Analysis method for quantitatively measuring fumaric acid by adopting ultraviolet spectrophotometry based on copper sulfate

Abstract

The invention discloses an analysis method for quantitatively measuring fumaric acid by adopting an ultraviolet spectrophotometric method based on copper sulfate, and belongs to the technical field of test and analysis of physical and chemical properties of materials. The method comprises the following steps: 1, preparing a plurality of fumaric acid standard solutions with different concentrations, preparing a copper sulfate solution, mixing the fumaric acid standard solutions with the copper sulfate solution, and carrying out a complex reaction; 2, performing ultraviolet spectrophotometry after the reaction is completed, determining the maximum absorption wavelength of the complex, and drawing a standard curve; and 3, dissolving a to-be-detected sample in water to obtain a to-be-detected sample solution, adding a copper sulfate solution, mixing, carrying out a complex reaction, carrying out ultraviolet spectrophotometric determination after completion of the complex reaction to obtain absorbance at the wavelength of 804 nm, and substituting the absorbance into the equation of the standard curve to obtain the concentration of fumaric acid in the to-be-detected sample. The method has the advantages of simplicity and convenience in operation, low cost, high sensitivity and the like, and is widely applicable to quantitative analysis of fumaric acid in environmental samples, food samples, medicines and industrial products.

Description

Technical Field

[0001] The invention belongs to the technical field of testing and analyzing the physicochemical properties of materials, and specifically relates to an analytical method for quantitatively determining fumaric acid by ultraviolet spectrophotometry based on copper sulfate. The method can be widely used in the fields of environmental science, food chemistry, drug analysis, industrial process control, etc., and is of great significance for the quantitative analysis of fumaric acid. Background Art

[0002] Fumaric acid is an important organic compound, widely used in many fields such as food, medicine, and chemical industry. In the food industry, fumaric acid is often used as an acidulant and preservative to improve food flavor and extend shelf life; in the pharmaceutical field, fumaric acid has significant anti-inflammatory and immunomodulatory effects and is often used in the preparation of related drugs; in the chemical industry, fumaric acid is used as a raw material for synthetic resins and plastics and other products. Based on this, there is a wide demand for the quantitative analysis of fumaric acid in the fields of environmental science, food chemistry, drug analysis, and industrial process control.

[0003] The chemical name, molecular formula, structural formula and molecular weight of fumaric acid are as follows.

[0004]

Chemical name

[0005]

Molecular formula

[0006]

Structural formula

[0007]

Molecular weight

[0008] The methods for determining fumaric acid in the prior art mainly include the following: 1. Titration: Titration is a method for determining the content of fumaric acid by chemical reaction, usually using standard alkali solution for titration. Although this method is simple and easy to operate, it has low sensitivity and accuracy and is easily interfered by other coexisting substances. 2. High performance liquid chromatography: HPLC is a highly sensitive and highly selective analytical method that separates and detects fumaric acid by liquid chromatography. This method has high accuracy, but the operation is complicated and the equipment is expensive, and it is not suitable for high-throughput routine detection. 3. Gas chromatography: GC separates fumaric acid by gas chromatography and then detects it. This method is suitable for the analysis of volatile or volatile derivatives, but it also has problems such as complicated operation and long detection time. 4. Liquid chromatography-mass spectrometry technology: LC-MS quantitative fumaric acid has high sensitivity and high selectivity, and can accurately analyze low-concentration fumaric acid in complex matrices, but its high equipment and operating costs, complex operation, cumbersome sample pretreatment and potential matrix effect interference limit its wide application. These shortcomings limit its application in daily monitoring.

[0009] In contrast, ultraviolet spectrophotometry has become a widely used analytical method due to its advantages such as simple operation, high sensitivity, high accuracy and good repeatability. This method achieves quantitative analysis of the target substance by measuring the absorbance of the solution at a specific wavelength. However, fumaric acid itself does not have strong ultraviolet absorption, and it is necessary to select a suitable reagent to react with it to form a complex with characteristic absorption for detection.

[0010] Therefore, the present invention proposes a novel method for quantitative analysis of fumaric acid, which utilizes copper-fumaric acid complex reaction and ultraviolet spectrophotometry, has the characteristics of low cost, simple operation and high sensitivity, and is suitable for the quantitative analysis needs of fumaric acid in environmental monitoring, food safety testing, drug quality control and industrial production processes. Summary of the invention

[0011] In view of the problems existing in the above-mentioned prior art, the purpose of the present invention is to design and provide a method for quantitative analysis of fumaric acid based on copper-fumaric acid complex reaction combined with ultraviolet spectrophotometry. The present invention provides a simple, rapid and accurate method for determining the concentration of fumaric acid. The method utilizes the characteristic absorption wavelength of the complex generated by copper sulfate and fumaric acid, and uses an ultraviolet spectrophotometer to measure the absorbance at the maximum absorption wavelength of the mixed solution to achieve accurate quantification of the fumaric acid concentration. The method has the advantages of simple operation, low cost and high sensitivity, and is widely applicable to the quantitative analysis of fumaric acid in environmental samples, food samples, medicines and industrial products.

