CN105548458B - A kind of detection method of composite fertilizer's nitrogen content - Google Patents
A kind of detection method of composite fertilizer's nitrogen content Download PDFInfo
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- CN105548458B CN105548458B CN201510943522.XA CN201510943522A CN105548458B CN 105548458 B CN105548458 B CN 105548458B CN 201510943522 A CN201510943522 A CN 201510943522A CN 105548458 B CN105548458 B CN 105548458B
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- sodium hydroxide
- detection method
- sulfuric acid
- compound fertilizer
- nitrogen content
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- 239000003337 fertilizer Substances 0.000 title claims abstract description 34
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 title claims abstract description 28
- 229910052757 nitrogen Inorganic materials 0.000 title claims abstract description 14
- 238000001514 detection method Methods 0.000 title claims abstract description 11
- 239000002131 composite material Substances 0.000 title abstract 4
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims abstract description 60
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims abstract description 36
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims abstract description 26
- IAZDPXIOMUYVGZ-UHFFFAOYSA-N Dimethylsulphoxide Chemical compound CS(C)=O IAZDPXIOMUYVGZ-UHFFFAOYSA-N 0.000 claims abstract description 22
- KJFMBFZCATUALV-UHFFFAOYSA-N phenolphthalein Chemical compound C1=CC(O)=CC=C1C1(C=2C=CC(O)=CC=2)C2=CC=CC=C2C(=O)O1 KJFMBFZCATUALV-UHFFFAOYSA-N 0.000 claims abstract description 18
- 238000000034 method Methods 0.000 claims abstract description 12
- 238000001035 drying Methods 0.000 claims abstract description 7
- 238000007873 sieving Methods 0.000 claims abstract description 3
- 150000001875 compounds Chemical class 0.000 claims description 29
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 15
- -1 ammonium ions Chemical class 0.000 claims description 13
- 239000012153 distilled water Substances 0.000 claims description 7
- 238000005303 weighing Methods 0.000 claims description 6
- 238000001816 cooling Methods 0.000 claims description 5
- 238000010438 heat treatment Methods 0.000 claims description 5
- 230000003472 neutralizing effect Effects 0.000 claims description 2
- 238000004448 titration Methods 0.000 abstract description 11
- 230000029087 digestion Effects 0.000 abstract description 4
- QGZKDVFQNNGYKY-UHFFFAOYSA-O Ammonium Chemical compound [NH4+] QGZKDVFQNNGYKY-UHFFFAOYSA-O 0.000 abstract description 2
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 abstract description 2
- 230000008901 benefit Effects 0.000 abstract description 2
- 229910052796 boron Inorganic materials 0.000 abstract description 2
- 239000003153 chemical reaction reagent Substances 0.000 abstract description 2
- 238000004821 distillation Methods 0.000 abstract description 2
- 239000003814 drug Substances 0.000 abstract 1
- 239000000463 material Substances 0.000 abstract 1
- 239000000243 solution Substances 0.000 description 18
- 239000002253 acid Substances 0.000 description 3
- 238000007696 Kjeldahl method Methods 0.000 description 2
- 239000007864 aqueous solution Substances 0.000 description 2
- LBOVMDOAMWYGHK-UHFFFAOYSA-N ethanol;methylsulfinylmethane Chemical compound CCO.CS(C)=O LBOVMDOAMWYGHK-UHFFFAOYSA-N 0.000 description 2
- 239000006260 foam Substances 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 1
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 1
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 238000009825 accumulation Methods 0.000 description 1
- 238000002479 acid--base titration Methods 0.000 description 1
- 239000000908 ammonium hydroxide Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000010494 dissociation reaction Methods 0.000 description 1
- 230000005593 dissociations Effects 0.000 description 1
- 238000004817 gas chromatography Methods 0.000 description 1
- 238000004128 high performance liquid chromatography Methods 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 125000001477 organic nitrogen group Chemical group 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N31/00—Investigating or analysing non-biological materials by the use of the chemical methods specified in the subgroup; Apparatus specially adapted for such methods
