CN118010917A - Method for detecting magnesium content in inorganic compound fertilizer - Google Patents
Method for detecting magnesium content in inorganic compound fertilizer Download PDFInfo
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- CN118010917A CN118010917A CN202410280344.6A CN202410280344A CN118010917A CN 118010917 A CN118010917 A CN 118010917A CN 202410280344 A CN202410280344 A CN 202410280344A CN 118010917 A CN118010917 A CN 118010917A
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- 239000011777 magnesium Substances 0.000 title claims abstract description 75
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 title claims abstract description 68
- 229910052749 magnesium Inorganic materials 0.000 title claims abstract description 68
- 239000003337 fertilizer Substances 0.000 title claims abstract description 65
- 229910010272 inorganic material Inorganic materials 0.000 title claims abstract description 57
- 150000002484 inorganic compounds Chemical class 0.000 title claims abstract description 56
- 238000000034 method Methods 0.000 title claims abstract description 45
- 239000000243 solution Substances 0.000 claims abstract description 62
- 239000011575 calcium Substances 0.000 claims abstract description 45
- 229910052791 calcium Inorganic materials 0.000 claims abstract description 45
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 claims abstract description 44
- 238000004448 titration Methods 0.000 claims abstract description 43
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims abstract description 34
- UXVMQQNJUSDDNG-UHFFFAOYSA-L Calcium chloride Chemical compound [Cl-].[Cl-].[Ca+2] UXVMQQNJUSDDNG-UHFFFAOYSA-L 0.000 claims abstract description 27
- 238000012360 testing method Methods 0.000 claims abstract description 25
- 239000001110 calcium chloride Substances 0.000 claims abstract description 24
- 229910001628 calcium chloride Inorganic materials 0.000 claims abstract description 24
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 23
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 claims abstract description 22
- GSEJCLTVZPLZKY-UHFFFAOYSA-N Triethanolamine Chemical compound OCCN(CCO)CCO GSEJCLTVZPLZKY-UHFFFAOYSA-N 0.000 claims abstract description 22
- 239000000706 filtrate Substances 0.000 claims abstract description 20
- 238000002156 mixing Methods 0.000 claims abstract description 18
- 239000003109 Disodium ethylene diamine tetraacetate Substances 0.000 claims abstract description 15
- 235000019301 disodium ethylene diamine tetraacetate Nutrition 0.000 claims abstract description 15
- 239000007853 buffer solution Substances 0.000 claims abstract description 11
- 229910021529 ammonia Inorganic materials 0.000 claims abstract description 10
- 239000012086 standard solution Substances 0.000 claims abstract description 10
- 238000001914 filtration Methods 0.000 claims abstract description 9
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 claims abstract description 8
- 238000009835 boiling Methods 0.000 claims abstract description 7
- AMMWFYKTZVIRFN-UHFFFAOYSA-N sodium 3-hydroxy-4-[(1-hydroxynaphthalen-2-yl)diazenyl]-7-nitronaphthalene-1-sulfonic acid Chemical compound [Na+].C1=CC=CC2=C(O)C(N=NC3=C4C=CC(=CC4=C(C=C3O)S(O)(=O)=O)[N+]([O-])=O)=CC=C21 AMMWFYKTZVIRFN-UHFFFAOYSA-N 0.000 claims abstract description 7
- 238000001816 cooling Methods 0.000 claims abstract description 4
- ZGTMUACCHSMWAC-UHFFFAOYSA-L EDTA disodium salt (anhydrous) Chemical compound [Na+].[Na+].OC(=O)CN(CC([O-])=O)CCN(CC(O)=O)CC([O-])=O ZGTMUACCHSMWAC-UHFFFAOYSA-L 0.000 claims abstract 4
- 239000000523 sample Substances 0.000 claims description 31
- 238000002360 preparation method Methods 0.000 claims description 11
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 claims description 10
- 238000004458 analytical method Methods 0.000 claims description 10
- NLXLAEXVIDQMFP-UHFFFAOYSA-N Ammonia chloride Chemical compound [NH4+].[Cl-] NLXLAEXVIDQMFP-UHFFFAOYSA-N 0.000 claims description 8
- 239000003153 chemical reaction reagent Substances 0.000 claims description 7
- 238000000227 grinding Methods 0.000 claims description 7
- 239000011780 sodium chloride Substances 0.000 claims description 5
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 claims description 4
- 235000019270 ammonium chloride Nutrition 0.000 claims description 4