[0012] In order to achieve the above object, the present invention adopts the following technical solutions:

[0013] An analytical method for quantitatively determining fumaric acid based on copper sulfate and ultraviolet spectrophotometry comprises the following steps:

[0014] (1) preparing a plurality of fumaric acid standard solutions of different concentrations, preparing a copper sulfate solution, mixing the fumaric acid standard solution with the copper sulfate solution, and performing a complex reaction;

[0015] (2) After the complexation reaction is completed, ultraviolet spectrophotometry is performed to determine the maximum absorption wavelength of the complex and draw a standard curve;

[0016] (3) Take the sample to be tested, dissolve it in water to obtain a sample solution to be tested, add the copper sulfate solution, mix, and carry out complexation reaction. After the reaction is completed, perform ultraviolet spectrophotometry to obtain the absorbance at a wavelength of 802 to 806 nm, substitute it into the equation of the standard curve, and obtain the concentration of fumaric acid in the sample to be tested.

[0017] In the analytical method, the concentration of the fumaric acid standard solution in step (1) is 0.02-0.10M.

[0018] In the analysis method, the concentration of the copper sulfate solution in step (1) is 0.05-0.20M.

[0019] In the analytical method, the volume ratio of the fumaric acid standard solution to the copper sulfate solution in step (1) is 2:1 to 1:2;

[0020] In the analytical method, the conditions of the complexation reaction in step (1) are: time 10 to 50 minutes, and temperature is room temperature.

[0021] In the analysis method, the maximum absorption wavelength in step (2) is 802-806 nm; preferably, the maximum absorption wavelength is 804 nm.

[0022] In the analytical method, the equation of the standard curve in step (2) is y=0.0005x+0.6103, R 2 =0.9992, where y is the absorbance and x is the fumaric acid concentration in mM.

[0023] In the analytical method, the volume ratio of the sample solution to be tested and the copper sulfate solution in step (3) is 2:1 to 1:2, and the time of the complex reaction is 10 to 50 minutes.

[0024] In the analytical method, the sample to be tested in step (3) is one of environmental water, soil, food or medicine.

[0025] Application of any one of the analytical methods described in the quantitative determination of the content of fumaric acid in a sample or in the production process of the sample.

[0026] The principle of the reaction of copper sulfate and fumaric acid to form a copper-fumaric acid complex is shown as follows:

[0027] The carboxylic acid group (-COOH) in fumaric acid (C4H4O4) loses a proton to form a carboxylate radical (-COO - ):

[0028] C4H4O4→C4H2O4 2- +2H +

[0029] The formed carboxylate (-COO-) undergoes coordination reaction with copper ions (Cu2):

[0030] C4H2O4 2- +Cu2→[Cu(C4H2O4)] 2-

[0031] Fumaric acid is a bidentate ligand that can form a stable complex with metal ions (Cu2) through its two carboxylic acid groups (-COOH). The reaction equation is as follows:

[0032] C4H4O4+Cu2→[Cu(C4H2O4)] 2- .

[0033] Compared with the prior art, this application has the following beneficial effects:

[0034] 1. The present invention proposes a method for quantitatively determining the concentration of fumaric acid by reacting copper sulfate with fumaric acid to generate a copper-fumaric acid complex and measuring the absorbance of the solution to be tested by an ultraviolet spectrophotometer.

[0035] 2. The method of the present invention has simple operation steps, does not require complicated pre-treatment steps, is suitable for rapid analysis, can accurately determine fumaric acid in a short time, and is suitable for routine detection in laboratories and industries.

