Fertilizers. Determination of total nitrogen nitrogen content
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ICS 65.080
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Agricultural Industry Standard of the People's Republic of China
NY/T2542—2014
Determination of total nitrogen
Fertilizers-Determination of total nitrogen contentReleased on 2014-03-24
Implemented on 2014-06-01
Ministry of Agriculture of the People's Republic of China
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This standard was drafted in accordance with the rules given in GB/T1.1-2009. This standard was proposed by the Ministry of Agriculture of the People's Republic of China and is classified as NY/T2542-2014
Drafting units of this standard: National Fertilizer Quality Supervision and Inspection Center (Beijing), Beijing Fertilizer Quality Supervision and Inspection Station. The main drafters of this standard: Bao Wankui, Sun Youning, Liu Mi, Liu Shanjiang, Lin Yin, and Hou Xiaona. T
Download Fromhttp://bbs.infoeach.com1 Scope
DownloadFromhttp://bbs.infoeach.com Fertilizer, determination of total nitrogen content
NY/T2542—2014
This standard specifies the test methods for determination of total nitrogen content in fertilizers, such as back titration after distillation, direct titration after distillation, and Dumas combustion method:
The standard is applicable to the determination of total nitrogen content in solid or liquid fertilizers. This standard is also applicable to soil conditioners. 2 Normative references
The following documents are indispensable for the application of this document. For all dated references, the version with the date is applicable to this document. For all undated references, the latest version (including all amendments) is applicable to this document. HG/T3696 Preparation of standard solutions, preparations and products for chemical analysis of inorganic chemical products NY/T887 Determination of density of liquid fertilizers
3 Back titration after distillation
3.1 Principle
Directly distill ammonia in an alkaline medium or directly heat-titrate ammonia after reducing nitrate with nitrogen alloy; or convert the original nitrate into ammonium salt in an acidic medium, and digest it with concentrated sulfuric acid in the presence of a catalyst to convert organic nitrogen or amide nitrogen into ammonium salt. Distill ammonia from the alkaline solution. Absorb nitrogen in excess sulfuric acid solution, and back titrate with sodium hydroxide standard titration solution in the presence of methyl red and methylene blue mixed indicators to determine the total nitrogen content.
3.2 Reagents and materials
The preparation of reagents, water and solutions used shall be carried out in accordance with the provisions of HG/T3696 when the specifications and preparation methods are not specified. 3.2.1 Sulfuric acid.
3.2.2 Hydrochloric acid.
3.2.3 Chromium powder: fineness less than 250μ1.
3.2.4 Sodium sulfate hydrate
3.2.5 Nitrogen alloy (Cu: 50%, Al: 45%, Zn: 5%): fineness less than 850um. 3.2.6 Mixed catalyst: grind 1000g potassium sulfate and 50g copper sulfate pentahydrate respectively and mix them thoroughly. 3.2.7 Hydrochloric acid solution: 1+1
3.2. 8 Sulfuric acid solution: c(1/2H,S0,)=0. 5 mol/ L, 3.2.9 Sodium hydroxide solution: p(NaOH)=400 g/L. 3.2.10 Standard sodium hydroxide titration solution: c(NaOH)=0.5I1ol/1 3.2.11 Methyl red and methylene blue mixed reagent: add 0.10g methyl red and 0.05g methylene blue to about 501m3 ethanol, dissolve them, dilute to 100ml with ethanol, mix: 3.2.12 Universal pH test paper,
3.3 Instruments
3.3.1 Common laboratory instruments.
3.3.2 Multi-hole digestion instrument with a temperature of up to 400℃, 3.3.3 Nitrogen determination distillation instrument or distillation apparatus with the same function. DownloadFromhttp://bbs.infoeach.comNY/T2542—2014
3.4 Preparation of Samples
DownloadFromhttp://bbs.infoeach.comSolid sample is reduced to about 100g and quickly ground until it passes through a .50 rrirn test sieve (if the sample is moist, it can pass through a 1.00 3.5 Preparation of test solution
3.5.1 Selection of preparation method
For samples with unknown nitrogen forms, the appropriate preparation method can be selected: For samples with unknown nitrogen forms, the reduction digestion method can be selected directly, or the corresponding preparation method can be selected after qualitative identification of the nitrogen form (see Appendix A): The acid dissolution method is applicable to samples containing ammonium nitrogen: The reduction method is applicable to samples containing nitrate nitrogen, or samples containing only nitrate nitrogen and ammonium nitrogen; The digestion method is applicable to all samples not containing nitrate nitrogen: The reduction digestion method is applicable to samples that are not suitable for the above methods and for samples that have been identified. 3.5.2 Acid dissolution method
Weigh a sample containing no more than 235 mg of total nitrogen (0.2g~-2g (accurate to 0.0001) into a digestion (distillation) tube, add 10ml of water and 2ml of hydrochloric acid solution (3.2.7), shake to dissolve the sample: Note: For samples that may be lost due to selection, the weighing and dissolution processes should be completed quickly. 3.5.3 Reduction method
Weigh a sample containing no more than 235 mg of total nitrogen and no more than 60 mg of nitrate nitrogen (0.2g~2g (accurate to 0.0001g) into a digestion (distillation) tube, add 70ml of water and shake until the sample is dissolved, then add 3g of nitrogen determination alloy (3.2.5), connect the digestion (distillation) tube to the marking plate. Prepare the nitrogen determination distillation instrument (3.3.3). After connecting all the devices, add 20mL of sodium hydroxide solution (3.2.9) and let it stand for 10 minutes to distill.
