CN114674888B - Controllable polymer film modified electrode, preparation method thereof and detection method of luteolin - Google Patents

Abstract

The invention provides a controllable polymer film modified electrode, its preparation method and a detection method of luteolin, which belong to the technical field of electrochemical analysis methods. Using β-cyclodextrin and functionalized ionic liquid 1-hydroxyethyl-3-methylimidazole tetrafluoroborate as the polymer solution, the polymer film was modified on the glassy carbon electrode through continuous scanning by cyclic voltammetry, and the preparation The controllable polymer film modified electrode has a simple preparation method and good operability and repeatability. Based on the prepared controllable polymer film modified electrode, the electrochemical analysis method is used to detect the luteolin content in Chinese medicine samples, which has high sensitivity, good selectivity, repeatability and stability can be guaranteed.

Description

Controllable polymer film modified electrode, its preparation method and detection of luteolin method

Technical field

The invention belongs to the technical field of electrochemical analysis methods, and specifically relates to a controllable polymer film modified electrode, its preparation method and a detection method of luteolin.

Background technique

Luteolin is an important natural antioxidant, its chemical name is 3',4',5,7-tetrahydroxyflavone, its molecular formula is C ₁₅ H ₁₀ O ₆ , it has a C ₆ -C ₃ -C ₆ structure, and contains (A,B) Two benzene rings, oxygen-containing C ring and C2-C3 double bond, are weakly acidic. Luteolin is commonly found in plants such as celery, coriander, green peppers, chrysanthemums, carrots, and perilla leaves, and has a variety of biological activities and pharmacological effects, such as antibacterial, anti-inflammatory, antioxidant, cataract prevention, and cardiovascular protection. Recent studies have also shown that luteolin can inhibit the proliferation of tumor cells by inhibiting the activity of certain intracellular kinases and arresting the cell cycle. In addition, luteolin can also induce apoptosis in tumor cells. In traditional Chinese medicine, plants rich in luteolin are used to treat conditions such as high blood pressure, inflammation and cancer.

Various technologies including thin layer chromatography (TLC), high performance liquid chromatography (HPLC), ultraviolet spectrophotometry (UV), and capillary electrophoresis (CE) are used in the detection of luteolin. Although these technologies have the advantages of higher sensitivity and better accuracy, they also have shortcomings such as time-consuming, complex operations, and expensive costs. Electrochemical technology has attracted widespread attention from the scientific community due to its simplicity, speed, sensitivity, and low instrument cost. Currently, a variety of electrochemical analysis methods for detecting luteolin have been proposed and proven to be applicable to trace analysis of luteolin. For example, Shang Yonghui et al. used N-butylpyridine triflate ionic liquid to prepare modified carbon paste electrodes, and studied the presence of luteolin in N-butylpyridine triflate ([BP _y ] OTF) modified electrochemical behavior on carbon paste electrodes. The experiment found that in the citric acid-sodium citrate buffer system with pH=3.0, luteolin produced a pair of obvious redox peaks at 0.6221V and 0.4267V, and the current signals were 2.06 times and 5.8 times that of the bare electrode respectively, indicating that [BP _y ]OTF has a certain catalytic sensitization effect on luteolin, and on this basis, the interaction between luteolin and bovine serum albumin was studied. Wen Xiaoyong and others used n-hexylpyridine hexafluorophosphate as a binder to prepare an ionic liquid modified carbon paste electrode (CILE), and modified the palladium-graphene (Pd-GR) composite material on the surface of the CILE to prepare a modified electrode. (Pd-GR/CILE), and then used cyclic voltammetry and differential pulse voltammetry (DPV) to study the electrochemical behavior of luteolin on the modified electrode. The results show that in a phosphate buffer solution with pH 1.5, a pair of redox peaks with good peak shapes were obtained during cyclic voltammetric scanning of luteolin on the electrode, indicating that the electrochemical reaction of luteolin was realized. Under the optimized conditions measured in the experiment, it was found that the oxidation peak current of luteolin has a linear relationship with its concentration in the range of 1.0×10 ^-9 ~ 1.0×10 ^-6 mol/L, and the detection limit is 3.3×10 ^-10 mol/ L(3σ). This method was then used to determine the content of luteolin in Duyiwei capsules. The recovery rate was in the range of 95.6% to 104.8%, and the relative standard deviation (RSD) was lower than 3.43%. Wang Shanshan and others modified one of the isomers of the new C ₆₀ pyrrolidine derivative (FPD) on the surface of the glassy carbon electrode, and then studied the electrochemical behavior of luteolin on FPD/GCE through cyclic voltammetry. The results It was shown that the electrode has good electrocatalytic activity for the redox process of luteolin. Under optimal experimental conditions, within the concentration range of 2×10 ^-8 mol/L to 2×10 ^-5 mol/L, the oxidation peak current has a good linear relationship with the concentration of luteolin, and its linear equation is: : I _pc =-0.0103C-3.5955 (R ² =0.9901), the detection limit is 6.6×10 ^-9 mol/L. The results show that the prepared modified electrode has high sensitivity and good selectivity for the determination of luteolin.