- 235000011114 ammonium hydroxide Nutrition 0.000 claims description 4
- HEQBUZNAOJCRSL-UHFFFAOYSA-N iron(ii) chromite Chemical compound [O-2].[O-2].[O-2].[Cr+3].[Fe+3] HEQBUZNAOJCRSL-UHFFFAOYSA-N 0.000 claims description 4
- 239000012488 sample solution Substances 0.000 claims description 4
- 238000004090 dissolution Methods 0.000 claims description 3
- 238000012546 transfer Methods 0.000 claims description 2
- 238000001514 detection method Methods 0.000 abstract description 8
- 238000005259 measurement Methods 0.000 abstract description 6
- LXAHHHIGZXPRKQ-UHFFFAOYSA-N 5-fluoro-2-methylpyridine Chemical compound CC1=CC=C(F)C=N1 LXAHHHIGZXPRKQ-UHFFFAOYSA-N 0.000 abstract 1
- KCXVZYZYPLLWCC-UHFFFAOYSA-N EDTA Chemical compound OC(=O)CN(CC(O)=O)CCN(CC(O)=O)CC(O)=O KCXVZYZYPLLWCC-UHFFFAOYSA-N 0.000 description 17
- TWRXJAOTZQYOKJ-UHFFFAOYSA-L Magnesium chloride Chemical compound [Mg+2].[Cl-].[Cl-] TWRXJAOTZQYOKJ-UHFFFAOYSA-L 0.000 description 6
- 238000010521 absorption reaction Methods 0.000 description 5
- 230000000873 masking effect Effects 0.000 description 5
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 4
- WTDHULULXKLSOZ-UHFFFAOYSA-N Hydroxylamine hydrochloride Chemical compound Cl.ON WTDHULULXKLSOZ-UHFFFAOYSA-N 0.000 description 4
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 4
- 239000003795 chemical substances by application Substances 0.000 description 4
- PIICEJLVQHRZGT-UHFFFAOYSA-N Ethylenediamine Chemical compound NCCN PIICEJLVQHRZGT-UHFFFAOYSA-N 0.000 description 3
- ZFXVRMSLJDYJCH-UHFFFAOYSA-N calcium magnesium Chemical compound [Mg].[Ca] ZFXVRMSLJDYJCH-UHFFFAOYSA-N 0.000 description 3
- 238000000354 decomposition reaction Methods 0.000 description 3
- 229910001629 magnesium chloride Inorganic materials 0.000 description 3
- TVBSSDNEJWXWFP-UHFFFAOYSA-N nitric acid perchloric acid Chemical compound O[N+]([O-])=O.OCl(=O)(=O)=O TVBSSDNEJWXWFP-UHFFFAOYSA-N 0.000 description 3
- 239000002244 precipitate Substances 0.000 description 3
- 238000011084 recovery Methods 0.000 description 3
- 239000002689 soil Substances 0.000 description 3
- 238000010561 standard procedure Methods 0.000 description 3
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 2
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 2
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 description 2
- 229920002472 Starch Polymers 0.000 description 2
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 2
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 2
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 2
- 229910052782 aluminium Inorganic materials 0.000 description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 229910052804 chromium Inorganic materials 0.000 description 2
- 239000011651 chromium Substances 0.000 description 2
- 150000001875 compounds Chemical class 0.000 description 2
- 239000010949 copper Substances 0.000 description 2
- 229910052802 copper Inorganic materials 0.000 description 2
- 229910052742 iron Inorganic materials 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- WPBNNNQJVZRUHP-UHFFFAOYSA-L manganese(2+);methyl n-[[2-(methoxycarbonylcarbamothioylamino)phenyl]carbamothioyl]carbamate;n-[2-(sulfidocarbothioylamino)ethyl]carbamodithioate Chemical compound [Mn+2].[S-]C(=S)NCCNC([S-])=S.COC(=O)NC(=S)NC1=CC=CC=C1NC(=S)NC(=O)OC WPBNNNQJVZRUHP-UHFFFAOYSA-L 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- 239000011574 phosphorus Substances 0.000 description 2
- 229910052698 phosphorus Inorganic materials 0.000 description 2
- 239000011591 potassium Substances 0.000 description 2
- 229910052700 potassium Inorganic materials 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 235000019698 starch Nutrition 0.000 description 2
- 239000008107 starch Substances 0.000 description 2
- 238000003860 storage Methods 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 239000011593 sulfur Substances 0.000 description 2
- 229910052717 sulfur Inorganic materials 0.000 description 2
- 229910052719 titanium Inorganic materials 0.000 description 2
- 239000010936 titanium Substances 0.000 description 2
- 239000011573 trace mineral Substances 0.000 description 2
- 235000013619 trace mineral Nutrition 0.000 description 2
- 239000011701 zinc Substances 0.000 description 2
- 229910052725 zinc Inorganic materials 0.000 description 2
