Portable chlorogenic acid electrochemical sensor and preparation method thereof

Abstract

The invention belongs to the technical field of chlorogenic acid electrochemical sensors, and discloses a portable chlorogenic acid electrochemical sensor and a preparation method thereof, and the method comprises the following steps: S1, preparing a faint yellow powder solid Pd-ZIF-8; s2, weighing a finished product obtained in the step S1, and preparing TA-coated Pd-ZIF-8; s3, weighing a finished product in the step S2 to prepare a PdZn / NP-C dispersion liquid; s4, dropwise adding the dispersion liquid on the surface of a silk-screen printing working electrode to prepare a chlorogenic acid electrochemical sensor; the PdZn / NP coated C / SPE modified working electrode is utilized, and the portable workstation is adopted for testing, so that the problems of poor portability, higher minimum detection limit and narrow detection linear range of the existing detection method are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of chlorogenic acid electrochemical sensors, and in particular to a portable chlorogenic acid electrochemical sensor and a preparation method thereof. Background Art

[0002] Chlorogenic acid (CGA) is a phenolic acid compound naturally present in many plants. It has a variety of biological activities and health benefits, such as strong antioxidant, anti-inflammatory, hypoglycemic effects, etc. It is widely used in food, medicine, cosmetics and other fields. Therefore, in order to ensure that the content of chlorogenic acid in food or medicine is within a safe range, avoid the adverse effects of excessive intake, and ensure the quality and efficacy of medicines, it is necessary to test the content of chlorogenic acid.

[0003] The currently commonly used method for detecting chlorogenic acid is to use a desktop electrochemical workstation. This method has poor portability, a high limit of detection (LOD), and a narrow detection linear range, which is not convenient for practical application. Summary of the invention

[0004] The present invention aims to provide a portable chlorogenic acid electrochemical sensor and a preparation method thereof, which utilizes PdZn / NP@C / SPE to modify the working electrode and adopts a portable workstation for testing, thereby solving the problems of poor portability, high minimum detection limit and narrow detection linear range of existing detection methods.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

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

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

[0008] Will Zn(NO 3 ) 2 6H 2 O was dissolved in the first portion of methanol and Pd(NO 3 ) 2 solution to obtain solution A; dissolving 2-methylimidazole in the second portion of methanol to obtain solution B; mixing solution A and solution B evenly, and heating to react, and after the reaction is cooled, washing and vacuum drying to obtain a light 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, add it to the tannic acid solution, stir to react, perform hollow etching on the Pd-ZIF-8, wash, and vacuum dry to obtain a yellow powder solid TA@Pd-ZIF-8;

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

[0012] Weigh NaH 2 PO 2 ·H 2 O and the TA@Pd-ZIF-8 obtained in step S2 are mixed and ground, and then annealed at high temperature to obtain a black solid, which is then soaked in HCl, washed, and vacuum-dried to obtain a black solid PdZn / NP@C, which is then dispersed 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 is measured and added dropwise to the surface of the screen-printed working electrode of the portable workstation, and dried to obtain a chlorogenic acid electrochemical sensor.

[0015] Furthermore, in S1, Pd(NO 3 ) 2 The volume fraction of the solution was 2v%, the volume ratio of the first methanol to the second methanol was 1:1, and Zn(NO 3 ) 2 6H 2 The molar ratio of O to 2-methylimidazole is 1:4.

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

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

[0018] Furthermore, in S3, TA@Pd-ZIF-8 and NaH 2 PO 2 ·H 2 The mass ratio of O was 1:1, and the concentration of HCl was 0.1 M.

[0019] Furthermore, in S3, the high temperature annealing includes two stages, the annealing temperature of the first stage is 300°C, the time is 2h, and the annealing temperature of the second stage is 800°C, the time is 2h, and the heating rate is 5°C / min.

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

[0021] A chlorogenic acid electrochemical sensor is prepared according to the above-mentioned 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 the present invention are abundant, low-cost, environmentally friendly, and simple to prepare. Moreover, by modifying the screen-printed working electrode of the portable workstation, the portable workstation can be used for testing, thereby increasing the portability of the detection.

