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

Controllable polymer film modified electrode, preparation method thereof and luteolin detection method Download PDF

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CN114674888B
CN114674888B CN202210189154.4A CN202210189154A CN114674888B CN 114674888 B CN114674888 B CN 114674888B CN 202210189154 A CN202210189154 A CN 202210189154A CN 114674888 B CN114674888 B CN 114674888B
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luteolin
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CN114674888A (en
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刘新胜
李永红
张小敏
王燕
王坤
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Ningxia Medical University
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Abstract

The invention provides a controllable polymer film modified electrode, a preparation method thereof and a luteolin detection method, and belongs to the technical field of electrochemical analysis methods. The beta-cyclodextrin and the functionalized ionic liquid 1-hydroxyethyl-3-methylimidazole tetrafluoroborate are used as polymerization liquid, and the polymer film is modified on the glassy carbon electrode through continuous scanning by cyclic voltammetry to prepare the controllable polymer film modified electrode, so that the preparation method is simple and has good operability and repeatability. Based on the prepared controllable polymer film modified electrode, the luteolin content in the traditional Chinese medicine sample is detected by adopting an electrochemical analysis method, so that the electrode has higher sensitivity, better selectivity and repeatability and stability.

Description

Controllable polymer film modified electrode, preparation method thereof and luteolin detection method
Technical Field
The invention belongs to the technical field of electrochemical analysis methods, and particularly relates to a controllable polymer film modified electrode, a preparation method thereof and a luteolin detection method.
Background
Luteolin is an important natural antioxidant, and has chemical name of 3 ', 4', 5, 7-tetrahydroxy flavone and molecular formula of C 15 H 10 O 6 Having C 6 -C 3 -C 6 The structure contains (A, B) two benzene rings, an oxygen-containing C ring and a C2-C3 double bond, and has weak acidity. Luteolin is commonly found in celery, coriander, green pepper, chrysanthemum, carrot, perilla leaf and other plants, and has various biological activities and pharmacological actions, such as antibiosis, anti-inflammation, antioxidation, cataract prevention and cardiovascular protection. Recent studies have also shown that luteolin can treat swelling by inhibiting the activity of certain kinases in the cell and blocking the cell cycleThe proliferation of tumor cells can be inhibited, and in addition, luteolin can induce apoptosis of tumor cells. In the traditional Chinese medicine, luteolin-rich plants are used for treating diseases such as hypertension, inflammation, cancer and the like.
Various techniques including Thin Layer Chromatography (TLC), high Performance Liquid Chromatography (HPLC), ultraviolet spectrophotometry (UV), and Capillary Electrophoresis (CE) are applied to the detection of luteolin. Although the techniques have the advantages of higher sensitivity and better accuracy, the techniques have the disadvantages of time consumption, complex operation, high cost and the like. The electrochemical technology has the characteristics of simplicity, rapidness, sensitivity, lower instrument cost and the like, and is widely focused by the scientific community. At present, various electrochemical analysis methods for detecting luteolin have been proposed and proved to be applicable to trace analysis of luteolin. For example, shang Yonghui et al studied luteolin in N-butylpyridinium triflate ([ BP) using N-butylpyridinium triflate ionic liquids to prepare modified carbon paste electrodes y ]OTF) modifies the electrochemical behaviour on the carbon paste electrode. Experiments find that in a citric acid-sodium citrate buffer system with ph=3.0, luteolin produced a pair of distinct redox peaks at 0.6221V and 0.4267V, and the current signal was 2.06 times and 5.8 times that of the bare electrode, respectively, indicating [ BP y ]OTF has certain catalytic sensitization effect to luteolin, and on the basis, interaction between luteolin and bovine serum albumin is studied. Wen Jiaoyong et al prepared an ionic liquid modified carbon paste electrode (CILE) using n-hexylpyridine hexafluorophosphate as a