- 208000008167 Magnesium Deficiency Diseases 0.000 description 1
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 238000000184 acid digestion Methods 0.000 description 1
- 238000003321 atomic absorption spectrophotometry Methods 0.000 description 1
- -1 calcium carboxylic acid Chemical class 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 230000008094 contradictory effect Effects 0.000 description 1
- 230000029087 digestion Effects 0.000 description 1
- 238000007865 diluting Methods 0.000 description 1
- 238000011978 dissolution method Methods 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 235000013399 edible fruits Nutrition 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000005562 fading Methods 0.000 description 1
- 235000013305 food Nutrition 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 235000004764 magnesium deficiency Nutrition 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 229910017604 nitric acid Inorganic materials 0.000 description 1
- 235000021048 nutrient requirements Nutrition 0.000 description 1
- 235000015097 nutrients Nutrition 0.000 description 1
- 238000006864 oxidative decomposition reaction Methods 0.000 description 1
- 230000000243 photosynthetic effect Effects 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 238000003908 quality control method Methods 0.000 description 1
- 230000036632 reaction speed Effects 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 238000011410 subtraction method Methods 0.000 description 1
- 230000001502 supplementing effect Effects 0.000 description 1
- 230000002195 synergetic effect Effects 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
- 238000005406 washing Methods 0.000 description 1
- 238000005303 weighing Methods 0.000 description 1
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- Investigating Or Analyzing Non-Biological Materials By The Use Of Chemical Means (AREA)
Abstract
The invention discloses a method for detecting magnesium content in an inorganic compound fertilizer, which solves the problem of inaccurate measurement of the existing detection method, and comprises the steps of S1, mixing an inorganic compound fertilizer sample with hydrochloric acid solution, boiling for dissolving, cooling after transferring, and obtaining filtrate by constant volume and then filtering; s2, mixing the filtrate with water, triethanolamine and potassium hydroxide solution, adding a calcium indicator, quantitatively adding an excessive EDTA disodium standard titration solution, using the calcium chloride standard solution to back titrate the solution until the red color is the end point, and measuring the total calcium content of the inorganic compound fertilizer sample; and S3, mixing the filtrate with water, triethanolamine and an ammonia buffer solution, adding a chrome black T indicator and an excessive disodium ethylenediamine tetraacetate standard titration solution, and determining the total calcium and magnesium of the inorganic compound fertilizer sample by using the titration of the calcium chloride standard titration solution to the end point of red. The method does not need a large-scale testing instrument, is simple to operate, is easy to judge the titration end point, and has high accuracy of results and time and labor saving compared with the traditional titration method.
Description
Technical Field
The invention relates to the technical field of fertilizers, in particular to a method for detecting the magnesium content in an inorganic compound fertilizer.
Background
Magnesium is a medium element necessary for crop growth, and magnesium deficiency can cause plant dwarf, slow growth, reduced root cap ratio and reduced transportation rate of photosynthetic products into roots, fruits and tubers. The long-term application of the macroelements nitrogen, phosphorus and potassium only can lead to excessive consumption of medium and trace elements in soil not to be supplemented, so that crops lack elements and the yield and quality are affected. The addition of magnesium element in the compound fertilizer is beneficial to meeting the nutrient requirements of crops, improves the utilization rate of the fertilizer by utilizing the synergistic effect among the nutrients, and is also effective for supplementing the magnesium in the soil.
