ (H2SO4) = 1.84 g/ml, pure class distinctions.
5.3 of concentrated hydrochloric acid. ρ (HCl) = 1.19 g/ml.
5.4 perchloric acid. ρ (HClO4) = 1.768 g/ml.
Ethanol 25.5. ρ (C2H6O) = 0.79 g/ml.
5.6 potassium sulfate (K2SO4).
5.7 pentahydrate (CuSO4 • 5H2O).
5.8 Titanium dioxide (TiO2). pure class distinctions.
5.9, sodium thiosulfate pentahydrate (Na2S2O3 • 5H2O).
5.10 sodium hydroxide (NaOH). pure class distinctions.
5.11 boric acid (H3BO3). pure class distinctions.
5.12 anhydrous sodium carbonate (Na2CO3). reference reagents.
5.13 Catalyst.200 g potassium sulphate (5.6), 6 g of copper sulfate pentahydrate (5.7) and 6 g of titanium dioxide (5.8) in a glass mortar (6.2) are thoroughly mixed
Uniform, fine, stored in the reagent bottle to save.
5.14 reductant. sodium thiosulfate pentahydrate (5.9) after grinding through the 0.25 mm (60 mesh) sieve (6.3), with the existing Pro.
5.15 Sodium hydroxide solution. ρ (NaOH) = 400 g/L.
Weigh 400 g of sodium hydroxide (5.10) was dissolved in 500 ml of water, cooled to room temperature and diluted to 1000 ml.
5.16 boric acid solution. ρ (H3BO3) = 20 g/L.
Weigh 20 g of boric acid (5.11) dissolved in water and diluted to 1000 ml.
5.17 Sodium carbonate standard solution. c (1/2 Na2CO3) = 0.0500 mol/L.
Weigh 2.6498 g (dried at 250 ℃ 4h and cooled to room temperature, the dryer) of anhydrous sodium carbonate (5.12), was dissolved in a small amount of water,
Moved into 1000 ml flask, diluted with water to the mark, shake. Stored in polyethylene bottles, storage time should not exceed one week.
5.18 methyl orange indicator solution. ρ = 0.5 g/L.
Weigh 0.1 g of methyl orange dissolved in water and diluted to 200 ml.
5.19 hydrochloric acid standard stock solution. c (HCl) ≈0.05 mol/L.
The indexing Pipette 4.20 ml of concentrated hydrochloric acid (5.3), and diluted with water to 1000 ml, the solution concentration of about 0.05 mol/L. Its quasi
Calibration concentration determined in the following manner.
With no indexing Pipette 25.00 ml of standard solution of sodium carbonate (5.17) in 250 ml Erlenmeyer flask, dilute with water to about 100 ml,
Add 3 drops of methyl orange indicator solution (5.18), with a hydrochloric acid standard stock solution was titrated to an orange color from orange to become just recorded hydrochloric acid standard
The amount of standard solution. Its exact concentration is calculated as follows.
VC
0500.000.25 (1)
Where. Standard C-- hydrochloric acid solution concentration, mol/L;
V - the amount of hydrochloric acid standard solution, ml.
5.20 hydrochloric acid standard solution. c (HCl) ≈0.01 mol/L.
Draw 50.00 ml stock standard solution of hydrochloric acid (5.19) in 250 ml flask, diluted with water to the mark.
5.21 mixed indicator. A 0.1 g and 0.02 g bromocresol green methyl red dissolved in 100 ml of anhydrous ethanol (5.5) in.
6 Equipment
6.1 mill.
6.2 glass mortar.
36.3 Soil sieve. aperture of 2 mm (10 mesh); 0.25 mm (60 mesh).
6.4 Analytical balance. accuracy of 0.0001 g and 0.001 g.
6.5 special perforated digestion or a hot plate (temperature up to 400 ℃).
6.6 Kjeldahl distillation apparatus (see FIG. 1) or ammonia distillation apparatus (see HJ 537).
5- heating apparatus; 1- Kjeldahl distillation flask; 2- Nitrogen ball; 3 - Straight condenser; 4- receiving flask
Figure 1 Kjeldahl distillation apparatus
6.7 Kjeldahl digestion flask. volume 50 ml or 100 ml.
6.8 Acid burette (minimum scale ≤0.1 ml). 25 ml or 50 ml.
6.9 conical flask. volume 250 ml.
