A method for detecting and analyzing complexing agents in complexed iron desulfurization solutions.

Abstract

The present invention discloses a detection and analysis method for complexing agents in a complex iron desulfurization solution. The complexing agents are ethylenediaminetetraacetic acid and nitrilotriacetic acid. The detection and analysis method includes: adding a reducing agent to a sample to be tested to reduce the Fe 3+ complex in the complex iron desulfurization solution into Fe 2+ complex, obtaining a sample solution to be tested; adding a nickel salt derivatization reagent and an ion pair reagent to the mobile phase of a high performance liquid chromatography, and adjusting the pH value of the mobile phase to 5.8 - 6.2; using the high performance liquid chromatography to detect and analyze the sample solution to be tested. The detection and analysis method of the present invention simplifies the pretreatment process, and the analysis result is accurate and reliable.

Description

Technical Field

[0001] This invention belongs to the field of gas purification and analysis technology, specifically relating to a method for detecting and analyzing complexing agents in a complexed iron desulfurization solution. Background Technology

[0002] The complexing iron method is mainly used for desulfurization of sulfur-containing gases with medium-scale potential flow rates. It is particularly advantageous when treating natural gas with potential flow rates between 0.1 and 5 t / d, or natural gas with high potential flow rates where sulfur recovery using a Claus unit is difficult. This process involves a binary complex system, primarily using ethylenediaminetetraacetic acid (EDTA) and aminotriacetic acid (ATA) as iron ion complexing agents. These agents prevent the hydrolysis of iron ions under alkaline process conditions, which would precipitate Fe(OH)3 and affect the effective iron content in the complexing iron solution and the quality of the purified gas. Therefore, detecting the content of EDA and ATA in the complexing iron desulfurization solution is crucial for guiding the timing of complexing agent addition during unit operation.

[0003] Currently, the analysis and detection of ethylenediaminetetraacetic acid (EDTA) and aminotriacetic acid (NTA) both domestically and internationally mainly target the food, pharmaceutical, water quality, and detergent industries. Commonly used methods include high-performance liquid chromatography (HPLC), complexometric titration analysis, and gas chromatography. However, gas chromatography requires derivatization of EDTA and NTA, making sample pretreatment steps cumbersome. Complexometric titration analysis primarily detects the overall complexing capacity of a solution but cannot distinguish the content and type of specific complexing agents. The national standard GB 5009.278—2016, "National Food Safety Standard - Determination of Ethylenediaminetetraacetic Acid in Food," discloses a method of directly adding iron ions to the test solution for derivatization, purification via a mixed-type anion exchange (PXA) solid-phase extraction column, and then detection using HPLC.

[0004] The composition of complexed iron desulfurization solutions is complex, mainly consisting of a Na₂CO₃-NaHCO₃ system with a pH of 8.0–8.5. The iron catalyst content is approximately 500–3000 mg / L, and the solution also contains high levels of thiosulfate, oxalate, and sulfate. The ratio of complexing agent to iron catalyst is greater than 1:1, indicating an excess of complexing agent. However, the experimental conditions given in existing method standards and technical literature are not suitable for this complex complexed iron desulfurization solution system. To adapt to this system, copper salts with higher complexing constants are typically used as complexing agents to compete with the already chelated iron ions and the excess free ethylenediaminetetraacetic acid (EDTA) disodium salt and aminotriacetic acid (ATA), converting them entirely into copper EDA and ATA complexes. The pH of the mobile phase generally needs to be controlled around 4.2, and usually less than 4.2. However, industrial complexed iron desulfurization solutions contain approximately 5–100 g / L of thiosulfate ions (S₂O₃). 2-It also reacts with copper salt reagents, and the reaction equation is Cu 2+ +2S2O3 2- =2Cu + +S4O6 2- Cu + +2S2O3 2- =[Cu(S2O3)2] 3- Furthermore, at pH 4.2 or less, the S2O3 coexisting in the complexed iron desulfurization solution... 2- Will with H + The process generates elemental sulfur powder precipitate, and the precipitate surface adsorbs some of the complexing agent in the solution, resulting in a lower measured value for the complexing agent and thus inaccurate results. Furthermore, the mobile phase's pH of approximately 4.2 is not well-suited to the Na₂CO₃-NaHCO₃ sample system with a pH of 8.0–8.5, further affecting the measurement.