The inorganic compound fertilizer has complex composition, contains medium trace elements, organic matters and other effective components for improving soil and crops besides nitrogen, phosphorus and potassium, and can bring a lot of impurities in the production process. Some of these substances interfere with the detection of magnesium content, affecting the accuracy of the detection. When the detection is performed by different methods, the interference substances and the method for avoiding the interference influence are different.
The magnesium content detection generally comprises a pretreatment and a later test, wherein the pretreatment comprises a nitric acid perchloric acid digestion method, a hydrochloric acid dissolution method and the like, and the test method comprises an atomic absorption or ICP instrument analysis and titration method and the like. The method for decomposing the nitric acid perchloric acid is suitable for inorganic compound fertilizers containing organic components, and can oxidize and decompose the organic matters, however, the method has long decomposition time, usually the whole process reaches more than 1 hour, the method is time-consuming and easy to evaporate, and the possibility that the decomposition is incomplete or new insoluble matters are generated in the decomposition process exists, so that the detection accuracy is affected. Therefore, the inorganic compound fertilizer without organic matters can be dissolved by hydrochloric acid washing, and the method is safe and simple.
The method for testing the magnesium content in the digestion liquid is instrument analysis, and the titration method is generally adopted under the condition of no instrument analysis condition. The titration method of the magnesium content in the inorganic composite fertilizer in national standard GB/T19203-2003 is summarized as follows: quantitatively absorbing and removing the boiling solution, adding a soluble starch solution, ethylenediamine, triethanolamine solution, a pH=10 buffer solution and hydroxylamine hydrochloride, and quantitatively titrating the total calcium and magnesium by using an EDTA solution after adding an indicator; re-quantitatively sucking the boiled liquid, and adding soluble starch solution, ethylenediamine and triethanolamine solution. Adjusting the pH value to be more than or equal to 12 by using a KOH solution, and quantitatively titrating the calcium content by using an EDTA solution after adding an indicator; the magnesium content in the fertilizer was calculated using a difference subtraction method.
However, in the application process of the method, for part of inorganic compound fertilizers, the measurement result is often small, mainly because when the total amount of calcium and magnesium is measured, under the condition of pH=10, calcium and magnesium are easy to form precipitates, EDTA can complex calcium and magnesium in the precipitates, but the reaction speed is slower, so that the end point judgment is difficult, the method of shaking for half a minute and not fading in the national standard is tedious and time-consuming, and the result in practical application is inaccurate.
Disclosure of Invention
The invention provides a method for detecting magnesium content in an inorganic compound fertilizer, which aims to solve the technical problem of inaccurate measurement of the existing detection method.
The application provides a method for detecting magnesium content in an inorganic compound fertilizer, which specifically comprises the following steps:
S1, mixing an inorganic compound fertilizer sample with a hydrochloric acid solution, boiling for dissolution, transferring, cooling to room temperature, and performing constant volume and filtration to obtain a filtrate;
s2, titration of calcium: mixing the filtrate obtained in the step S1 with water, triethanolamine and potassium hydroxide solution, adding a calcium indicator, quantitatively adding excessive disodium ethylenediamine tetraacetate standard titration solution, using the calcium chloride standard solution to back titrate the solution until the red color is the end point, and determining the total calcium content of the inorganic compound fertilizer sample; the influence of ions such as iron, aluminum, manganese, copper, zinc and titanium in the filtrate can be masked by the triethanolamine, so that the accuracy of a titration result is improved, and a small amount of triethanolamine is added because the content of the elements such as iron, aluminum, manganese, copper, zinc and titanium in the inorganic compound fertilizer is low;
S3, titration of total calcium and magnesium: mixing the filtrate obtained in the step S1 with water, triethanolamine and an ammonia buffer solution, adding a chrome black T indicator and excessive disodium ethylenediamine tetraacetate standard titration solution, wherein the solution is blue, and determining the total calcium and magnesium of the inorganic compound fertilizer sample by using the titration of the calcium chloride standard titration solution to the end point;
And S4, subtracting the total calcium and magnesium obtained in the step S3 from the total calcium content obtained in the step S2 to obtain the magnesium content.