3.5.4 Digestion method
Weigh 0.2g~2g of the sample containing 35mg of total nitrogen (accurate to 0.0001g) into the digestion (distillation) tube, add 0.5 pentahydrate sulfuric acid lock (3.2.4), carefully add 10ml of sulfuric acid (3.2.1), insert the long-necked slope funnel, place it on the digestion instrument (3.3.2), set the temperature to 380℃, digest until it is clear or flake-colored, then heat for 2011min and stop, wait for the digestion (distillation) tube to cool to room temperature and carefully add 70ml of water. When the sample contains organic nitrogen, use 2g of mixed catalyst (3.2.6) instead of 0.5g of copper sulfate pentahydrate (3.2.4). 3.5.5 Reduction digestion method
Weigh 0.2g to 2g (accurate to 0.0001g) of a sample containing no more than 235mg of total nitrogen and no more than 60mg of nitrate nitrogen into a digestion (steaming) tube, add 5ml of water, shake, and after the sample is dissolved, add 1.2g of chromium powder (3.2.3) and 7mL of hydrochloric acid (3.2.2) and let it stand for 5min [0mn Insert a long-necked glass funnel: Place the digestion (distillation) tube on the F digestion instrument, adjust the temperature to 100°C and heat until boiling and large dark green bubbles are produced, continue heating for 2min~3min, cool to room temperature, add 2 mixed catalysts (3.2.6), carefully add 10ml. sulfuric acid (3.2.1), insert a long-necked glass funnel, then place the digestion (distillation) tube on the D digestion instrument, gradually heat to 200℃-250℃, and after the dark green bubbles are significantly reduced or disappear, heat to 380℃ for reverse digestion. The digestion tube should be shaken continuously during the digestion process to ensure that the solution in the tube does not clump. After the digestion sample solution turns purple-red, heat it for another 20)min and stop, and carefully add 70ml. water after the digestion (distillation) tube cools to room temperature.
Note: After adding 10l sulfuric acid, soak overnight before digestion. 3.6 Distillation
Accurately add 50.0ml sulfuric acid solution (3.2.8) and 4~5 drops of methyl red and methyl blue mixed indicator (3.2.11) to a 500ml conical flask. Place the conical flask on the hydrogen liquid receiving tray of the distillation instrument. Connect the digestion (distillation) tube to the distillation head of the ammonia distiller (3.3.3). Add sodium hydroxide solution (3.2.9) and distill. When the distillate reaches 300ml or more, use pFI test paper (3.2.12) to check the drops of ammonia liquid inlet ratio tube. If it does not show alkalinity, end the distillation. Note: Sodium hydroxide solution (3.2.The amount of acid added should be based on the amount of acid added to neutralize the sample solution. It is advisable to add 20 ml more. 3.7 Titration
The sulfuric acid solution after titration with sodium oxychloride standard titration solution (3.2.10) is gray-green. 2
DownloadFromhttp://bbs.infoeach.com3.8 Blank test
DownloadFromhttp://bbs.infoeach.comExcept for not adding sample, the other steps are the same as the sample solution. 3.9 Expression of analysis results
The total nitrogen () content is expressed as mass fraction u, and the value is expressed as percentage, calculated according to formula (1): (V,-Vo)c≥0.01401/100%
Wu Zhong:
NY/T 2542—2014
In the blank test, the volume of sodium hydroxide standard titration solution is in liters (ml); When measuring the sample, the volume of sodium hydroxide standard titration solution is in milliliters (mL); The concentration of sodium hydroxide standard titration solution is in mol/l for the sample and blank test. The millimolar mass of nitrogen is in grams per mole (g/natnol); The mass of the sample is in grams (g)
The arithmetic mean of the parallel determination results is the determination result, and the result is retained to two decimal places. 3.10 Allowable difference
The absolute difference of the parallel determination results shall not exceed 10.30. The absolute difference of the determination results of different laboratories shall not exceed 0.50%. 4 Direct titration after distillation
4.1 Principle
Directly distill ammonia in alkaline medium or reduce nitrate with nitrogen alloy and distill hydrogen directly; or reduce nitrate to ammonium salt in acrid medium. In the presence of catalyst, digest with concentrated sulfuric acid to convert organic nitrogen or amide nitrogen into ammonium salt. Distill ammonia from alkaline solution. Absorb ammonia in boric acid solution and titrate directly with sulfuric acid standard titration suspension in the presence of methyl red and bromocresol green mixed indicator to determine the total nitrogen content:
4.2 Reagents and materials
The preparation of reagents, water and solution used shall be carried out in accordance with HG/T3696 when the specifications and preparation methods are not specified. 4.2.1 Boric acid solution = p(H:BO),) = 20 g/L. 4.2.2 Standard sulfuric acid titration solution: (1/2H2S),) = .5mol/L. 4.2.3 Mixed indicator of methyl red and bromocresol green: Add 0.07 g of methyl red and 0.10 g of bromocresol green to about 0 ml of ethanol. After dissolving, dilute to 100 ml with ethanol.