Although there have been some relevant reports in the literature on the use of electrochemical methods for the detection of luteolin, the optimization of sensor preparation methods, improvement of sensor selectivity and sensitivity are still hot topics for scientific researchers.

Contents of the invention

Based on this, the present invention provides a controllable polymer film modified electrode to solve the technical problems in the prior art of poor selectivity and low sensitivity when detecting luteolin using electrochemical analysis methods.

The invention also provides a method for preparing a controllable polymer film modified electrode, which is simple, has strong operability, strong repeatability, and the thickness of the polymer film is controlled.

The invention also provides a detection method for luteolin, which is based on the above-mentioned controllable polymer film modified electrode. The detection method has good sensitivity, good selectivity and good reproducibility.

The technical solutions of the present invention to solve the above technical problems are as follows:

A controllable polymer film modified electrode, including:

glassy carbon electrode; and

A polymer film modified on the glassy carbon electrode, the polymer film is composed of a polymer of β-cyclodextrin and 1-hydroxyethyl-3-methylimidazole tetrafluoroborate.

A method for preparing a controllable polymer film modified electrode, including the following steps:

Prepare glassy carbon electrode;

Configure β-CD-IL solution: Mix β-cyclodextrin and IL solution to form β-CD-IL solution; wherein, the IL solution is composed of 1-hydroxyethyl-3-methylimidazole tetrafluoroborate and ultrapure water configuration;

Make a controllable polymer film modified electrode: put the glassy carbon electrode into the β-CD-IL solution, continuously scan with cyclic voltammetry in the potential range of 0 to 1.3V, take it out and rinse it with ultrapure water at room temperature. After drying, the controllable polymer film modified electrode can be obtained.

Preferably, the volume concentration of 1-hydroxyethyl-3-methylimidazole tetrafluoroborate in the IL solution is 1% to 7.5%.

Preferably, the volume concentration of 1-hydroxyethyl-3-methylimidazole tetrafluoroborate in the IL solution is 5%.

Preferably, the concentration of β-cyclodextrin in the β-CD-IL solution is 0.005 mol/L to 0.02 mol/L.

Preferably, the concentration of β-cyclodextrin in the β-CD-IL solution is 0.01 mol/L.

Preferably, in the step "Preparing a controllable polymer film modified electrode", the glassy carbon electrode is placed in the β-CD-IL solution, and the cyclic voltammetry is used to scan continuously for 10 to 25 times in the potential range of 0 to 1.3V. lock up.

A method for detecting luteolin, including the following steps:

Constructing an electrochemical sensor using a controllable polymer film modified electrode as a working electrode as described above;

Obtain the sample solution to be tested;

Construct an electrolyte system, which consists of ABS buffer and the sample solution to be tested;

Detect the concentration of luteolin.