Further, in the step S1, the ratio of the inorganic compound fertilizer sample to the hydrochloric acid solution is 3-10 g: 30-100 mL, excessive hydrochloric acid can enable the inorganic compound fertilizer sample to be more fully dissolved, and the ratio of hydrochloric acid to water in the hydrochloric acid solution is 1:1 to 9.
Further, in step S1, the boiling time is 15 to 30 minutes.
Further, in the step S2, the volume ratio of the triethanolamine to the filtrate is 5-10: 25, in the step S3, the volume ratio of the triethanolamine to the filtrate is 5-10: 25.
Further, in step S1, the filtering is performed by dry filtration.
Further, the preparation method of the ammonia buffer solution comprises the steps of dissolving ammonium chloride in water, adding ammonia water and diluting with water; the preparation method of the chrome black T indicator comprises the step of grinding and uniformly mixing chrome black and sodium chloride dried at the temperature of 105-110 ℃.
Further, the concentration of the disodium ethylenediamine tetraacetate is 0.01-0.1 mol/L; the concentration of the calcium chloride is 0.01-0.1 mol/L.
Further, the content w (Mg) of magnesium in the inorganic compound fertilizer sample is calculated by the following formula:
w(Mg)＝[C(V02-V2)/V4-C(V01-V1)/V3]×24.31/(1000×m/V5)×100,
Wherein:
w (Mg) is the content of magnesium in the inorganic compound fertilizer, and the unit is percentage content (%); c is the concentration of a standard titration solution of calcium chloride, and the unit is mol/L; v 02 is the standard titration solution volume of calcium chloride which is consumed in blank when the total amount of calcium and magnesium is measured, and the unit is mL; v 2 is the volume of the standard titration solution of calcium chloride consumed in measuring the total amount of calcium and magnesium, and the unit is mL; v 4 is the volume of the sample solution sucked when the total amount of calcium and magnesium is measured, and the unit is mL; v 1 is the volume of the standard calcium chloride solution consumed in measuring the content of calcium, and the unit is mL; v 01 is the volume of standard titration solution of calcium chloride consumed by a blank test when the content of calcium is measured, and the unit is mL; v 3 is the volume of the sample solution sucked when the content of calcium is measured, and the unit is mL; v 5 is the transfer constant volume in mL; m is the sample mass, and the unit is g.
The beneficial effects realized by the invention are as follows:
According to the method for detecting the magnesium content in the inorganic compound fertilizer, when the total content of calcium and magnesium is measured, excessive disodium ethylenediamine tetraacetate standard solution is quantitatively added, so that the solution and the calcium and magnesium which can be complexed by disodium ethylenediamine tetraacetate in the precipitate are complexed at one time, and the rest disodium ethylenediamine tetraacetate is subjected to back titration by the standard calcium chloride titration solution. The method does not need a large-scale testing instrument, is simple to operate, is easy to judge the titration end point, and has high accuracy of results and time and labor saving compared with the traditional titration method.
Detailed Description
The following description of the technical solutions in the embodiments of the present invention will be clear and complete, and it is obvious that the described embodiments are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention. In addition, the technical solutions of the embodiments may be combined with each other, but it is necessary to base that the technical solutions can be realized by those skilled in the art, and when the technical solutions are contradictory or cannot be realized, the combination of the technical solutions should be considered to be absent and not within the scope of protection claimed in the present invention.
The technical scheme of the invention is described in detail.
The applicant has found through research and comparison that the determination of calcium, magnesium and sulfur is carried out by digesting the inorganic compound fertilizer with nitric acid perchloric acid in the national standard, because the inorganic compound fertilizer often contains organic matters, the organic matters can be determined by entering the solution after oxidative decomposition, and in addition, some prior art also promotes the dissolution of calcium and magnesium by mixing hydrochloric acid and nitric acid. However, the scheme of the embodiment of the application is to measure the magnesium in the inorganic compound fertilizer, so that the magnesium in the fertilizer can be completely dissolved in the hydrochloric acid solution. After the inorganic compound fertilizer sample is dissolved, the volume is fixed and then the filtration is carried out to obtain filtrate.
Titration of total calcium: mixing the quantitative filtrate with water, triethanolamine and potassium hydroxide solution, adding a calcium indicator, quantitatively adding excessive disodium ethylenediamine tetraacetate solution, wherein the solution is blue, and back titrating the solution with a calcium chloride standard solution until the indicator turns red. And simultaneously, a blank is prepared, and except for no sample, the blank is subjected to parallel test by adopting the same reagent, dosage and analysis steps as those used for sample measurement.