binder, modified electrodes (Pd-GR/CILE) were prepared by modifying palladium-graphene (Pd-GR) composites on the surface of the CILE, and then the electrochemical behavior of luteolin on the modified electrodes was studied using cyclic voltammetry and Differential Pulse Voltammetry (DPV). The results show that the luteolin in phosphate buffer solution with pH of 1.5 circularly scans the electrode by volt-ampere to obtain a pair of oxidation-reduction peaks with good peak shape, which indicates that the electrochemical reaction of the luteolin is realized. Under the optimized conditions measured by experiments, the oxidation peak current and the concentration of luteolin are found to be 1.0x10 -9 ～1.0×10 -6 The linear relation exists in mol/L, and the detection limit is 3.3X10 -10 mol/L(3σ)。Then the method is used for measuring the content of luteolin in the lamiophlomis rotata capsules, and the recovery rate is detected to be within the range of 95.6-104.8 percent, and the Relative Standard Deviation (RSD) is lower than 3.43 percent. Wang Shanshan et al will be novel C 60 One of isomers of a pyrrolidine derivative (FPD) is modified on the surface of a glassy carbon electrode, and then electrochemical behaviors of luteolin on the FPD/GCE are studied through a cyclic voltammetry, so that the electrode has good electrocatalytic activity on the oxidation-reduction process of the luteolin. And under the optimal experimental conditions, the temperature is 2 multiplied by 10 -8 mol/L～2×10 -5 In the range of the concentration interval of mol/L, the oxidation peak current and the concentration of luteolin have good linear relation, and the linear equation is as follows: i pc ＝-0.0103C-3.5955(R 2 = 0.9901), the detection limit is 6.6x10 -9 mol/L. The result shows that the prepared modified electrode has higher sensitivity and good selectivity to the measurement of luteolin.
Although some reports exist in the literature of electrochemical methods for luteolin detection, optimization of the preparation method of the sensor, improvement of the selectivity of the sensor and improvement of the sensitivity remain hot spots for research by researchers.
Disclosure of Invention
Based on the above, the invention provides a controllable polymer film modified electrode to solve the technical problems of poor selectivity and low sensitivity in the detection of luteolin by using an electrochemical analysis method in the prior art.
The invention also provides a preparation method of the controllable polymer film modified electrode, which is simple, strong in operability and repeatability and controlled in polymer film thickness.
The invention also provides a method for detecting luteolin, which is based on the controllable polymer film modified electrode, has good sensitivity, better selectivity and better reproducibility.
The technical scheme for solving the technical problems is as follows:
a controllable polymer film modified electrode comprising:
a glassy carbon electrode; and
a polymer film modified on the glassy carbon electrode, the polymer film consisting of a polymer of beta-cyclodextrin and 1-hydroxyethyl-3-methylimidazole tetrafluoroborate.
The preparation method of the controllable polymer film modified electrode comprises the following steps:
preparing a glassy carbon electrode;
preparing beta-CD-IL solution: mixing beta-cyclodextrin and an IL solution to form a beta-CD-IL solution; wherein the IL solution is prepared from 1-hydroxyethyl-3-methylimidazole tetrafluoroborate and ultrapure water;
manufacturing a controllable polymer film modified electrode: and (3) placing the glassy carbon electrode into a beta-CD-IL solution, continuously scanning by using a cyclic voltammetry in a potential range of 0-1.3V, taking out, flushing with ultrapure water, and drying at room temperature to obtain the controllable polymer film modified electrode.
Preferably, the volume concentration of the 1-hydroxyethyl-3-methylimidazole tetrafluoroborate in the IL solution is 1-7.5%.
Preferably, the IL solution has a volume concentration of 5% 1-hydroxyethyl-3-methylimidazole tetrafluoroborate.
Preferably, the concentration of the beta-cyclodextrin in the beta-CD-IL solution is 0.005mol/L to 0.02mol/L.
Preferably, the concentration of beta-cyclodextrin in the beta-CD-IL solution is 0.01mol/L.
Preferably, in the step of manufacturing the controllable polymer film modified electrode, the glassy carbon electrode is placed in a beta-CD-IL solution and continuously scanned for 10-25 circles by cyclic voltammetry in a potential range of 0-1.3V.