[0005] Therefore, this patent application is filed. Summary of the Invention

[0006] This invention addresses the technical problems mentioned above, such as the formation of elemental sulfur powder precipitate during the conversion of copper salts as complexing agents into copper ethylenediaminetetraacetic acid complexes and copper ammonitrile triacetic acid complexes, and the incompatibility with the Na₂CO₃-NaHCO₃ sample system at pH 8.0–8.5, leading to inaccurate measurement results. The invention provides a method for detecting and analyzing the complexing agent in a complexed iron desulfurization solution, which involves detecting the Fe in the sample solution... 3+ The complex is reduced to Fe 2+ The complex was filtered and directly injected into the liquid chromatography system. Nickel nitrate derivatization reagent and ion-pairing reagent were added to the mobile phase of the liquid chromatography system, and the pH of the mobile phase was adjusted to ensure that the metal ions would not hydrolyze and that no elemental sulfur powder precipitate would be produced. The system was well compatible with the sample system to be tested, and the test results were accurate.

[0007] This invention is achieved through the following technical solution:

[0008] A method for detecting and analyzing complexing agents in a complexed iron desulfurization solution, wherein the complexing agents are ethylenediaminetetraacetic acid (EDTA) and aminotriacetic acid (ATA), and the detection and analysis method includes:

[0009] A reducing agent is added to the sample to be tested to remove Fe from the complexed iron desulfurization solution. 3+ The complex is reduced to Fe 2+ The complex was obtained to yield the sample solution to be tested;

[0010] Nickel salt derivatization reagent and ion-pairing reagent were added to the mobile phase of high performance liquid chromatography, and the pH of the mobile phase was adjusted to 5.8–6.2.

[0011] High performance liquid chromatography (HPLC) was used to detect and analyze the sample solution.

[0012] As described in the background section, current methods using copper salts as complexing agents to convert copper ethylenediaminetetraacetic acid (EDTA) and copper aminotriacetic acid (ATA) complexes result in the formation of elemental sulfur powder precipitates. Furthermore, the pH needs to be adjusted to 4.2 or less. This system is not well-compatible with the Na₂CO₃-NaHCO₃ sample system with a pH of 8.0–8.5, leading to inaccurate measurement results. If the pH is increased to address the formation of elemental sulfur powder precipitates and to ensure compatibility with the Na₂CO₃-NaHCO₃ sample system with a pH of 8.0–8.5, hydrolysis of copper ions occurs, making it difficult to balance the system's pH, the hydrolysis of copper ions, and the formation of sulfur powder precipitates.

[0013] In this invention, the nickel salt derivatization reagent is used in the mobile phase for detection and analysis. This eliminates the cumbersome pre-derivatization process and the complex and time-consuming pretreatment steps of purification using a mixed-type anion exchange (PXA) solid-phase extraction column. Instead, only a reducing agent needs to be added, diluted, and brought to volume before direct injection into high-performance liquid chromatography (HPLC). Furthermore, the addition of the nickel salt derivatization reagent and ion-pairing reagent to the mobile phase, and the adjustment of the pH to approximately 6.0, prevents the hydrolysis of metal ions, such as S2O3. 2- Will not with H + It produces elemental sulfur powder and is also highly compatible with the test sample system of Na2CO3-NaHCO3 with a pH of 8.0-8.5.

[0014] In an optional embodiment, the reducing agent is any one or a mixture of two or more of hydroxylamine hydrochloride, ascorbic acid, thiourea, formaldehyde, and hydrazine (NH2-NH2). Using the above reducing agents, Fe... 3+ The complex is reduced to Fe 2+ Complexes. These reducing agents are all commonly used, low-cost reagents that utilize redox reaction mechanisms to change the valence state of iron ions, Fe... 2+ The complex formed with EDTA and NTA is more Fe 3+ The complexes formed with EDTA and NTA are much less stable, creating favorable conditions for the formation of nickel complexes.

