Electrochemical sensor as well as preparation method, detection system and application thereof

Abstract

The invention discloses an electrochemical sensor, a preparation method thereof, a detection system and application. The preparation method of the electrochemical sensor comprises the following steps: step 1, modifying a glassy carbon electrode with carbon nano onion; step 2, putting the glassy carbon electrode modified in the step 1 into a prepolymerization solution containing metoprolol for cyclic electropolymerization treatment; 3, the glassy carbon electrode treated in the step 2 is placed in a hydrochloric acid solution to be subjected to elution treatment, and the electrochemical sensor is obtained after elution is completed. Aiming at the technical bottleneck of rapid detection of metoprolol, the invention provides the electrochemical sensor, the electrochemical sensor shows excellent selectivity, repeatability and stability on metoprolol, the measurement has a wide linear range, the limit of detection (LOD) value is extremely low, and the electrochemical sensor can be used for detecting the concentration of metoprolol in metoprolol tablets or urine.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of electrochemical sensors, and particularly relates to an electrochemical sensor, a preparation method thereof, a detection system and application. BACKGROUND

[0002] Metoprolol (MTP) is a typical beta 1 receptor blocker, which can effectively reduce heart rate and relieve anxiety, and is used as one of the anti-stimulant detection indicators for competitive sports athletes. At present, various quantitative determination methods of metoprolol have been developed, including spectrophotometry, capillary electrophoresis and various chromatographic techniques. Although these methods show relatively high sensitivity and accuracy, the high detection cost, complex sample pretreatment procedures and high requirements for professional operators make them difficult to meet the actual needs of on-site detection or large-scale screening. Compared with the above methods, the electrochemical method detects target substances by directly measuring the change of current or impedance, and has the characteristics of rapid response, portable equipment and strong anti-matrix interference ability, and is particularly suitable for on-site rapid analysis. The electrochemical deposition of molecularly imprinted film is considered to be the simplest and most practical technology for depositing stable polymer film on the surface of electrode, which can form a polymer film with precise thickness on the electrode by electrochemical method, however, the sensitivity of the traditional molecularly imprinted polymer sensor is still limited by the efficiency of electrode interface electron transfer. SUMMARY

[0003] In order to solve the above technical problems, the purpose of the present application is to provide a preparation method of an electrochemical sensor which is simple to prepare and has high sensitivity.

[0004] In order to achieve the above-mentioned purpose, the technical scheme of the present application is as follows: a preparation method of an electrochemical sensor, comprising the following steps:

[0005] Step 1: modifying the glassy carbon electrode with carbon nanometer onion;

[0006] Step 2: placing the glassy carbon electrode modified in step 1 in a pre-polymerization solution containing metoprolol for cyclic electropolymerization treatment;

[0007] Step 3: placing the glassy carbon electrode treated in step 2 in a hydrochloric acid solution for elution treatment, and obtaining the electrochemical sensor after elution.

[0008] In the above technical scheme, the glassy carbon electrode is polished on the surface with alumina slurry before modification, and after polishing, the glassy carbon electrode is ultrasonically cleaned in anhydrous ethanol and ultrapure water respectively for multiple times; in step 1, the glassy carbon electrode is modified with carbon nanometer onion by dropping the carbon nanometer onion dispersion liquid on the surface of the glassy carbon electrode, and drying.

[0009] The carbon nanometer onion dispersion liquid is obtained by ultrasonic dispersion of carbon nanometer onion in anhydrous ethanol, and the concentration of the carbon nanometer onion dispersion liquid is 1 mg / mL.

[0010] The drop coating amount of the carbon nanometer onion dispersion liquid on the surface of the glassy carbon electrode is 140-170 μL / cm 2 .

[0011] The preparation method of the prepolymerization solution in step 2 is as follows: mixing o-phenylenediamine and metoprolol in Britton-Robinson buffer solution and placing in a 4 ℃ refrigerator for 8-14 h to obtain the prepolymerization solution, wherein the concentrations of o-phenylenediamine and metoprolol in the prepolymerization solution are 20 mM and 2 mM respectively.

[0012] The specific operation of the cyclic electro-polymerization treatment in step 2 is as follows: placing the glassy carbon electrode in the prepolymerization solution and performing 5 times of cyclic electro-polymerization by cyclic voltammetry at a potential range of 0-1 V and a scanning rate of 0.1 V / s.

