A method for detecting the content of gallic acid in food

Abstract

The application discloses a method for detecting the content of gallic acid in food, and relates to the technical field of electrochemical detection, and has the technical scheme as follows: Co(NO3)2.6H2O is dissolved in a mixture of methanol and ethanol; 2-methyl imidazole and phthalocyanine iron are added into the mixture of methanol and ethanol, and then subjected to magnetic stirring at room temperature, centrifugation, cleaning and vacuum drying; the dried material is slowly put into a high-temperature tube furnace, nitrogen is introduced, the temperature is programmed to 800 DEG C and maintained for 3h, the crucible is taken out after being cooled to room temperature, polished, ultrasonically cleaned in ethanol and ultrapure water, and naturally dried; the material obtained by pyrolysis is dissolved in ultrapure water and subjected to ultrasonic treatment to prepare a solution, which is dropped on a cleaned and dried glassy carbon electrode and dried. The detection method has the advantages of low cost, simple operation, high efficiency, high sensitivity, strong specificity and the like, and can realize rapid and sensitive detection of gallic acid in food.

Description

Technical Field

[0001] This invention relates to the field of electrochemical detection technology, and more specifically, to a method for detecting the gallic acid content in food. Background Technology

[0002] Gallic acid (GA, 3,4,5-trihydroxybenzoic acid) is a natural phenolic compound found in plants such as black tea, green tea, and grapes. Due to its high reducing properties, GA is widely used as an antioxidant in beverages, foods, health supplements, and pharmaceuticals. Furthermore, gallic acid equivalent (GAE) is often considered an indicator of the total antioxidant capacity of a sample. However, GA exhibits slight toxicity at low concentrations and is difficult to biodegrade; long-term accumulation in the body can be harmful. Therefore, the detection of gallic acid is crucial for human health and the quality control of pharmaceuticals and health supplements.

[0003] To date, various techniques for gallic acid detection have been developed, including chromatography, spectrophotometry, capillary electrophoresis, and oscillatory chemical reactions. However, these methods often have limitations in terms of sensitivity, stability, or the need for complex and expensive instruments. To address these shortcomings, we synthesized an iron-cobalt composite material using a simple method and applied it to a modified glassy carbon electrode. This led to the development of a low-cost, simple-to-operate, highly efficient, sensitive, and specific electrochemical detection method for the rapid and sensitive detection of gallic acid in food. Summary of the Invention

[0004] The purpose of this invention is to provide a method for detecting gallic acid content in food. This method is low in cost, simple to operate, highly efficient, highly sensitive, and highly specific, enabling rapid and sensitive detection of gallic acid in food.

[0005] The above-mentioned technical objective of the present invention is achieved through the following technical solution: a method for detecting gallic acid content in food, comprising three steps: synthesizing materials, preparing modified electrodes, and detecting gallic acid. The specific operation of synthesizing materials is as follows: 1.455g of Co(NO3)2·6H2O is dissolved in 80mL of a methanol and ethanol mixture with a volume ratio of 1:1; 1.642g of 2-methylimidazole and 0mg of ferric phthalocyanine are dissolved in 80mL of a methanol and ethanol mixture with a volume ratio of 1:1; the above solutions are mixed together, magnetically stirred at room temperature for 24h, centrifuged, washed three times with methanol, and vacuum dried at 60℃ to obtain material 1;

[0006] Following the same procedure described above, the amount of ferric phthalocyanate added was successively changed to 5 mg, 10 mg, and 15 mg to prepare materials 2, 3, and 4. The optimal amount of ferric phthalocyanate added was determined to be 5 mg using differential pulse voltammetry, meaning that material 2 was the optimal material.

[0007] Fill the crucible with sufficient material 2, cover it, and slowly place it into a high-temperature tube furnace. Pour nitrogen gas into the high-temperature tube furnace for 30 min, then raise the temperature at a rate of 5℃ / min to 700℃ and maintain it for 3 h. After the temperature naturally drops to room temperature, remove the crucible.

[0008] Following the same procedure described above, the material 2 was pyrolyzed at 800℃ and 900℃ respectively; the optimal pyrolysis temperature was determined to be 800℃ using differential pulse voltammetry; the material obtained after pyrolysis was collected, weighed, and recorded.

[0009] The invention is further configured as follows: the glassy carbon electrode is polished with 0.5 mm Al2O3, then ultrasonically cleaned in ethanol and ultrapure water for 5 minutes in sequence, and then naturally dried in air; 2 mg of the material obtained by pyrolysis of material 2 at 800℃ is dissolved in 1 mL of ultrapure water and ultrasonically treated for 0.5 h to prepare a 2 mg / mL solution, 6 μL of which is dropped onto the cleaned and dried glassy carbon electrode and dried under an infrared lamp.