- G01N31/16—Investigating or analysing non-biological materials by the use of the chemical methods specified in the subgroup; Apparatus specially adapted for such methods using titration
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- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Molecular Biology (AREA)
- Physics & Mathematics (AREA)
- Chemical & Material Sciences (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Fertilizers (AREA)
Abstract
The present invention relates to a kind of detection method of the detection method, more particularly to composite fertilizer's nitrogen content of material element content, belong to analytical chemistry field.A kind of detection method of composite fertilizer's nitrogen content, it is by composite fertilizer drying to constant weight, crush, drying to constant weight again after sieving, required amount is weighed to be digested with sulfuric acid, digestion is used after terminating in sodium hydroxide and remaining sulfuric acid, ethanol, dimethyl sulfoxide (DMSO) are added, using phenolphthalein as indicator, ammonium ion is titrated using sodium hydroxide solution.The present invention is simple and practicable, compared with Kjeldahl's method, eliminates alkalization distillation, boron absorbs, three steps of acidometric titration.In addition required equipment and instrument of the invention, medicine and reagent are laboratory ordinary articles, there is obvious economic benefit.
Description
Technical Field
The invention relates to a method for detecting the content of substance elements, in particular to a method for detecting the nitrogen content of a compound fertilizer, belonging to the field of analytical chemistry.
Background
In the production practice, the nitrogen content of the fertilizer is a very important factor. The traditional determination method comprises a Kjeldahl method, a special Kjeldahl apparatus is needed in the method, and the steps are complicated and the time consumption is long. The modern measurement of nitrogen content usually adopts high performance liquid chromatography or gas chromatography, although the detection speed is high, the instrument, equipment and maintenance cost are expensive, and the wide application in common laboratories and production units is difficult. In addition, the method has high requirements on standard products, and the selection of substances such as a mobile phase, a chromatographic column and the like has great influence on detection results.
Disclosure of Invention
Aiming at the problems of complicated steps, high cost and the like of the existing determination method, the invention aims to provide an economical, reasonable, simple and feasible detection method.
In order to achieve the purpose, the invention adopts the following technical scheme: a method for detecting nitrogen content of a compound fertilizer comprises the following steps:
1) crushing the compound fertilizer, sieving, drying to constant weight, and measuring the water content;
2) weighing a compound fertilizer, placing the compound fertilizer in a flask, adding sulfuric acid, digesting for 3-5 min at 180-200 ℃, increasing the temperature to 350-360 ℃, continuing to digest for 10-12 min, reducing the temperature to 100-120 ℃, heating for 1-2 min, cooling to room temperature, and adding distilled water;
3) neutralizing the residual sulfuric acid in the step 2) by using sodium hydroxide;
4) adding ethanol and dimethyl sulfoxide into the solution obtained in the step 3), titrating ammonium ions by using a sodium hydroxide solution by taking phenolphthalein as an indicator, wherein the volume ratio of the ethanol to the dimethyl sulfoxide is 1: 1-1: 2, the volume ratio of the ethanol to the solution obtained in the step 3) is 1: 0.8-1: 1.
it is preferable that: in the step 2), the weight of the compound fertilizer needs to be weighed to be 0.3-0.5 g, and 30-50 mL of sulfuric acid needs to be added into each gram of the compound fertilizer.
It is preferable that: the mass percentage concentration of the sulfuric acid in the step 2) is 95-98%.
It is preferable that: the adding amount of the distilled water in the step 2) is 2-3 times of the volume of the sulfuric acid.
It is preferable that: the concentration of the sodium hydroxide in the step 3) is 0.1-0.5 mol/L.
It is preferable that: the concentration of the sodium hydroxide solution in the step 4) is 0.5-1 mol/L.