[0013] The specific operation of step 3 is as follows: immersing the glassy carbon electrode in a hydrochloric acid solution with a concentration of 0.1 M, simultaneously stirring the hydrochloric acid solution, and eluting for 20-30 min.

[0014] The second purpose of the present application is to provide an electrochemical sensor with simple structure and high sensitivity in detection.

[0015] In order to achieve the above purpose, the technical scheme of the present application is as follows: an electrochemical sensor is prepared by the preparation method described above.

[0016] The third purpose of the present application is to provide a metoprolol detection system with simple structure and capable of rapidly detecting the concentration of metoprolol.

[0017] In order to achieve the above purpose, the technical scheme of the present application is as follows: a metoprolol detection system comprises an electrochemical workstation and an electrochemical sensor as described above, and the electrochemical sensor and the electrochemical workstation detect the concentration of metoprolol by taking K3[Fe(CN)6] solution as an electron transfer medium.

[0018] The fourth purpose of the present application is to provide an application of the electrochemical sensor as described above in rapid detection of the concentration of metoprolol in a solution.

[0019] The beneficial effects of the present application are that the present application proposes an electrochemical sensor (also known as a carbon nanometer onion modified molecular imprinting electrochemical sensor) for the technical bottleneck of rapid detection of metoprolol, which has a wide linear range (0.04 μM-8.0 μM) for the determination of metoprolol, and a very low limit of detection (LOD) value (specifically 3.33 x 10 -8 mol / L). This electrochemical sensor shows excellent selectivity, repeatability and stability, providing an effective solution for rapid detection of metoprolol, and also providing valuable insights for the design of sensing platforms for other prohibited drug molecules. In the future, by combining the miniaturized electrochemical system with the wireless transmission module, the practical application of this technology in the field of anti-doping can be further promoted. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 Optimization curve diagram of the amount of carbon nanometer onion drop coating for preparing the electrochemical sensor of the present application;

[0021] Figure 2 Optimization curve diagram of the pH value of Britton-Robinson buffer for preparing the electrochemical sensor of the present application;

[0022] Figure 3 Optimization curve diagram of the template molecule elution condition for preparing the electrochemical sensor of the present application;

[0023] Figure 4 Optimization curve diagram of the incubation time after the preparation of the electrochemical sensor of the present application is completed;

[0024] Figure 5 SEM image of the CNO sensor in the present application;

[0025] Figure 6 One of the SEM images of the MIP sensor in the present application;

[0026] Figure 7 The second SEM image of the MIP sensor in the present application;

[0027] Figure 8 EDS mapping analysis diagram of the modification layer on the surface of the CNO sensor in the present application;

[0028] Figure 9 EDS mapping analysis diagram of the modification layer on the surface of the MIP adduct sensor in the present application;

[0029] Figure 10 EDS mapping analysis diagram of the modification layer on the surface of the MIP sensor in the present application;

[0030] Figure 11Cyclic voltammogram of each sensor in the present application;

[0031] Figure 12 Differential pulse voltammetry (DPV) response graph of each sensor in the present application;

[0032] Figure 13 Calibration curve for the analysis and determination of metoprolol molecules in the present application;

[0033] Figure 14 Schematic diagram of determination reproducibility of the MIP sensor prepared in the present application;

[0034] Figure 15 Schematic diagram of determination stability of the MIP sensor prepared in the present application;

[0035] Figure 16 Schematic diagram of detection specificity of the MIP sensor and the NIP sensor in the present application for metoprolol and two interfering substances. DETAILED DESCRIPTION

[0036] The principles and features of the present application are described below in conjunction with the accompanying drawings, which are only used to explain the present application and are not intended to limit the scope of the present application. In the following paragraphs, the present application is described in more detail by way of example with reference to the accompanying drawings. The advantages and features of the present application will be more apparent from the following description and claims. It should be noted that the drawings are very simplified and all use non-precise proportions, only to facilitate, clearly assist in explaining the purpose of the embodiments of the present application.

