阅读说明：本技术 活性腐植酸有机肥料中活化棕黑腐植酸含量的测定方法 (Method for determining content of activated brown black humic acid in active humic acid organic fertilizer ) 是由 王守全 于 2020-06-10 设计创作，主要内容包括：本发明公开了活性腐植酸有机肥料中活化棕黑腐植酸含量的测定方法,包括如下步骤：S1、溶解抽提：称取1.0g～3.0g的试样于250mL锥形瓶中,加入100mL柠檬酸-柠檬酸钠抽提液,摇动锥形瓶使样品润湿,在锥形瓶口盖一小漏斗,置于沸水浴中,加热抽提；同时进行空白试验；S2、过滤：取出锥形瓶,冷却到室温,将抽提液及残渣全部转入200mL容量瓶中,用水稀释到刻度,摇匀后为A液,用中速定性滤纸干过滤,弃去最初的约5ml溶液,随后滤出150mL～180mL滤液,得B液。本发明通过采用酸沉淀容量法对活性腐植酸有机肥料中活化棕黑腐植酸的含量进行测定,使活化腐植酸的测定结果允许差较小,测定结果较准确。(The invention discloses a method for measuring the content of activated brown black humic acid in an active humic acid organic fertilizer, which comprises the following steps: s1, dissolving and extracting: weighing 1.0 g-3.0 g of sample into a 250mL conical flask, adding 100mL of citric acid-sodium citrate extraction solution, shaking the conical flask to moisten the sample, placing the conical flask in a small funnel at the opening of the conical flask, and heating and extracting the sample in a boiling water bath; simultaneously carrying out a blank test; s2, filtering: taking out the conical flask, cooling to room temperature, transferring all the extract and the residue into a 200mL volumetric flask, diluting to a scale with water, shaking uniformly to obtain solution A, performing dry filtration by using medium-speed qualitative filter paper, discarding about 5mL of the initial solution, and then filtering 150 mL-180 mL of filtrate to obtain solution B. According to the method, the content of the activated brown black humic acid in the active humic acid organic fertilizer is measured by adopting an acid precipitation volumetric method, so that the allowable difference of the measurement result of the activated humic acid is small, and the measurement result is accurate.)

1. The method for measuring the content of activated brown black humic acid in the active humic acid organic fertilizer is characterized by comprising the following steps:

s1, dissolving and extracting: weighing 1.0 g-3.0 g of sample into a 250mL conical flask, adding 100mL of citric acid-sodium citrate extraction solution, shaking the conical flask to moisten the sample, placing the conical flask in a small funnel at the opening of the conical flask, and heating and extracting the sample in a boiling water bath; simultaneously carrying out a blank test;

s2, filtering: taking out the conical flask, cooling to room temperature, transferring all the extract and residues into a 200mL volumetric flask, diluting with water to a scale, shaking up to obtain solution A, performing dry filtration by using medium-speed qualitative filter paper, discarding about 5mL of the initial solution, and then filtering out 150 mL-180 mL of filtrate to obtain solution B;

s3, centrifugal precipitation: accurately sucking 100mL of the B liquid into a centrifuge cup by using a 50mL pipette, slowly adding a sulfuric acid solution, adjusting the pH value of the solution to be 2.00, centrifuging the suspension at 3000r/min for 30min, decanting the supernatant liquid, collecting, washing the centrifugation residue for 3 times by using a sulfuric acid washing liquid, wherein the dosage of the supernatant liquid and the washing liquid is 20mL each time, and then combining the supernatant liquid and the washing liquid to obtain a C liquid;

s4, dissolving precipitate: dissolving the precipitate in the centrifuge cup with 50mL of sodium hydroxide solution, transferring the precipitate to a 200mL volumetric flask, washing the centrifuge cup with 20mL of water each time, repeating the washing for 3-4 times, transferring the washing liquid into the volumetric flask, and fixing the volume to obtain solution D;

s5, oxidative titration: accurately sucking 10mL of D liquid into a 250mL conical flask, accurately adding 5mL of 0.4mol/L potassium dichromate solution and 15mL of sulfuric acid by using a pipette, placing the mixture in a boiling water bath, oxidizing for 30min, and carrying out amplitude of 20 r/min-30 r/min, then taking down the mixture, cooling the mixture to room temperature, diluting the mixture by using water to about 100mL, adding 3 drops of phenanthroline indicator after cooling, and titrating the mixture to brick red by using an ammonium ferrous sulfate standard solution; simultaneously, measuring a blank value according to the steps;

s6, calculating the result: the content of active brown black humic acid BHAad is expressed by% and calculated according to the following formula:

2. the method for determining the content of activated brown black humic acid in the active humic acid organic fertilizer as claimed in claim 1, wherein in S1, the citric acid-sodium citrate extract is prepared by mixing 70mL of citric acid solution with 930mL of sodium citrate solution and shaking up, and the concentration of the citric acid-sodium citrate extract is 0.1mol/L and the pH value is 6-7.