4.3 Instruments
4.3.1 Common laboratory instruments.
4.3.2 Multi-hole digester with a concentration of up to 400%. 4.3.3 Full-scale nitrogen analyzer, nitrogen determination distillation instrument or distillation apparatus with the same function. 4.4 Preparation of samples, preparation of sample solutions and distillation Except for adding 50 ml of boric acid solution (4.2.1) and 1 to 5 drops of methyl red and bromocresol green mixed indicator (1.2.3) to a 500 ml flask, the preparation of other samples, preparation of sample solutions and distillation are the same as 3.1, 3.5 and 3.6 respectively. Note: When using a fully automatic nitrogen analyzer to measure the test solution prepared by the reduction method, the delay time must be set to more than 10 minutes. 4.5 Titration
Use sulfuric acid standard titration solution (4.2.2) to directly titrate the receiving solution until the solution screen turns purple-red. Note: When the automatic nitrogen determination is performed, the distillation and titration steps are automatically completed. 4.6 Blank test
Except for not adding the sample, the other steps are the same as the sample solution. 3
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4.7 Expression of analysis results
DownloadFromhttp://bbs.infoeach.comThe total nitrogen (N) content is expressed as mass fraction - the value is expressed as percentage, calculated according to formula (2), (V, -V): X0. 014 01 × 100%
Wu Zhong:
When determining the sample, the volume of the sulfuric acid standard titration solution is millimole (iI); when testing the empty cavity, the volume of the sulfuric acid standard titration solution is liter (ml). When testing the sample and the empty cavity, the concentration of the sulfuric acid standard titration solution is mole per liter (mol/L); the millimole mass of nitrogen is gram per millimole (g/mmiol); the mass of the sample is gram (g).
Take the arithmetic mean of the parallel determination results as the determination result, and retain the result to two decimal places. 4.8 Allowable Difference
The allowable difference between the parallel determination results and the determination results of different laboratories shall comply with the requirements of Table 1. Table 1
Total mass fraction.
Absolute difference of the semi-parallel determination results,
Absolute difference of the results of different laboratories, %
5 Dumas combustion method
5.1 Principle
Under high temperature and oxygen-rich environment, the sample is quantitatively burned and digested, and the nitrogen in the sample is converted into molecular nitrogen and nitrogen oxides. Driven by the carrier gas (), the nitrogen oxides enter the reduction area and are converted into molecular nitrogen. The other gaseous interfering components generated are removed by appropriate absorbents. The separated nitrogen is then tested in a thermal conductivity detector. 5.2 Reagents and Materials
5.2.1 Carbon dioxide (CO2): purity not less than 99.995% 5.2.2 Oxygen (0): purity not less than 99.995%. 5.2.3 Aspartic acid or urea: purity not less than 99%. 5.3 Instruments
5.3.1 Common laboratory instruments
5.3.2 Arbor-Smith nitrogen analyzer, equipped with a thermal conductivity detector. 5.4 Analysis steps
5.4.1 Preparation of samples
Solid samples are reduced to about 100, and quickly rubbed until they all pass through a 0.50mm aperture test sieve (if the sample is damp, it can pass through a 1.00mm test sieve) and mixed evenly. Place in a clean, dry container; after shaking the liquid sample several times, quickly take 100ml and place in a clean, dry container.