[0036] 3. The method of the present invention can significantly improve the efficiency and reliability of fumaric acid determination, and meet the needs of various industries for fumaric acid detection. It is suitable for fumaric acid determination within different concentration ranges, and is not interfered by other common coexisting substances. It has broad application prospects and covers multiple important fields. Specifically, in environmental science, the present invention can be used for monitoring and analysis of fumaric acid in water and soil samples, providing an effective tool for the detection and control of environmental pollutants. In food chemistry, the present invention can be used for quantitative analysis of fumaric acid and related organic acids in food samples, which is helpful for the detection and control of food quality and safety. In drug analysis, the present invention can be used for the accurate determination of fumaric acid content in drugs, providing a reliable method for drug quality control and research and development. In addition, in industrial process control, the present invention can be used for quantitative monitoring of fumaric acid in industrial production processes, helping process optimization and product quality control. These applications not only expand the practical use of fumaric acid analysis technology, but also provide scientific basis and technical support for solving related problems in various fields. The multifaceted application of this technology can not only improve the technical level in the field of analytical chemistry, but also provide effective solutions for environmental protection, food safety, drug research and development, and industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 Schematic diagram of the chemical reaction of fumaric acid and copper sulfate to form a copper-fumaric acid complex;

[0038] Figure 2 The spectral scanning result diagram of the absorbance of a blank sample made of 100 mM fumaric acid solution and an equal volume of deionized water versus wavelength;

[0039] Figure 3 The spectral scanning result diagram of the absorbance of a blank sample made of 100 mM copper sulfate solution and an equal volume of deionized water versus wavelength;

[0040] Figure 4 This is a spectrum scanning result diagram showing the absorbance variation of "standard sample 1" made of 100mM copper sulfate and an equal volume of 20mM fumaric acid as a function of wavelength;

[0041] Figure 5 This is a spectrum scanning result diagram showing the absorbance variation of "standard sample 2" made of 100mM copper sulfate and an equal volume of 40mM fumaric acid as a function of wavelength;

[0042] Figure 6 This is a spectrum scanning result diagram showing the absorbance variation with wavelength of "standard sample 3" made of 100mM copper sulfate and an equal volume of 60mM fumaric acid;

[0043] Figure 7 This is a spectrum scanning result diagram of the absorbance variation of "standard sample 4" made of 100mM copper sulfate and an equal volume of 80mM fumaric acid as a function of wavelength;

[0044] Figure 8 This is a spectrum scanning result diagram showing the absorbance variation of "standard sample 5" made of 100mM copper sulfate and an equal volume of 100mM fumaric acid as a function of wavelength;

[0045] Fig. 9 The standard curve is made with the concentration of the mixed standard solution of fumaric acid-copper sulfate as the x-axis and the corresponding absorbance as the y-axis. DETAILED DESCRIPTION

[0046] In order to make the above-mentioned purpose, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below in conjunction with specific examples. In the following specific embodiments, the part without specifying specific experimental steps or conditions can be operated with reference to the standard experimental steps or conditions described in the conventional literature in this area. The reagents used or the instruments without specifying the manufacturer are all commercially available conventional reagent products. Unless otherwise indicated, the percentages herein all refer to weight / weight percentages.

[0047] In the following examples of the present invention, the relevant information of the reagents and drugs used is as follows in Table 1:

[0048] Table 1 Reagent drug information

[0049]

[0050] In the following examples of the present invention, the relevant information of the instruments used is as shown in Table 2:

[0051] Table 2 Instrument information used

[0052]

[0053]

[0054] Embodiment 1:

[0055] 1. Prepare fumaric acid standard solution:

[0056] (1) Accurately weigh 1.1607 g of fumaric acid (C4H4O4, molecular weight 116.07 g / mol) and dissolve it in 50 mL of deionized water (the solubility of fumaric acid is not high, and increasing the solvent temperature appropriately can significantly increase the solubility of fumaric acid).

[0057] (2) Transfer the solution to a 100 mL volumetric flask and dilute to volume with deionized water to obtain a 0.1 M fumaric acid standard stock solution.

[0058] (3) Take 2.0 mL, 4.0 mL, 6.0 mL, 8.0 mL and 10.0 mL of the fumaric acid mother solution, transfer them to a 10 mL volumetric flask, and dilute to 10 mL with deionized water to obtain 0.02 M, 0.04 M, 0.06 M, 0.08 M and 0.10 M fumaric acid standard solutions, respectively.

[0059] 2. Prepare copper sulfate solution:

[0060] (1) Accurately weigh 2.4968 g of copper sulfate pentahydrate (CuSO4·5H2O, molecular weight 249.68 g / mol) and dissolve it in 50 mL of deionized water.

[0061] (2) Transfer the solution to a 100 mL volumetric flask and dilute to volume with deionized water to obtain a 0.1 M copper sulfate solution.

[0062] 3. Formation of copper-fumaric acid complex

[0063] (1) Take 5.0 mL of 0.02 M, 0.04 M, 0.06 M, 0.08 M and 0.10 M fumaric acid standard solutions respectively, and add 5.0 mL of 0.1 M copper sulfate solution to each sample.