3. The method for measuring the content of activated brown black humic acid in the active humic acid organic fertilizer as claimed in claim 1, wherein in S3, the preparation method of the sulfuric acid solution is as follows: diluting 28ml of 98% sulfuric acid with water, metering to 1000ml volumetric flask, and shaking up.

4. The method for determining the content of activated brown black humic acid in the active humic acid organic fertilizer as claimed in claim 1, wherein in S3, the sulfuric acid lotion is prepared by mixing and shaking up a sulfuric acid solution and water according to a volume ratio of 1: 9.

5. The method for determining the content of activated brown black humic acid in the active humic acid organic fertilizer as claimed in claim 1, wherein in S5, concentrated sulfuric acid with the concentration of 98% is adopted; the preparation method of the potassium dichromate solution comprises the following steps: weighing 20g of potassium dichromate, dissolving in a proper amount of water, metering the volume to a volumetric flask of 1000ml, and shaking up.

6. The method for measuring the content of activated brown black humic acid in the active humic acid organic fertilizer as claimed in claim 1, wherein in S5, the ammonium ferrous sulfate standard solution is prepared by the following method: weighing 40g of ferrous ammonium sulfate, dissolving the ferrous ammonium sulfate in water, adding 20mL of sulfuric acid with the concentration of 98%, metering the volume to a 1000mL brown volumetric flask, shaking up, and storing the mixture in a dark place.

7. The method for determining the content of activated brown black humic acid in the active humic acid organic fertilizer as claimed in claim 1, wherein in S5, the ammonium ferrous sulfate standard solution is calibrated by 0.1mol/L potassium dichromate solution according to the following method: accurately sucking 25ml of potassium dichromate standard solution, putting the solution into a 250ml conical flask, then adding 70ml to 80ml of distilled water and 10ml of 98% sulfuric acid, cooling, adding 3 drops of phenanthroline indicator, and titrating the solution by using ammonium ferrous sulfate standard solution until the solution is changed from orange to brick red; the preparation method of the phenanthroline indicator comprises the following steps: weighing 1.5g of phenanthroline, 1g of ammonium ferrous sulfate or 0.7g of ferrous sulfate, dissolving in 100ml of water, and uniformly mixing.

8. The method for determining the content of activated brown black humic acid in the active humic acid organic fertilizer as claimed in claim 7, wherein the concentration of the ammonium ferrous sulfate standard solution is C, and the unit is moL/L, and the calculation formula is as follows:wherein v is the volume value of the ammonium ferrous sulfate standard solution for titrating 25ml of potassium dichromate standard solution, and the unit is ml.

9. The method for determining the content of activated brown black humic acid in the active humic acid organic fertilizer as claimed in claim 1, wherein in S6, v is₀The volume of the blank consumed ammonium ferrous sulfate standard solution is titrated, and the unit is mL; v. of₁The volume of the standard solution of ferrous ammonium sulfate consumed by the titration test solution is a numerical value, and the unit is milliliter (mL); c is an accurate value of the concentration of the ammonium ferrous sulfate standard solution, and the unit is mol/L; r is the carbon content of humic acid, and the value is 0.58; m is the numerical value of the mass of the sample, and the unit is g; a is the total volume of the extract after constant volumeNumerical values in mL, wherein a is 200 in the method; d is the numerical value of the total volume of the acid precipitate after alkali dissolution and volume fixing, the unit is mL, and d is 200 in the method; b is the numerical value of the volume of the test solution taken in the acidification, the unit is mL, and b is 100 in the method; e is the volume value of the test solution taken in the oxidation measurement, the unit is mL, and e is 10 in the method; 0.003 is a number corresponding to a mass of carbon in g for 1.00mL of a 1.000mol/L solution of ferrous ammonium sulfate C (Fe2 +); 1.05 is an oxidation correction factor.

Technical Field

The invention relates to the related technical field of organic fertilizers, in particular to a method for measuring the content of activated brown black humic acid in an active humic acid organic fertilizer.