[0037] I. Reagents:

[0038] Metoprolol (MTP, ≥98%) was purchased from Huawuerke Chemical Co., Ltd.;

[0039] o-Phenylenediamine (o-PD, ≥98%) was purchased from Luoe Chemical Reagent Co., Ltd.;

[0040] Acetic acid (HAc), phosphoric acid (H3PO4), boric acid (H3BO3), sodium hydroxide (NaOH), hydrochloric acid (HCl), potassium chloride (KCl), potassium ferricyanide (K3[Fe(CN)6]), atenolol and propranolol were purchased from Xilong Chemical Co., Ltd.; all chemical reagents were of analytical purity.

[0041] Carbon nano onions (CNOs) were self-made, and the preparation method was according to the method recorded in the published paper (Bian Y, Liu L, Liu D, Zhu Z, Shao Y, Li M. Electrochemical synthesis of carbon nano onions. Inorganic Chemistry Frontiers 2020; 7: 4404-4411).

[0042] Preparation of carbon nano onion dispersion: CNOs were uniformly dispersed in anhydrous ethanol to form a carbon nano onion dispersion with a concentration of 1 mg / mL. The carbon nano onion dispersion needs to be ultrasonically treated before use to ensure that the CNOs are fully mixed with the anhydrous ethanol.

[0043] Preparation of pre-polymerization solution: o-phenylenediamine and metoprolol were mixed in Britton-Robinson buffer and placed in a 4℃ refrigerator overnight (dark condition) to obtain a pre-polymerization solution, wherein the concentrations of o-phenylenediamine and metoprolol in the pre-polymerization solution were 20 mM and 2 mM, respectively.

[0044] The water used in the experiment was all double-distilled water.

[0045] II. Instruments and equipment

[0046] All electrochemical experiments were carried out at room temperature using an electrochemical workstation (CHI660D, Shanghai Chenhua Instrument Co., Ltd.).

[0047] The differential pulse voltammetry (DPV) and cyclic voltammetry (CV) experiments used a three-electrode system, in which the glassy carbon electrode modified by the carbon nano onions in the application was used as the working electrode, and the existing carbon electrode and saturated calomel electrode (SCE) were used as the counter electrode and reference electrode, respectively.

[0048] The scanning electron microscope (SEM) images were collected on an S-4800 electron microscope (Hitachi, Japan).

[0049] The pH value was measured by a pH meter (MP 230, Mettler-Toledo, Switzerland).

[0050] III. Preparation of electrochemical sensor (according to the optimized conditions)

[0051] The electrochemical sensor prepared in this example has high sensitivity to metoprolol, and the specific preparation scheme is as follows:

[0052] First step: polishing pretreatment of glassy carbon electrode, specifically is first in turn using 0.3 μm, 0.1 μm and 0.05 μm alumina slurry to polish the surface of glassy carbon electrode (first using 0.3 μm and 0.1 μm alumina slurry on polishing cloth with "8" shape track polishing 2-3 minutes, removing the glassy carbon electrode surface large particle contaminants, then using 0.05 μm alumina slurry repeatedly polishing 1-2 minutes, until the glassy carbon electrode surface presents mirror gloss, then the polishing treatment of glassy carbon electrode in turn in ethanol and ultrapure water each ultrasonic cleaning 5 minutes, can be considered to completely remove the glassy carbon electrode surface alumina particles).

[0053] Second step: using drop coating method to coat carbon nanometer onion dispersion liquid on the surface of glassy carbon electrode (drop coating amount is 11 μL, the surface area of glassy carbon electrode is 0.07 cm 2 , drop coating amount is equivalent to 157 μL / cm 2 ), after infrared drying can obtain carbon nanometer onion modified glassy carbon electrode.

[0054] Third step: using metoprolol as template to prepare molecularly imprinted polymer film (MIP) on the surface of glassy carbon electrode by electropolymerization of o-phenylenediamine monomer, the specific operation is:

[0055] The carbon nanometer onion modified glassy carbon electrode is immersed in the prepolymerization solution, and 5 times of cyclic voltammetry (CV) is carried out at the potential range of 0-1 V (relative to saturated calomel electrode) with the scanning rate of 0.1 V / s.