[0064] (2) After fully mixing, let it stand for 30 minutes to ensure that the complexation reaction is complete. This step is carried out at room temperature (25°C). Figure 1 Schematic diagram of the chemical reaction of fumaric acid and copper sulfate to form a copper-fumaric acid complex.

[0065] 4. Perform UV spectrophotometry

[0066] (1) The solution after the above reaction was transferred to a quartz cuvette with a light path of 1 cm.

[0067] (2) Use an ultraviolet spectrophotometer to scan a blank sample made of a 100 mM fumaric acid solution and an equal volume of deionized water, a blank sample made of a 100 mM copper sulfate solution and an equal volume of deionized water, and standard samples 1-5 made of 0.02 M, 0.04 M, 0.06 M, 0.08 M and 0.10 M fumaric acid standard solutions and an equal volume of 100 mM copper sulfate in the wavelength range of 200 nm to 1000 nm. The scanning results are as follows: Figures 2 to 8 As shown, the maximum absorption wavelength (λmax=804nm) was determined.

[0068] (3) After determining λmax, measure the absorbance of each standard solution at this wavelength (804 nm). The absorbance of each standard solution is shown in Table 3 below.

[0069] Table 3 Absorbance of each standard solution

[0070]

[0071] 5. Draw the standard curve

[0072] (1) Plot the concentration (x-axis) of the standard solution of fumaric acid of different concentrations against its absorbance at 804 nm (y-axis), as shown in Fig. 9 shown.

[0073] (2) The standard curve equation was obtained using the linear regression analysis method: y = 0.0005x + 0.6103, R 2 =0.9992. Wherein, y is absorbance, x is fumaric acid concentration (mM), 0.0005 and 0.6103 are regression coefficients. It can be seen that the standard curve shows a good linear relationship between absorbance and fumaric acid concentration.

[0074] 6. Determine the concentration of fumaric acid in the sample to be tested

[0075] (1) Weigh 1.0 g of fumaric acid, dissolve it in deionized water, transfer it to a 100 mL volumetric flask, and dilute to the mark to prepare a fumaric acid sample.

[0076] (2) Take 5.0 mL of the sample solution and mix it with 5.0 mL of the 0.1 M copper sulfate solution prepared above. After the reaction, let it stand for 30 minutes to ensure that the complexation reaction is complete.

[0077] (3) The sample solution after the reaction was transferred to a quartz cuvette with a pathlength of 1 cm, and its absorbance was measured at 804 nm using a UV spectrophotometer. The results are shown in Table 4 below. The average absorbance was 0.652.

[0078] Table 4 Absorbance of fumaric acid samples

[0079]

[0080] (4) According to the standard curve equation y = 0.0005x + 0.6103, R 2 =0.9992, calculate the concentration of fumaric acid in the sample. The calculation result shows that the concentration of fumaric acid in the sample is 0.086M.

[0081] 7. Experimental precautions

[0082] (1) Ensure the reaction is complete: Ensure that the reaction time is long enough to ensure that the complexation reaction is complete.

[0083] (2) Accurate measurement: Ensure that the volume and mass of all solutions are measured accurately to reduce errors.

[0084] Embodiment 2:

[0085] (1) Accurately prepare a 0.005 M fumaric acid sample to be tested: weigh 0.058 g of fumaric acid, dissolve it in deionized water, transfer it to a 100 mL volumetric flask, and dilute to the mark to prepare the fumaric acid sample to be tested.

[0086] (2) 5.0 mL of the sample solution was mixed with 5.0 mL of the 0.1 M copper sulfate solution prepared in Example 1. After the reaction, the mixture was allowed to stand for 30 minutes to ensure that the complexation reaction was completely carried out.

[0087] (3) The sample solution after the reaction was transferred to a quartz cuvette with a pathlength of 1 cm, and its absorbance was measured at 804 nm using a UV spectrophotometer. The results are shown in Table 5 below. The average absorbance was 0.6127.

[0088] Table 5 Absorbance of 0.005M Fumaric Acid Sample

[0089]

[0090] (4) According to the standard curve equation y = 0.0005x + 0.6103, R 2 =0.9992, the concentration of fumaric acid in the sample is calculated to be 0.0048 M. The experimental results show that the concentration of fumaric acid in the sample is 0.0048 M, and the error with the standard value of 0.005 M is less than 5%, indicating that the sensitivity of this method is reliable.