5.4.2 Sample weighing
Weigh 0.1g~0.4g (accurate to 0.0001g) of the fertilizer sample that passes through a 0.50mm aperture test sieve. Wrap the solid sample in tin foil (or nitrogen-free paper) specially used for the Fermi nitrogen analyzer, and directly weigh the solid sample into the tin foil and seal it for testing. 5.4.3 Instrument calibration
Perform blank test and conditional test according to the instrument calibration procedure. After meeting the requirements, perform determination with 250 m aspartic acid and/or 1001 g urea (5.2.3) and wait for the average calibration factor to be obtained. 4
DownloadFromhttp://bbs.infoeach.com5.4.4 Sample determination
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Put the prepared sample into the sample tray, select the best conditions for sample determination, and use the calibration factor to calibrate the determination result. Note: Reference conditions of Muramas nitrogen analyzer: heating furnace combustion tube temperature 960%, secondary combustion section temperature 800℃, reduction tube overflow 815℃: oxygen (pressure relief valve gas pressure 0.22MPa. Carbon dioxide pressure relief gas output 0.12MPa: oxygen flow 100)mL/min～170)ml/min: oxygen flow time 60s~-801 5
5.5 Expression of analysis results
Total nitrogen content is expressed as mass fraction, and the value is expressed as percentage, which is given directly by the instrument. The arithmetic mean of the parallel determination results is taken as the determination result, and the result is retained to two decimal places. 5.6 Allowable difference
The allowable difference between the parallel determination results and the determination results of different laboratories shall meet the requirements of Table 2. Table 2
Total nitrogen mass fraction, %
Absolute difference of parallel determination results, %
Absolute difference of results from different laboratories, %
6 Conversion of mass concentration
10. 00~~20. 00
The total nitrogen content of the liquid sample is expressed as mass concentration p(N), expressed in grams per liter (g/L), and calculated according to formula (3). o(N) = 1 000up
Where:
1000 —
-The coefficient for converting grams per milliliter to grams per liter, expressed in milliliters per liter (mI./I.); Mass fraction of total nitrogen (N) in the sample:
Density of the liquid sample, expressed in grams per milliliter (g/rnl.) The result is retained to the decimal place.
The determination of the density of the liquid sample shall be carried out in accordance with the provisions of NY/T887. DownloadFromhttp://bbs.infoeach.com20.00
NY/T 2542—2014
A.1 Scope
DownloadFromhttp:/bbs.infoeach.comAppendix A
【Informative Appendix】
Qualitative Identification of Nitrogen Forms in Fertilizers
Appendix A specifies the qualitative identification methods of nitrate nitrogen, organic fluorine and amide nitrogen in fertilizers. A.2 Reagents and Materials
The preparation of reagents, water and solutions used shall be in accordance with HG/T3696 when the specifications and preparation methods are not specified: A.2.1 Sulfuric acid.
A.2.2 Acid solution: $(CH:00H) 20ml/1sA.2.3 Sodium hydroxide solution: p(Na0H) 400/1.A.2.4 Nitric acid test powder: weigh 4.0 & para-aminobenzenesulfonic acid (C:H,N0).S), 2.0 g naphthylamine (C1.H,V) and 150 g citric acid (CIH.0,), grind into a fine mixture, protect from moisture and light, and mix with B powder. Mix zinc powder and manganese sulfate (MnS0,) in a 1:1 fine mixture and add:
A.2.5 pH test paper
A.3 Identification method
A.3.1 Identification of nitrate nitrogen
Dissolve a small amount of sample in water and filter. Add about 0.5% nitric acid test powder (A, 2.4) to the filtrate and add 5 to 10 drops of acetic acid solution (A.2.2). If the filtrate turns obviously pink within 2 minutes, it indicates that it contains nitrate nitrogen. A.3.2 Identification of organic nitrogen
Take a small amount of sample and put it into a digestion (steaming) tube. Add 3m[~5ml. sulfuric acid (A.2.1). After shaking, observe that the color turns black, indicating that it contains organic nitrogen.bZxz.net
A.3.3 Identification of amide nitrogen
Put a small amount of sample into a digestion (distillation) tube, add water to dissolve, add 10ImI. sodium hydroxide solution (A, 2.3) and distill. When the distillate in the receiving bottle reaches 40:3 ml or more, use pH test paper (A.2.5) to check whether there are drops of ammonia liquid in the ammonia delivery pipe 11: If pH is less than 7, it indicates that there is no amide nitrogen; if pH is greater than 7, continue distillation for 2 minutes and check again. If pH is still greater than 7, it indicates that there is amide nitrogen. ti
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Agricultural Industry Standard
Determination of Total Content of Fertilizer
NY/T 242---2u11
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