[0056] Fourth step: the glassy carbon electrode after electropolymerization is immersed in the hydrochloric acid solution with the concentration of 0.1 M, and is stirred by the magnetic stirrer for 25 minutes, so as to ensure that the template molecule (metoprolol) is completely eluted from the matrix of molecularly imprinted polymer, and the specific molecularly imprinted polymer film (MIPs) is obtained, that is, the electrochemical sensor (in this embodiment, it is referred to as MIP sensor) is completed.

[0057] As a comparison, an NIP sensor is prepared by the same method, and the preparation process of the NIP sensor is only different from the preparation of the above-mentioned electrochemical sensor in that the metoprolol is not added in the prepolymerization solution. As a comparison, an uneluted sensor (referred to as MIP plus sensor) is prepared by the same method without the elution process of the fourth step. As a comparison, a glassy carbon electrode only modified with carbon nanometer onion (referred to as CNOs sensor) is prepared by the same method without the third step and the fourth step.

[0058] Another glassy carbon electrode without any treatment is taken as a control (referred to as Bare sensor). Four, optimization of electrochemical sensor preparation conditions

[0059] 4.1 Optimization of the drop-casting amount of carbon nanon-onions

[0060] In order to achieve the best conductivity, the drop-casting amount of carbon nanon-onions was systematically optimized, and the results are shown in Figure 1 The experimental results show that the conductive performance of the glassy carbon electrode (surface area of 0.07 cm 2 ) gradually increases with the increase of the drop-casting amount of carbon nanon-onions. When the drop-casting amount is 11 μL, the response current reaches the peak value; however, if the drop-casting amount is further increased, the response current shows a downward trend. This may be due to the excessive physical accumulation of carbon nanon-onions, which forms a non-uniform thick film on the electrode surface, thereby destroying the topological structure of the conductive network. In addition, in the high-concentration carbon nanon-onion layer, due to the action of van der Waals force, obvious agglomeration phenomenon occurs, which significantly reduces the effective electrochemical specific surface area of the active material and increases the resistance of charge transfer. According to the above analysis, and considering the experimental data and performance, the optimal drop-casting amount of carbon nanon-onions on the surface of the glassy carbon electrode is set to 11 μL.

[0061] 4.2 Optimization of the pH value of Britton-Robinson buffer

[0062] In order to achieve the best electrochemical imprinting effect, the influence of the pH value of Britton-Robinson buffer on the electrochemical performance of the prepared MIP sensor was investigated. As shown in Figure 2 , within the range of pH value from 5.0 to 7.0, the oxidation peak current difference of the MIP sensor shows a significant difference with the change of pH value. Specifically, when the pH value increases from 5.0 to 6.0, the electrochemical response gradually increases; however, when the pH value exceeds 6.0, the response intensity begins to decrease. This phenomenon indicates that when the pH value is 6.0, the interaction between o-phenylenediamine and metoprolol molecules is the strongest, thereby forming more specific imprinting sites in the molecularly imprinted polymer film. Based on the above results, the pH value of Britton-Robinson buffer is selected as 6.0 as the optimal condition in the subsequent experiments of the present application.

[0063] 4.3 Optimization of the template molecule elution conditions

[0064] The elution of template molecules is a key step in the formation of specific molecularly imprinted polymer, because it can directly affect the selectivity and sensitivity of MIP sensor by successfully removing template molecules from the surface of glassy carbon electrode and generating specific cavities. In the present invention, water, hydrochloric acid, anhydrous ethanol, Britton-Robinson buffer or a mixture of Britton-Robinson buffer and anhydrous ethanol (volume ratio 1:3) were used as eluent respectively, and the results showed that 0.1M hydrochloric acid solution could remove template molecules more quickly and completely. Subsequently, the elution time in 0.1M hydrochloric acid solution was further optimized. As shown in Figure 3 , with the extension of elution time, the peak current increased rapidly; however, after 25 minutes, the upward trend of the peak current gradually leveled off, indicating that the template molecules on the electrode surface had been almost completely removed, at which time the electrode showed relatively high porosity. Therefore, the present invention ultimately determined 25 minutes as the optimal elution time.

