Method for accurately measuring ammonia content in solution

Abstract

The invention discloses a method for accurately measuring the content of ammonia in a solution. The method comprises the following steps: mixing pure water with a set volume and an acid standard solution with a set volume to prepare a blank solution; titrating the blank solution with an alkali standard solution until an end point, uniformly mixing pure water with a set volume and an acid standard solution with a set volume, and adding a sample with a set mass into the mixture to prepare a solution to be detected; and titrating the to-be-detected solution with the alkali standard solution until the end point. On the basis of an acid-base neutralization titration principle, firstly, a sample and a constant amount of acid are subjected to a neutralization reaction quickly in a closed space, then excessive acid is titrated with an alkali standard solution, and the ammonia content is obtained through calculation. The operation not only reduces the chance of contact between people and ammonia, but also reduces the volatilization of ammonia in the titration process, and improves the data accuracy.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of polyacrylonitrile solution polymerization, and particularly relates to a method for accurately measuring ammonia content in a solution. BACKGROUND

[0002] At present, in GB / T 631-2007 Chemical Reagents Ammonia Water, the test method of ammonia content in an aqueous solution is described, the determination principle of which is acid-base neutralization titration, and the detection method of which is a manual indicator direct titration method.

[0003] The above method meets the detection requirements to a certain extent, but also has certain disadvantages. Because the direct titration method is a continuous and sustained process for a period of time, ammonia water has a risk of volatilization in the process, which also increases the contact opportunity between people and ammonia. In addition, the manual titration method greatly affects the detection results of the same sample by different operators and different laboratory environmental conditions, introduces a large error, leads to inaccurate experimental results, and cannot correctly guide the actual production. In addition, the above method only provides a test method of ammonia content in an aqueous solution, and does not provide a test method of ammonia content in other systems. SUMMARY

[0004] The purpose of the present application is to make up for the defects of the prior art, and provide a method for accurately measuring ammonia content in a solution. The present application reduces ammonia volatilization, has a small error range, accurately determines the end point, obtains accurate data, and correctly guides the actual production.

[0005] The present application is achieved by the following technical solutions: A method for accurately measuring ammonia content in a solution, comprising the following steps: 1) preparing a blank solution A set volume of pure water and a set volume of acid standard solution are mixed to prepare a blank solution; 2) blank solution titration The blank solution is titrated with an alkali standard solution to the end point, wherein the volume of the alkali standard solution consumed is recorded as V0; 3) preparing a sample solution A set volume of pure water and a set volume of acid standard solution are mixed and then a set mass of sample is added to prepare a sample solution; 4) sample solution titration The sample solution is titrated with an alkali standard solution to the end point, wherein the volume of the alkali standard solution consumed is recorded as V; 5) calculating the ammonia content in the sample.

[0006] The volume of pure water used in step 1) and step 3) is the same, set at 40~80mL; the concentration and volume of the acid standard solution used in step 1) and step 3) are the same, and the volume is set at 20mL.

[0007] If the sample is purchased ammonia water with a mass fraction of 25~28wt% or prepared ammonia water with a mass fraction of 0.15~3wt%, then the concentration of the acid standard solution is 1mol / L and the concentration of the alkali standard solution is 0.5mol / L; if the sample is an ammonia solution from the polymerization process with a mass fraction of 0~0.15wt%, then the concentration of the acid standard solution is 0.1mol / L and the concentration of the alkali standard solution is 0.1mol / L, or the acid standard solution is 1 / 2H2SO4 standard solution and the alkali standard solution is NaOH standard solution.

[0008] In step 3), the sample mass is set to be 0.5~25g in the step of preparing the test solution.

[0009] If the sample is purchased ammonia water with a mass fraction of 25~28wt%, the sample mass is set to 0.5~1.2g; if the sample is prepared ammonia water with a mass fraction of 0.15~3wt%, the sample mass is set to 8~12g; if the sample is an ammonia solution from the polymerization process with a mass fraction of 0~0.15wt%, the sample mass is set to 15~25g.