Background

Humic acid is a macromolecular organic substance widely existing in nature, and is widely applied to various fields of agriculture, forestry, pasturing, petroleum, chemical industry, building materials, medicine, health, environmental protection and the like. Particularly, ecological agricultural construction, pollution-free agricultural production, green food, pollution-free and environment-friendly properties and the like are advocated at present, and the humic acid is highly advocated; it has been proved that human life and survival cannot be separated from humic acid, which is remains of animals and plants, mainly plants, and organic substances caused and accumulated by a series of processes of microbial decomposition and transformation and geochemistry. Its total amount is surprisingly large, measured in trillions of tons. The river, lake and sea, soil coal mine and most of the earth surface have its trace. Due to its wide existence, it has great influence on the earth, and relates to carbon circulation, mineral migration and accumulation, soil fertility, ecological balance and other aspects. The total amount of humic acid contained in the soil is the largest, but the content in the soil is less than one percent on average, and the total amount contained in the brackish water is not small, but the concentration is lower; the basic structure of the macromolecule of humic acid is aromatic ring and alicyclic ring, the functional groups of carboxyl, hydroxyl, carbonyl, quinonyl, methoxyl, etc. are connected on the ring, the humic acid is a mixture of aromatic amorphous high molecular compounds rich in oxygen-containing functional groups of carboxyl, phenolic hydroxyl, methoxyl, etc., the synergistic effect of the humic acid on fertilizer is very obvious, and the humic acid is widely used as a synergist of the fertilizer. The humic acid compound fertilizer has huge capacity, the main part of the humic acid synergistic fertilizer is activated humic acid, and the activated humic acid is usually used for representing the activation degree of the humic acid in the fertilizer.

In order to control the product quality of the humic acid organic fertilizer and promote the healthy development of the humic acid synergistic fertilizer, the content of activated brown black humic acid in the product needs to be detected; however, at present, no scientific and accurate method for measuring the content of the activated brown black humic acid in the active humic acid organic fertilizer exists, so that a scientific and accurate method for measuring the content of the activated brown black humic acid in the active humic acid organic fertilizer is found, and has important influence on controlling the product quality of the humic acid organic fertilizer and promoting the healthy development of the humic acid synergistic fertilizer.

Disclosure of Invention

The invention aims to provide a method for measuring the content of activated brown black humic acid in an active humic acid organic fertilizer, which aims to solve the problems that the product quality of a humic acid organic fertilizer is controlled, the healthy development of a humic acid synergistic fertilizer is promoted, and the content of the activated brown black humic acid in the product needs to be detected; but the problem of a scientific and accurate method for measuring the content of the activated brown black humic acid in the active humic acid organic fertilizer does not exist at present.

In order to achieve the purpose, the invention provides the following technical scheme: the method for measuring the content of activated brown black humic acid in the active humic acid organic fertilizer comprises the following steps:

s1, dissolving and extracting: weighing 1.0 g-3.0 g of sample into a 250mL conical flask, adding 100mL of citric acid-sodium citrate extraction solution, shaking the conical flask to moisten the sample, placing the conical flask in a small funnel at the opening of the conical flask, and heating and extracting the sample in a boiling water bath; simultaneously carrying out a blank test;

s2, filtering: taking out the conical flask, cooling to room temperature, transferring all the extract and residues into a 200mL volumetric flask, diluting with water to a scale, shaking up to obtain solution A, performing dry filtration by using medium-speed qualitative filter paper, discarding about 5mL of the initial solution, and then filtering out 150 mL-180 mL of filtrate to obtain solution B;

s3, centrifugal precipitation: accurately sucking 100mL of the B liquid into a centrifuge cup by using a 50mL pipette, slowly adding a sulfuric acid solution, adjusting the pH value of the solution to be 2.00, centrifuging the suspension at 3000r/min for 30min, decanting the supernatant liquid, collecting, washing the centrifugation residue for 3 times by using a sulfuric acid washing liquid, wherein the dosage of the supernatant liquid and the washing liquid is 20mL each time, and then combining the supernatant liquid and the washing liquid to obtain a C liquid;

s4, dissolving precipitate: dissolving the precipitate in the centrifuge cup with 50mL of sodium hydroxide solution, transferring the precipitate to a 200mL volumetric flask, washing the centrifuge cup with 20mL of water each time, repeating the washing for 3-4 times, transferring the washing liquid into the volumetric flask, and fixing the volume to obtain solution D;