A method for detecting luteolin comprises the following steps:
constructing an electrochemical sensor, wherein the electrochemical sensor takes the controllable polymer film modified electrode as a working electrode;
obtaining a sample solution to be detected;
constructing an electrolyte system, wherein the electrolyte system consists of an ABS buffer solution and the sample solution to be detected;
the concentration of luteolin was measured.
Preferably, the pH value of the ABS buffer solution is 2-5.
Preferably, the "detecting the concentration of luteolin" comprises the following steps: at room temperature, adopting square wave voltammetry to enrich for 30-120 s at open circuit potential.
Compared with the prior art, the invention has at least the following advantages:
the beta-cyclodextrin and the functionalized ionic liquid 1-hydroxyethyl-3-methylimidazole tetrafluoroborate are used as polymerization liquid, and the polymer film is modified on the glassy carbon electrode through continuous scanning by cyclic voltammetry to prepare the controllable polymer film modified electrode, so that the preparation method is simple and has good operability and repeatability. Based on the prepared controllable polymer film modified electrode, detecting the content of luteolin in a traditional Chinese medicine sample by adopting an electrochemical analysis method, wherein the oxidation peak current and the concentration of the luteolin have linear relations in two ranges, and the linear ranges are respectively as follows: 0.001-0.1 mu M (linear equation is I (mu A) = 49.4479c (mu M) +1.7985 (r) 2 0.9934) and 0.1 to 10 μm (linear equation I (μa) = 2.3152c (μm) +4.3166 (r) 2 =0.9965), the detection limit is 0.5nM (S/n=3), with higher sensitivity and wider linear range. Also, 500 times of Na + 、K + 、Ca 2+ 、Mg 2+ And 200 times of glucose, uric acid, tyrosine and the like have small influence on peak current of 5 mu M luteolin (the relative standard deviation is less than +/-5%), which shows that the method has better selectivity. Meanwhile, experiments also show that the method for detecting the luteolin content in the traditional Chinese medicine sample by adopting an electrochemical analysis method based on the prepared controllable polymer film modified electrode can ensure the repeatability and stability.
Drawings
FIG. 1 is (a) GCE; (b) IL/GCE; (c) Cyclic voltammogram of β -CD-IL/GCE in 5mM probe, scan rate: 50mV s -1 。
FIG. 2 is a graph of 10. Mu.M luteolin in (a) GCE; (b) IL/GCE; (c) square wave voltammogram of beta-CD-IL/GCE.
FIG. 3 is a graph showing the effect of IL concentration in a polymer solution on peak current of 10. Mu.M luteolin oxidation.
FIG. 4 is the effect of the number of polymerization cycles on the peak current of 10. Mu.M luteolin.
FIG. 5 is a square wave voltammogram of 10. Mu.M luteolin in 0.2M ABS solutions at various pH values (pH: a-f:2,3,4,5,6, 7).
FIG. 6 is a graph showing the effect of pH on peak current and peak potential of 10. Mu.M luteolin.
FIG. 7 effect of enrichment time on peak current of 10. Mu.M luteolin oxidation.
FIG. 8 is a square wave voltammogram of luteolin at various concentrations (high concentrations) (concentrations from bottom to top: 0.1,0.5,1,5, 10. Mu.M luteolin, respectively), wherein the inset is a plot of the peak current versus concentration of luteolin.
FIG. 9 is a square wave voltammogram of luteolin at various concentrations (low concentration) (concentration: 0.0005,0.001,0.005,0.01,0.05,0.1. Mu.M luteolin from bottom to top, respectively), wherein the inset is a plot of the peak current versus concentration of luteolin.
Detailed Description
It should be noted that, without conflict, the embodiments of the present invention and features of the embodiments may be combined with each other. The technical solution of the present invention will be further described below with reference to the accompanying drawings of the embodiments of the present invention, and the present invention is not limited to the following specific embodiments.