[0010] The present invention is further configured such that the specific operating steps for detecting gallic acid are as follows:

[0011] Differential pulse voltammetry was used to detect gallic acid in food. The electrode was replaced with a modified electrode, and the content of gallic acid in the food was obtained through its corresponding current signal.

[0012] The present invention is further configured as follows: To obtain the optimal performance of the material for gallic acid detection, we investigated the detection effect of gallic acid under different pH conditions. As the PBS buffer solution changed from 1.5 to 4.5, the peak potential in cyclic voltammetry showed a negative shift, indicating that protons participated in the oxidation reaction of gallic acid, and proton transfer occurred during this process. As the PBS buffer solution changed from 1.5 to 3.0, the peak current of gallic acid oxidation showed an increasing trend, while the peak current of oxidation showed a decreasing trend as the PBS buffer solution changed from 3.0 to 4.5. Therefore, we used a buffer solution with pH=3.0 as the optimal pH for further in-depth investigation.

[0013] The present invention further includes the following: To improve the detection effect, the influence of enrichment potential and enrichment time on electrochemical detection was studied using DPV. We found that the optimal enrichment potential is 0.2V and the optimal enrichment time is 300 seconds.

[0014] In summary, the present invention has the following advantages: the detection method is low in cost, simple to operate, highly efficient, highly sensitive, and highly specific, and can achieve rapid and sensitive detection of gallic acid in food. Attached Figure Description

[0015] Figure 1This is a schematic diagram showing the current response of the present invention under different amounts of ferric phthalocyanate.

[0016] Figure 2 This is a schematic diagram of the current response of the present invention at different pH values;

[0017] Figure 3 This is a schematic diagram of the current response of the present invention under different enrichment potentials;

[0018] Figure 4 This is a schematic diagram of the current response of the present invention under different enrichment times;

[0019] Figure 5 This is the linear fitting curve of the present invention;

[0020] Figure 6 This is the linear detection range of gallic acid concentration in actual testing according to the present invention. Detailed Implementation

[0021] Example: A method for detecting gallic acid content in food includes three steps: synthesizing materials, preparing modified electrodes, and detecting gallic acid. The specific operation of synthesizing materials is as follows: 1.455g of Co(NO3)2·6H2O is dissolved in 80mL of a 1:1 mixture of methanol and ethanol; 1.642g of 2-methylimidazole and 0mg of ferric phthalocyanine are dissolved in 80mL of a 1:1 mixture of methanol and ethanol. The above solutions are mixed together, magnetically stirred at room temperature for 24h, centrifuged, washed three times with methanol, and vacuum dried at 60℃ to obtain material 1.

[0022] Following the same procedure described above, the amount of ferric phthalocyanate added was successively changed to 5 mg, 10 mg, and 15 mg to prepare materials 2, 3, and 4. The optimal amount of ferric phthalocyanate added was determined to be 5 mg using differential pulse voltammetry, meaning that material 2 was the optimal material.

[0023] Fill the crucible with sufficient material 2, cover it, and slowly place it into a high-temperature tube furnace. Pour nitrogen gas into the high-temperature tube furnace for 30 min, then raise the temperature at a rate of 5℃ / min to 700℃ and maintain it for 3 h. After the temperature naturally drops to room temperature, remove the crucible.

[0024] Following the same procedure described above, the material 2 was pyrolyzed at 800℃ and 900℃ respectively; the optimal pyrolysis temperature was determined to be 800℃ using differential pulse voltammetry; the material obtained after pyrolysis was collected, weighed, and recorded.

[0025] Response currents when different amounts of ferric phthalocyanine are added:

[0026]

[0027] Table 1

[0028] Response current at the optimal ferric phthalocyanate addition amount and different temperatures:

[0029]

[0030] Table 2

[0031] The specific operation for preparing the modified electrode is as follows: polish the glassy carbon electrode with 0.5 mm Al2O3, then ultrasonically clean it in ethanol and ultrapure water for 5 minutes in sequence, and let it air dry naturally; dissolve 2 mg of the material obtained by pyrolysis of material 2 at 800℃ in 1 mL of ultrapure water and ultrasonically treat it for 0.5 h to prepare a 2 mg / mL solution, take 6 μL and drop it onto the cleaned and dried glassy carbon electrode, and dry it under an infrared lamp.

