CN114839248A - Method for detecting imidacloprid by electrochemical sensor - Google Patents
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- YWTYJOPNNQFBPC-UHFFFAOYSA-N imidacloprid Chemical compound [O-][N+](=O)\N=C1/NCCN1CC1=CC=C(Cl)N=C1 YWTYJOPNNQFBPC-UHFFFAOYSA-N 0.000 title claims abstract description 123
- 239000005906 Imidacloprid Substances 0.000 title claims abstract description 119
- 229940056881 imidacloprid Drugs 0.000 title claims abstract description 119
- 238000000034 method Methods 0.000 title claims abstract description 71
- WHGYBXFWUBPSRW-FOUAGVGXSA-N beta-cyclodextrin Chemical compound OC[C@H]([C@H]([C@@H]([C@H]1O)O)O[C@H]2O[C@@H]([C@@H](O[C@H]3O[C@H](CO)[C@H]([C@@H]([C@H]3O)O)O[C@H]3O[C@H](CO)[C@H]([C@@H]([C@H]3O)O)O[C@H]3O[C@H](CO)[C@H]([C@@H]([C@H]3O)O)O[C@H]3O[C@H](CO)[C@H]([C@@H]([C@H]3O)O)O3)[C@H](O)[C@H]2O)CO)O[C@@H]1O[C@H]1[C@H](O)[C@@H](O)[C@@H]3O[C@@H]1CO WHGYBXFWUBPSRW-FOUAGVGXSA-N 0.000 claims abstract description 88
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Abstract
The invention belongs to the technical field of electrochemical detection, and discloses a method for detecting imidacloprid by an electrochemical sensor. The detection limit of the invention reaches 1.33 multiplied by 10 ‑10 And mol/L is applied to detection of actual samples, the recovery rate is 92.0-110.0%, and the sensitivity of the sensor is greatly improved. The invention introduces a multiple amplification strategy in the process of preparing the modified electrode sensor. Due to GO-The sensitivity of the sensor applied to imidacloprid residue detection in agricultural product samples such as bananas is effectively improved by adopting AuNPs/beta-CD multiple amplification strategy.
Description
Technical Field
The invention belongs to the technical field of electrochemical detection, and particularly relates to a method for detecting imidacloprid by an electrochemical sensor.
Background
Currently, imidacloprid is a neonicotinoid insecticide that exerts its effects as an insect neurotoxin. The imidacloprid is widely applied to agricultural planting, and the residue of the imidacloprid in agricultural products is common. Researches show that the residue of imidacloprid in agricultural products and production area environment is a potential hazard to human health, and has important significance for monitoring imidacloprid residue. The conventional imidacloprid detection method generally comprises a liquid chromatography method, a liquid chromatography-mass spectrometry combined method, a colorimetric method, a fluorescence method and the like. But the chromatography has high sensitivity and good selectivity, but needs large-scale equipment and has complex pretreatment, so the method is not suitable for quick detection on site; colorimetry and fluorescence are simple and rapid, but the sensitivity cannot generally adapt to the requirements of trace detection. Therefore, the new method for detecting the imidacloprid, which is rapid and sensitive, has good selectivity and is used for sample pretreatment detection, is especially important to research.
The electrochemical sensor has the advantages of high sensitivity, good selectivity, rapidness, simplicity and the like, so that more and more attention is paid to pesticide residue detection. The imidacloprid has electric activity, so that the imidacloprid can be directly detected by an electrochemical method simply and quickly. However, for electroactive substances with low current response (such as imidacloprid), the sensitivity of the direct detection method is low, and the requirement of trace analysis cannot be met. Therefore, it is a common strategy to introduce functional nanomaterials to amplify the detection signal. Among them, Graphene (GE) and gold nanoparticles (Au NPs) are functional materials that have received much attention. Graphene Oxide (GO) is an oxide of graphene, and after graphene is oxidized, oxygen-containing functional groups are increased, so that the graphene is more active in property, and the graphene has a higher specific surface area, rich functional groups on the surface and excellent electron transfer efficiency, and has remarkable performance in the aspect of catalyzing and amplifying electrochemical signals of a target object. The gold nano material is gold micro particles, the diameter of the gold micro particles is 1-100 nm, the gold nano material has high electron density, dielectric property and catalytic action, can be combined with various biological macromolecules, and does not influence the biological activity of the gold nano material. By virtue of the good catalytic current effect, graphene and gold nanoparticles have been widely used in the field of electrochemical catalysis. Therefore, the composite nano or multi-nano combined catalysis is expected to obtain more excellent catalytic performance, and the electrochemical sensor with multi-catalysis superposition effect has unique advantages in the detection of imidacloprid and other pesticide residues.