s5, oxidative titration: accurately sucking 10mL of D liquid into a 250mL conical flask, accurately adding 5mL of 0.4mol/L potassium dichromate solution and 15mL of sulfuric acid by using a pipette, placing the mixture in a boiling water bath, oxidizing for 30min, and carrying out amplitude of 20 r/min-30 r/min, then taking down the mixture, cooling the mixture to room temperature, diluting the mixture by using water to about 100mL, adding 3 drops of phenanthroline indicator after cooling, and titrating the mixture to brick red by using an ammonium ferrous sulfate standard solution; simultaneously, measuring a blank value according to the steps;

s6, calculating the result: the content of active brown black humic acid BHAad is expressed by% and calculated according to the following formula:

preferably, in S1, the citric acid-sodium citrate extract is prepared by mixing 70mL of citric acid solution and 930mL of sodium citrate solution and shaking uniformly, and the concentration of the citric acid-sodium citrate extract is 0.1mol/L, and the pH value is 6-7.

Preferably, in S3, the sulfuric acid solution is prepared as follows: diluting 28ml of 98% sulfuric acid with water, metering to 1000ml volumetric flask, and shaking up.

Preferably, in S3, the sulfuric acid washing solution is prepared by mixing and shaking a sulfuric acid solution and water in a volume ratio of 1: 9.

Preferably, in S5, the sulfuric acid is concentrated sulfuric acid with a concentration of 98%; the preparation method of the potassium dichromate solution comprises the following steps: weighing 20g of potassium dichromate, dissolving in a proper amount of water, metering the volume to a volumetric flask of 1000ml, and shaking up.

Preferably, in S5, the standard solution of ferrous ammonium sulfate is prepared as follows: weighing 40g of ferrous ammonium sulfate, dissolving the ferrous ammonium sulfate in water, adding 20mL of sulfuric acid with the concentration of 98%, metering the volume to a 1000mL brown volumetric flask, shaking up, and storing the mixture in a dark place.

Preferably, in S5, the standard solution of ferrous ammonium sulfate is calibrated with 0.1mol/L potassium dichromate solution according to the following method: accurately sucking 25ml of potassium dichromate standard solution, putting the solution into a 250ml conical flask, then adding 70ml to 80ml of distilled water and 10ml of 98% sulfuric acid, cooling, adding 3 drops of phenanthroline indicator, and titrating the solution by using ammonium ferrous sulfate standard solution until the solution is changed from orange to brick red; the preparation method of the phenanthroline indicator comprises the following steps: weighing 1.5g of phenanthroline, 1g of ammonium ferrous sulfate or 0.7g of ferrous sulfate, dissolving in 100ml of water, and uniformly mixing.

Preferably, the concentration of the standard solution of ferrous ammonium sulfate is C, and the unit is moL/L, and the calculation formula is as follows:wherein v is the volume value of the ammonium ferrous sulfate standard solution for titrating 25ml of potassium dichromate standard solution, and the unit is ml.

Preferably, in S6, v₀The volume of the blank consumed ammonium ferrous sulfate standard solution is titrated, and the unit is mL; v. of₁The volume of the standard solution of ferrous ammonium sulfate consumed by the titration test solution is a numerical value, and the unit is milliliter (mL); c is an accurate value of the concentration of the ammonium ferrous sulfate standard solution, and the unit is mol/L; r is the carbon content ratio of humic acid,the value is 0.58; m is the numerical value of the mass of the sample, and the unit is g; a is the numerical value of the total volume of the extract after constant volume, the unit is mL, and a is 200 in the method; d is the numerical value of the total volume of the acid precipitate after alkali dissolution and volume fixing, the unit is mL, and d is 200 in the method; b is the numerical value of the volume of the test solution taken in the acidification, the unit is mL, and b is 100 in the method; e is the volume value of the test solution taken in the oxidation measurement, the unit is mL, and e is 10 in the method; 0.003 is a number corresponding to a mass of carbon in g for 1.00mL of a 1.000mol/L solution of ferrous ammonium sulfate C (Fe2 +); 1.05 is an oxidation correction factor.