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 there are terms such as "upper", "lower", "front", "rear", "left", "right", "top", "bottom", etc., that indicate an azimuth or a positional relationship based on the directions or the positional relationships shown in the drawings, it is only for convenience of describing the present invention and simplifying the description, but not for indicating or suggesting that the apparatus or element to be referred to must have a specific azimuth, be constructed and operated in a specific azimuth, so that the terms describing the positional relationship in the drawings are merely for exemplary illustration and should not be construed as limitations of the present patent, and that the specific meanings of the terms described above may be understood by those skilled in the art according to specific circumstances.
In one embodiment, a controllable polymer film modified electrode comprises: a glassy carbon electrode; and a polymer film modified on the glassy carbon electrode, the polymer film being composed of a polymer of beta-cyclodextrin and 1-hydroxyethyl-3-methylimidazolium tetrafluoroborate.
In yet another embodiment, a method for preparing a controllable polymer film modified electrode comprises the steps of:
s10, preparing a glassy carbon electrode.
Specifically, the Glassy Carbon Electrode (GCE) was first treated with 1.0 μm, 0.3 μm, 0.05 μm alumina (Al) 2 O 3 ) Grinding and polishing the powder into a mirror surface, then ultrasonically cleaning the mirror surface by using absolute ethyl alcohol and ultrapure water for 10min, and airing the mirror surface at room temperature for standby.
S20, preparing beta-CD-IL solution: mixing beta-cyclodextrin and an IL solution to form a beta-CD-IL solution; wherein the IL solution is prepared from 1-hydroxyethyl-3-methylimidazole tetrafluoroborate and ultrapure water.
Preparing an IL solution: accurately measuring a specified volume of 1-hydroxyethyl-3-methylimidazole tetrafluoroborate in a 100mL volumetric flask, using ultrapure water to fix the volume to 100mL, shaking uniformly, and preparing an IL solution with a specified volume concentration for later use. Preferably, the IL solution has a volume concentration of 1% to 7.5%. For example, accurately measuring 5mL of 1-hydroxyethyl-3-methylimidazole tetrafluoroborate in a 100mL volumetric flask, using ultrapure water to fix the volume to 100mL, shaking uniformly, and preparing an IL solution with a volume concentration of 5% for later use.
Preparing beta-CD-IL solution: accurately measuring beta-CD with preset mass in a 10mL volumetric flask, and fixing the volume to 10mL by using IL solution with specified concentration, and shaking uniformly for later use. Preferably, the concentration of the beta-cyclodextrin in the beta-CD-IL solution is 0.005mol/L to 0.02mol/L. For example, 0.1135g (0.0001 mol) of beta-CD was accurately measured in a 10mL volumetric flask, and the volume was adjusted to 10mL with 5% IL, and shaken well for use.
S30, manufacturing a controllable polymer film modified electrode: and (3) placing the glassy carbon electrode into a beta-CD-IL solution, continuously scanning by using a cyclic voltammetry in a potential range of 0-1.3V, taking out, flushing with ultrapure water, and drying at room temperature to obtain the controllable polymer film modified electrode.
Preferably, the glassy carbon electrode is placed in a beta-CD-IL solution and scanned continuously for 10-25 circles by cyclic voltammetry in the potential range of 0-1.3V. For example, the glassy carbon electrode is placed in a beta-CD-IL solution and scanned continuously for 15 cycles by cyclic voltammetry at a potential in the range of 0 to 1.3V.
In another embodiment, a method for detecting luteolin comprises the following steps:
t10. an electrochemical sensor is constructed with the controllable polymer film modified electrode as described above as a working electrode.
For example, an electrochemical sensor was constructed with the controllable polymer film modified electrode (diameter=3.0 mm) prepared by the above procedure as a working electrode, a Saturated Calomel Electrode (SCE) as a reference electrode, and a platinum wire electrode as a counter electrode.
T20. obtaining the sample solution to be detected.
If the sample to be detected is liquid, the sample is directly used as the sample solution to be detected, or the sample solution to be detected is obtained after dilution by a plurality of times.