Through the above analysis, the problems and defects of the prior art are as follows:
(1) the conventional imidacloprid detection method needs large-scale equipment and complex pretreatment, is not suitable for on-site rapid detection and cannot meet the requirement of trace detection.
(2) For electroactive substances with low current response (such as imidacloprid), the sensitivity is low by adopting a direct detection method, and the requirement of trace analysis cannot be met.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides a method for detecting imidacloprid by an electrochemical sensor, and particularly relates to a method, equipment and medium for detecting imidacloprid by an electrochemical sensor based on a GO/AuNPs/beta-CD multiple amplification strategy.
The invention is realized in such a way that an electrochemical sensor detects imidacloprid, and the method for detecting imidacloprid by the electrochemical sensor comprises the following steps:
graphene GE, gold nano AuNPs and beta-cyclodextrin beta-CD are introduced to the surface of a glassy carbon electrode, a GO/AuNPs/beta-CD thin film modified Glassy Carbon Electrode (GCE) sensor is prepared while the GE is reduced to graphene oxide GO by adopting a cyclic voltammetry method, and a new method for detecting imidacloprid by using an electrochemical sensor is established.
Further, the method for detecting imidacloprid by using the electrochemical sensor also comprises the following steps:
polymerizing graphene, gold nanoparticles and beta-cyclodextrin to the surface of a glassy carbon electrode GCE by cyclic voltammetry, electrically reducing the graphene to prepare a graphene oxide/gold nanoparticles/beta-cyclodextrin GO/AuNPs/beta-CD modified GCE sensor, and placing the sensor in a solution containing an imidacloprid sample to detect a current response signal of the imidacloprid.
Further, the method for detecting imidacloprid by using the electrochemical sensor comprises the following steps:
step one, preparing a GO/AuNPs/beta-CD modified GCE sensor;
step two, carrying out electrochemical detection;
and step three, preparing a sample.
Further, the preparation of the GO/AuNPs/beta-CD modified GCE sensor in the first step comprises the following steps:
(1) adding 3mg GE, 6 mu LAuNPs, 3mg beta-CD and 5mL of secondary water into a 10.0mL test tube, uniformly mixing, and performing ultrasonic treatment for 30 min;
(2) preparing a GO/Au NPs/beta-CD film on the surface of the treated clean GCE by a cyclic voltammetry method, wherein the polymerization potential is-0.2-1.0V, the scanning speed is 0.1V/s, the GE is oxidized into GO in the polymerization process, and the GO/AuNPs/beta-CD modified electrode is obtained by drying after film polymerization;
(3) scanning a GO/AuNPs/beta-CD modified electrode in PBS (0.1 mol/LpH-7.0) for 5 circles from 0 to-1.7V by adopting a cyclic voltammetry method, and carrying out electrochemical reduction; and the scanning speed is 0.1V/s, and finally the graphene oxide modified electrode oxidized and reduced by the electrochemical method is obtained.
Further, the electrochemical detection in the second step comprises:
(1) putting the prepared sensor in 10mLB-R buffer solution to carry out Differential Pulse Voltammetry (DPV) to obtain different response signals of imidacloprid on the electrodes;
(2) the scanning direction of the differential pulse voltammetry DPV is from 0V to-1.4V, and the scanning rate is 0.050V/s; and analyzing the preparation process and the performance of the sensor by adopting an electrochemical method.
Further, the pH of the B-R buffer was 5.02, and 10mL of imidacloprid was contained at different concentrations;
the electrochemical methods include cyclic voltammetry CV and alternating impedance EIS.
Further, the CV scanning range is 0V to-1.4V, and the scanning speed is 0.050V/s; EIS detection at 3X 10 - 4 mol/L of K 3 [Fe(CN) 6 ]/K 4 [Fe(CN) 6 ]The process is carried out in solution, the potential is set to be 0.15V, the amplitude is 5mV, and the frequency range is 100 mHz-100 kHz; said K 3 [Fe(CN) 6 ]/K 4 [Fe(CN) 6 ]The solution contained 0.5 mol/LKCl.