The invention provides a method for measuring the content of activated brown black humic acid in an active humic acid organic fertilizer, which has the following beneficial effects:

according to the invention, the citric acid-sodium citrate mixed extract is adopted to extract the humic acid fertilizer, so that the extraction effect is very good; the content of the activated brown black humic acid in the active humic acid organic fertilizer is measured by adopting an acid precipitation volumetric method, so that the allowable difference of the measurement result of the activated humic acid is small, the measurement result is accurate, and meanwhile, the measurement method is convenient to operate and is easy to control errors; the method meets the operation requirements of most enterprises and quality inspection units, is simple and rapid to operate, has good reproducibility and high accuracy, and has great significance for quality control of active humic acid organic fertilizer products.

Detailed Description

Example 1:

the method for measuring the content of activated brown black humic acid in the active humic acid organic fertilizer comprises the following steps:

s1, dissolving and extracting: weighing 1.0g of sample into a 250mL conical flask, adding 100mL of citric acid-sodium citrate extraction solution, shaking the conical flask to moisten the sample, placing the conical flask in a boiling water bath through a small funnel at the opening of the conical flask, and heating and extracting; simultaneously carrying out a blank test; wherein the citric acid-sodium citrate extraction liquid is prepared by mixing 70mL of citric acid solution and 930mL of sodium citrate solution and shaking uniformly, the concentration of the citric acid-sodium citrate extraction liquid is 0.1mol/L, and the pH value is 6-7;

s2, filtering: taking out the conical flask, cooling to room temperature, transferring all the extract and residues into a 200mL volumetric flask, diluting with water to a scale, shaking up to obtain solution A, dry-filtering with medium-speed qualitative filter paper, discarding about 5mL of the initial solution, and then filtering out 150mL of filtrate to obtain solution B;

s3, centrifugal precipitation: accurately sucking 100mL of the B liquid into a centrifuge cup by using a 50mL pipette, slowly adding a sulfuric acid solution, adjusting the pH value of the solution to be 2.00, centrifuging the suspension at 3000r/min for 30min, decanting the supernatant liquid, collecting, washing the centrifugation residue for 3 times by using a sulfuric acid washing liquid, wherein the dosage of the supernatant liquid and the washing liquid is 20mL each time, and then combining the supernatant liquid and the washing liquid to obtain a C liquid; the preparation method of the sulfuric acid solution comprises the following steps: diluting 28ml of 98% sulfuric acid with water, metering to 1000ml volumetric flask, and shaking up; the sulfuric acid washing liquor is prepared by mixing and shaking up a sulfuric acid solution and water according to the volume ratio of 1: 9;

s4, dissolving precipitate: dissolving the precipitate in the centrifuge cup with 50mL of sodium hydroxide solution, transferring to a 200mL volumetric flask, washing the centrifuge cup with 20mL of water each time, repeating for 3 times, transferring the washing solution into the volumetric flask, and fixing the volume to obtain solution D;

s5, oxidative titration: accurately sucking 10mL of D liquid into a 250mL conical flask, accurately adding 5mL of 0.4mol/L potassium dichromate solution and 15mL of sulfuric acid by using a pipette, placing the solution in a boiling water bath, oxidizing for 30min, and taking down the solution, cooling to room temperature, diluting by using water to about 100mL, adding 3 drops of phenanthroline indicator after cooling, and titrating to brick red by using an ammonium ferrous sulfate standard solution; simultaneously, measuring a blank value according to the steps; wherein, the sulfuric acid adopts concentrated sulfuric acid with the concentration of 98 percent; the preparation method of the potassium dichromate solution comprises the following steps: weighing 20g of potassium dichromate, dissolving in a proper amount of water, fixing the volume to a volumetric flask of 1000ml, and shaking up; the standard solution of ferrous ammonium sulfate is prepared by the following steps: weighing 40g of ferrous ammonium sulfate, dissolving the ferrous ammonium sulfate in water, adding 20mL of sulfuric acid with the concentration of 98%, metering the volume to a 1000mL brown volumetric flask, and shaking up; before the ammonium ferrous sulfate standard solution is used, a 0.1mol/L potassium dichromate solution is used for calibration according to the following method: accurately sucking 25ml of potassium dichromate standard solution, putting the solution into a 250ml conical flask, then adding 70ml of distilled water and 10ml of 98% sulfuric acid, cooling, adding 3 drops of phenanthroline indicator, and using ammonium ferrous sulfate standardTitrating the solution until the solution changes from orange to brick red; the preparation method of the phenanthroline indicator comprises the following steps: weighing 1.5g of phenanthroline, 1g of ammonium ferrous sulfate or 0.7g of ferrous sulfate, dissolving in 100ml of water, and uniformly mixing; the concentration of the ammonium ferrous sulfate standard solution is C, the unit is moL/L, and the calculation formula is as follows:wherein v is the numerical value of the volume of the ammonium ferrous sulfate standard solution for titrating 25ml of potassium dichromate standard solution, and the unit is ml;