[0010] In step 3): the acid standard solution is added to a container containing pure water, the container is sealed, and the mixture is mixed evenly and then sealed again; the sample is quickly added to the solution and shaken to obtain the solution to be tested; the sealing is done with a sealing film; the container is a beaker; the sample is injected into the solution by first inserting the needle into the sealing film with a disposable syringe, and ensuring that the needle is below the liquid surface before injection.

[0011] In step 1), pure water and acid standard solution are added sequentially to a container; the container is a beaker.

[0012] In steps 2) and 4), the titration is performed using a fully automatic potentiometric titrator, specifically a Metrohm 916 Ti-Touch fully automatic potentiometric titrator.

[0013] Step 5) involves calculating the ammonia content in the sample, as detailed below: Input the concentration value C of the alkaline standard solution into the fully automatic potentiometric titrator. 碱 The formula for calculating ammonia content and the method for testing ammonia content are established; wherein, the formula for calculating ammonia content is: , Wherein, ω represents the ammonia content in the sample, in percentage terms. m is the mass of the sample, in grams; C 碱 This represents the concentration of the alkaline standard solution, expressed in mol / L. V represents the volume of alkaline standard solution consumed in the titration of the solution to be tested, in mL; V0 is the volume of alkaline standard solution consumed in the titration of the blank solution, in mL; 17.03 is the mass number equivalent to one mole of ammonia, expressed in g / mol.

[0014] In step 4): Select the method for measuring ammonia content in the solution on the fully automatic potentiometric titrator and click start; titrate the solution to be tested with alkaline standard solution until the equivalence point appears; the fully automatic potentiometric titrator automatically records the volume V of alkaline standard solution consumed, and automatically calculates the ammonia content in the solution based on the input data and the automatically recorded data.

[0015] The advantages of this invention are: 1. This invention is based on the principle of acid-base neutralization titration. First, in a closed space, the sample undergoes a rapid neutralization reaction with a constant amount of acid. Then, the excess acid is titrated with a standard alkaline solution, and the ammonia content is calculated. This operation not only reduces the chance of human contact with ammonia but also reduces the volatilization of ammonia during the titration process and improves data accuracy.

[0016] 2. This invention utilizes a fully automatic potentiometric titrator to titrate the solution, avoiding the disadvantage of difficulty in determining the endpoint of indicator color change in traditional titration methods, reducing human subjective error, improving the accuracy of detection data, and providing accurate data assurance for the production process.

[0017] 3. The method of the present invention is convenient and easy to implement. As long as you follow certain operating steps, you can quickly master the method and obtain accurate and reliable results. Detailed Implementation

[0018] A method for accurately measuring the ammonia content in a solution, comprising the following steps: 1) Prepare a blank solution Prepare a blank solution by mixing a predetermined volume of pure water and a predetermined volume of acid standard solution; 2) Blank solution titration A fully automated potentiometric titrator is used to titrate a blank solution with an alkaline standard solution to the endpoint. The volume of the alkaline standard solution consumed is denoted as V0. The endpoint specifically refers to the point where the potential of the titration system changes abruptly. This point corresponds to the stoichiometric point (equivalence point) where the excess acid standard solution in the blank solution is completely neutralized by the alkaline standard solution. The titration termination signal is automatically determined by the fully automated potentiometric titrator based on the potential change.

[0019] 3) Prepare the test solution Mix a set volume of pure water and a set volume of acid standard solution thoroughly, then add a set mass of sample to prepare the test solution. 4) Titration of the test solution A fully automated potentiometric titrator was used to titrate the test solution with an alkaline standard solution to the endpoint. The volume of the alkaline standard solution consumed was denoted as V.

[0020] 5) Calculate the ammonia content in the sample.

[0021] Furthermore, in steps 1) and 3), the volume of pure water used is the same, set at 40~80mL, preferably 50mL.

[0022] Further, in steps 1) and 3), if the sample is purchased ammonia water (25~28wt%) and prepared ammonia water (0.15~3wt%), the concentration of the acid standard solution is 1mol / L and the concentration of the alkali standard solution is 0.5mol / L; if the sample is an ammonia solution (0~0.15wt%) from the polymerization process, the concentration of the acid standard solution is 0.1mol / L and the concentration of the alkali standard solution is 0.1mol / L; or the acid standard solution is 1 / 2H2SO4 standard solution and the alkali standard solution is NaOH standard solution.