[0015] In an optional embodiment, the concentration of the reducing agent is 10 g / L to 100 g / L. This concentration depends on the concentration of the iron catalyst in different processes. When the iron ion content is 300–1500 mg / L, the minimum concentration of the reducing agent can be 10 g / L; when the iron ion content is 1500–5000 mg / L, the concentration of the reducing agent can be 100 g / L; the purpose is to reduce the Fe... 3+ All ions were converted to Fe. 2+ ion.

[0016] In an optional embodiment, the nickel salt is nickel nitrate or nickel sulfate. Nickel sulfate is more preferably used.

[0017] In an optional embodiment, the concentration of the nickel salt is 0.05–0.5 mol / L.

[0018] In an optional embodiment, the preparation process of the mobile phase is as follows:

[0019] After mixing glacial acetic acid and nickel salt solution, add the appropriate amount of ion-pairing reagent, adjust the pH of the solution to 5.8-6.2 with alkaline solution, add an appropriate amount of methanol, dilute to the mark with deionized water and shake well, finally filter with a water-based filter membrane, and degas by ultrasonication to obtain the mobile phase for liquid chromatography.

[0020] In an optional embodiment, the ion-pairing reagent is any one of dodecyltrimethylammonium chloride, tetradecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide, or tetrabutylammonium hydroxide, and the amount of the ion-pairing reagent added is 0.1% to 0.5%. In this invention, the nickel complex is an anionic complex; therefore, a positively charged ion-pairing reagent is selected. Sufficient ion-pairing reagent is added to the mobile phase, and the hydrophobic group (C...) in the ion-pairing reagent... 12 ~C 16 Or butyl substituents) are attracted to the stationary phase and completely cover the surface of the stationary phase. The positive charge of the ion pair reagent extends towards the mobile phase and interacts with the negative charge (CH3COO) in the mobile phase. - The interaction maintains equilibrium. Under these ion pair conditions, such a negatively charged sample ion (nickel complex) interacts with CH3COO on the stationary phase surface. - Ion-pair exchange allows sample ions to be retained through ion exchange. By changing the amount of ion-pair reagents adsorbed by the stationary phase, the retention process is continuously changed from reversed-phase chromatography to ion-pair exchange chromatography. This change is achieved by altering the concentration of ion-pair reagents in the mobile phase and the resulting charge. As the concentration of ion-pair reagents in the mobile phase increases, the column adsorption also increases; when the column reaches saturation for ion-pair reagent adsorption, the column adsorption stabilizes. The longer the hydrophobic carbon chain (C...), the more... 18 >C 16 >C 12 It is also relatively robust, and the column becomes saturated when the concentration of ion-pair reagents in the mobile phase is low.

[0021] In an optional embodiment, the alkaline solution is a sodium hydroxide solution or an ammonia solution with a mass percentage of 5% to 10%.

[0022] In an optional embodiment, the amount of methanol added is 30% to 50%.

[0023] In an optional embodiment, the analytical conditions for high-performance liquid chromatography are as follows: the chromatographic column is bonded silica gel C2000. 18 Non-polar column, detector is diode array detector;

[0024] The mobile phase flow rate is 1.0 mL / min to 2.0 mL / min, the column temperature is 30℃ to 50℃, the detection wavelength is 260 nm, and the injection volume is 20 μL to 40 μL.

[0025] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0026] 1. The detection and analysis method provided by this invention can effectively eliminate the phenomenon of thiosulfate reacting with acid radicals in the mobile phase to form a dense sulfur precipitate in the desulfurization solution of complexed iron. Furthermore, the nickel complex is more resistant to hydrolysis than the copper complex, and the mobile phase is more compatible with the sample. Moreover, the sample treated by this invention does not require pretreatment with an anion exchange solid-phase extraction column; it only needs the addition of a reducing agent, dilution to a fixed volume, and filtration through a syringe filter membrane before direct injection for analysis.