[0024] 2. The electrochemical sensor of the present 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 than solid nanoparticles or thin film materials, so that more active sites can contact the target analyte, thereby improving the electrode's adsorption capacity for chlorogenic acid molecules, thereby enhancing the signal response; and the cavity structure inside the hollow nanocage helps to reduce the length of the electron transfer path and accelerate the transfer process of electrons from the electrode to the target molecule or vice versa, which helps to improve the detection speed and sensitivity; compared with solid nanomaterials, hollow nanocages have lower density and higher structural stability, which can prevent aggregation between nanoparticles to a certain extent, maintain the long-term activity of the electrode surface, and extend the service life of the sensor; and can effectively promote the oxidation reaction of chlorogenic acid and improve detection efficiency. Therefore, the PdZn / NP@C with a hollow nanocage morphology increases the sensitivity and service life of the sensor;

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

[0026] 4. The electrochemical sensor of the present invention has been tested and the relative standard deviation (RSD) of the peak current is 1.2%, which has good repeatability and reproducibility. 2 、NaSO 4 、Fe(NO 3 ) 3) and functional group analogues, including caffeic acid (CFA), myricetin (Myr), ascorbic acid (AA), citric acid (CTA), salicylic acid (SA), ursolic acid (URA), glucose (Glu), and fructose (Fru). These substances have almost no effect on the electrical signal of CGA, especially after the addition of Myr, the electrochemical window shows the peak signal of Myr, but the peak current of CGA is still 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, and the refrigerator stability test data on the 1st day and the 38th day, the RSD value of its peak current is 5.5%. Therefore, the CGA sensing platform of the present invention has good stability. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0029] Figure 3 The present invention is a curve diagram of the detection results of using the prepared sensor to detect the concentration of chlorogenic acid originally present in samples of Eucommia ulmoides leaves, honeysuckle, apples and pears, as well as the detection results after adding different concentrations of chlorogenic acid, respectively;

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

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

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

[0033] Figure 6 This is a current and voltage curve diagram of 7 parallel measurements using DVP in Example 1 of the present invention;

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

[0035] Figure 8 In Example 1 of the present invention, MgCl 2 、NaSO 4 、Fe(NO 3 ) 3 , current-voltage curves after CFA and Myr;

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

[0037] Fig.10 This is a CV overlay graph after 100 cycles (data is collected every 10 cycles) in Example 1 of the present invention;

[0038] Fig.11 The current-voltage curves of the refrigerator stability test on the 1st day and the 38th day in Example 1 of the present invention;

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

[0040] The names of the corresponding marks in the accompanying drawings are:

[0041] Processor 1, working electrode 21, reference electrode 22, auxiliary electrode 23, electrochemical cell 3, user interface 4, power supply 5. DETAILED DESCRIPTION

[0042] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments:

[0043] Example 1

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

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

[0046] First, prepare Pd(NO with a volume fraction of 2v% using deionized water. 3 ) 2 solution, Zn(NO3 ) 2 6H 2 O (1.069 g, 3.6 mmol) was dissolved in the first 20 mL of methanol, and 667 uL of Pd(NO 3 ) 2 Add dropwise to obtain solution A; then dissolve 2-methylimidazole (1.161 g, 14.2 mmol) in the second 20 mL methanol to obtain solution B; mix solutions A and B, stir vigorously to mix evenly, transfer to a 100 mL Teflon-lined stainless steel autoclave, and react at 120°C for 4 hours; after the reaction is cooled, centrifuge and wash with methanol to collect the product, and vacuum dry the product at 60°C overnight to obtain a light yellow powder solid Pd-ZIF-8;

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

[0048] Weigh 200 mg of the light yellow solid powder Pd-ZIF-8 obtained in step S1, add it to 200 mL of 7 mg / mL tannic acid solution, stir for 30 minutes, hollow-etch the Pd-ZIF-8, then wash and collect the product with methanol, and vacuum dry the product at 60° C. overnight to obtain a yellow solid powder TA@Pd-ZIF-8;