Further, the sample preparation in step three comprises:
(1) respectively taking 20g of smashed banana, mango and Chinese cabbage samples, adding 40mL of acetonitrile solution, homogenizing at high speed for 2min, filtering to a measuring cylinder with a plug containing 10g of sodium chloride, mixing uniformly, and standing for 30 min;
(2) taking 10mL of the lower acetonitrile solution into a 50mL rotary evaporation bottle, and carrying out vacuum rotary evaporation at 35 ℃ in a water bath until the solution is nearly dry; dissolved in a solution B-R at pH 5.02 of 10ml, and the solution was assayed.
In combination with the technical solutions and the technical problems to be solved, please analyze the advantages and positive effects of the technical solutions to be protected in the present invention from the following aspects:
first, aiming at the technical problems existing in the prior art and the difficulty in solving the problems, the technical problems to be solved by the technical scheme of the present invention are closely combined with results, data and the like in the research and development process, and some creative technical effects are brought after the problems are solved. The specific description is as follows:
the invention provides a novel strategy for preparing an electrochemical sensor with a multiple amplification strategy. On the surface of a glassy carbon electrode, Graphene (GE), gold nanoparticles (AuNPs) and beta-cyclodextrin (beta-CD) are introduced, and the GO/Au NPs/beta-CD film modified electrode sensor is prepared while the GE is reduced into Graphene Oxide (GO) by adopting a cyclic voltammetry method. Due to the multiple amplification effect of GO/AuNPs/beta-CD, the sensor effectively catalyzes and amplifies the reduction current of imidacloprid in B-R buffer solution with the pH value of 5.02, and the reduction electric response and the imidacloprid concentration are 5 multiplied by 10 -10 ～3000×10 -10 A good linear relation is formed in the concentration range of mol/L, so that a new method for detecting imidacloprid by an electrochemical sensor is established. The detection limit of the method reaches 1.33 multiplied by 10 -10 mol/L, should beThe method is used for detecting actual samples, and the recovery rate is 92.0-110.0%.
According to the invention, the graphene oxide, gold nanoparticles and beta-cyclodextrin are introduced for the first time to prepare the modified electrochemical sensor, so that the imidacloprid electrochemical sensor with multiple amplified detection signals is obtained, and the ultra-sensitive detection of imidacloprid is realized. Firstly, polymerizing graphene, gold nanoparticles and beta-cyclodextrin to the surface of a Glassy Carbon Electrode (GCE) by a cyclic voltammetry method, and then electrically reducing the graphene to prepare the graphene oxide/gold nanoparticles/beta-cyclodextrin (GO/AuNPs/beta-CD) modified GCE sensor. The sensor was placed in a solution containing an imidacloprid sample to detect the current response signal of imidacloprid. Due to the existence of multiple amplification effects, the sensitivity of the sensor is greatly improved.
Secondly, considering the technical scheme as a whole or from the perspective of products, the technical effect and advantages of the technical scheme to be protected by the invention are specifically described as follows: the invention introduces a multiple amplification strategy in the process of preparing the modified electrode sensor. Simultaneously introducing the gold nano-particles and graphene with the effect of catalyzing imidacloprid reduction current into the preparation process of the GCE modified electrode, and simultaneously adding the synergistic enhancement of the beta-CD to the catalytic effect, so that the detection signal of the prepared modified electrode sensor to the target molecule imidacloprid is catalytically amplified. Due to the GO/AuNPs/beta-CD multiple amplification strategy, the sensitivity of the sensor applied to imidacloprid residue detection in samples of agricultural products such as bananas is effectively improved.
Third, as an inventive supplementary proof of the claims of the present invention, there are also presented several important aspects:
(1) the expected income and commercial value after the technical scheme of the invention is converted are as follows: the electrochemical sensor with the imidacloprid multi-amplification effect can provide technical support for developing an imidacloprid sensor and developing a field, rapid and sensitive imidacloprid detection sensing technology.
(2) The technical scheme of the invention overcomes the technical prejudice whether: the imidacloprid has weak electrochemical activity, and the method for directly detecting the imidacloprid by using electrochemistry has lower current response signal and low sensitivity. The technical scheme adopts a multiple amplification strategy to realize effective amplification of the imidacloprid weak current signal and obtain the direct electrochemical method for detecting imidacloprid residue with high sensitivity, and has the characteristics of simplicity, rapidness and sensitivity.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments of the present invention will be briefly described below, and it is obvious that the drawings described below are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.