[0023] Furthermore, in steps 1) and 3), the concentration and volume of the acid standard solution used are the same, and the volume is set to 20 mL.

[0024] Further, in step 3), in the step of preparing the test solution, the set mass is 0.5~25g; preferably, if the sample is purchased ammonia water (25~28wt%), the set mass is 0.5~1.2g, preferably 1.0g; preferably, if the sample is prepared ammonia water (0.15~3wt%), the set mass is 8~12g, preferably 10g; preferably, if the sample is an ammonia solution (0~0.15wt%) from the polymerization production process, the set mass is 15~25g, preferably 20g.

[0025] Further, in step 3): the acid standard solution is added to a container containing pure water, the container is sealed, and the mixture is stirred evenly and then sealed again; the sample is quickly added to the solution and shaken to obtain the solution to be tested; preferably, a sealing film is used for sealing; preferably, a beaker is used to facilitate titration using a fully automatic potentiometric titrator; preferably, a disposable syringe is used to first insert the needle into the sealing film, inject the sample into the solution, and ensure that the needle is below the liquid surface before injection.

[0026] Further, in step 1), water and acid standard solution are added sequentially to the container; preferably, the container is a beaker to facilitate titration using a fully automatic potentiometric titrator.

[0027] Furthermore, in steps 2) and 4), the fully automatic potentiometric titrator is a Metrohm 916 Ti-Touch fully automatic potentiometric titrator.

[0028] Further, step 5) involves calculating the ammonia content in the sample, specifically as follows: Method setup steps: Input the concentration value C of the alkaline standard solution into the fully automatic potentiometric titrator. 碱 The formula for calculating ammonia content and the method for testing ammonia content are established; wherein, the formula for calculating ammonia content is as follows: , Wherein, ω represents the ammonia content in the sample, in percentage terms. m is the mass of the sample, in grams; C 碱 This represents the concentration of the alkaline standard solution, expressed in mol / L. V represents the volume of alkaline standard solution consumed by the test solution, in mL; V0 represents the blank solution and the volume of alkaline standard solution consumed, in mL. 17.03 is the mass number equivalent to one mole of ammonia, expressed in g / mol.

[0029] Further, in step 4): select the method for measuring the ammonia content in the solution on the fully automatic potentiometric titrator and click start; titrate the solution to be tested with alkaline standard solution until the equivalence point appears; the fully automatic potentiometric titrator automatically records the volume V of alkaline standard solution consumed, and automatically calculates the ammonia content in the solution based on the input data and the automatically recorded data.

[0030] This invention is based on the principles of acid-base neutralization titration and blank correction. By measuring the difference in reaction between ammonia and excess acid in a sample, the ammonia content is indirectly calculated. The core process is as follows: Basic Chemical Reactions Ammonia (NH3) is a basic substance and undergoes a neutralization reaction with acidic standard solutions (such as 1 / 2 H2SO4). 2NH3 + H2SO4→ (NH4)2SO4+2H2O A quantitative acid standard solution was added to both the blank solution and the test solution, including: In the blank solution, the acid is not consumed by ammonia, and the alkaline standard solution (such as NaOH) consumed in the titration is only used to neutralize all the acid (volume V0). In the test solution, the acid first reacts with the ammonia in the sample, and the remaining acid is then neutralized by the base (volume V).

[0031] Quantitative Relationship Derivation The amount of acid consumed by ammonia in the sample = total amount of acid in the blank solution - amount of acid remaining in the test solution, corresponding to the volume difference of the alkaline standard solution (V0 - V). Based on the stoichiometric relationship, the formula is: , Calculate the mass fraction of ammonia (17.03 is the molar mass of NH3, g / mol).

[0032] Instrument Assistance The fully automatic potentiometric titrator monitors the change in solution potential through electrodes, automatically determines the endpoint of acid-base neutralization (potential change point), accurately records the volume of alkaline standard solution consumed, and reduces human error.