If the sample to be detected is solid, the sample solution to be detected needs to be extracted from the sample to be detected. For example, taking several capsules of radix Lamiophlomidis Rotatae, taking out the powder, placing in the middle, and grinding into powder; accurately weighing the sample solution in a volumetric flask, using absolute ethyl alcohol to fix the volume, ultrasonically cleaning the sample solution for 30min, standing the sample solution for 5 to 10min, and taking the supernatant to prepare the sample solution to be detected for later use.
T30. constructing an electrolyte system, wherein the electrolyte system consists of an ABS buffer solution and the sample solution to be detected.
Preferably, an ABS buffer solution with the pH value of 2-5 is selected as a main electrolyte of the electrolyte system, and then a proper amount of luteolin-containing sample to be detected is added into the ABS buffer solution, so that the electrolyte system is obtained.
T40. the concentration of luteolin was measured.
Based on the electrochemical sensor and the electrolyte system, a square wave voltammetry is adopted at room temperature, enrichment is carried out at an open circuit potential for 30s-120s, a voltammetry curve of 0.1-0.7V of luteolin is obtained, and the concentration of luteolin is directly or indirectly obtained according to the linear relation between the oxidation peak current and the concentration of luteolin.
The technical scheme and the technical effects of the invention are further described through a specific experimental process.
The sources, specifications and types of experimental instruments used in the following experimental procedures are as follows: luteolin>98%, shanghai Ala Latin Biochemical technology Co., ltd.), beta-cyclodextrin (national medicine group chemical reagent Co., ltd.), lamiophlomis rotata capsule (Kangcounty lamiophlomis rotata biological pharmaceutical Co., ltd.), ionic liquid (1-hydroxyethyl-3-methylimidazole tetrafluoroborate)>99% of Kate Corp., lanzhou, ethanol, sodium chloride, magnesium chloride, calcium chloride, glucose, uric acid, tyrosine, potassium chloride, acetic acid, sodium acetate, which are all analytically pure, wherein acetic acid-sodium Acetate Buffer (ABS) is prepared from CH 3 COOH and CH 3 COONa was prepared and all water used in the experiment was ultrapure water.
Electrochemical workstation: shanghai Chen Hua electrochemical workstation (CHI 660E) wherein a chemically modified glassy carbon electrode (diameter=3.0 mm) was used as the working electrode, a Saturated Calomel Electrode (SCE) was used as the reference electrode, and a platinum wire electrode was used as the counter electrode. IKA magnetic stirrer (KMO 2).
Configuration of 10mM luteolin (Lu): accurately weighing 0.00286g of luteolin in a centrifuge tube, and fixing the volume to 1mL by using absolute ethyl alcohol, shaking uniformly for standby, wherein the preparation method of luteolin solution with other concentrations is the same.
Preparation of 5%1-hydroxyethyl-3-methylimidazolium tetrafluoroborate Ion (IL) liquid: accurately measuring 5mL of 1-hydroxyethyl-3-methylimidazole tetrafluoroborate in a 100mL volumetric flask, using ultrapure water to fix the volume to 100mL, shaking uniformly for later use, and preparing IL solutions with other concentrations by the same method.
beta-CD-5% IL solution preparation: accurately weighing 0.1135g of beta-CD, putting the beta-CD into a 10mL volumetric flask, fixing the volume to 10mL by using 5% IL, shaking uniformly for standby, and preparing beta-CD-IL solutions with other concentrations by the same method.
1. Preparation and modification of controllable polymer film modified electrode
Pretreatment of Glassy Carbon Electrode (GCE): GCE is first treated with 1.0 μm, 0.3 μm, 0.05 μm alumina (Al) 2 O 3 ) Grinding and polishing the powder into a mirror surface, then ultrasonically cleaning the mirror surface by using absolute ethyl alcohol and ultrapure water for 10min, and airing the mirror surface at room temperature for standby.
Preparation of a controllable Polymer film modified electrode (beta-CD-IL/GCE): the polished electrode is placed into 5mL beta-CD-5% IL, and is continuously scanned for 15 circles by Cyclic Voltammetry (CV) in the potential range of 0-1.3V, and the electrode is taken out, washed by ultrapure water to remove unpolymerized beta-CD, and dried at room temperature to obtain the beta-CD-IL/GCE. For comparison, IL/GCE was prepared by polymerizing 15 loops in 5% IL by the same method and dried at room temperature for use.