s6, calculating the result: the content of active brown black humic acid BHAad is expressed by% and calculated according to the following formula:wherein v is₀The volume of the blank consumed ammonium ferrous sulfate standard solution is titrated, and the unit is mL; v. of₁The volume of the standard solution of ferrous ammonium sulfate consumed by the titration test solution is a numerical value, and the unit is milliliter (mL); c is an accurate value of the concentration of the ammonium ferrous sulfate standard solution, and the unit is mol/L; r is the carbon content of humic acid, and the value is 0.58; m is the numerical value of the mass of the sample, and the unit is g; a is the numerical value of the total volume of the extract after constant volume, the unit is mL, and a is 200 in the method; d is the numerical value of the total volume of the acid precipitate after alkali dissolution and volume fixing, the unit is mL, and d is 200 in the method; b is the numerical value of the volume of the test solution taken in the acidification, the unit is mL, and b is 100 in the method; e is the volume value of the test solution taken in the oxidation measurement, the unit is mL, and e is 10 in the method; 0.003 is a number corresponding to a mass of carbon in g for 1.00mL of a 1.000mol/L solution of ferrous ammonium sulfate C (Fe2 +); 1.05 is an oxidation correction factor.

Example 2:

the method for measuring the content of activated brown black humic acid in the active humic acid organic fertilizer comprises the following steps:

s1, dissolving and extracting: weighing 2.0g of sample into a 250mL conical flask, adding 100mL of citric acid-sodium citrate extraction solution, shaking the conical flask to moisten the sample, placing the conical flask in a boiling water bath through a small funnel at the opening of the conical flask, and heating and extracting; simultaneously carrying out a blank test; wherein the citric acid-sodium citrate extraction liquid is prepared by mixing 70mL of citric acid solution and 930mL of sodium citrate solution and shaking uniformly, the concentration of the citric acid-sodium citrate extraction liquid is 0.1mol/L, and the pH value is 6-7;

s2, filtering: taking out the conical flask, cooling to room temperature, transferring all the extract and residues into a 200mL volumetric flask, diluting with water to a scale, shaking up to obtain solution A, dry-filtering with medium-speed qualitative filter paper, discarding about 5mL of the initial solution, and then filtering 160mL of filtrate to obtain solution B;

s3, centrifugal precipitation: accurately sucking 100mL of the B liquid into a centrifuge cup by using a 50mL pipette, slowly adding a sulfuric acid solution, adjusting the pH value of the solution to be 2.00, centrifuging the suspension at 3000r/min for 30min, decanting the supernatant liquid, collecting, washing the centrifugation residue for 3 times by using a sulfuric acid washing liquid, wherein the dosage of the supernatant liquid and the washing liquid is 20mL each time, and then combining the supernatant liquid and the washing liquid to obtain a C liquid; the preparation method of the sulfuric acid solution comprises the following steps: diluting 28ml of 98% sulfuric acid with water, metering to 1000ml volumetric flask, and shaking up; the sulfuric acid washing liquor is prepared by mixing and shaking up a sulfuric acid solution and water according to the volume ratio of 1: 9;

s4, dissolving precipitate: dissolving the precipitate in the centrifuge cup with 50mL of sodium hydroxide solution, transferring to a 200mL volumetric flask, washing the centrifuge cup with 20mL of water each time, repeating for 4 times, transferring the washing solution into the volumetric flask, and fixing the volume to obtain solution D;