Preferably, the pH value of the ABS buffer is 2-5.

Preferably, the "detecting the concentration of luteolin" includes the following steps: using square wave voltammetry at room temperature and enriching at open circuit potential for 30s to 120s.

Compared with the prior art, the present invention at least has the following advantages:

Using β-cyclodextrin and functionalized ionic liquid 1-hydroxyethyl-3-methylimidazole tetrafluoroborate as the polymer solution, the polymer film was modified on the glassy carbon electrode through continuous scanning by cyclic voltammetry, and the preparation The controllable polymer film modified electrode has a simple preparation method and good operability and repeatability. Based on the prepared controllable polymer film modified electrode, the electrochemical analysis method was used to detect the luteolin content in the traditional Chinese medicine samples. There was a linear relationship between the oxidation peak current and concentration of luteolin in two ranges, and the linear ranges were respectively are: 0.001～0.1μM (the linear equation is I(μA)=49.4479c(μM)+1.7985(r ² =0.9934) and 0.1～10μM (the linear equation is I(μA)=2.3152c(μM)+4.3166(r ² = 0.9965)), with a detection limit of 0.5nM (S/N = 3), high sensitivity and wide linear range. Moreover, 500 times of Na ⁺ , K ⁺ , Ca ²⁺ , Mg ²⁺ and 200 times glucose, uric acid, tyrosine, etc. have little effect on the peak current of 5 μM luteolin (relative standard deviation is less than ±5%), indicating that the method has good selectivity. At the same time, experiments also show that based on the prepared The controllable polymer film modified electrode uses electrochemical analysis methods to detect the luteolin content in Chinese medicine samples, and the repeatability and stability can be guaranteed.

Description of the drawings

Figure 1 shows the cyclic voltammograms of (a) GCE; (b) IL/GCE; (c) β-CD-IL/GCE in 5mM probe, scan speed: 50mVs ^-1 .

Figure 2 is the square wave voltammogram of 10 μM luteolin in (a) GCE; (b) IL/GCE; (c) β-CD-IL/GCE.

Figure 3 shows the effect of IL concentration in the polymerization solution on the oxidation peak current of 10 μM luteolin.

Figure 4 shows the effect of the number of polymerization circles on the peak current of 10 μM luteolin.

Figure 5 is the square wave voltammogram of 10 μM luteolin in 0.2M ABS solutions with different pH values (pH: a-f: 2, 3, 4, 5, 6, 7).

Figure 6 shows the effect of pH value on the peak current and peak potential of 10 μM luteolin.

Figure 7 Effect of enrichment time on oxidation peak current of 10 μM luteolin.

Figure 8 is the square wave voltammogram of luteolin at different concentrations (high concentration) (concentrations from bottom to top are: 0.1, 0.5, 1, 5, 10 μM luteolin, where the illustration is the peak current of luteolin vs. concentration linear relationship graph).

Figure 9 is the square wave voltammogram of luteolin at different concentrations (low concentration) (the concentrations from bottom to top are: 0.0005, 0.001, 0.005, 0.01, 0.05, 0.1 μM luteolin, where the illustration is luteolin Linear graph of peak current versus concentration).

Detailed ways

It should be noted that, as long as there is no conflict, the embodiments and features in the embodiments of the present invention can be combined with each other. The technical solutions of the present invention will be further described below with reference to the accompanying drawings of embodiments of the present invention. The present invention is not limited to the following specific implementations.

It should be understood that the same or similar reference numerals in the drawings of the embodiments correspond to the same or similar components. In the description of the present invention, it should be understood that if the terms "upper", "lower", "front", "back", "left", "right", "top", "bottom" etc. indicate the orientation Or the positional relationship is based on the orientation or positional relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. , therefore, the terms describing positional relationships in the drawings are only for illustrative purposes and cannot be understood as limitations of this patent. For those of ordinary skill in the art, the specific meanings of the above terms can be understood according to specific circumstances.