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

[0050] Weigh 200 mg of TA@Pd-ZIF-8 solid and 200 mg of NaH 2 PO 2 ·H 2 O was ground in a mortar and then placed in a muffle furnace at N 2 The high temperature annealing was carried out in an atmosphere, and the high temperature annealing included two stages. The annealing temperature of the first stage was 300°C, the time was 2h, and the annealing temperature of the second stage was 800°C, the time was 2h, and the heating rate was 5°C / min. After the annealing was completed, the obtained black solid was soaked in 0.1M HCl overnight, and then centrifuged and washed with water. The product was vacuum dried at 60°C overnight to obtain a black solid PdZn / NP@C. 2 mg of PdZn / NP@C was dispersed in 1 mL of deionized water, and ultrasonically homogenized to obtain a 2 mg / mL PdZn / NP@C dispersion. The SEM image of PdZn / NP@C is shown in FIG. Figure 1 As mentioned above, the TEM image of PdZn / NP@C is shown in Figure 2 As shown;

[0051] S4. Preparation of chlorogenic acid electrochemical sensor

[0052] 12 uL of the dispersion obtained in step S3 was measured and added dropwise to the surface of the screen-printed working electrode 21 of the portable workstation, and dried to obtain a chlorogenic acid electrochemical sensor.

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

[0054] Table 1 Test 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 by differential pulse voltammetry (DPV). Figure 4 The DPV overlay graphs of different CGA concentrations (0.005-7μM) are shown. As the CGA concentration increases, its oxidation peak current also increases. When the CGA concentration exceeds 1μM, the current value increases relatively slowly. Therefore, the quantitative analysis of CGA by this sensor can be divided into two linear relationships. The concentration-current relationship curve is shown in 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 is the current, C CGA is the concentration of chlorogenic acid, R 2 is the coefficient of determination of the relationship.

[0061] The results show that the chlorogenic acid sensor prepared by the method of the present invention has good CGA electrocatalytic performance, a wide detection linear range of 5nM-1000nM and 1000nM-7000nM, and a low minimum detection limit. Its minimum detection limit (LOD) is calculated by the formula LOD=3S a / b is determined to be 1.19 nM, and the electrochemical sensor of the present invention can perform trace amount portable detection of chlorogenic acid.

[0062] In addition, DPV was used to explore the repeatability, reproducibility, selectivity and stability of the chlorogenic acid sensor prepared in the present invention. The test results are as follows: Figures 6 to 11 shown. Figure 6 After 7 parallel measurements, the relative standard deviation (RSD) of the peak current was 1.2%. Figure 7 The electrochemical signal bar graph of 6 different chlorogenic acid sensors is shown, and the RSD value is 3.2%, indicating that the chlorogenic acid sensor prepared by the present invention has good repeatability and reproducibility; in practical applications, the electrolyte solution usually contains substances that may interfere with the electrical signal, so it is necessary to study the selectivity of the sensor. Common ions (MgCl 2 、NaSO 4 、Fe(NO 3 ) 3 ) and functional group analogs (CFA, Myr, AA, CTA, SA, URA, Glu, Fru) were selected as anti-interference experimental objects. The addition amount of CFA and Myr was twice that of CGA, and the addition amount of other substances was 10 times that of CGA. Figure 8-9 It can be seen that these substances have little effect on the electrical signal of CGA, especially after adding Myr, the electrochemical window shows the peak signal of Myr, but the peak current of CGA is still unaffected, indicating that the chlorogenic acid sensor prepared by the present invention has good anti-interference ability. In addition, the cyclic stability and long-term stability of the chlorogenic acid sensor prepared by the present invention were explored by CV and DPV respectively. Fig.10 This is a CV overlay after 100 cycles (data is collected every 10 cycles). After 100 cycles, the RSD value is still less than 10%. Fig.11 The refrigerator stability test data on the 1st day and the 38th day have 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 prepared according to the preparation method of a portable chlorogenic acid electrochemical sensor in Example 1;

[0065] like Fig.12As shown, specifically, the chlorogenic acid electrochemical sensor includes a portable workstation, the portable workstation includes a power supply 5, a processor 1, and an electrochemical cell 3. The power supply 5 can be a mobile power supply to provide a stable power supply for the entire portable workstation, and the electrochemical cell 3 is used to accommodate electrolytes; 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 the PdZn / NP@C dispersion prepared by the above method; the processor 1 is also connected to a user interface 4;

[0066] The processor 1 includes a signal generating module, a data acquisition module, a control module and a data processing module. The signal generating module is used to generate the required electrochemical signals, such as constant voltage, constant current, pulse voltage, etc.; the data acquisition module is used to collect current, voltage and other signals during the electrochemical reaction 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 collected by the electrochemical workstation and perform necessary calculations and analyses; the display is used to provide a display screen and buttons for displaying results and setting parameters.