[0027] 2. The analytical method provided by this invention has simpler analytical steps, improves sample pretreatment efficiency by 10 times, and has a faster analysis speed, which better meets the analytical and identification requirements of complexing agents in industrial complexed iron desulfurization solutions. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be considered as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort. In the drawings:

[0029] Figure 1 Analytical liquid chromatograms of standard solutions of ethylenediaminetetraacetic acid and aminotriacetic acid.

[0030] Figure 2 The image shows a liquid chromatogram of the complexing agent in the industrial complexed iron desulfurization solution, as determined by the detection and analysis method described in Example 1. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the embodiments. The illustrative embodiments and descriptions of this invention are only used to explain this invention and are not intended to limit this invention.

[0032] This invention provides an analytical method for detecting complexing agents in a complexed iron desulfurization solution, comprising the following steps:

[0033] (1) Sample preparation: Take a certain volume of complexed iron desulfurization solution, add a reducing agent to remove Fe from the complexed iron desulfurization solution. 3+ The complex is reduced to Fe 2+ The complex is diluted to a fixed volume to obtain the sample to be tested. The purpose of adding the reducing agent is to lower the apparent formation constant of iron with the complexing agents EDTA and NTA, and to raise the pH at which iron ions begin to hydrolyze and form a precipitate.

[0034] (2) Preparation of standard solutions: Accurately weigh appropriate amounts of disodium ethylenediaminetetraacetate and trisodium aminotriacetate standards, and prepare a mixed standard stock solution with a molar concentration of 50 mmol / L after conversion to acid. Accurately transfer a certain volume of the mixed standard stock solution and dilute it to standard solutions with concentrations of 0.25, 0.50, 1.0, 2.0, 3.0 and 4.0 mmol / L to obtain standard solutions.

[0035] (3) Preparation of the mobile phase for liquid chromatography: Transfer an appropriate amount of glacial acetic acid and nickel salt solution to a 500 mL beaker containing 200 mL of deionized water, add the corresponding amount of ion-pairing reagent, adjust the pH of the solution to 6.0 with alkaline solution, transfer to a 500 mL volumetric flask, add an appropriate amount of methanol, dilute to the mark with deionized water, and shake well. After filtering the mobile phase through a water-based filter membrane and degassing by sonication, it becomes the mobile phase for liquid chromatography.

[0036] Qualitative and quantitative analysis of samples: After powering on the instrument and equilibrating the column with the mobile phase, inject the standard solution and the sample solution to be tested separately into the high-performance liquid chromatography (HPLC) system. Detect the samples under optimal chromatographic conditions and plot a standard curve. Use the retention time of the standard sample for qualitative analysis and the concentration of the standard sample as the x-axis and the corresponding peak area as the y-axis to plot the standard curve. Record the peak area measured in the sample solution. Determine the molar concentrations of ethylenediaminetetraacetic acid (EDTA) and aminotriacetic acid (ATA) in the sample solution based on the standard curve.

[0037] For more details, see Examples 1 and 2.

[0038] Example 1:

[0039] The method steps for detecting the complexing agents ethylenediaminetetraacetic acid and aminotriacetic acid in the complexed iron desulfurization solution in this embodiment are as follows:

[0040] (1) Preparation of the test sample: Take 1 mL of complexed iron desulfurization solution into a 100 mL volumetric flask, add 5 mL of 10 g / L hydroxylamine hydrochloride solution, dilute with ultrapure water to obtain the test sample.

[0041] (2) Preparation of standard solutions: Accurately weigh 1.6810 g of disodium ethylenediaminetetraacetate (EDTA) and 1.0757 g of trisodium aminotriacetate (ATTA) standards, respectively, dissolve them in water, and dilute to 100 mL in a brown volumetric flask to obtain mixed standard stock solutions with concentrations of 0.05 mol / L. Transfer this solution to a storage bottle and store at 4 °C. Accurately transfer 0 mL, 0.25 mL, 0.5 mL, 1.0 mL, 2.0 mL, 3.0 mL, and 4.0 mL of the mixed standard stock solution with a concentration of 0.05 mol / L into 50 mL volumetric flasks, and dilute to the mark with deionized water. Filter through a 0.45 μm filter membrane to obtain a series of mixed standard solutions with concentrations of 0 mmol / L, 0.25 mmol / L, 0.5 mmol / L, 1.0 mmol / L, 2.0 mmol / L, and 4.0 mmol / L.