The invention has the following beneficial effects:
1. according to the invention, low-temperature digestion is adopted firstly, excessive foam accumulation in the digestion process is avoided, and when the foam is completely consumed, the temperature can be increased for further digestion, so that organic nitrogen in the compound fertilizer is degraded into inorganic ammonium ions; in order to facilitate subsequent titrations. The subsequent temperature reduction can completely remove the organic carbon and ensure the clarity of the solution.
2. The invention uses sodium hydroxide to neutralize the residual sulfuric acid in the solution, the sodium hydroxide can directly titrate the hydrogen ions in the solution, and the ammonium ions in the solution can not react with the sodium hydroxide solution because of weak acidity.
3. The dissociation constant (K) of aqueous solution is very small due to ammoniab＝1.8×10-5) Its conjugate acid (NH)4 +) Too weak (Ka ═ 5.6X 10)-10) CK cannot meet the classic acid-base titrationa≥10-8Thus it is difficult to directly titrate in aqueous solution with standard bases. According to the invention, ethanol and dimethyl sulfoxide are added before ammonium ion titration, and the addition of the ethanol and the dimethyl sulfoxide can enhance the strength of acid expressed by ammonium ions, because the ethanol-dimethyl sulfoxide can accept protons, so that the ammonium ions express stronger acidity. Therefore, ammonium ions which could not be directly titrated could be titrated smoothly. In addition, after the ethanol-dimethyl sulfoxide is added, the change of the titration endpoint is very obvious, so that the accuracy of the measurement result is high.
4. The method is simple and easy to implement, and compared with a Kjeldahl method, the method omits three steps of alkalization distillation, boron absorption and acid titration. In addition, the equipment, instruments and reagents required by the invention are common articles in laboratories, and have obvious economic benefit.
Detailed Description
The technical solution of the present invention is further described below, but the scope of the claimed invention is not limited to the described. The present invention will be described in further detail with reference to specific examples, but the embodiments of the present invention are not limited to the scope of the examples. These examples are intended to illustrate the invention only and are not intended to limit the scope of the invention. In addition, various modifications may occur to those skilled in the art upon reading the present disclosure, and such equivalent variations are within the scope of the present invention as defined in the appended claims.
Example 1
Drying the compound fertilizer at the temperature of 80 ℃ to constant weight, and measuring the water content of the compound fertilizer. Accurately weighing 0.3g of compound fertilizer (the balance is accurate to 0.0001 g) by a precise electronic balance, placing the compound fertilizer into a flask, adding 9mL of sulfuric acid with the mass percentage concentration of 95%, digesting at 180 ℃ for 5min, raising the temperature to 350 ℃, continuing to digest for 12min, reducing the temperature to 100 ℃, heating for 2min, cooling to room temperature, adding 27mL of distilled water, 3 drops of phenolphthalein and using 0.1mol/L of sodium hydroxide to titrate the residual sulfuric acid in the solution, adding 0.8 times of the volume of the solution after the titration is finished, adding dimethyl sulfoxide with the same volume as the ethanol, using the phenolphthalein as an indicator, using 0.5mol/L of sodium hydroxide solution to titrate ammonium ions, recording the titration volume, and calculating the nitrogen content.
Example 2
Drying the compound fertilizer at the temperature of 80 ℃ to constant weight, and measuring the water content of the compound fertilizer. Accurately weighing 0.4g of compound fertilizer (the balance is accurate to 0.0001 g) by a precise electronic balance, placing the compound fertilizer into a flask, adding 16mL of sulfuric acid with the mass percentage concentration of 96%, digesting at 190 ℃ for 4min, raising the temperature to 355 ℃, continuing to digest for 11min, reducing the temperature to 110 ℃, heating for 2min, cooling to room temperature, adding 36mL of distilled water, 3 drops of phenolphthalein and using 0.3mol/L sodium hydroxide to titrate the residual sulfuric acid in the solution, adding 0.9 times of ethanol in volume and 1.5 times of dimethyl sulfoxide in volume after the titration is finished, using phenolphthalein as an indicator, using 0.6mol/L sodium hydroxide solution to titrate ammonium ions, recording the titration volume, and calculating the nitrogen content.