[0033] This invention offers high measurement accuracy, with blank correction eliminating systematic errors: by subtracting interference from impurities in pure water and deviations in acid standard solutions through blank titration (V0), the results are ensured to reflect only the contribution of ammonia in the sample. This invention replaces manual judgment with potentiometric titration: a fully automatic potentiometric titrator (such as the Metrohm 916 Ti-Touch) objectively determines the endpoint through potential abrupt changes, avoiding subjective errors (such as color judgment deviation) in the traditional indicator method. This invention optimizes concentration adaptation: for samples of different concentrations (25~28wt%, 0.15~3wt%, 0~0.15wt%), it matches acid / base standard solutions of different concentrations and sampling volumes to ensure that the titration volume is within a reasonable range (neither too much nor too little), thereby improving calculation accuracy.

[0034] The standardized process of this invention has clear specifications from solution preparation (fixed volume of water and acid) to sample addition (sealing film protection, needle injection), reducing the impact of operational differences on results and ensuring the repeatability of operations by different batches or personnel.

[0035] This invention has a wide range of applications, covering high-concentration (purchasing ammonia water, 25~28wt%), medium-concentration (preparing ammonia water, 0.15~3wt%), and low-concentration (polymerizing ammonia solution, 0~0.15wt%) samples. It can achieve accurate measurement across the entire range by adjusting the detection parameters (standard solution concentration, sampling amount).

[0036] This invention reduces ammonia volatilization loss by using a "sealing film + needle-based sample injection" method during solution preparation to avoid ammonia volatilization loss, which is especially important for high-concentration ammonia water samples and ensures the accuracy of the measurement.

[0037] This invention achieves high precision, high repeatability, and wide applicability in ammonia content measurement by combining "chemical metrology, blank calibration, and instrument automation," and is especially suitable for the rapid detection of ammonia solutions of different concentrations in industrial production.

[0038] Example 1 This embodiment provides a method for determining the ammonia content in a solution; wherein the solution is sampled from an ammonia water raw material provided by a supplier: 1) Set the "ammonia content test method" on the fully automatic potentiometric titrator in advance, and input the concentration value C of the alkaline standard solution. 碱 Formula for calculating ammonia content, and endpoint conditions.

[0039] 2) Blank test procedure: Add 50 mL of ultrapure water and 20 mL of 0.5 mol / L acid standard solution (1 / 2 H2SO4 standard solution) sequentially to 150 mL, and seal the container; prepare two blank samples simultaneously, and titrate the endpoint with 0.5 mol / L alkali standard solution (NaOH standard solution) using a fully automatic potentiometric titrator; perform this process twice, and take the average of the volumes of alkali standard solution (NaOH standard solution) consumed, which is recorded as V0.

[0040] 3) Sample testing procedure: Add 50 mL of ultrapure water and 20 mL of 0.5 mol / L acid standard solution (1 / 2 H₂SO₄ standard solution) sequentially to 150 mL of solution. After sealing, use a disposable syringe to draw up the sample, quickly insert the needle into the sealing film, inject the sample, seal, and shake well. Accurately weigh the added sample using the differential method and record it as m. Simultaneously, prepare 8 samples with the following masses: 1.0987 g, 1.0546 g, 0.9009 g, 0.9285 g, 1.0021 g, 1.0165 g, 0.9975 g, and 1.0210 g, obtaining 8 parallel test samples. Set the "Ammonia Content Test Method" on the fully automatic potentiometric titrator, enter the blank volume V0 and sample mass m, and click the "Start" button. Titrate with 0.5 mol / L alkaline standard solution (NaOH standard solution) to the endpoint. The fully automatic potentiometric titrator will automatically stop and record the titration volume V of alkaline standard solution (NaOH standard solution) consumed, and automatically calculate the ammonia content result. As shown in Table 1.

[0041] Table 1 shows the experimental data on the ammonia content in the ammonia raw materials provided by the supplier.

[0042] Example 2

[0043] This embodiment provides a method for determining the ammonia content in a solution; wherein the solution is sampled from the preparation area of ​​a manufacturing plant. 1) Set the "ammonia content test method" on the fully automatic potentiometric titrator in advance, and input the concentration value C of the alkaline standard solution. 碱 Formula for calculating ammonia content, and endpoint conditions.