The applicant has found through research comparison that the combination masking is carried out by using three masking agents of ethylenediamine, triethanolamine and hydroxylamine hydrochloride in national standards, but the applicant has found that the effect of using only one masking agent of triethanolamine is not obvious from the measurement result of using the three masking agents for inorganic compound fertilizers. Thus, for ease of operation, a single masking agent is employed.
Titration of total calcium magnesium: mixing the filtrate with water, triethanolamine and an ammonia buffer solution, adding a chrome black T indicator, quantitatively adding an excessive disodium ethylenediamine tetraacetate solution, wherein the solution is blue, and back titrating the solution by using a calcium chloride standard solution until the indicator turns red. And simultaneously, a blank is prepared, and except for no sample, the blank is subjected to parallel test by adopting the same reagent, dosage and analysis steps as those used for sample measurement.
Further, the preparation method of the ammonia buffer solution provided by the embodiment of the application comprises the following steps: ammonium chloride was dissolved in water, aqueous ammonia was added and diluted with water.
The preparation method of the chromium black T indicator comprises the following steps: grinding and uniformly mixing the chrome black and the dried sodium chloride.
Illustratively, the disodium edetate concentration of the embodiments of the present application is 0.01-0.1 mol/L.
The preparation method of the disodium ethylenediamine tetraacetate standard titration solution with the concentration of 0.1mol/L comprises the following steps: 37.2g of disodium ethylenediamine tetraacetate is weighed into a 500mL beaker, and is added with about 300mL of water for stirring, after the reagents are completely dissolved, the mixture is cooled to room temperature, and water is added to 1000mL for uniform mixing.
Illustratively, the concentration of calcium chloride in the examples of the present application is 0.01 to 0.1mol/L.
The preparation method of the standard calcium chloride titration solution with the concentration of 0.05mol/L comprises the following steps: 0.55g of anhydrous calcium chloride is weighed into a 100mL beaker, dissolved in water, transferred into a 1L volumetric flask, and subjected to constant volume, wherein the calcium chloride is calibrated by using an EDTA standard titration solution.
1. Examples
Example 1:
The embodiment of the application provides a method for detecting the magnesium content in an organic-inorganic compound fertilizer, which comprises the following steps:
S1, pouring 5g of an inorganic compound fertilizer sample into a 500mL beaker, adding 50mL of hydrochloric acid with the volume concentration of 20%, covering a surface dish, heating for micro boiling for 15min, taking down and cooling to room temperature, fixing the volume to a 250mL volumetric flask, shaking uniformly, and drying and filtering to obtain filtrate;
S2, taking 15.00mL of filtrate in a 250mL triangular flask, adding 30mL of water, 10mL of triethanolamine with the volume concentration of 40% and 10mL of potassium hydroxide solution with the concentration of 200g/L, adding 0.1g of calcium indicator to make the solution red, adding 20mL of disodium ethylenediamine tetraacetate standard titration solution with the excess of 0.05mol/L, at the moment, using the standard solution of calcium chloride to back titrate the solution until the indicator becomes red, recording the consumed volume V 1, simultaneously making a blank, and carrying out parallel test on the blank and the sample by adopting the same reagent, the dosage and the analysis step except no sample, and recording the consumed volume V 01;
the preparation method of the calcium indicator comprises the following steps: taking 1g of calcium carboxylic acid and 100g of sodium chloride which is dried at 105-110 ℃ in advance, carefully grinding, uniformly mixing, and placing in a grinding bottle for storage.
S3, taking 10.00mL of filtrate in a 250mL triangular flask, adding 30mL of water, 10mL of triethanolamine with the volume concentration of 40%, 10mL of ammonia buffer solution with the pH value of 10, adding 0.1g of chromium black T indicator to make the solution red, adding 20mL of disodium ethylenediamine tetraacetate standard titration solution with the excess of 0.05mol/L, at this time, using calcium chloride standard solution to back titrate the solution until the indicator becomes red, recording the consumed volume V 2, simultaneously making a blank, and carrying out parallel test on the blank and the sample by adopting the same reagent, the same amount and the same analysis step except no sample, and recording the consumed volume V 02;
w(Mg)＝(C(V02-V2)/10-C(V01-V1)/10)×24.31/(1000×5/250)×100
the preparation method of the ammonia buffer solution comprises the following steps: 67.5g of ammonium chloride was weighed and dissolved in water, 570mL of aqueous ammonia (ρ=0.90 g/mL) was added, diluted to 1L with water, and mixed well.