In a specific embodiment, a controllable polymer film modified electrode includes: a glassy carbon electrode; and a polymer film modified on the glassy carbon electrode, the polymer film is composed of β-cyclodextrin and 1- Polymer composition of hydroxyethyl-3-methylimidazole tetrafluoroborate.

In yet another specific embodiment, a method for preparing a controllable polymer film modified electrode includes the following steps:

S10. Prepare the glassy carbon electrode.

Specifically, before use, the glassy carbon electrode (GCE) is first polished to a mirror surface with 1.0 μm, 0.3 μm, and 0.05 μm aluminum oxide (Al ₂ O ₃ ) powder, and then ultrasonically cleaned with absolute ethanol and ultrapure water for 10 minutes. , dry at room temperature and set aside.

S20. Prepare β-CD-IL solution: Mix β-cyclodextrin and IL solution to form β-CD-IL solution; wherein, the IL solution is composed of 1-hydroxyethyl-3-methylimidazole tetrafluoroborate Salt and ultrapure water configuration.

Configure IL solution: Accurately measure the specified volume of 1-hydroxyethyl-3-methylimidazole tetrafluoroborate in a 100mL volumetric flask, dilute to 100mL with ultrapure water, shake well, and prepare IL with the specified volume concentration. The solution is ready for later use. Preferably, the volume concentration of the IL solution is 1% to 7.5%. For example, accurately measure 5 mL of 1-hydroxyethyl-3-methylimidazole tetrafluoroborate in a 100 mL volumetric flask, dilute to 100 mL with ultrapure water, shake well, and prepare an IL solution with a volume concentration of 5%. ,spare.

Prepare β-CD-IL solution: Accurately measure the predetermined mass of β-CD into a 10mL volumetric flask, dilute to 10mL with the specified concentration of IL solution, shake well, and set aside. Preferably, the concentration of β-cyclodextrin in the β-CD-IL solution is 0.005 mol/L to 0.02 mol/L. For example, accurately measure 0.1135g (0.0001mol) of β-CD into a 10mL volumetric flask, dilute to 10mL with 5% IL, shake well, and set aside.

S30. Make a controllable polymer film modified electrode: Put the glassy carbon electrode into the β-CD-IL solution, continuously scan with cyclic voltammetry in the potential range of 0 to 1.3V, and rinse with ultrapure water after taking it out. , the controllable polymer film modified electrode can be obtained after drying at room temperature.

Preferably, the glassy carbon electrode is placed in the β-CD-IL solution, and cyclic voltammetry is used to scan continuously for 10 to 25 cycles in the potential range of 0 to 1.3V. For example, the glassy carbon electrode is placed in a β-CD-IL solution, and cyclic voltammetry is used to continuously scan for 15 cycles in the potential range of 0 to 1.3V.

In yet another specific embodiment, a method for detecting luteolin includes the following steps:

T10. Construct an electrochemical sensor that uses the controllable polymer film-modified electrode as described above as a working electrode.

For example, the controllable polymer film modified electrode (diameter = 3.0 mm) prepared by the above process is used as the working electrode, the saturated calomel electrode (SCE) is used as the reference electrode, and the platinum wire electrode is used as the counter electrode to construct an electrochemical sensor.

T20. Obtain the sample solution to be tested.

If the sample to be tested is a liquid, it can be used directly as the sample solution to be tested, or after being diluted several times, it can be used as the sample solution to be tested.

If the sample to be tested is solid, the sample solution to be tested needs to be extracted from the sample to be tested. For example, if the sample to be tested is a unique-flavor capsule sample, take a few unique-flavor capsules, take out the powder and grind it into powder; accurately weigh it into a volumetric flask, dilute it with absolute ethanol, and then ultrasonically clean it for 30 minutes and then let it stand for 30 minutes. Leave for 5 to 10 minutes, take the supernatant, and prepare the sample solution to be tested for later use.