[0032] The specific steps for detecting gallic acid are as follows:

[0033] Differential pulse voltammetry was used to detect gallic acid in food. The electrode was replaced with a modified electrode, and the content of gallic acid in the food was obtained through its corresponding current signal.

[0034] To obtain the optimal performance of the material for gallic acid detection, we investigated the detection effect of gallic acid under different pH conditions. As the PBS buffer solution changed from 1.5 to 4.5, the peak potential in cyclic voltammetry showed a negative shift, indicating that protons participated in the oxidation reaction of gallic acid, and proton transfer occurred during this process. As the PBS buffer solution changed from 1.5 to 3.0, the peak current of gallic acid oxidation showed an increasing trend, while the peak current of oxidation showed a decreasing trend as the PBS buffer solution changed from 3.0 to 4.5. Therefore, we used a buffer solution with pH=3.0 as the optimal pH for further investigation.

[0035] Response current at different pH values:

[0036]

[0037] Table 3

[0038] To improve detection efficiency, the effects of enrichment potential and enrichment time on electrochemical detection were investigated using DPV. We found that the optimal enrichment potential was 0.2 V and the optimal enrichment time was 300 seconds.

[0039] Response current at different enrichment potentials:

[0040]

[0041] Table 4

[0042] Response current at different enrichment times:

[0043]

[0044] Table 5

[0045] Linear range detection and recovery in actual samples:

[0046] (1) Linear range

[0047] The sensor was tested in a PBS buffer solution at pH = 3 to measure the GA concentration in the modified working electrode. The DPV response current signal increased with increasing Bn concentration and exhibited a strong linear relationship between 5 nM and 4500 nM, including two segments of linearity:

[0048] ipa = 0.0423C GA -0.3047 (5nM≤C GA ≤700 nM, R 2 = 0.9989)

[0049] ipa = 0.0134C GA +22.266 (700nM≤C GA ≤4500 nM, R 2 = 0.9922).

[0050] (2) Recovery of actual samples

[0051] Grapes, tomatoes, apples, and wine were purchased from a local supermarket. The solutions were refluxed in ethanol at 60°C for 1 hour, then diluted several times with 0.1M PBS (pH=3.0) solution. Electrochemical detection was performed on the diluted solutions. The oxidation current in the blank and spiked solutions was obtained using DPV, and the GA concentration was calculated based on the current, yielding satisfactory results.

[0052] Optimal detection of gallic acid in different samples:

[0053]

[0054] Table 6

[0055] This specific embodiment is merely an explanation of the present invention and is not intended to limit the invention. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they are within the scope of the claims of the present invention.

Claims

1. A method for detecting gallic acid content in food, characterized in that: The process includes three steps: synthesizing materials, preparing modified electrodes, and detecting gallic acid. The specific steps for synthesizing the materials are as follows: (1) Dissolve 1.455g Co(NO3)2·6H2O in 80mL of a 1:1 mixture of methanol and ethanol; dissolve 1.642g 2-methylimidazole and 5mg ferric phthalocyanine in 80mL of a 1:1 mixture of methanol and ethanol, mix the two solutions, stir magnetically at room temperature for 24h, centrifuge, wash three times with methanol, and dry under vacuum at 60℃ to obtain the optimal material; (2) Fill the crucible with sufficient amount of the optimal material, cover it, and slowly place it into a high-temperature tube furnace. Purge the high-temperature tube furnace with nitrogen for 30 min, and then raise the temperature at a rate of 5℃ / min to 800℃ and maintain it for 3 h. After the temperature naturally drops to room temperature, remove the crucible; collect, weigh and record the material obtained after pyrolysis. The specific steps for preparing the modified electrode are as follows: The glassy carbon electrode was polished with 0.5 mm Al2O3, then ultrasonically cleaned in ethanol and ultrapure water for 5 minutes in sequence, and air-dried naturally. 2 mg of the pyrolysis material was dissolved in 1 mL of ultrapure water and ultrasonically treated for 0.5 h to prepare a 2 mg / mL solution. 6 μL of the solution was dropped onto the cleaned and dried glassy carbon electrode and dried under an infrared lamp. The specific steps for detecting gallic acid are as follows: Gallic acid in food was detected using differential pulse voltammetry. The electrode was replaced with a modified electrode, and the content of gallic acid in the food was obtained from the corresponding current signal. The detection of gallic acid was performed at pH 3.0, enrichment potential of 0.2V, and enrichment time of 300s.

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