The preparation method of the chrome black T indicator comprises the following steps: taking 1g of chrome black and 100g of sodium chloride which is dried at 105-110 ℃ in advance, carefully grinding, uniformly mixing, and placing in a grinding bottle for storage.
Example 2:
Example 2 was substantially identical to the method for detecting magnesium content in the inorganic compound fertilizer of example 1, except that the hydrochloric acid volume fraction in example 2 was 10%.
Example 3:
example 3 was substantially the same as the method for detecting magnesium content in the inorganic compound fertilizer of example 1, except that the amount of hydrochloric acid used in example 3 was 30mL.
Example 4:
example 4 was essentially identical to the method for detecting magnesium content in the inorganic compound fertilizer of example 1, except that the volume fractions of triethanolamine in the total calcium and calcium magnesium titration step in example 4 were 25%.
Example 5:
Example 5 is essentially the same as the method for detecting the calcium and magnesium content in the inorganic compound fertilizer of example 1, except that the volume of triethanolamine in the total calcium and calcium magnesium titration step of example 5 is 5mL.
2. Test examples
Test example 1:
The magnesium content in each of 6 inorganic compound fertilizer samples 1 and 6 inorganic compound fertilizer sample 2 was measured by the method for detecting magnesium content in inorganic compound fertilizer of example 1, and the results are shown in table 1.
Table 1 magnesium content in inorganic compound fertilizer sample 1 and inorganic compound fertilizer sample 2
As can be seen from the results in Table 1, the laboratory variation coefficient of the method for detecting the calcium and magnesium content in the inorganic compound fertilizer in the embodiment of the application meets the relevant requirements in GB/T27404 "laboratory quality control Specification food physicochemical detection".
Test example 2:
3 inorganic compound fertilizer samples are selected, each sample is prepared into 3 parts, the first part is detected by adopting the method for detecting the magnesium content in the inorganic compound fertilizer in the embodiment 1 of the application, the second part is detected by adopting the national standard method GBT19203-2003 'determination of the content of calcium, magnesium and sulfur in compound fertilizer', the third part of pretreatment is carried out by adopting the method in the embodiment 1 of the application, and then the magnesium content is determined by adopting an atomic absorption spectrophotometry. The results are shown in Table 2.
TABLE 2
As can be seen from the results in Table 2, the deviation between the method for detecting the magnesium content in the inorganic compound fertilizer and the national standard method in the embodiment of the application is 0.21, and compared with the result of an atomic absorption test, the deviation is tightly 0.03, which shows that the titration method of the application is similar to the magnesium result of the atomic absorption test, and the atomic absorption method is an instrument analysis method commonly used for testing calcium and magnesium in the fertilizer.
Test example 3:
3 inorganic compound fertilizer samples are selected, 3 parts of the inorganic compound fertilizer samples are prepared, before acid is added after weighing, magnesium chloride standard solution is added into a beaker, so that the content of magnesium added into the sample is 2%, the magnesium content is detected by the three methods respectively, and the standard adding recovery rate is calculated. The results are shown in Table 3.
TABLE 3 Table 3
Table 3 demonstrates the conclusion of test example 2 that after the standard solution of magnesium chloride is added, the difference of magnesium content measured by the method and the atomic absorption method is small, and the recovery rate is high, which indicates that the added magnesium chloride is completely detected, and the recovery rate measured by the national standard method is low.
The foregoing embodiment numbers of the present application are merely for the purpose of description, and do not represent the advantages or disadvantages of the embodiments. The foregoing description is only of the preferred embodiments of the present application, and is not intended to limit the scope of the application, but rather is intended to cover any equivalents of the structures disclosed herein or modifications in the equivalent processes, or any application of the structures disclosed herein, directly or indirectly, in other related arts.