T30. Construct an electrolyte system, which consists of ABS buffer and the sample solution to be tested.

Preferably, an ABS buffer with a pH value of 2 to 5 is selected as the main electrolyte of the electrolyte system, and then an appropriate amount of the sample to be detected containing luteolin is added to the ABS buffer to obtain the electrolyte system.

T40. Detect the concentration of luteolin.

Based on the electrochemical sensor and the electrolyte system, at room temperature, square wave voltammetry is used to enrich the open circuit potential for 30s to 120s to obtain a voltammetry curve of 0.1 to 0.7V for luteolin. According to the oxidation peak The linear relationship between the current and the concentration of luteolin can directly or indirectly obtain the concentration of luteolin.

The technical solutions and technical effects of the present invention will be further described below through specific experimental procedures.

The sources, specifications and types of experimental instruments used in the following experimental procedures are as follows: luteolin (>98%, Shanghai Aladdin Biochemical Technology Co., Ltd.), β-cyclodextrin (Sinopharm Chemical Reagent Co., Ltd.) , Duyiwei Capsule (Kangxian Duyiwei Biopharmaceutical Company), ionic liquid (1-hydroxyethyl-3-methylimidazole tetrafluoroborate) (>99%, Lanzhou Zhongke Keteke Industry and Trade Co., Ltd.), Ethanol, sodium chloride, magnesium chloride, calcium chloride, glucose, uric acid, tyrosine, potassium chloride, acetic acid, sodium acetate, the above reagents are of analytical grade, among which acetic acid-sodium acetate buffer (ABS) is composed of CH ₃ COOH and CH ₃ COONa. All water used in the experiment was ultrapure water.

Electrochemical workstation: Shanghai Chenhua electrochemical workstation (CHI660E), in which chemically modified glassy carbon electrode (diameter = 3.0mm) is used as the working electrode, saturated calomel electrode (SCE) is used as the reference electrode, and platinum wire electrode is used as the counter electrode. IKA magnetic stirrer (KMO2).

Preparation of 10mM luteolin (Lu): Accurately weigh 0.00286g luteolin in a centrifuge tube, dilute to 1mL with absolute ethanol, shake well, and set aside. The preparation method for other concentrations of luteolin solutions is the same.

Preparation of 5% 1-hydroxyethyl-3-methylimidazole tetrafluoroborate ion (IL) liquid: accurately measure 5mL of 1-hydroxyethyl-3-methylimidazole tetrafluoroborate in a 100mL volumetric flask , use ultrapure water to adjust the volume to 100mL, shake well, and set aside. The preparation method for other concentrations of IL solutions is the same.

Preparation of β-CD-5% IL solution: Accurately measure 0.1135g β-CD in a 10mL volumetric flask, dilute to 10mL with 5% IL, shake well, and set aside. The preparation method for β-CD-IL solutions of other concentrations is the same. .

1. Preparation and modification of controllable polymer film modified electrodes

Pretreatment of glassy carbon electrode (GCE): Before use, GCE is first polished and polished to a mirror surface with 1.0 μm, 0.3 μm, and 0.05 μm aluminum oxide (Al ₂ O ₃ ) powder, and then ultrasonicated with absolute ethanol and ultrapure water. Wash for 10 minutes, dry at room temperature and set aside.

Preparation of controllable polymer film modified electrode (β-CD-IL/GCE): Put the polished electrode into 5mLβ-CD-5%IL, and use cyclic voltammetry (CV) in the potential range of 0 to 1.3V. ) Scan continuously for 15 circles, take it out and rinse it with ultrapure water to remove unpolymerized β-CD. After drying at room temperature, β-CD-IL/GCE can be obtained. For comparison, IL/GCE was prepared by polymerizing in 5% IL for 15 cycles using the same method, and dried at room temperature before use.