[0065] 4.4 Optimization of incubation time

[0066] In order to optimize the adsorption efficiency of molecularly imprinted polymer film layer to analyte, the effect of incubation time on the response of MIP sensor to metoprolol molecules was investigated. Specifically, after removing the template molecules, the MIP sensor was placed in a 0.4μM metoprolol solution and incubated for different times. As shown in Figure 4 , the peak current gradually decreased with the extension of incubation time and stabilized at 15 minutes, indicating that the adsorption process had basically reached equilibrium. Further extension of incubation time had no significant effect on the peak current value; therefore, 15 minutes was ultimately determined as the incubation time.

[0067] V. Introduction of electroanalytical measurement method

[0068] In a three-electrode system, cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were used to evaluate NIP sensor, MIP adduct sensor, CNOs sensor, Bare sensor or MIP sensor respectively, and the redox probe solution was prepared by adding potassium chloride (concentration 0.1M) to 5.0mM potassium ferricyanide solution (potassium ferricyanide as electron transfer mediator, indirect reaction to the concentration of metoprolol at the modified electrode interface). CV measurement was carried out at a potential range of -0.6V to 0.8V with a scan rate of 0.1V / s. DPV measurement was carried out under the following parameters: initial potential -0.2V, final potential 0.8V, incremental potential 0.004V, amplitude 0.05V, pulse width 0.05s, sampling width 0.0167s and pulse period 0.2s. All electrochemical measurements were carried out at room temperature.

[0069] 6. Analysis

[0070] 6.1 Characterization of modified electrodes

[0071] The surface morphology of the glassy carbon electrode at different modification stages was systematically characterized by scanning electron microscopy (SEM). Figure 5 As shown in Figure 2, the surface of the CNOs sensor exhibits a significant rough structure, and the carbon nano-onion particles are in a bead-like morphology. Figure 6 and Figure 7 As shown, no obvious membrane structure was observed, and the image was blurred and uneven in thickness. This may be attributed to the unique structural characteristics of carbon nano-onions and the relatively thin specific molecular imprinting polymer film formed on their surface. In addition, elemental analysis of the glassy carbon electrode at different modification stages was carried out to systematically study the changes in elemental composition during the preparation process. The modified layer on the surface of the CNOs sensor was mainly composed of carbon (99.36±0.5%), and the contents of nitrogen and oxygen were relatively low, at 0.64±0.3% and 0.12±0.1%, respectively ( Figure 8 The nitrogen and oxygen contents of the modified layer on the surface of the MIP adduct sensor increased significantly, reaching 6.7±0.6% and 0.74±0.1%, respectively ( Figure 9 ), and this enhancement was mainly attributed to the incorporation of amino groups in o-phenylenediamine and the contribution of hydroxyl groups in metoprolol molecules. It is worth noting that the nitrogen content in the MIP sensor decreased by about 59% (to 2.74±0.4%), while the oxygen content was slightly reduced to 0.16±0.1% ( Figure 10 ). These results confirmed that a portion of the metoprolol was effectively removed while the polymer backbone remained intact.

[0072] 6.2. Electrochemical Behavior of MIP and NIP Sensors

[0073] The electrochemical behaviors of different sensors were studied in redox probe solution using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Figure 11 ) It can be seen that the redox peak of potassium ferrocyanide is present on both the bare glassy carbon electrode and the carbon nano-onion modified electrode. After electropolymerization of the MIP adduct sensor and the NIP sensor, the redox peak disappears due to the formation of a poly(o-phenylenediamine) film on the corresponding electrode surface. In addition, after the template molecule (metoprolol) is eluted from the o-phenylenediamine polymer matrix, the corresponding cyclic voltammetry curve of the MIP sensor shows a redox peak again. The appearance of the redox peak after the removal of metoprolol indicates that holes are generated in the molecularly imprinted polymer, thereby enhancing the electron transfer between the glassy carbon electrode surface and the redox probe.

[0074] From the differential pulse voltammetry (DPV) response ( Figure 12 ) also obtained similar observations. The Bare sensor exhibited a higher peak current. Compared with the Bare sensor, the peak current of the CNOs sensor increased significantly, indicating that the conductivity of the glassy carbon electrode was enhanced after the carbon nano-onion was modified. Compared with the CNOs sensor, the peak current of the MIP adduct sensor almost disappeared, which showed that the molecular imprinting polymer film was insulating, hindering the electron transfer process and thus suppressing the current. Compared with the MIP adduct sensor, after the template molecule was removed from the molecular imprinting polymer film, the current in the corresponding DPV reappeared. In addition, on the NIP sensor, there was no significant change in the current before and after its rebinding with the metoprolol molecule, indicating that the NIP sensor lacks the specific recognition performance for the metoprolol molecule.