Example 3
Drying the compound fertilizer at the temperature of 80 ℃ to constant weight, and measuring the water content of the compound fertilizer. Precisely weighing 0.5g of compound fertilizer (the balance is accurate to 0.0001 g) by using a precise electronic balance, placing the compound fertilizer into a flask, adding 25mL of sulfuric acid with the mass percentage concentration of 98%, digesting the compound fertilizer for 3min at 200 ℃, increasing the temperature to 360 ℃, continuing to digest the compound fertilizer for 10min, reducing the temperature to 120 ℃, heating the compound fertilizer for 1min, cooling the compound fertilizer to room temperature, adding 50mL of distilled water, 3 drops of phenolphthalein and using 0.5mol/L of sodium hydroxide to titrate the residual sulfuric acid in the solution, adding ethanol with one time of the volume of the solution and dimethyl sulfoxide with 2 times of the volume of the ethanol after the titration is finished, using the phenolphthalein as an indicator, using 1mol/L of the sodium hydroxide solution to titrate ammonium ions, recording the titration volume, and.
The total nitrogen content in the above examples was calculated as follows:
total nitrogen content ═ C0×V×M0)/m0×(1-WWater (W)) Wherein,
C0titrating the molar concentration of sodium hydroxide used by ammonium ions;
v, titrating the volume of ammonium hydroxide consumed by ammonium ions;
M0the molar mass of nitrogen;
m0weighing the sample amount;
Wwater (W)The water content is determined.
Claims (4)
1. The method for detecting the nitrogen content of the compound fertilizer is characterized by comprising the following steps of:
1) crushing the compound fertilizer, sieving, drying to constant weight, and measuring the water content;
2) weighing 0.3-0.5 g of compound fertilizer, and adding 30-50 mL of sulfuric acid into each gram of compound fertilizer; digesting for 3-5 min at 180-200 ℃, increasing the temperature to 350-360 ℃, continuing to digest for 10-12 min, reducing the temperature to 100-120 ℃, heating for 1-2 min, cooling to room temperature, and adding distilled water;
3) neutralizing the residual sulfuric acid in the step 2) by using sodium hydroxide;
4) adding ethanol and dimethyl sulfoxide into the solution obtained in the step 3), titrating ammonium ions by using a sodium hydroxide solution by taking phenolphthalein as an indicator, wherein the volume ratio of the ethanol to the dimethyl sulfoxide is 1: 1-1: 2, the volume ratio of the ethanol to the solution obtained in the step 3) is 1: 0.8-1: 1.
the mass percentage concentration of the sulfuric acid in the step 2) is 95-98%.
2. The detection method according to claim 1, wherein the amount of the distilled water added in the step 2) is 2 to 3 times the volume of the sulfuric acid.
3. The detection method according to claim 1, wherein the concentration of sodium hydroxide in the step 3) is 0.1-0.5 mol/L.
4. The detection method according to claim 1, wherein the concentration of the sodium hydroxide solution in the step 4) is 0.5-1 mol/L.
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| CN108828155B (en) * | 2018-03-22 | 2020-09-22 | 中国科学院新疆生态与地理研究所 | Method for detecting nitrogen content of cotton plants |
| CN111272603A (en) * | 2020-02-18 | 2020-06-12 | 北京中化联合认证有限公司 | Detection method of ammoniation guniting compound fertilizer |
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Inventor after: Zhou Changping Inventor after: Chen Sifan Inventor after: Wang Yao Inventor after: Chen Wenxing Inventor after: Tian Juan Inventor before: Chen Wenxing Inventor before: Zhou Changping Inventor before: Yang Jie Inventor before: Chen Sifan Inventor before: Wang Yao Inventor before: Tian Juan |
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