2. Experimental process

A three-electrode system was used to record the cyclic voltammogram curves of GCE, IL/GCE, and β-CD-IL/GCE in a 5mM probe solution in the potential range of -0.2 to 0.6V. Three electrodes, GCE, IL/GCE, and β-CD-IL/GCE, were used to perform square wave voltammetric scanning on luteolin in the potential range of 0.1 to 0.7 V to study the electrochemistry of luteolin on these three electrodes. Behavior.

3. Electrochemical characterization of modified electrodes

The cyclic voltammetry curves of three different electrodes (a) GCE; (b) IL/GCE; (c) β-CD-IL/GCE in 5mM probe solution were investigated. The results are shown in Figure 1. It can be seen from curve a that a pair of reversible redox peaks can be observed on GCE. The oxidation peak current (I _pa ) and reduction peak current (I _pc ) are 90.07 μA and 90.64 μA respectively, and the peak potential difference (△E _p ) is approximately 147mV, which is the electrochemical performance of the electrochemically active probe solution (Fe[(CN) ₆ ] ^3-/4- solution) on the electrode. A pair of reversible redox peaks also appeared on IL/GCE (curve b). The oxidation peak current (I _pa ) and reduction peak current (I _pc ) increased to 100.5 μA and 100.6 μA respectively, while the peak potential difference ( △E _p ) is reduced by 35mV. This phenomenon shows that the electropolymerization of functionalized ionic liquid IL with high conductivity on the electrode surface can promote the electron transfer rate of the probe and enhance its electrochemical response signal. However, the oxidation peak current (I _pa ) and reduction peak current (I _pc ) decreased on β-CD-IL/GCE (curve c), which were 85.11 μA and 88.16 μA respectively. This shows that polyβ-cyclodextrin with poor conductive properties has been successfully modified onto the electrode surface.

4. Electrochemical behavior of luteolin

The square wave voltammogram curves of 10 μM luteolin in ABS solution at pH 4.0 on three different electrodes were investigated. As can be seen from Figure 2, in the potential range of 0.1 to 0.7V, luteolin has an oxidation peak with a peak current of about 9.737μA at 0.396V on GCE (curve a); on IL/GCE (curve b), The peak current of luteolin increased significantly, with a peak current of approximately 24.56 μA; and on β-CD-IL/GCE (curve c), the peak current of luteolin further increased, with a peak current (34.67 μA) of approximately GCE 3.7 times. This is because the host-guest interaction of β-CD can effectively improve the adsorption performance of luteolin on the modified electrode, resulting in an increase in the adsorption amount of luteolin on the surface of the modified electrode. The results show that the prepared modified electrode has good electrocatalytic activity for luteolin.

5. Effect of ionic liquid concentration in polymerization solution on oxidation peak current

β-CD solutions were prepared using IL with concentrations of 0.5%, 1%, 2%, 5%, and 7.5% (V/V) as solvents respectively. The concentration of β-CD was 0.01 mol/L. Dip the polished GCE into the above polymerization solution for electropolymerization to prepare the corresponding polymer film modified electrode, and examine the electrochemical response of 10 μM luteolin on the modified electrode. As shown in Figure 3, as the concentration of ionic liquid in the polymerization solution changes, the oxidation peak current of luteolin also changes accordingly. When the concentration of ionic liquid in the polymerization solution is 5%, the polymer film electrode prepared is very sensitive to luteolin. element has a larger response current.

6. Influence of the number of aggregation circles

The thickness of the polymer film can be controlled by the number of polymerization turns. This experiment examined the effect of the number of polymerization turns on the peak current of luteolin. It can be seen from Figure 4 that when the number of polymerization cycles increases from 5 to 15 cycles, the oxidation peak current of luteolin increases with the increase in the number of scanning cycles. When the number of polymerization cycles is 15 cycles, the oxidation peak current reaches the maximum. value. When the number of polymerization turns further increases, the peak current decreases instead. This phenomenon may be caused by the following reasons: a polyβ-CD film with an appropriate thickness can effectively increase the adsorption capacity of the modified electrode for luteolin, thereby improving the electrode's response to luteolin. However, if the polymer film is too thick, it will Impeding the electron transfer rate causes a decrease in the response current.