[0075] 6.3 Performance of MIP Sensor

[0076] 6.3.1 Analysis and determination of metoprolol molecules

[0077] The MIP sensor was incubated in metoprolol solutions with different concentrations. The sensor performance was then measured by differential pulse voltammetry (DPV). Figure 13 As shown, the calibration curve is based on the change in current response, that is, ΔI=I0-I c , where “I0” represents the current response value of the MIP sensor under the condition of no metoprolol rebinding, “I c " represents the current response value of the MIP sensor under the condition of metoprolol rebinding. As can be seen from the figure, at 4.0×10 -8 to 8.0×10 -6 In the range of mol / L, there is a good linear correlation between the current change and the metoprolol concentration. The linear regression equation is y = 4.324x + 45.657, and the correlation coefficient R 2 =0.9957. In addition, the detection limit (LOD) of this MIP sensor is 1.33×10 -8 mol / L(S / N=3).

[0078] 6.3.2 Repeatability and stability

[0079] In order to evaluate the reproducibility of the prepared MIP sensor, three sensors (corresponding to Figure 14 1#, 2# and 3#), and the metoprolol solution with a concentration of 0.4 μM ( Figure 14 The relative standard deviation (RSD) calculated based on the response current was 2.04%, indicating that the MIP sensor has excellent reproducibility.Figure 15 To evaluate the long-term stability of the sensor, continuous detection was performed over 30 days, and in the first 5 days, the same concentration (0.4 μΜ) of metoprolol solution was measured every day; then repeated measurements were performed every 5 days to monitor its rebinding ability to metoprolol molecules. During the experiment, the unused metoprolol solution was stored in a refrigerator at 4 °C to ensure its structural stability. The results showed that the retention rate of the electrochemical signal reached 94.3% over 30 days, which confirmed that the prepared MIP sensor had good stability in the determination of metoprolol molecules.

[0080] 6.3.3 Selectivity and specificity of MIP sensor

[0081] To evaluate the selectivity of the MIP sensor, two different metoprolol analogues were selected as interfering substances [propranolol and atenolol] for comparative analysis in the present application (metoprolol and interfering substances were prepared into target solutions with a concentration of 0.4 μΜ, respectively). After incubating the MIP sensor and NIP sensor in the three target solutions, the differential pulse voltammetry (DPV) response signal was measured in K3[Fe(CN)6] solution. As shown in Figure 16 The MIP sensor exhibited significant recognition selectivity for metoprolol. This excellent selectivity can be attributed to the high complementarity of metoprolol to the recognition sites on the surface of the specific molecularly imprinted polymer film in terms of size, shape, and functional group distribution. In addition, the experiment showed that the adsorption capacity of the NIP sensor surface for metoprolol, propranolol, and atenolol was almost the same, and significantly lower than that of the MIP sensor. Therefore, it can be concluded that there are a large number of specific adsorption cavities for metoprolol on the surface of the MIP sensor.

[0082] 6.3.4. Analysis of actual samples

[0083] The performance of the sensor was tested by determining the metoprolol concentration in tablet and urine samples. Metoprolol tablets purchased from a local pharmacy were chosen as the test target [The metoprolol drug was crushed and prepared into metoprolol concentration gradient solutions with a concentration of 0.04 μM, 0.4 μM and 4.0 μM using Britton-Robinson buffer as the solvent (ultrasonic oscillation and 0.45 μm filter were performed during preparation)]. A certain level of metoprolol was added to the urine and analyzed using the MIP sensor-based sensor. During the experiment, the MIP sensor was incubated in the above-mentioned sample solutions with different concentrations, and the current response was determined by differential pulse voltammetry (DPV) in K3[Fe(CN)6] solution. All measurements were repeated three times to ensure the reliability of the data. The analysis results of metoprolol in the actual sample are summarized in Tables 1 and 2. The results show that the MIP sensor exhibits good recovery in the actual sample. In addition, due to the high selectivity and specificity of the cavities, it is further confirmed that the developed MIP sensor can be accurately and reliably used for quantitative analysis of metoprolol in natural samples and complex matrices.