2. Experimental procedure
The cyclic voltammograms of the three electrodes GCE, IL/GCE, beta-CD-IL/GCE in 5mM probe solution were recorded using a three electrode system over a potential range of-0.2 to 0.6V. Square wave voltammetric scanning is carried out on luteolin by using three electrodes of GCE, IL/GCE and beta-CD-IL/GCE in the potential range of 0.1-0.7V, and the electrochemical behaviors of the luteolin on the three electrodes are studied.
3. Electrochemical characterization of modified electrodes
Three different electrodes (a) GCE were examined; (b) IL/GCE; (c) The cyclic voltammogram of β -CD-IL/GCE in 5mM probe solution is shown in FIG. 1. From curve a, a pair of reversible redox peaks was observed on GCE, whose oxidation peak currents (I pa ) And reduction peak current (I) pc ) 90.07 μA and 90.64 μA respectively, and peak potential difference (. DELTA.E) p ) About 147mV, which is an electrochemically active probe solution (Fe [ (CN) 6 ] 3-/4- Solution) on the electrode. A pair of reversible redox peaks likewise appear on IL/GCE (curve b), the oxidation peak current (I pa ) And reduction peak current (I) pc ) Respectively 100.5 μA and 100.6 μA, and peak potential difference (. DELTA.E) p ) 35mV was reduced. This phenomenon indicates that the electropolymerization of the functionalized ionic liquid IL with high conductivity on the electrode surface can promote the electron transfer rate of the probe and make the probe electrochemically soundThe signal should be enhanced. But on the beta-CD-IL/GCE (curve c) the peak oxidation current (I pa ) And reduction peak current (I) pc ) But reduced by 85.11 and 88.16 mua, respectively. This suggests that the less conductive poly-beta-cyclodextrin has been successfully modified to the electrode surface.
4. Electrochemical behavior of luteolin
Square wave voltammograms of 10 μm luteolin on three different electrodes in ABS solution at pH 4.0 were examined. As can be seen from FIG. 2, in the potential range of 0.1 to 0.7V, luteolin has an oxidation peak with a peak current of about 9.737. Mu.A at 0.396V on GCE (curve a); on IL/GCE (curve b), luteolin peak current increased significantly, with peak current of about 24.56. Mu.A; whereas on beta-CD-IL/GCE (curve c), the peak current of luteolin was further increased, with a peak current (34.67. Mu.A) of about 3.7 times that on GCE. This is because the interaction of the host and guest of the beta-CD can effectively improve the adsorption performance of the modified electrode to the luteolin, so that the adsorption amount of the luteolin on the surface of the modified electrode is increased. The result shows that the prepared modified electrode has better electrocatalytic activity to luteolin.
5. Influence of the concentration of the Ionic liquid in the polymerization liquid on the Oxidation Peak Current
beta-CD solutions were prepared using IL at concentrations of 0.5%, 1%, 2%, 5%, 7.5% (V/V) as solvent, respectively, and beta-CD at a concentration of 0.01mol/L. Immersing the polished GCE into the polymerization solution for electropolymerization, preparing a corresponding polymer film modified electrode, and examining the electrochemical response of 10 mu M luteolin on the modified electrode. As shown in FIG. 3, the oxidation peak current of luteolin changes along with the change of the concentration of the ionic liquid in the polymer liquid, and the prepared polymer film electrode has larger response current to the luteolin when the concentration of the ionic liquid in the polymer liquid is 5%.
6. Effect of the number of polymerization turns
The thickness of the polymer film can be controlled by the polymerization circle number, and the influence of the polymerization circle number on the peak current of luteolin is examined in the experiment. As can be seen from fig. 4, the peak current of luteolin increases with the number of scanning turns as the number of polymerization turns increases from 5 to 15, and reaches a maximum value as the number of polymerization turns is 15. And as the number of polymerization turns further increases, the peak current decreases instead. This phenomenon may be caused by: the poly beta-CD film with proper thickness can effectively increase the adsorption capacity of the modified electrode to luteolin, so that the response capability of the electrode to luteolin is improved, however, the too thick polymer film can prevent the transfer rate of electrons to cause the reduction of response current.