[0044] 2) Blank test procedure: Add 50 mL of ultrapure water and 20 mL of 0.5 mol / L acid standard solution (1 / 2 H2SO4 standard solution) sequentially to 150 mL, and seal the container; prepare two blank samples simultaneously, and titrate the endpoint with 0.5 mol / L alkali standard solution (NaOH standard solution) using a fully automatic potentiometric titrator; perform this process twice, and take the average of the volumes of alkali standard solution (NaOH standard solution) consumed, which is recorded as V0.

[0045] 3) Sample testing procedure: Add 50 mL of ultrapure water and 20 mL of 0.5 mol / L acid standard solution (1 / 2 H₂SO₄ standard solution) sequentially to 150 mL of solution. After sealing, use a disposable syringe to draw up the sample, quickly insert the needle into the sealing film, inject the sample, seal, and shake well. Accurately weigh the added sample using the differential method and record it as m. Simultaneously, prepare 8 samples with the following masses: 10.0218 g, 10.5689 g, 9.8699 g, 9.8964 g, 10.1224 g, 9.9643 g, 11.2342 g, and 10.2097 g, obtaining 8 parallel test samples. Set the "Ammonia Content Test Method" on the fully automatic potentiometric titrator, enter the blank volume V0 and sample mass m, and click the "Start" button. Titrate with 0.5 mol / L alkaline standard solution (NaOH standard solution) to the endpoint. The fully automatic potentiometric titrator will automatically stop and record the titration volume V of alkaline standard solution (NaOH standard solution) consumed, and automatically calculate the ammonia content result. As shown in Table 2.

[0046] Table 2 shows the experimental data on ammonia content in the sample solutions from the preparation area.

[0047] Example 3

[0048] This embodiment provides a method for determining the ammonia content in a solution; wherein the solution is sampled from a recovery tower at a production plant: 1) Set the "ammonia content test method" on the fully automatic potentiometric titrator in advance, and input the concentration value C of the alkaline standard solution. 碱 Formula for calculating ammonia content, and endpoint conditions.

[0049] 2) Blank test procedure: Add 50 mL of ultrapure water and 20 mL of 0.05 mol / L acid standard solution (1 / 2 H2SO4 standard solution) sequentially to 150 mL, and seal the container; prepare two blank samples simultaneously, and titrate the endpoint with 0.1 mol / L alkali standard solution (NaOH standard solution) using a fully automatic potentiometric titrator; perform this process twice, and take the average of the volumes of alkali standard solution (NaOH standard solution) consumed, which is recorded as V0.

[0050] 3) Sample testing procedure: Add 50 mL of ultrapure water and 20 mL of 0.05 mol / L acid standard solution (1 / 2 H₂SO₄ standard solution) sequentially to 150 mL of solution. After sealing, use a disposable syringe to draw up the sample, quickly insert the needle into the sealing film, inject the sample, seal, and shake well. Accurately weigh the added sample using the differential method and record it as m. Simultaneously, prepare 8 samples with the following masses: 20.1562 g, 19.9568 g, 20.0023 g, 20.5686 g, 19.4325 g, 19.8569 g, 20.0018 g, and 21.0123 g, obtaining 8 parallel test samples. Set the "Ammonia Content Test Method" on the fully automatic potentiometric titrator, enter the blank volume V0 and sample mass m, and click the "Start" button. Titrate with 0.1 mol / L alkaline standard solution (NaOH standard solution) to the endpoint. The fully automatic potentiometric titrator will automatically stop and record the titration volume V of alkaline standard solution (NaOH standard solution) consumed, and automatically calculate the ammonia content result. As shown in Table 3.

[0051] Table 3 shows the experimental data on ammonia content in samples from the recovery tower at the production plant.

[0052] The above three embodiments are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way.