[0084] Table 1 Test results of metoprolol tablets (n = 3)

[0085] Actual metoprolol concentration (μM) Detected metoprolol concentration (μM) Recovery (%) 0.04 0.048 101.2 0.4 0.395 98.8 4.0 4.061 101.5

[0086] Table 2 Test results of urine (n = 3)

[0087] Actual metoprolol concentration (μM) Detected metoprolol concentration (μM) Recovery (%) 0.04 0.039 99.3 0.4 0.386 96.5 4.0 4.120 103.0

[0088] The above is only a preferred embodiment of the present application, and does not limit the present application in any form; anyone skilled in the art can easily implement the present application according to the drawings shown in the specification and the above description; however, any equivalent changes, modifications and evolution made by those skilled in the art within the scope of the technical solutions of the present application, using the technical content disclosed above, are equivalent embodiments of the present application; at the same time, any equivalent changes, modifications and evolution of the above embodiments according to the essential technology of the present application are still within the protection scope of the technical solutions of the present application.

Claims

1. A method of preparing an electrochemical sensor, characterized by, It comprises the following steps: Step 1: the glassy carbon electrode is modified by carbon nanometer onion; Step 2: the glassy carbon electrode modified in step 1 is placed in a pre-polymerization solution containing metoprolol for cyclic electro-polymerization treatment; Step 3: the glassy carbon electrode treated in step 2 is placed in a hydrochloric acid solution for elution treatment, and the electrochemical sensor is obtained after elution.

2. The method of claim 1, wherein the method further comprises, In step 1, the glassy carbon electrode is polished on the surface by alumina slurry before modification, and after polishing, the glassy carbon electrode is ultrasonically cleaned in anhydrous ethanol and ultrapure water respectively; in step 1, the glassy carbon electrode is modified by carbon nanometer onion, and the specific operation is to drop the carbon nanometer onion dispersion liquid on the surface of the glassy carbon electrode, and then dry it.

3. The method of claim 2, wherein the step of applying the first and second electrodes to the substrate comprises applying the first and second electrodes to the substrate by screen printing. The carbon nanometer onion dispersion liquid is obtained by ultrasonic dispersion of carbon nanometer onion in anhydrous ethanol, and the concentration of the carbon nanometer onion dispersion liquid is 1 mg / mL.

4. The method of claim 3, wherein the step of applying the first and second electrodes to the substrate comprises applying the first and second electrodes to the substrate by screen printing. The drop-casting amount of the carbon nanometer onion dispersion solution on the surface of the glassy carbon electrode is 140-170 μL / cm 2 .

5. The method of claim 1, wherein the electrochemical sensor is a glucose sensor. In step 2, the preparation method of the pre-polymerization solution is as follows: o-phenylenediamine and metoprolol are mixed in Britton-Robinson buffer solution and placed in a 4℃ refrigerator for 8-14h to obtain the pre-polymerization solution, wherein the concentrations of o-phenylenediamine and metoprolol in the pre-polymerization solution are 20mM and 2mM respectively.

6. The method of claim 1, wherein the electrochemical sensor is a glucose sensor. In step 2, the specific operation of the cyclic electro-polymerization treatment is as follows: the glassy carbon electrode is placed in the pre-polymerization solution, and cyclic voltammetry is carried out at a potential range of 0-1V and a scanning rate of 0.1V / s for 5 times.

7. The method of claim 1, wherein the method further comprises: The specific operation of step 3 is to immerse the glassy carbon electrode in a hydrochloric acid solution with a concentration of 0.1M, and simultaneously stir the hydrochloric acid solution, and elute for 20-30min.

8. An electrochemical sensor, characterized in that The preparation method is prepared by any one of claims 1-7.

9. A metoprolol detection system characterized by, It comprises an electrochemical workstation and an electrochemical sensor as claimed in claim 8, and the electrochemical sensor and the electrochemical workstation detect the concentration of metoprolol by using K3[Fe(CN)6] solution as an electron transfer medium.

10. Use of an electrochemical sensor according to claim 8, characterized in that, The application in the rapid detection of the concentration of metoprolol in the solution.

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