[0091] Embodiment 3:

[0092] In order to verify the quantitative ability of this method for fumaric acid in complex samples, a sample containing fumaric acid, dimethyl fumarate and monomethyl fumarate was prepared. The specific operation is as follows: accurately weigh fumaric acid, dimethyl fumarate and monomethyl fumarate in a mass ratio of 1:1:1. Mix the components and dissolve them in anhydrous ethanol to prepare a uniform solution so that the content of fumaric acid in the sample can be clearly known. This sample contains fumaric acid and its esterified derivatives, which can simulate a complex matrix environment and is used to verify the accuracy and reliability of the analytical method in such complex samples.

[0093] (1) Weigh 1.0 g of fumaric acid, 1.0 g of dimethyl fumarate, and 1.0 g of monomethyl fumarate, dissolve them in anhydrous ethanol, transfer them to a 100 mL volumetric flask, and dilute to the mark with anhydrous ethanol to prepare a sample solution to be tested.

[0094] (2) 5.0 mL of the sample solution to be tested was mixed thoroughly with 5.0 mL of the 0.1 M copper sulfate solution prepared in Example 1 above, and allowed to stand for 50 minutes after the reaction to ensure that the complexation reaction was completely carried out.

[0095] (3) The sample solution after the reaction was transferred to a quartz cuvette with a pathlength of 1 cm, and its absorbance was measured at 804 nm using a UV spectrophotometer. The results are shown in Table 6 below. The average absorbance was 0.652.

[0096] Table 6 Absorbance of samples

[0097]

[0098] (4) According to the standard curve equation y = 0.0005x + 0.6103, R 2 =0.9992, the concentration of fumaric acid in the sample is calculated to be 0.084 M. The experimental results show that the concentration of fumaric acid in the sample is 0.084 M, and the error with the theoretical value of 0.0862 M is less than 5%, indicating that the accuracy of this method is reliable. The error range is within the allowable range of the measurement results, which is known and understood by those skilled in the art.

[0099] It should be noted that the above contents are only preferred embodiments of the present invention, which are intended to explain the principles of the present invention, rather than to limit the present invention. Although the present invention has been described in detail through the above embodiments, those skilled in the art can still modify these technical solutions or perform equivalent substitutions on some of the technical features. Any modification, equivalent substitution or improvement made within the spirit and principle of the present invention shall be deemed to be included in the protection scope of the present invention.

Claims

1. An analytical method for quantitatively determining fumaric acid based on copper sulfate and ultraviolet spectrophotometry, characterized in that: The following steps are involved: (1) preparing a plurality of fumaric acid standard solutions of different concentrations, preparing a copper sulfate solution, mixing the fumaric acid standard solution with the copper sulfate solution, and performing a complex reaction; (2) After the complexation reaction is completed, ultraviolet spectrophotometry is performed to determine the maximum absorption wavelength of the complex and draw a standard curve; (3) Take the sample to be tested, dissolve it in water to obtain a sample solution to be tested, add the copper sulfate solution, mix, and perform a complex reaction. After the reaction is completed, perform ultraviolet spectrophotometry to obtain the absorbance at a wavelength of 804 nm, substitute it into the equation of the standard curve, and obtain the concentration of fumaric acid in the sample to be tested.

2. The analysis method according to claim 1, characterized in that The concentration of the fumaric acid standard solution in step (1) is 0.02-0.10M.

3. The analysis method according to claim 1, characterized in that The concentration of the copper sulfate solution in step (1) is 0.05-0.20M.

4. The analysis method according to claim 1, characterized in that The volume ratio of the fumaric acid standard solution to the copper sulfate solution in step (1) is 2:1 to 1:

2.

5. The analysis method according to claim 1, characterized in that The conditions of the complexation reaction in step (1) are: time 10 to 50 minutes, temperature is room temperature.

6. The analysis method according to claim 1, characterized in that The maximum absorption wavelength in step (2) is 802-806 nm; Preferably, the maximum absorption wavelength is 804 nm.

7. The analysis method according to claim 1, characterized in that The equation of the standard curve in step (2) is y=0.0005x+0.6103, R 2 =0.9992, where y is the absorbance and x is the fumaric acid concentration in mM.

8. The analysis method according to claim 1, characterized in that In step (3), the volume ratio of the sample solution to be tested to the copper sulfate solution is 2:1 to 1:2, and the time of the complex reaction is 10 to 50 minutes.

9. The analysis method according to claim 1, characterized in that The sample to be tested in step (3) is one of environmental water, soil, food or medicine.

10. Use of the analytical method according to any one of claims 1 to 9 in the quantitative determination of the content of fumaric acid in a sample or in the production process of a sample.

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