A portable electrochemical sensor for chlorogenic acid and its preparation method

Abstract

This invention belongs to the field of chlorogenic acid electrochemical sensor technology, and discloses a portable chlorogenic acid electrochemical sensor and its preparation method. The method includes the following steps: S1, preparing a light yellow powder solid Pd-ZIF-8; S2, weighing the product from step S1 to prepare TA@Pd-ZIF-8; S3, weighing the product from step S2 to prepare a PdZn / NP@C dispersion; S4, dropping the dispersion onto the surface of a screen-printed working electrode to prepare a chlorogenic acid electrochemical sensor. This invention utilizes PdZn / NP@C / SPE to modify the working electrode and uses a portable workstation for testing, solving the problems of poor portability, high minimum detection limit, and narrow detection linear range of existing detection methods.

Description

Technical Field

[0001] This invention relates to the field of chlorogenic acid electrochemical sensor technology, specifically to a portable chlorogenic acid electrochemical sensor and its preparation method. Background Technology

[0002] Chlorogenic acid (CGA) is a phenolic acid compound naturally found in many plants. It possesses various biological activities and health benefits, such as strong antioxidant, anti-inflammatory, and hypoglycemic effects, and is widely used in food, pharmaceuticals, and cosmetics. Therefore, to ensure that the chlorogenic acid content in food or pharmaceuticals is within a safe range, to avoid potential adverse effects from excessive intake, and to ensure the quality and efficacy of pharmaceuticals, it is necessary to test the chlorogenic acid content.

[0003] The commonly used method for detecting chlorogenic acid is to use a benchtop electrochemical workstation. This method is not portable, has a high limit of detection (LOD), and a narrow linear range, making it inconvenient for practical applications. Summary of the Invention

[0004] The present invention aims to provide a portable chlorogenic acid electrochemical sensor and its preparation method. The working electrode is modified with PdZn / NP@C / SPE and the test is performed using a portable workstation, which solves the problems of poor portability, high minimum detection limit and narrow detection linear range of existing detection methods.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A method for preparing a portable chlorogenic acid electrochemical sensor includes the following steps:

[0007] S1. Preparation of pale yellow powder solid Pd-ZIF-8

[0008] Zn(NO3)2·6H2O was dissolved in the first part of methanol, and Pd(NO3)2 solution was added dropwise to obtain solution A; 2-methylimidazole was dissolved in the second part of methanol to obtain solution B; solutions A and B were mixed evenly and heated to react. After the reaction was cooled, the mixture was washed and dried under vacuum to obtain a pale yellow powder solid Pd-ZIF-8.

[0009] S2. Preparation of yellow powder solid TA@Pd-ZIF-8

[0010] Weigh the Pd-ZIF-8 obtained in step S1 and add it to the tannic acid solution. Stir the reaction and perform hollow etching on Pd-ZIF-8. Wash and vacuum dry to obtain yellow powder solid TA@Pd-ZIF-8.

[0011] S3. Preparation of PdZn / NP@C dispersion

[0012] Weigh NaH2PO2·H2O and TA@Pd-ZIF-8 obtained in step S2, mix and grind them, then anneal at high temperature to obtain a black solid, soak it in HCl, then wash and vacuum dry it to obtain a black solid PdZn / NP@C, and disperse it in deionized water to obtain a PdZn / NP@C dispersion.

[0013] S4. Preparation of chlorogenic acid electrochemical sensor

[0014] The dispersion obtained in step S3 was measured and added to the surface of the screen-printed working electrode of the portable workstation, and then dried to obtain the chlorogenic acid electrochemical sensor.

[0015] Furthermore, in S1, the volume fraction of Pd(NO3)2 solution is 2v%, the volume ratio of the first part of methanol to the second part of methanol is 1:1, and the molar ratio of Zn(NO3)2·6H2O to 2-methylimidazole is 1:4.

[0016] Furthermore, in S1, the heating reaction temperature is 120°C, the heating reaction time is 4 hours, and the vacuum drying temperature is 60°C.