s5, oxidative titration: accurately sucking 10mL of D liquid into a 250mL conical flask, accurately adding 5mL of 0.4mol/L potassium dichromate solution and 15mL of sulfuric acid by using a pipette, placing the solution in a boiling water bath, oxidizing for 30min, and carrying out amplitude 25r/min, then taking down the solution, cooling to room temperature, diluting by using water to about 100mL, adding 3 drops of phenanthroline indicator after cooling, and titrating to brick red by using an ammonium ferrous sulfate standard solution; simultaneously, measuring a blank value according to the steps; wherein, the sulfuric acid adopts concentrated sulfuric acid with the concentration of 98 percent; the preparation method of the potassium dichromate solution comprises the following steps: weighing 20g of potassium dichromate, dissolving in a proper amount of water, fixing the volume to a volumetric flask of 1000ml, and shaking up; the standard solution of ferrous ammonium sulfate is prepared by the following steps: weighing 40g of ferrous ammonium sulfate, dissolving the ferrous ammonium sulfate in water, adding 20mL of 98% sulfuric acid, and fixing the volume to 1000mL of brown containerShaking up in a measuring flask; before the ammonium ferrous sulfate standard solution is used, a 0.1mol/L potassium dichromate solution is used for calibration according to the following method: accurately sucking 25ml of potassium dichromate standard solution, putting the potassium dichromate standard solution into a 250ml conical flask, then adding 70ml of distilled water and 10ml of sulfuric acid with the concentration of 98%, cooling, adding 3 drops of phenanthroline indicator, and titrating the solution by using ammonium ferrous sulfate standard solution until the solution is changed from orange into brick red; the preparation method of the phenanthroline indicator comprises the following steps: weighing 1.5g of phenanthroline, 1g of ammonium ferrous sulfate or 0.7g of ferrous sulfate, dissolving in 100ml of water, and uniformly mixing; the concentration of the ammonium ferrous sulfate standard solution is C, the unit is moL/L, and the calculation formula is as follows:wherein v is the numerical value of the volume of the ammonium ferrous sulfate standard solution for titrating 25ml of potassium dichromate standard solution, and the unit is ml;

s6, calculating the result: the content of active brown black humic acid BHAad is expressed by% and calculated according to the following formula:wherein v is₀The volume of the blank consumed ammonium ferrous sulfate standard solution is titrated, and the unit is mL; v. of₁The volume of the standard solution of ferrous ammonium sulfate consumed by the titration test solution is a numerical value, and the unit is milliliter (mL); c is an accurate value of the concentration of the ammonium ferrous sulfate standard solution, and the unit is mol/L; r is the carbon content of humic acid, and the value is 0.58; m is the numerical value of the mass of the sample, and the unit is g; a is the numerical value of the total volume of the extract after constant volume, the unit is mL, and a is 200 in the method; d is the numerical value of the total volume of the acid precipitate after alkali dissolution and volume fixing, the unit is mL, and d is 200 in the method; b is the numerical value of the volume of the test solution taken in the acidification, the unit is mL, and b is 100 in the method; e is the volume value of the test solution taken in the oxidation measurement, the unit is mL, and e is 10 in the method; 0.003 is a number corresponding to a mass of carbon in g for 1.00mL of a 1.000mol/L solution of ferrous ammonium sulfate C (Fe2 +); 1.05 is an oxidation correction factor.

Example 3:

the method for measuring the content of activated brown black humic acid in the active humic acid organic fertilizer comprises the following steps:

s1, dissolving and extracting: weighing 1.0 g-3.0 g of sample into a 250mL conical flask, adding 100mL of citric acid-sodium citrate extraction solution, shaking the conical flask to moisten the sample, placing the conical flask in a small funnel at the opening of the conical flask, and heating and extracting the sample in a boiling water bath; simultaneously carrying out a blank test; wherein the citric acid-sodium citrate extraction liquid is prepared by mixing 70mL of citric acid solution and 930mL of sodium citrate solution and shaking uniformly, the concentration of the citric acid-sodium citrate extraction liquid is 0.1mol/L, and the pH value is 6-7;

s2, filtering: taking out the conical flask, cooling to room temperature, transferring all the extract and residues into a 200mL volumetric flask, diluting with water to a scale, shaking up to obtain solution A, dry-filtering with medium-speed qualitative filter paper, discarding about 5mL of the initial solution, and then filtering out 180mL of filtrate to obtain solution B;

s3, centrifugal precipitation: accurately sucking 100mL of the B liquid into a centrifuge cup by using a 50mL pipette, slowly adding a sulfuric acid solution, adjusting the pH value of the solution to be 2.00, centrifuging the suspension at 3000r/min for 30min, decanting the supernatant liquid, collecting, washing the centrifugation residue for 3 times by using a sulfuric acid washing liquid, wherein the dosage of the supernatant liquid and the washing liquid is 20mL each time, and then combining the supernatant liquid and the washing liquid to obtain a C liquid; the preparation method of the sulfuric acid solution comprises the following steps: diluting 28ml of 98% sulfuric acid with water, metering to 1000ml volumetric flask, and shaking up; the sulfuric acid washing liquor is prepared by mixing and shaking up a sulfuric acid solution and water according to the volume ratio of 1: 9;