6.10 General common laboratory equipment.
7 Sample
Sample collection and preservation 7.1
Soil samples were collected and stored with reference to HJ/T 166 relevant regulations.
7.2 Preparation of the sample
The air-dried soil sample was placed in the dish, flat to 2 ~ 3 cm thick, thin, first removing plants, insects, stones and other debris, or with a hammer
Porcelain pestle to crush clods, turning several times a day to dry naturally.
Mix well air-dried soil, using quartering, whichever is two, one retained by a grinder (6.1) all through the ground to 2 mm
(10 mesh) soil sieve (6.3). Soil samples were taken 10 g ~ 20 g sifted, milled to all through the 0.25 mm (60 mesh) sieve soil
(6.3), installed in a sample bag or vial.
7.3 Determination of dry matter content
Weighed over 2 mm (10 mesh) sieve soil samples (6.3) after the reference to HJ 613 Determination of dry matter content of the soil.
Analysis Step 8
8.1 Digestion
Weighed amount sample (7.2) 0.2000g ~ 1.0000g (nitrogen-containing approximately 1mg), accurate to 0.1mg, into the Kjeldahl digestion flask (6.7)
4 with a small amount of water (about 0.5ml ~ 1ml) wetting 4ml was added concentrated sulfuric acid (5.2), small funnel cover bottle, bottle rotation Kjeldahl digestion
(6.7) to mix uniformly, soaked over 8 hours.
Using a dry, long-necked funnel 0.5g reductant (5.14) (6.7) was added to the bottom of the Kjeldahl digestion flask, placed digestion (or electric
Board) (6.5) on the heat until smoke stops heating. After cooling, the catalyst was added 1.1g (5.13), shake, continued digestion (or electricity
Hot plate) (6.5) on Digestion. When holding Digestion micro-boiling state, the white smoke to reach the bottleneck 1/3 roundabout until Digestion liquid and soil samples all turned gray
After greenish color, indicating complete digestion, and then continue Digestion 1h, cooled. In soil samples Digestion process, if not completely digested,
After adding a few drops of perchloric acid may be cooled before Digestion.
Note 1. The digestion temperature must not exceed 400 ℃, high temperature to prevent sidewall leaving salt thermal decomposition, resulting in the loss of nitrogen.
8.2 Distillation
8.2.1 distillation apparatus according to Figure 1 is connected, check the tightness of distilled prior to distillation apparatus, and wash pipe.
8.2.2 The digestion solution (8.1) all transferred to a distillation flask, and washed with water Kjeldahl digestion flask (6.7) 4 to 5 times the total amount does not exceed 80ml,
Connected to the Kjeldahl nitrogen (or ammonia) on the distillation apparatus (6.6). 20ml of boric acid solution in a 250ml Erlenmeyer flask (6.9) in (5.16) and
3 drops of mixed indicator (5.21) absorbed distillate catheter tip inserted into the absorbing liquid below the liquid level. The distillation flask into a 45 ° inclined, slowly along the wall
Sodium hydroxide solution was added 20ml (5.15), it is formed in the bottom layer of lye. Nitrogen ball quickly connect and condenser, shake retort so
Mix the solution thoroughly, began to distill, to be a distillate volume of about 100ml, distillation was complete. Adjusted to pH4.5 with a small amount of wash water condensation
End of the tube.
Note 2. If the digestion digestion flask precipitate adhering to the sides of the bottle, using a small amount of water may be added after the ultrasonic oscillators which was dissolved in water and then completely transferred
To the distillation flask.
8.3 Titration
With hydrochloric acid standard solution (5.20) titration after distillation distillate (8.2.2), the solution color from blue to green to red and purple, used for recording
Standard hydrochloric acid solution volume.
Note 3. If the content of the sample is greater than 104mg/kg, can be used instead of hydrochloric acid at a concentration of standard 0.0500mol/L of stock solution (5.19) titration.
Note 4. If you use automatic Kjeldahl apparatus, according to the instruction digestion, distillation and titration of the sample.
8.4 blank test
Kjeldahl digestion flask (6.7) was not added to the sample, following the procedure of determination of 8.1 to 8.3, the volume of records with standard hydrochloric acid solution.
9 Results Calculation and representation
Soil total nitrogen content (mg/kg) according to the formula (2).