7. Effect of pH value of acetate buffer on oxidation peak current and peak potential

The effects of ABS buffers of different pH on the determination of 10 μM luteolin were investigated in the range of pH 2 to 7. The results are shown in Figure 5 and Figure 6. When the pH value of the buffer changes, the peak current of the oxidation peak and the The peak potential also changes accordingly. When the pH is 4.0, the peak current of the oxidation peak reaches the maximum value (Figure 6). When the pH of the buffer increases, the oxidation peak potential of luteolin shifts negatively, indicating that protons participate in the reaction of the electrode. The oxidation peak potential and pH value show a good linear relationship, and the linear equation is: E(V)=-0.0514pH+0.6061 (r ² =0.9916). The slope of 51.4mVpH ^-1 is close to the theoretical value, indicating that luteolin undergoes an electrochemical reaction involving isoelectrons and other protons on the modified electrode.

8. Influence of enrichment potential and enrichment time

First, the enrichment time was fixed at 60 s, and the enrichment potential was changed in the range of -1.4 to 0.4 V to examine the effect of the enrichment potential on the luteolin oxidation peak current (results not shown). It was found that the maximum peak current appeared at the enrichment potential of -1.1V, which was 29.16μA. At the same time, the impact of open circuit potential enrichment on the detection of luteolin was examined. When the enrichment time is 60 s, the peak current of luteolin under open-circuit enrichment is about 32.08 μA, which is slightly larger than the peak current measured under enrichment potential.

At the open circuit potential, the enrichment time was changed in the range of 10 to 180s (10s, 30s, 60s, 90s, 120s, 150s, 180s). The results are shown in Figure 7. When the enrichment time is 60s, the concentration of luteolin The oxidation peak current is the largest. When the enrichment time is greater than 60 s, the oxidation peak current decreases as the enrichment time increases.

9. Reproducibility, stability and interference research

β-CD-IL/GCE was continuously scanned 6 times by square wave voltammetry in 10 μM luteolin, and the relative deviation of the peak current was 2.09%, which showed that β-CD-IL/GCE was in acetic acid at pH 4.0. Good reproducibility in salt buffer.

After leaving β-CD-IL/GCE at room temperature for a month, the measured current value in response to luteolin only dropped 3.8% from the initial current, indicating that the sensor has good stability.

The experiment also examined the effects of some common inorganic ions and organic substances on the response current of luteolin. Interference studies show that 500 times of Na ⁺ , K ⁺ , Ca ²⁺ , Mg ²⁺ and 200 times of glucose, uric acid, tyrosine, etc. have little effect on the peak current of 5 μM luteolin (relative standard deviation is less than ±5% ), indicating that this method has good selectivity.

10. Linear range and detection limit

Under the optimal experimental conditions, record the square wave voltammogram curves of different concentrations of luteolin on β-CD-IL/GCE, and draw a standard curve, as shown in Figure 8. As the concentration increases, the oxidation peak current of luteolin increases. It can be seen from the figure that there is a linear relationship between the peak current and concentration of luteolin in two ranges, and their linear ranges are: 0.001 ~ 0.1μM (the linear equation is I (μA) = 49.4479c (μM) + 1.7985 (r ² =0.9934) and 0.1~10μM (the linear equation is I(μA)=2.3152c(μM)+4.3166(r2=0.9965)). Under the condition of signal-to-noise ratio of 3, the detection limit is 0.5nM.