[0017] Furthermore, in S2, the concentration of the tannic acid solution is 7 mg / mL.

[0018] Furthermore, in S3, the mass ratio of TA@Pd-ZIF-8 to NaH2PO2·H2O is 1:1, and the concentration of HCl is 0.1M.

[0019] Furthermore, in S3, the high-temperature annealing includes two stages: the first stage annealing temperature is 300℃ and the time is 2h, and the second stage annealing temperature is 800℃ and the time is 2h, with a heating rate of 5℃ / min for both stages.

[0020] Furthermore, in S4, the concentration of the PdZn / NP@C dispersion is 2 mg / mL.

[0021] A chlorogenic acid electrochemical sensor was prepared according to the above-described method for preparing a portable chlorogenic acid electrochemical sensor.

[0022] The beneficial effects of the technical solution are:

[0023] 1. The raw materials used in this invention are abundant, inexpensive, and environmentally friendly. The preparation method is simple. Furthermore, by modifying the screen-printed working electrode of the portable workstation, testing can be performed using a portable workstation, increasing the portability of the test.

[0024] 2. The electrochemical sensor of this invention first etches Pd-ZIF-8 to form a hollow structure, and then performs phosphating treatment during annealing to form N, P element dual-doped PdZn / NP@C with a hollow nanocage morphology. Due to its unique three-dimensional structure, the hollow nanocage has a larger effective surface area compared to solid nanoparticles or thin film materials, allowing more active sites to contact the target analyte, improving the electrode's adsorption capacity for chlorogenic acid molecules, thereby enhancing the signal response. Furthermore, the hollow cavity structure inside the hollow nanocage helps reduce the electron transfer path length, accelerating the transfer of electrons from the electrode to the target molecule or vice versa, which helps improve detection speed and sensitivity. Compared to solid nanomaterials, the hollow nanocage has lower density and higher structural stability, which can, to some extent, prevent the aggregation between nanoparticles, maintain the long-term activity of the electrode surface, and extend the sensor's lifespan. It can also effectively promote the oxidation reaction of chlorogenic acid, improving detection efficiency. Therefore, the hollow nanocage morphology of PdZn / NP@C increases the sensor's sensitivity and lifespan.

[0025] 3. The electrochemical sensor of the present invention has a wide detection linear range, which is 5nM-1000nM and 1000nM-7000nM, and a low detection limit, which is 1.19nM. The electrochemical sensor of the present invention can perform trace portable detection of chlorogenic acid.

[0026] 4. The electrochemical sensor of this invention, after testing, exhibits a relative standard deviation (RSD) of 1.2% for the peak current, demonstrating good repeatability and reproducibility. Common ions (MgCl2, NaSO4, Fe(NO3)3) and functional group analogs, including caffeic acid (CFA), myricetin (Myr), ascorbic acid (AA), citric acid (CTA), salicylic acid (SA), ursolic acid (URA), glucose (Glu), and fructose (Fru), have almost no effect on the CGA electrical signal. In particular, after the addition of Myr, the electrochemical window shows the peak signal of Myr, but the peak current of CGA remains unaffected. Therefore, PdZn / NP@C / SPE has good anti-interference ability. Furthermore, after cyclic voltammetry (CV) and differential pulse voltammetry (DPV) tests, the RSD of its peak current is still less than 10% after 100 cycles. The refrigerator stability test data on day 1 and day 38 shows an RSD of 5.5% for the peak current. Therefore, the CGA sensing platform of this invention has good stability. Attached Figure Description

[0027] Figure 1 This is a scanning electron microscope (SEM) image of PdZn / NP@C in step S3 of Embodiment 1 of the present invention;

[0028] Figure 2 This is a transmission electron microscope (TEM) image of PdZn / NP@C in step S3 of Embodiment 1 of the present invention;

[0029] Figure 3 In Example 1 of this invention, the sensor was used to detect the concentration of chlorogenic acid originally present in samples of Eucommia ulmoides leaves, honeysuckle, apples and pears, and the detection result curves after adding different concentrations of chlorogenic acid.