[0042] (3) Preparation of the mobile phase for liquid chromatography: Transfer 10 mL of glacial acetic acid and 8 mL of 0.05 mol / L nickel nitrate solution to a 500 mL beaker containing 200 mL of deionized water. Add 1 g of dodecyltrimethylammonium chloride, which has been dissolved in a small amount of hot water beforehand. Adjust the pH of the solution to 6.0 with 10% NaOH solution. Transfer the solution to a 500 mL volumetric flask, add 175 mL of methanol, and dilute to the mark with deionized water. After filtering the mobile phase through a water-based filter membrane and degassing by sonication, the mobile phase for liquid chromatography is obtained.

[0043] (5) Qualitative and quantitative analysis of samples:

[0044] Inject and analyze the sample under the chromatographic conditions described below:

[0045] 1) Using a high-performance liquid chromatograph equipped with a DAD detector, bonded silica gel C 18 The chromatographic column and the mobile phase described above were used; the run time was 25 minutes.

[0046] 2) Mobile phase flow rate: 1.0 mL / min;

[0047] 3) Column temperature: 30℃;

[0048] 4) Detector wavelength: 260nm;

[0049] 5) Injection volume: 40 μL.

[0050] The peak areas of the nickel ethylenediaminetetraacetic acid (EDTA) and nickel aminotriacetic acid (CAT) complexes in the standard solution and the sample were recorded. The retention time of the EDTA complex was 16.0 min, and that of the CAT complex was 5.4 min. Retention time was used for qualitative analysis, and a standard curve was plotted with the peak area of ​​the standard solution on the x-axis and the concentration on the y-axis. The test results showed a good linear relationship between the concentration of each component and the chromatographic peak area. The regression equation for the quantitative calibration curve was y = ax + b. Table 1 lists the slope 'a' and intercept 'b' of the regression lines for these components. The correlation coefficients R are all close to 1, indicating that within the measured range, the concentration of each component has a good linear relationship with the peak area, and accurate quantification can be achieved using the external standard method.

[0051] The peak areas of the nickel ethylenediaminetetraacetic acid (EDTA) and nickel ethylenediaminetetraacetic acid (EDTA) complexes in the test solution at retention times of 5.4 min and 16.0 min, respectively, were recorded. The concentrations of EDTA and EDTA in the test solution were calculated based on the standard curve. For the same sample, five consecutive determinations were performed, with a relative standard deviation of less than 1%. The results are shown in Table 2. The spiked recovery results are shown in Table 3. The recoveries ranged from 98.4% to 102.2%, demonstrating the good accuracy of the analytical method.

[0052] Table 1. Constants of the regression linear equation for the quantitative correction of complexing agents.

[0053]

[0054] Table 2 Results of precision test of complexing agent in samples

[0055]

[0056] Table 3. Accuracy test of the detection and analysis method of this invention.

[0057]

[0058] The desulfurization solution in the LO-CAT unit is taken from an existing iron-based liquid-phase catalytic oxidation-reduction desulfurization unit.

[0059] Combination Figure 1 The analytical liquid chromatograms of ethylenediaminetetraacetic acid and aminotriacetic acid standard solutions in the sample, and Figure 2 As can be seen from the liquid chromatogram of the industrial complexed iron desulfurization solution determined by the method of Example 1, the detection and analysis method of the present invention can effectively detect EDTA nickel complex and NTA nickel complex in the industrial complexed iron desulfurization solution, and can achieve good separation and detection between the two.

[0060] Example 2:

[0061] The method steps for detecting the complexing agents ethylenediaminetetraacetic acid and aminotriacetic acid in the complexed iron desulfurization solution in this embodiment are as follows:

[0062] (1) Preparation of test sample: Take 1 mL of complexed iron desulfurization solution into a 100 mL volumetric flask, add 2.5 mL of 100 g / L ascorbic acid solution, dilute with ultrapure water to obtain the test sample.