7. Effect of acetate buffer pH on oxidation Peak Current and Peak potential
The effect of different pH ABS buffers on the measurement of 10. Mu.M luteolin was examined in the pH range of 2 to 7, and as shown in FIGS. 5 and 6, the peak current and peak potential of the oxidation peak were changed when the pH of the buffer was changed. At a pH of 4.0, the peak current of the oxidation peak reached a maximum value (FIG. 6). When the pH of the buffer solution is increased, the oxidation peak potential of luteolin is shifted negatively, which indicates that protons participate in the reaction of the electrode. The oxidation peak potential and the pH value show good linear relation, and the linear equation is as follows: e (V) = -0.0514ph+0.6061 (r) 2 = 0.9916). Slope 51.4mVPH -1 The theoretical value is close to the theoretical value, which indicates that luteolin generates an electrochemical reaction participated by protons such as isoelectric electrons on the modified electrode.
8. Influence of enrichment potential and enrichment time
The enrichment time was fixed at 60s, the enrichment potential was varied in the range of-1.4 to 0.4V, and the effect of the enrichment potential on the luteolin oxidation peak current was examined (results not shown). As a result, it was found that the maximum peak current at the enrichment potential of-1.1V was 29.16. Mu.A. Meanwhile, the influence on luteolin detection under open circuit potential enrichment is examined. At an enrichment time of 60s, the peak current of luteolin under open-circuit enrichment was about 32.08 μA, slightly greater than the peak current measured at the enrichment potential.
The enrichment time (10 s, 30s, 60s, 90s, 120s, 150s, 180 s) was varied in the range of 10 to 180s at the open circuit potential, and as a result, as shown in FIG. 7, the oxidation peak current of luteolin was maximized when the enrichment time was 60 s. When the enrichment time is longer than 60s, the oxidation peak current is reduced with the increase of the enrichment time.
9. Reproducibility, stability and interference studies
The beta-CD-IL/GCE was scanned 6 times continuously in 10. Mu.M luteolin by square wave voltammetry with a relative peak current deviation of 2.09%, thus demonstrating the good reproducibility of the beta-CD-IL/GCE in acetate buffer at pH 4.0.
After the beta-CD-IL/GCE is placed at room temperature for one month, the response current value of the beta-CD-IL/GCE to luteolin is measured to be reduced by 3.8% compared with the initial current, which shows that the sensor has good stability.
Experiments also examined the influence of some common inorganic ions and organic matters on luteolin response current. Interference studies showed 500 times Na + 、K + 、Ca 2+ 、Mg 2+ And 200 times of glucose, uric acid, tyrosine and the like have small influence on peak current of 5 mu M luteolin (the relative standard deviation is less than +/-5%), which shows that the method has better selectivity.
10. Linear range and detection limit
Under the optimal experimental conditions, square wave voltammograms of luteolin on beta-CD-IL/GCE were recorded at different concentrations and standard curves were plotted as shown in FIG. 8. As the concentration increases, the peak current of luteolin oxidation increases. From the graph, the peak current and the concentration of luteolin have linear relations in two ranges, and the linear ranges are respectively: 0.001-0.1 mu M (linear equation is I (mu A) = 49.4479c (mu M) +1.7985 (r) 2 = 0.9934) and 0.1 to 10 μm (linear equation I (μa) = 2.3152c (μm) +4.3166 (r2=0.9965)), with a signal-to-noise ratio of 3, the detection limit is 0.5nM.