N =
dm
HCl
wm
cVV
10000.14) (01 (2)
Where. N - the total nitrogen content of the soil, mg/kg;
V1-- sample consumption volume of hydrochloric acid standard solution, ml;
Volume V0-- blank consumption hydrochloric acid standard solution, ml;
HClc - concentration of hydrochloric acid standard solution, mol/L;
514.0-- nitrogen molar mass, g/mol;
dmw - dry matter content of the soil sample,%;
m-- said soil samples quality, g.
Results reserved three significant digits in scientific notation.
10 precision and accuracy
10.1 Precision
6 laboratories nitrogen content was 250mg/kg, 500 mg/kg and 1.50 × 103mg/kg of unified samples were measured. Experiments
Indoor relative standard deviation. 2.0% to 13%, 3.1% 7.3% 2.2% - 4.8%; interlaboratory relative standard deviation. 5.1%, 6.9%
5.0%; repeatability limit. 66mg/kg, 77mg/kg, 122 mg/kg; reproducibility limit. 71mg/kg, 126mg/kg, 220mg/kg.
10.2 Accuracy
6 laboratories nitrogen content was 265mg/kg, 435mg/kg and 1.33 × 103mg/kg actual soil samples were spiked points
Analysis of measurement. The recoveries were 88.4% ~ 105%, 88.2% ~ 109%, 87.3% ~ 99.4%; recoveries final value
(94.0 ± 11.8)%, (96.0 ± 14.0)%, (92.9 ± 7.8)%.
4 laboratory nitrogen content (720 ± 90) mg/kg of standard samples were analyzed, and the relative error of the final value (-0.5 ± 4.4)
%.
11 Quality Assurance and Quality Control
11.1 blank test
Each batch of samples should be done at least two full-program blank, blank value (blank sample volume of standard solution of hydrochloric acid consumed) should be less than 0.80ml.
Parallel sample measured 11.2
Each batch of samples shall be 10% of the sample was measured in parallel, when 10 samples or less, at least one parallel samples. Parallel twin-like measurement results
If the relative deviation should be within 15%.
11.3 Determination of the standard sample
Each batch of samples measured parallel twin QC samples, the measured value must fall to ensure quality control sample values (95% confidence level) within range.
11.4 recoveries were measured
If there is no standard soil samples, each batch of samples should be 10% to 20% recovery rate determined number of samples less than 10, the appropriate increase
Gaga standard frequency. The actual sample recoveries should be within 75% to 115%.
12 waste disposal
High-concentration samples and analysis of the waste generated during the experiment after, should be placed in an appropriate closed container preservation, and entrusted capital
Quality processing units, personnel and prevent damage to the environment.
6 Appendix A
(Informative)
Precision and accuracy
Table A.1 precision test data collection sheet Unit. mg/kg
laboratory
Numbering
Sample 1 Sample 2 Sample 3
ix is
RSDi
(%) Ix is
RSDi
(%) Ix is
RSDi
(%)
1 246 29.7 13 520 26.9 5.2 1.33 × 103 41.1 3.1
2 252 19.3 7.6 541 30.6 5.7 1.40 × 103 46.5 3.3
3 273 28.8 10.6 512 37.4 7.3 1.27 × 103 60.3 4.8
4 274 5.47 2.0 612 19.1 3.1 1.46 × 103 42.2 2.9
5 280 21.3 7.6 523 25.8 4.9 1.32 × 103 29.4 2.2
6 269 27.6 11 525 22.3 4.2 1.36 × 103 35.5 2.6
x 266 539 1.36 × 103
S '13.5 37.1 66.5
RSD '(%) 5.1 6.9 5.0
Repeatability limit r 66 77 122
Reproducibility limit
Table A.2 actual spiked test summary table
Lab ID
Sample 1 Sample 2 Sample 3
iP (%) iP (%) iP (%)
1 90.0 94.2 91.7
2 88.4 88.2 93.8
3 94.0 94.6 92.2
94.8 96.8 99.4 4
5,105,109 87.3
6 91.4 93.3 92.7
P (%) 93.9 96.0 92.9
PS (%) 5.9 7.0 3.9
7 Table A.3 certified reference sample test data summary table
Lab ID
North China Plain GSS-13 content (mg/kg)
ix iRE (%)
1702 -2.5
2716 -0.6
3739 2.6
6711 -1.3
) (% RE - -0.5
) (% RES - 2.2
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