[0063] (2) Preparation of standard solutions: Accurately weigh 1.6810 g of disodium ethylenediaminetetraacetate (EDTA) and 1.0757 g of trisodium aminotriacetate (ATTA) standards, respectively, dissolve them in water, and dilute to 100 mL in a brown volumetric flask to obtain mixed standard stock solutions with concentrations of 0.05 mol / L. Transfer this solution to a storage bottle and store at 4 °C. Accurately transfer 0 mL, 0.25 mL, 0.5 mL, 1.0 mL, 2.0 mL, 3.0 mL, and 4.0 mL of the mixed standard stock solution with a concentration of 0.05 mol / L into 50 mL volumetric flasks, and dilute to the mark with deionized water. Filter through a 0.45 μm filter membrane to obtain a series of mixed standard solutions with concentrations of 0 mmol / L, 0.25 mmol / L, 0.5 mmol / L, 1.0 mmol / L, 2.0 mmol / L, and 4.0 mmol / L.

[0064] (3) Preparation of the mobile phase for liquid chromatography: Transfer 5 mL of glacial acetic acid and 8 mL of 0.5 mol / L nickel nitrate solution to a 500 mL beaker containing 200 mL of deionized water. Add 5 g of hexadecyltrimethylammonium bromide dissolved in a small amount of hot water beforehand. Adjust the pH of the solution to 6.0 with 10% ammonia solution. Transfer the solution to a 500 mL volumetric flask, add 250 mL of methanol, and dilute to the mark with deionized water. After filtering the mobile phase through a water-based filter membrane and degassing by sonication, the mobile phase for liquid chromatography is obtained.

[0065] (4) Qualitative and quantitative analysis of samples:

[0066] Inject and analyze the sample under the chromatographic conditions described below:

[0067] Using a high-performance liquid chromatograph equipped with a DAD detector, bonded silica gel C 18 The chromatographic column and the mobile phase described above were used; the run time was 25 minutes.

[0068] Mobile phase flow rate: 1.5 mL / min;

[0069] Column temperature: 50℃;

[0070] Detector wavelength: 260nm;

[0071] Injection volume: 20 μL.

[0072] Record the peak areas of the nickel complexes of ethylenediaminetetraacetic acid and aminotriacetic acid in the standard solution and the sample. The retention time of the nickel complex of ethylenediaminetetraacetic acid is 13.4 min and the retention time of the nickel complex of aminotriacetic acid is 4.6 min. Use the retention time for qualitative analysis and plot the standard curve with the peak area of ​​the standard solution as the x-axis and the concentration as the y-axis.

[0073] The results showed that the concentration of each component had a good linear relationship with the chromatographic peak area, and the regression equation of the quantitative calibration curve was y = ax + b. Table 4 lists the slope 'a' and intercept 'b' of the regression lines for these components, and their correlation coefficients R are all close to 1, indicating that within the measurement range, the concentration of each component has a good linear relationship with the peak area, and the external standard method can be used for accurate quantification.

[0074] The peak areas of the nickel ethylenediaminetetraacetic acid (EDTA) and nickel ethylenediaminetetraacetic acid (EDTA) complexes in the test solution at retention times of 5.4 min and 16.0 min, respectively, were recorded. The concentrations of EDTA and EDTA in the test solution were calculated based on the standard curve. For the same sample, five consecutive determinations were performed, with a relative standard deviation of less than 1%. The results are shown in Table 5. The spiked recovery results are shown in Table 6. The recoveries ranged from 98.1% to 98.9%, demonstrating the good accuracy of the analytical method.

[0075] Table 4. Constants of the regression linear equation for quantitative correction of complexing agents.