Claims

1. A method for accurately measuring the ammonia content in a solution, characterized in that, Includes the following steps: 1) Prepare a blank solution Prepare a blank solution by mixing a set volume of pure water and a set volume of acid standard solution; 2) Blank solution titration A blank solution is titrated with an alkaline standard solution to the endpoint, wherein the volume of the alkaline standard solution consumed is denoted as V0. 3) Prepare the test solution Mix a set volume of pure water and a set volume of acid standard solution thoroughly, then add a set mass of sample to prepare the test solution. 4) Titration of the test solution The solution to be tested is titrated with an alkaline standard solution to the endpoint, wherein the volume of the alkaline standard solution consumed is denoted as V; 5) Calculate the ammonia content in the sample.

2. The method for accurately measuring the ammonia content in a solution according to claim 1, characterized in that, The volume of pure water used in step 1) and step 3) is the same, set at 40~80mL; the concentration and volume of the acid standard solution used in step 1) and step 3) are the same, and the volume is set at 20mL.

3. The method for accurately measuring the ammonia content in a solution according to claim 1, characterized in that, If the sample is purchased ammonia water with a mass fraction of 25~28wt% or prepared ammonia water with a mass fraction of 0.15~3wt%, then the concentration of the acid standard solution is 1mol / L and the concentration of the alkali standard solution is 0.5mol / L; if the sample is an ammonia solution from the polymerization process with a mass fraction of 0~0.15wt%, then the concentration of the acid standard solution is 0.1mol / L and the concentration of the alkali standard solution is 0.1mol / L, or the acid standard solution is 1 / 2H2SO4 standard solution and the alkali standard solution is NaOH standard solution.

4. The method for accurately measuring the ammonia content in a solution according to claim 1, characterized in that, In step 3), the sample mass is set to be 0.5~25g in the step of preparing the test solution.

5. The method for accurately measuring the ammonia content in a solution according to claim 4, characterized in that, If the sample is purchased ammonia water with a mass fraction of 25~28wt%, the sample mass is set to 0.5~1.2g; if the sample is prepared ammonia water with a mass fraction of 0.15~3wt%, the sample mass is set to 8~12g; if the sample is an ammonia solution from the polymerization process with a mass fraction of 0~0.15wt%, the sample mass is set to 15~25g.

6. The method for accurately measuring the ammonia content in a solution according to claim 1, characterized in that, In step 3): the acid standard solution is added to a container containing pure water, the container is sealed, and the mixture is mixed evenly and then sealed again; the sample is quickly added to the solution and shaken to obtain the solution to be tested; the sealing is done with a sealing film; the container is a beaker; the sample is injected into the solution by first inserting the needle into the sealing film with a disposable syringe, and ensuring that the needle is below the liquid surface before injection.

7. The method for accurately measuring the ammonia content in a solution according to claim 1, characterized in that, In step 1), pure water and acid standard solution are added sequentially to a container; the container is a beaker.

8. The method for accurately measuring the ammonia content in a solution according to claim 1, characterized in that, In steps 2) and 4), the titration is performed using a fully automatic potentiometric titrator, specifically a Metrohm 916 Ti-Touch fully automatic potentiometric titrator.

9. The method for accurately measuring the ammonia content in a solution according to claim 8, characterized in that, Step 5) involves calculating the ammonia content in the sample, as detailed below: Input the concentration value C of the alkaline standard solution into the fully automatic potentiometric titrator. 碱 The formula for calculating ammonia content and the method for testing ammonia content are established; wherein, the formula for calculating ammonia content is: ， Wherein, ω represents the ammonia content in the sample, in percentage terms. m is the mass of the sample, in grams; C 碱 This represents the concentration of the alkaline standard solution, expressed in mol / L. V represents the volume of alkaline standard solution consumed in the titration of the solution to be tested, in mL; V0 is the volume of alkaline standard solution consumed in the titration of the blank solution, in mL; 17.03 is the mass number equivalent to one mole of ammonia, expressed in g / mol.

10. A method for accurately measuring the ammonia content in a solution according to claim 9, characterized in that, In step 4): Select the method for measuring ammonia content in the solution on the fully automatic potentiometric titrator and click start; titrate the solution to be tested with alkaline standard solution until the equivalence point appears; the fully automatic potentiometric titrator automatically records the volume V of alkaline standard solution consumed, and automatically calculates the ammonia content in the solution based on the input data and the automatically recorded data.

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