[0030] In the figure, A is the current-voltage curve of Eucommia ulmoides leaf and the addition of 50 nM, 150 nM, and 250 nM chlorogenic acid, respectively; B is the curve of the relationship between the concentration of chlorogenic acid added to Eucommia ulmoides leaf and the current; C is the curve of honeysuckle and the addition of 50 nM, 150 nM, and 250 nM chlorogenic acid, respectively; D is the curve of the relationship between the concentration of chlorogenic acid added to honeysuckle and the current; E is the curve of apple and the addition of 100 nM and 200 nM chlorogenic acid, respectively; F is the curve of the relationship between the concentration of chlorogenic acid added to apple and the current; G is the curve of pear and the addition of 50 nM and 100 nM chlorogenic acid, respectively; H is the curve of the relationship between the concentration of chlorogenic acid added to pear and the current; and I is a bar chart of the concentration of Eucommia ulmoides leaf, honeysuckle, apple, and pear.

[0031] Figure 4 This is a DPV overlay image of different CGA concentrations (0.005-7 μM) in Example 1 of the present invention;

[0032] Figure 5 This is a graph showing the relationship between the current and chlorogenic acid concentration in the quantitative analysis of CGA in Example 1 of the present invention.

[0033] Figure 6 This is a current and voltage curve obtained from seven parallel measurements performed using DVP in Embodiment 1 of the present invention.

[0034] Figure 7 This is a bar chart of electrochemical signals measured using six different chlorogenic acid sensors in Example 1 of the present invention;

[0035] Figure 8 This is a current-voltage curve diagram of Example 1 of the present invention after adding MgCl2, NaSO4, Fe(NO3)3, CFA and Myr to a CGA electrolyte solution, respectively.

[0036] Figure 9 This is a current-voltage curve diagram of Example 1 of the present invention after adding AA, CTA, SA, URA, Glu, and Fru to a CGA electrolyte solution, respectively.

[0037] Figure 10This is a CV overlay image obtained after 100 cycles (data is taken once every 10 cycles) in Embodiment 1 of the present invention;

[0038] Figure 11 This is a current-voltage curve of the refrigerator stability test on day 1 and day 38 in Embodiment 1 of the present invention;

[0039] Figure 12 This is a schematic diagram of the portable chlorogenic acid sensor in Embodiment 2 of the present invention;

[0040] The names of the corresponding labels in the attached diagram are:

[0041] Processor 1, Working electrode 21, Reference electrode 22, Auxiliary electrode 23, Electrochemical cell 3, User interface 4, Power supply 5. Detailed Implementation

[0042] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments:

[0043] Example 1

[0044] A method for preparing a portable chlorogenic acid electrochemical sensor includes the following steps:

[0045] S1. Preparation of pale yellow powder solid Pd-ZIF-8

[0046] First, a 2v% Pd(NO3)2 solution was prepared using deionized water. Zn(NO3)2·6H2O (1.069 g, 3.6 mmol) was dissolved in a 20 mL volume of methanol, and then 667 μL of Pd(NO3)2 was added dropwise to obtain solution A. Next, 2-methylimidazole (1.161 g, 14.2 mmol) was dissolved in a second 20 mL volume of methanol to obtain solution B. Solutions A and B were mixed and vigorously stirred until homogeneous. The mixture was then transferred to a 100 mL Teflon-lined stainless steel autoclave and reacted at 120 °C for 4 hours. After cooling, the product was collected by centrifugation with methanol and then vacuum-dried overnight at 60 °C to obtain a pale yellow powder solid, Pd-ZIF-8.

[0047] S2. Preparation of yellow powder solid TA@Pd-ZIF-8

[0048] Weigh 200 mg of the pale yellow powder solid Pd-ZIF-8 obtained in step S1 and add it to 200 mL of tannic acid solution with a concentration of 7 mg / mL. Stir for 30 minutes to perform hollow etching on Pd-ZIF-8. Then wash with methanol to collect the product and dry the product under vacuum at 60 °C overnight to obtain yellow powder solid TA@Pd-ZIF-8.