11. Actual sample testing

In order to verify the practical application capability of the modified electrode, this experiment measured luteolin in Duyiwei capsule samples. Take 6 unique capsules, take out the powder and grind it into powder; accurately weigh 1.5g into a 100mL volumetric flask, dilute it to 100mL with absolute ethanol, ultrasonically clean it for 30 minutes, then let it stand for 5 to 10 minutes, and take it out Prepare the sample solution from the clear liquid for later use. The results are shown in Table 1. The average content of luteolin in the sample solution was measured to be 0.58 μM, the spike recovery rate was 97.5%-99.5%, and the relative standard deviation was less than 4.17%. It shows that this method can be used for the detection of actual samples.

Table 1 β-CD-IL/GCE determination of luteolin in samples (n=3 ^a )

aThe average of three measurements

It can be seen from the above experimental process that the present invention prepared polymer film-controlled β-CD-IL/GCE through electrochemical polymerization, and studied the electrochemical behavior of luteolin on the modified electrode. Through polymerization conditions and detection The optimization of conditions established a method for the detection of luteolin. Poly-β-CD can effectively improve the adsorption capacity of the modified electrode for luteolin. At the same time, the highly conductive ionic liquid can promote the electron transfer of luteolin. The prepared electrode has good electrocatalytic activity for luteolin and can detect The limit reached 0.5nM. The sensor has good sensitivity and selectivity and can be used for the detection of luteolin in actual samples.

Obviously, the above-mentioned embodiments of the present invention are only examples to clearly illustrate the present invention, and are not intended to limit the implementation of the present invention. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. An exhaustive list of all implementations is neither necessary nor possible. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims (8)

1. A method for preparing a controllable polymer film modified electrode for detecting luteolin, which is characterized by comprising the following steps: Prepare glassy carbon electrode; Configure β-CD-IL solution: Mix β-cyclodextrin and IL solution to form β-CD-IL solution; wherein, the IL solution is composed of 1-hydroxyethyl-3 with a volume concentration of 1%-7.5% -Methylimidazole tetrafluoroborate and ultrapure water configuration; Make a controllable polymer film modified electrode: Put the glassy carbon electrode into the β-CD-IL solution, scan continuously for 10-25 circles using cyclic voltammetry in the potential range of 0~1.3 V, take it out and use ultrapure After being rinsed with water and dried at room temperature, the controllable polymer film modified electrode can be obtained. 2. The preparation method of a controllable polymer film modified electrode for detecting luteolin according to claim 1, characterized in that, in the IL solution, 1-hydroxyethyl-3-methylimidazole tetrafluoroethylene The volume concentration of borate is 5%. 3. The preparation method of a controllable polymer film modified electrode for detecting luteolin as claimed in claim 1, characterized in that, in the β-CD-IL solution, the concentration of β-cyclodextrin is 0.005 mol/L-0.02mol/L. 4. The preparation method of a controllable polymer film modified electrode for detecting luteolin as claimed in claim 1, characterized in that, in the β-CD-IL solution, the concentration of β-cyclodextrin is 0.01 mol/L. 5. A controllable polymer film modified electrode for detecting luteolin, characterized in that the preparation of a controllable polymer film modified electrode for detecting luteolin according to any one of claims 1 to 4 Prepared by methods including: glassy carbon electrode; and A polymer film modified on the glassy carbon electrode, the polymer film is composed of a polymer of β-cyclodextrin and 1-hydroxyethyl-3-methylimidazole tetrafluoroborate. 6. A method for detecting luteolin, characterized by comprising the following steps: Constructing an electrochemical sensor, the electrochemical sensor uses the controllable polymer film modified electrode for detecting luteolin as claimed in claim 5 as a working electrode; Obtain the sample solution to be tested; Construct an electrolyte system, which consists of ABS buffer and the sample solution to be tested; Detect the concentration of luteolin. 7. The method for detecting luteolin according to claim 6, wherein the pH value of the ABS buffer is 2-5. 8. The detection method of luteolin as claimed in claim 7, characterized in that, the detection of the concentration of luteolin includes the following steps: At room temperature, use square wave voltammetry and enrich at open circuit potential for 30s-120s.