Claims (8)
1. The method for detecting the magnesium content in the inorganic compound fertilizer is characterized by comprising the following steps of:
S1, mixing an inorganic compound fertilizer sample with a hydrochloric acid solution, boiling for dissolution, transferring, cooling to room temperature, and performing constant volume and filtration to obtain a filtrate;
S2, titration of calcium: mixing the filtrate obtained in the step S1 with water, triethanolamine and potassium hydroxide solution, adding a calcium indicator, quantitatively adding excessive disodium ethylenediamine tetraacetate standard titration solution, taking the solution as blue, using the calcium chloride standard solution to back titrate the solution until the red is taken as an end point, recording the consumed volume V 1, simultaneously taking a blank, and taking parallel test with the test sample except that no test sample is added, wherein the blank and the test sample are completely the same in reagent, dosage and analysis step, and recording the consumed volume V 01;
S3, titration of total calcium and magnesium: mixing the filtrate obtained in the step S1 with water, triethanolamine and an ammonia buffer solution, adding a chrome black T indicator and excessive disodium ethylenediamine tetraacetate standard titration solution, wherein the solution is blue, titrating to red by using calcium chloride standard titration solution as an endpoint, recording the consumed volume V 2, simultaneously making a blank, and carrying out parallel test by adopting the same reagent, dosage and analysis step as the test sample except that the test sample is not added, and recording the consumed volume V 02;
S4, calculating the magnesium content in the inorganic compound fertilizer in a column mode.
2. The method for detecting the magnesium content in the inorganic compound fertilizer according to claim 1, wherein in the step S1, the ratio of the inorganic compound fertilizer sample to the hydrochloric acid solution is 3-10 g: 30-100 mL, wherein in the hydrochloric acid solution, the ratio of hydrochloric acid to water is 1:1 to 9.
3. The method for detecting the magnesium content in the inorganic compound fertilizer according to claim 1, wherein in the step S1, the boiling time is 15-30 min.
4. The method for detecting the magnesium content in the inorganic compound fertilizer according to claim 1, wherein in the step S2, the volume ratio of triethanolamine to filtrate is 5-10: 25, in the step S3, the volume ratio of the triethanolamine to the filtrate is 5-10: 25.
5. The method for detecting the magnesium content in the inorganic compound fertilizer according to claim 1, wherein in the step S1, the filtration is a dry filtration mode.
6. The method for detecting the magnesium content in the inorganic compound fertilizer according to claim 1, wherein the preparation method of the ammonia buffer solution is that ammonium chloride is dissolved in water, ammonia water is added and the ammonia buffer solution is diluted by water; the preparation method of the chrome black T indicator comprises the step of grinding and uniformly mixing chrome black and sodium chloride dried at the temperature of 105-110 ℃.
7. The method for detecting the magnesium content in the inorganic compound fertilizer according to claim 1, wherein the concentration of the disodium edetate is 0.01-0.1 mol/L; the concentration of the calcium chloride is 0.01-0.1 mol/L.
8. The method for detecting the magnesium content in the inorganic compound fertilizer according to claim 1, wherein the magnesium content w (Mg) in the inorganic compound fertilizer sample is calculated by the following formula:
w(Mg)＝[C(V02-V2)/V4-C(V01-V1)/V3]×24.31/(1000×m/V5)×100,
Wherein:
w (Mg) is the content of magnesium in the inorganic compound fertilizer, and the unit is percentage content (%); c is the concentration of a standard titration solution of calcium chloride, and the unit is mol/L; v 01 is the volume of standard titration solution of calcium chloride consumed by a blank test when the content of calcium is measured, and the unit is mL; v 02 is the standard titration solution volume of calcium chloride which is consumed in blank when the total amount of calcium and magnesium is measured, and the unit is mL; v 1 is the volume of the standard calcium chloride solution consumed in measuring the content of calcium, and the unit is mL; v 2 is the volume of the standard titration solution of calcium chloride consumed in measuring the total amount of calcium and magnesium, and the unit is mL; v 3 is the volume of the sample solution sucked when the content of calcium is measured, and the unit is mL; v 4 is the volume of the sample solution sucked when the total amount of calcium and magnesium is measured, and the unit is mL; v 5 is the transfer constant volume in mL; m is the sample mass, and the unit is g.
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