[0049] S3. Preparation of PdZn / NP@C dispersion

[0050] 200 mg of TA@Pd-ZIF-8 solid and 200 mg of NaH2PO2·H2O were weighed and ground together in a mortar. The mixture was then placed in a muffle furnace for high-temperature annealing under a N2 atmosphere. The high-temperature annealing consisted of two stages: the first stage was annealed at 300℃ for 2 hours, and the second stage was annealed at 800℃ for 2 hours, with a heating rate of 5℃ / min for both stages. After annealing, the resulting black solid was soaked in 0.1 M HCl overnight, followed by washing with water by centrifugation. The product was then vacuum-dried overnight at 60℃ to obtain black solid PdZn / NP@C. 2 mg of PdZn / NP@C was dispersed in 1 mL of deionized water and sonicated to obtain a 2 mg / mL PdZn / NP@C dispersion. The SEM image of PdZn / NP@C is shown below. Figure 1 The TEM image of PdZn / NP@C is as follows: Figure 2 As shown;

[0051] S4. Preparation of chlorogenic acid electrochemical sensor

[0052] 12 μL of the dispersion obtained in step S3 was measured and added to the surface of the screen-printed working electrode 21 of the portable workstation. After drying, the chlorogenic acid electrochemical sensor was obtained.

[0053] The sensor prepared using the above method was used to detect the original chlorogenic acid concentration, the chlorogenic acid concentration after adding different concentrations of chlorogenic acid, the recovery rate, the standard deviation, and the original chlorogenic acid concentration measured using a benchtop workbench in samples of Eucommia ulmoides leaves, honeysuckle, apples, and pears. The detection results are shown in Table 1; the test result curves are shown in... Figure 3 As shown;

[0054] Table 1. Detection results of Eucommia ulmoides leaves, honeysuckle, apples, and pears.

[0055]

[0056]

[0057] Under the above optimal experimental conditions, the electrochemical performance of the chlorogenic acid sensor of the present invention was analyzed using differential pulse voltammetry (DPV). Figure 4 The DPV overlay plots for different CGA concentrations (0.005-7 μM) are shown. As the CGA concentration increases, the oxidation peak current also increases. When the CGA concentration exceeds 1 μM, the current increase is relatively slow. Therefore, the quantitative analysis of CGA by this sensor can be divided into two linear relationships, as shown in the concentration-current curve. Figure 5 As shown, the linear relationship is as follows:

[0058] i pa (μA)=40.571C CGA (μM)+0.7779(0.005-1μM,R 2 =0.9902)

[0059] i pa (μA)=8.0591C CGA (μM)+33.873(1-7μM, R) 2 =0.9983)

[0060] i pa For current, C CGA R represents the concentration of chlorogenic acid. 2 is the coefficient of determination of the relation.

[0061] The results show that the chlorogenic acid sensor prepared by the method of this invention has good CGA electrocatalytic performance, a wide detection linear range (5 nM-1000 nM and 1000 nM-7000 nM), and a low limit of detection (LOD), which can be obtained by the formula LOD = 3S. a With / b set at 1.19 nM, the electrochemical sensor of this invention enables portable trace detection of chlorogenic acid.