[0067] In summary, the raw materials used in the present invention are abundant, low-cost, environmentally friendly, and simple to prepare. Moreover, by modifying the screen-printed working electrode 21 of the portable workstation, the portable workstation can be used for testing, thereby increasing the portability of the detection.

[0068] First, Pd-ZIF-8 is etched to form a hollow structure, and then phosphating is performed during the annealing process to form N, P element 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 than 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; and the cavity structure inside the hollow nanocage helps to reduce the length of the electron transfer path and accelerate the transfer process of electrons from the electrode to the target molecule or vice versa, which helps to improve the detection speed and sensitivity; compared with solid nanomaterials, hollow nanocages have lower density and higher structural stability, which can prevent aggregation between nanoparticles to a certain extent, maintain the long-term activity of the electrode surface, and extend the service life of the sensor; and can effectively promote the oxidation reaction of chlorogenic acid and improve detection efficiency. Therefore, the PdZn / NP@C with a hollow nanocage morphology increases the sensitivity and service life of the sensor;

[0069] The electrochemical sensor has a wide detection linear range of 5nM-1000nM and 1000nM-7000nM, and a low minimum detection limit of 1.19nM. The electrochemical sensor of the present invention can perform trace portable detection of chlorogenic acid; the electrochemical sensor of the present invention has been tested, and the relative standard deviation (RSD) of the peak current is 1.2%, which has good repeatability and reproducibility, and common ions (MgCl 2 、NaSO 4 、Fe(NO 3 ) 3 ) and functional group analogues (CFA, Myr, AA, CTA, SA, URA, Glu, Fru) have almost no effect on the electrical signal of CGA, especially after the addition of Myr, the electrochemical window shows the peak signal of Myr, but the peak current of CGA is still 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, and the refrigerator stability test data on the 1st day and the 38th day, 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 is only an embodiment of the present invention, and the common knowledge such as the known specific technical solutions or characteristics in the solution is not described in detail here. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the technical solution of the present invention, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records 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: The following steps are involved: S1. Preparation of pale yellow powder solid Pd-ZIF-8 Dissolve Zn(NO3)2·6H2O in the first portion of methanol, and drop Pd(NO3)2 solution into it to obtain solution A; dissolve 2-methylimidazole in the second portion of methanol to obtain solution B; mix solution A and solution B evenly, and heat to react. After the reaction is cooled, wash and vacuum dry to obtain light 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, add it to the tannic acid solution, stir to react, perform hollow etching on the Pd-ZIF-8, wash, and vacuum dry to obtain a yellow powder solid TA@Pd-ZIF-8; S3. Preparation of PdZn / NP@C dispersion Weighing NaH2PO2·H2O and TA@Pd-ZIF-8 obtained in step S2, mixing and grinding, and then annealing at high temperature to obtain a black solid, and then soaking it with HCl, then washing and vacuum drying to obtain a black solid PdZn / NP@C, and dispersing it in deionized water to obtain a PdZn / NP@C dispersion; S4. Preparation of chlorogenic acid electrochemical sensor The dispersion obtained in step S3 is measured and added dropwise to the surface of the screen-printed working electrode of the portable workstation, and dried to obtain a 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 methanol to the second 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°C, the heating reaction time is 4 hours, and the vacuum drying temperature is 60°C.

4. The method for preparing a portable chlorogenic acid electrochemical sensor according to claim 1, characterized in that: In S2, the concentration of the tannic acid solution was 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 and NaH2PO2·H2O was 1:1, and the concentration of HCl was 0.1M.

6. The method for preparing a portable chlorogenic acid electrochemical sensor according to claim 1, characterized in that: In S3, high temperature annealing includes two stages. The annealing temperature of the first stage is 300°C and the time is 2h. The annealing temperature of the second stage is 800°C and the time is 2h. The heating rate is 5°C / min.

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

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

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