11. Actual sample detection
In order to verify the practical application capability of the modified electrode, the test is carried out on luteolin in the lamiophlomis rotata capsule sample. Taking 6-granule lamiophlomis rotata capsules, taking out and placing the medicinal powder, and grinding into powder; accurately weighing 1.5g in a 100mL volumetric flask, using absolute ethyl alcohol to fix the volume to 100mL, ultrasonically cleaning for 30min, standing for 5-10 min, and taking supernatant to prepare a sample solution for later use. The results are shown in Table 1, the average content of luteolin in the sample solution is measured to be 0.58 mu M, the standard recovery rate is 97.5% -99.5%, and the relative standard deviation is smaller than 4.17%. It is explained that the method can be used for detection of an actual sample.
Table 1 beta-CD-IL/GCE assay of luteolin in samples (n=3 a )
a average of three measurements
According to the experimental process, the polymer film-controllable beta-CD-IL/GCE is prepared by an electrochemical polymerization method, the electrochemical behavior of luteolin on the modified electrode is researched, and a method for detecting the luteolin is established by optimizing polymerization conditions and detection conditions. The poly beta-CD can effectively improve the adsorption capacity of the modified electrode to luteolin, meanwhile, the highly conductive ionic liquid can promote electron transfer of the luteolin, and the prepared electrode has good electrocatalytic activity to the luteolin, and the detection limit reaches 0.5nM. The sensor has better sensitivity and selectivity, and can be used for detecting luteolin in actual samples.
It is to be understood that the above examples of the present invention are provided by way of illustration only and not by way of limitation of the embodiments of the present invention. Other variations or modifications of the above teachings will be apparent to those of ordinary skill in the art. It is not necessary here nor is it exhaustive of all embodiments. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (8)

1. The preparation method of the controllable polymer film modified electrode for detecting luteolin is characterized by comprising the following steps of:
preparing a glassy carbon electrode;
preparing beta-CD-IL solution: mixing beta-cyclodextrin and an IL solution to form a beta-CD-IL solution; wherein the IL solution is prepared from 1-hydroxyethyl-3-methylimidazole tetrafluoroborate with the volume concentration of 1-7.5% and ultrapure water;
manufacturing a controllable polymer film modified electrode: and (3) placing the glassy carbon electrode into a beta-CD-IL solution, continuously scanning for 10-25 circles by using a cyclic voltammetry within a potential range of 0-1.3V, taking out, flushing with ultrapure water, and drying at room temperature to obtain the controllable polymer film modified electrode.
2. The method of preparing a controllable polymer film modified electrode for detecting luteolin according to claim 1, wherein the volume concentration of 1-hydroxyethyl-3-methylimidazolium tetrafluoroborate in the IL solution is 5%.
3. The method for preparing a controllable polymer film modified electrode for detecting luteolin according to claim 1, wherein the concentration of beta-cyclodextrin in the beta-CD-IL solution is 0.005mol/L to 0.02mol/L.
4. The method for preparing a controllable polymer film modified electrode for detecting luteolin according to claim 1, wherein the concentration of beta-cyclodextrin in the beta-CD-IL solution is 0.01mol/L.
5. A controllable polymer film modified electrode for detecting luteolin, characterized by being produced by the method for producing a controllable polymer film modified electrode for detecting luteolin according to any one of claims 1 to 4, comprising:
a glassy carbon electrode; and
a polymer film modified on the glassy carbon electrode, the polymer film consisting of a polymer of beta-cyclodextrin and 1-hydroxyethyl-3-methylimidazole tetrafluoroborate.
6. The method for detecting luteolin is characterized by comprising the following steps:
constructing an electrochemical sensor, wherein the electrochemical sensor takes the controllable polymer film modified electrode for detecting luteolin as claimed in claim 5 as a working electrode;
obtaining a sample solution to be detected;
constructing an electrolyte system, wherein the electrolyte system consists of an ABS buffer solution and the sample solution to be detected;
the concentration of luteolin was measured.
7. The method for detecting luteolin according to claim 6, wherein the pH value of the ABS buffer solution is 2-5.
8. A method for detecting luteolin as defined in claim 7, wherein said detecting the concentration of luteolin comprises the steps of:
the enrichment was performed at room temperature using square wave voltammetry for 30s-120s at open circuit potential.
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