[0062] Furthermore, the repeatability, reproducibility, selectivity, and stability of the chlorogenic acid sensor prepared in this invention were investigated using DPV. The test results are as follows: Figures 6 to 11 As shown. Figure 6 The results showed that after seven parallel measurements, the relative standard deviation (RSD) of the peak current was 1.2%. Figure 7 The bar chart shows the electrochemical signal measured using six different chlorogenic acid sensors, with an RSD of 3.2%, indicating that the chlorogenic acid sensor prepared in this invention has good repeatability and reproducibility. In practical applications, the electrolyte solution often contains substances that may interfere with the electrical signal; therefore, it is necessary to study the selectivity of the sensor. Common ions (MgCl2, NaSO4, Fe(NO3)3) and functional group analogs (CFA, Myr, AA, CTA, SA, URA, Glu, Fru) were selected as anti-interference experimental targets. The amount of CFA and Myr added was twice that of CGA, and the amount of other substances added was 10 times that of CGA. Figure 8-9 As can be seen, these substances have almost no effect on the CGA electrical signal, especially after the addition of Myr. The electrochemical window shows the peak signal of Myr, but the peak current of CGA remains unaffected, indicating that the chlorogenic acid sensor prepared in this invention has good anti-interference ability. In addition, the cycling stability and long-term stability of the chlorogenic acid sensor prepared in this invention were investigated using CV and DPV, respectively. Figure 10This is a CV overlay plot after 100 cycles (data is taken every 10 cycles). After 100 cycles, its RSD value is still less than 10%. Figure 11 The data are the refrigerator stability test data for day 1 and day 38, with an RSD of 5.5%, indicating that the CGA sensing platform proposed in this study has good stability.

[0063] Example 2

[0064] A chlorogenic acid electrochemical sensor was prepared according to the preparation method of a portable chlorogenic acid electrochemical sensor in Example 1;

[0065] like Figure 12 As shown, specifically, the chlorogenic acid electrochemical sensor includes a portable workstation, which includes a power supply 5, a processor 1, and an electrochemical cell 3. The power supply 5 can be a portable power source to provide a stable power supply for the entire portable workstation, and the electrochemical cell 3 is used to contain the electrolyte. The processor 1 includes a working electrode 21, a reference electrode 22, and an auxiliary electrode 23. The screen-printed working electrode 21 of the portable workstation is modified with a PdZn / NP@C dispersion prepared by the above method. The processor 1 is also connected to a user interface 4.

[0066] Processor 1 includes a signal generation module, a data acquisition module, a control module, and a data processing module. The signal generation module is used to generate the required electrochemical signals, such as constant voltage, constant current, and pulse voltage. The data acquisition module is used to acquire current, voltage, and other signals during the electrochemical reaction process and convert them into digital signals. The control module is used to control the operation of the entire system and execute the experimental parameters and programs set by the user. The data processing module is used to process the data acquired by the electrochemical workstation and perform necessary calculations and analyses. The display provides a screen and buttons for displaying results and setting parameters.

[0067] In summary, the raw materials used in this invention are abundant, inexpensive, and environmentally friendly. The preparation method is simple, and by modifying the screen-printed working electrode 21 of the portable workstation, testing can be performed using a portable workstation, increasing the portability of the test.

[0068] First, Pd-ZIF-8 is etched to form a hollow structure. Then, during annealing, phosphating is performed to form N,P dual-doped PdZn / NP@C with a hollow nanocage morphology. Due to its unique three-dimensional structure, the hollow nanocage has a larger effective surface area compared to solid nanoparticles or thin film materials, allowing more active sites to contact the target analyte, improving the electrode's adsorption capacity for chlorogenic acid molecules, thereby enhancing the signal response. Furthermore, the hollow cavity structure inside the nanocage helps reduce the electron transport path length, accelerating the transfer of electrons from the electrode to the target molecule or vice versa, which helps improve detection speed and sensitivity. Compared to solid nanomaterials, hollow nanocages have lower density and higher structural stability, which can prevent the aggregation of nanoparticles to a certain extent, maintain the long-term activity of the electrode surface, and extend the sensor's lifespan. It can also effectively promote the oxidation reaction of chlorogenic acid, improving detection efficiency. Therefore, the hollow nanocage morphology of PdZn / NP@C increases the sensor's sensitivity and lifespan.