[0076]

[0077] Table 5 Results of precision test of complexing agent in samples

[0078]

[0079] Table 6 Accuracy Test

[0080]

[0081] The present invention provides a method for analyzing and detecting the content of complexing agents ethylenediaminetetraacetic acid (EDTA) and aminotriacetic acid (ATA). In the pretreatment of industrial samples, only a reducing agent needs to be added to reduce all high-valence iron ions to divalent iron ions. A nickel salt derivatizing reagent is added to the mobile phase instead of a copper salt derivatizing reagent. The apparent formation constant of nickel and the complexing agent is close to that of the copper complex. At this point, the pH of the mobile phase can be controlled to around pH 6, ensuring compatibility between the mobile phase and the complexed iron solution. When these two meet, no dense red precipitate will form in the solution system. Then, high-performance liquid chromatography (HPLC) is used to qualitatively and quantitatively analyze the content of the complexing agent using the principle of ion-pair chromatography. The analytical method provided by this invention can simultaneously analyze and detect the complexing agents EDTA and ATA in the complex system of complexed iron desulfurization solution, significantly shortening the sample pretreatment time and providing accurate and reliable analytical results.

[0082] The above specific embodiments further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for detecting and analyzing complexing agents in a complexed iron desulfurization solution, characterized in that, The complexing agents are ethylenediaminetetraacetic acid and aminotriacetic acid, and the detection and analysis methods include: A reducing agent is added to the sample to be tested to remove Fe from the complexed iron desulfurization solution. 3+ The complex is reduced to Fe 2+ The complex was obtained to yield the sample solution to be tested; Nickel salt derivatization reagent and ion-pairing reagent were added to the mobile phase of high performance liquid chromatography, and the pH of the mobile phase was adjusted to 5.8–6.

2. High performance liquid chromatography (HPLC) was used to detect and analyze the sample solution.

2. The method for detecting and analyzing complexing agents in a complexed iron desulfurization solution according to claim 1, characterized in that, The reducing agent is any one or a mixture of two or more of the following: hydroxylamine hydrochloride, ascorbic acid, thiourea, formaldehyde, and hydrazine (NH2-NH2).

3. The method for detecting and analyzing complexing agents in a complexed iron desulfurization solution according to claim 1 or 2, characterized in that, The concentration of the reducing agent is 10 g / L to 100 g / L.

4. The method for detecting and analyzing complexing agents in a complexed iron desulfurization solution according to claim 1, characterized in that, The nickel salt is nickel nitrate or nickel sulfate.

5. The method for detecting and analyzing complexing agents in a complexed iron desulfurization solution according to claim 1 or 4, characterized in that, The concentration of the nickel salt is 0.05–0.5 mol / L.

6. The method for detecting and analyzing complexing agents in a complexed iron desulfurization solution according to claim 1 or 4, characterized in that, The preparation process of the mobile phase is as follows: After mixing glacial acetic acid and nickel salt solution, add the appropriate amount of ion-pairing reagent, adjust the pH of the solution to 5.8-6.2 with alkaline solution, add an appropriate amount of methanol, dilute to the mark with deionized water and shake well, finally filter with a water-based filter membrane, and degas by ultrasonication to obtain the mobile phase for liquid chromatography.

7. The method for detecting and analyzing complexing agents in a complexed iron desulfurization solution according to claim 6, characterized in that, The ion-pairing reagent is any one of dodecyltrimethylammonium chloride, tetradecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide, or tetrabutylammonium hydroxide, and the amount of the ion-pairing reagent added is 0.1% to 0.5%.

8. The method for detecting and analyzing complexing agents in a complexed iron desulfurization solution according to claim 6, characterized in that, The alkaline solution is a sodium hydroxide solution or an ammonia solution with a mass percentage of 5% to 10%.

9. The method for detecting and analyzing complexing agents in a complexed iron desulfurization solution according to claim 6, characterized in that, The amount of methanol added is 30% to 50%.

10. The method for detecting and analyzing complexing agents in a complexed iron desulfurization solution according to claim 1, characterized in that, The analytical conditions for high performance liquid chromatography (HPLC) are as follows: the chromatographic column is bonded silica gel C2000. 18 Non-polar column, detector is diode array detector; The mobile phase flow rate is 1.0 mL / min to 2.0 mL / min, the column temperature is 30℃ to 50℃, the detection wavelength is 260 nm, and the injection volume is 20 μL to 40 μL.

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