s4, dissolving precipitate: dissolving the precipitate in the centrifuge cup with 50mL of sodium hydroxide solution, transferring to a 200mL volumetric flask, washing the centrifuge cup with 20mL of water each time, repeating for 4 times, transferring the washing solution into the volumetric flask, and fixing the volume to obtain solution D;

s5, oxidative titration: accurately sucking 10mL of D liquid into a 250mL conical flask, accurately adding 5mL of 0.4mol/L potassium dichromate solution and 15mL of sulfuric acid by using a pipette, placing the solution in a boiling water bath, oxidizing for 30min, taking down the solution, cooling to room temperature, diluting by using water to about 100mL, adding 3 drops of phenanthroline indicator after cooling, and titrating to brick red by using an ammonium ferrous sulfate standard solution; simultaneously, measuring a blank value according to the steps; wherein, sulfurThe acid is concentrated sulfuric acid with the concentration of 98 percent; the preparation method of the potassium dichromate solution comprises the following steps: weighing 20g of potassium dichromate, dissolving in a proper amount of water, fixing the volume to a volumetric flask of 1000ml, and shaking up; the standard solution of ferrous ammonium sulfate is prepared by the following steps: weighing 40g of ferrous ammonium sulfate, dissolving the ferrous ammonium sulfate in water, adding 20mL of sulfuric acid with the concentration of 98%, metering the volume to a 1000mL brown volumetric flask, and shaking up; before the ammonium ferrous sulfate standard solution is used, a 0.1mol/L potassium dichromate solution is used for calibration according to the following method: accurately sucking 25ml of potassium dichromate standard solution, putting the potassium dichromate standard solution into a 250ml conical flask, then adding 70ml of distilled water and 10ml of sulfuric acid with the concentration of 98%, cooling, adding 3 drops of phenanthroline indicator, and titrating the solution by using ammonium ferrous sulfate standard solution until the solution is changed from orange into brick red; the preparation method of the phenanthroline indicator comprises the following steps: weighing 1.5g of phenanthroline, 1g of ammonium ferrous sulfate or 0.7g of ferrous sulfate, dissolving in 100ml of water, and uniformly mixing; the concentration of the ammonium ferrous sulfate standard solution is C, the unit is moL/L, and the calculation formula is as follows:wherein v is the numerical value of the volume of the ammonium ferrous sulfate standard solution for titrating 25ml of potassium dichromate standard solution, and the unit is ml;

s6, calculating the result: the content of active brown black humic acid BHAad is expressed by% and calculated according to the following formula:wherein v is₀The volume of the blank consumed ammonium ferrous sulfate standard solution is titrated, and the unit is mL; v. of₁The volume of the standard solution of ferrous ammonium sulfate consumed by the titration test solution is a numerical value, and the unit is milliliter (mL); c is an accurate value of the concentration of the ammonium ferrous sulfate standard solution, and the unit is mol/L; r is the carbon content of humic acid, and the value is 0.58; m is the numerical value of the mass of the sample, and the unit is g; a is the numerical value of the total volume of the extract after constant volume, the unit is mL, and a is 200 in the method; d is the numerical value of the total volume of the acid precipitate after alkali dissolution and volume fixing, the unit is mL, and d is 200 in the method; b is the numerical value of the volume of the test solution taken in the acidification, the unit is mL, and b is 100 in the method;e is the volume value of the test solution taken in the oxidation measurement, the unit is mL, and e is 10 in the method; 0.003 is a number corresponding to a mass of carbon in g for 1.00mL of a 1.000mol/L solution of ferrous ammonium sulfate C (Fe2 +); 1.05 is an oxidation correction factor.

Example 4:

the results obtained in examples 1-3 were compared to the allowable difference table, which is shown below:

BHAad％	the same laboratory ad%	Different labs ad%
			＜1.5	0.1	0.15
≥1.5	0.15	0.2

And (4) conclusion:

in conclusion, the humic acid fertilizer is extracted by adopting the citric acid-sodium citrate mixed extract, so that the extraction effect is very good; the content of the activated brown black humic acid in the active humic acid organic fertilizer is measured by adopting an acid precipitation volumetric method, so that the allowable difference of the measurement result of the activated humic acid is small, the measurement result is accurate, and meanwhile, the measurement method is convenient to operate and is easy to control errors; the method meets the operation requirements of most enterprises and quality inspection units, is simple and rapid to operate, has good reproducibility and high accuracy, and has great significance for quality control of active humic acid organic fertilizer products.

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.