[0069] The electrochemical sensor exhibits a wide detection linear range of 5 nM-1000 nM and 1000 nM-7000 nM, with a low limit of detection (LOD) of 1.19 nM. This invention enables portable trace detection of chlorogenic acid. The electrochemical sensor, after testing, shows a relative standard deviation (RSD) of 1.2% for the peak current, demonstrating good repeatability and reproducibility. It detects common ions (MgCl2, NaSO4, Fe(NO3)3) and functional group analogs (CFA, Myr, AA, CTA, SA, URA, G...). The presence of lumen and fructose has almost no effect on the electrical signal of the CGA. In particular, after the addition of Myr, the electrochemical window shows the peak signal of Myr, but the peak current of the CGA remains unaffected. Therefore, PdZn / NP@C / SPE has good anti-interference ability. In addition, after cyclic voltammetry (CV) and differential pulse voltammetry (DPV) tests, the RSD value of its peak current is still less than 10% after 100 cycles. The refrigerator stability test data on day 1 and day 38 shows that the RSD value of its peak current is 5.5%. Therefore, the CGA sensing platform of the present invention has good stability.

[0070] The above descriptions are merely embodiments of the present invention, and common knowledge regarding specific technical solutions or characteristics is not elaborated upon here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical solutions of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A method for preparing a portable chlorogenic acid electrochemical sensor, characterized in that, Includes the following steps: S1. Preparation of pale yellow powder solid Pd-ZIF-8 Zn(NO3)2·6H2O was dissolved in the first part of methanol, and Pd(NO3)2 solution was added dropwise to obtain solution A; 2-methylimidazole was dissolved in the second part of methanol to obtain solution B; solutions A and B were mixed evenly and heated to react. After the reaction was cooled, the mixture was washed and dried under vacuum to obtain a pale yellow powder solid Pd-ZIF-8. S2. Preparation of yellow powder solid TA@Pd-ZIF-8 Weigh the Pd-ZIF-8 obtained in step S1 and add it to the tannic acid solution. Stir the reaction and perform hollow etching on Pd-ZIF-8. Wash and vacuum dry to obtain yellow powder solid TA@Pd-ZIF-8. S3. Preparation of nitrogen- and phosphorus-doped PdZn / NP@C dispersions with hollow nanocage morphology. Weigh NaH2PO2·H2O and TA@Pd-ZIF-8 obtained in step S2, mix and grind them, then anneal at high temperature to obtain a black solid, soak it in HCl, then wash and vacuum dry it to obtain a black solid PdZn / NP@C, and disperse it in deionized water to obtain a nitrogen and phosphorus dual-doped PdZn / NP@C dispersion with hollow nanocage morphology. The high-temperature annealing process includes two stages: the first stage annealing temperature is 300℃ and the time is 2 hours; the second stage annealing temperature is 800℃ and the time is 2 hours; the heating rate for both stages is 5℃ / min. S4. Preparation of chlorogenic acid electrochemical sensor The dispersion obtained in step S3 was measured and added to the surface of the screen-printed working electrode of the portable workstation, and then dried to obtain the chlorogenic acid electrochemical sensor.

2. The method for preparing a portable chlorogenic acid electrochemical sensor according to claim 1, characterized in that: In S1, the volume fraction of Pd(NO3)2 solution is 2v%, the volume ratio of the first part of methanol to the second part of methanol is 1:1, and the molar ratio of Zn(NO3)2·6H2O to 2-methylimidazole is 1:

4.

3. The method for preparing a portable chlorogenic acid electrochemical sensor according to claim 1, characterized in that: In S1, the heating reaction temperature is 120℃, the heating reaction time is 4h, and the vacuum drying temperature is 60℃.

4. The method for preparing a portable chlorogenic acid electrochemical sensor according to claim 1, characterized in that: In S2, the concentration of tannic acid solution is 7 mg / mL.

5. The method for preparing a portable chlorogenic acid electrochemical sensor according to claim 1, characterized in that: In S3, the mass ratio of TA@Pd-ZIF-8 to NaH2PO2·H2O is 1:1, and the concentration of HCl is 0.1M.

6. The method for preparing a portable chlorogenic acid electrochemical sensor according to claim 1, characterized in that: In S4, the concentration of the PdZn / NP@C dispersion is 2 mg / mL.

7. A chlorogenic acid electrochemical sensor prepared by the method for preparing a portable chlorogenic acid electrochemical sensor according to any one of claims 1 to 6.

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