FIG. 1A is a TEM image of AuNPs provided by the embodiment of the present invention;
fig. 1B is a TEM image of graphene provided by an embodiment of the present invention;
FIG. 1C is a TEM image of GO/AuNPs/β -CD provided by an embodiment of the present invention;
FIG. 1D is an XRD spectrum of GO/AuNPs/β -CD provided by an embodiment of the present invention;
FIG. 1E is an EIS spectrum of the GO/AuNPs/beta-CD before and after modification; a. an unmodified GCE electrode, b. a GCE electrode after GO/AuNPs/beta-CD modification;
FIG. 2A is a 1.5X 10 schematic representation of an embodiment of the present invention -7 A schematic diagram of the electrochemical behavior of mol/L imidacloprid on a GCE electrode; a. a bare GCE electrode; GO/AuNPs/beta-CD modified GCE electrode;
FIG. 2B is a 1.5X 10 schematic representation of an embodiment of the present invention -7 DPV response spectrograms of mol/L imidacloprid on different GCE electrodes; a. a bare GCE electrode; au NPs modify GCE electrodes; GO modifies a GCE electrode; GO/AuNPs modified GCE electrode; AuNPs/beta-CD modified GCE electrode; GO/beta-CD modified GCE electrode; GO/AuNPs/beta-CD modified GCE electrode;
FIG. 3 shows the different factors of imidacloprid (1.0X 10) -7 mol/L) effect of DPV response signal intensity on sensor;
fig. 3A shows the dosage of graphene to imidacloprid (1.0 × 10) provided by the embodiment of the present invention -7 mol/L) effect of DPV response signal intensity on sensor;
FIG. 3B shows the dose of AuNPs versus imidacloprid (1.0X 10) provided by the examples of the present invention -7 mol/L) effect of DPV response signal intensity on sensor;
FIG. 3C shows that the dosage of beta-CD provided by the embodiment of the invention exceeds 3mg of p-imidacloprid (1.0X 10) -7 mol/L) influence of DPV response signal intensity on the sensor;
FIG. 3D shows the pH value of B-R buffer solution to imidacloprid (1.0X 10) -7 mol/L) effect of DPV response signal intensity on sensor;
FIG. 4A is a graph showing the DPV response signal intensity of imidacloprid at various concentrations on the sensor provided by the embodiment of the invention; imidacloprid concentration a-k: (5, 50, 100, 200, 500, 1000, 1500, 2000, 2500, 3000). times.10 -10 mol/L；
FIG. 4B is a schematic diagram of a calibration curve provided by an embodiment of the present invention;
FIG. 5 shows a sensor of 1.0 × 10 in accordance with an embodiment of the present invention -8 mol/L imidacloprid and 1.0X 10 - 6 A schematic diagram of the selectivity in B-R solutions of mol/L of other pesticides; a. thiamethoxam, b, clothianidin, c, acetamiprid, d, nitenpyram, e, imidaclothiz, f, aldicarb, g, carbofuran, h, carbaryl, i, isoprocarb, j, fenobucarb, k, carbaryl and pesticide mixture of 11 above l;
fig. 6 is a flowchart of a method for detecting imidacloprid by using an electrochemical sensor according to an embodiment of the invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Aiming at the problems in the prior art, the invention provides a method for detecting imidacloprid by using an electrochemical sensor, and the invention is described in detail below with reference to the accompanying drawings.
First, an embodiment is explained. This section is an explanatory embodiment expanding on the claims so as to fully understand how the present invention is embodied by those skilled in the art.
The method for detecting imidacloprid by the electrochemical sensor provided by the embodiment of the invention comprises the following steps: graphene GE, gold nano Au NPs and beta-cyclodextrin beta-CD are introduced to the surface of a glassy carbon electrode, a GO/AuNPs/beta-CD film modified electrode sensor is prepared while the GE is reduced to graphene oxide GO by adopting a cyclic voltammetry method, and a new method for detecting imidacloprid by an electrochemical sensor is established.
The method for detecting imidacloprid by using the electrochemical sensor provided by the embodiment of the invention also comprises the following steps: polymerizing graphene, gold nanoparticles and beta-cyclodextrin onto the surface of a glassy carbon electrode GCE through a cyclic voltammetry method, electrically reducing the graphene to prepare a graphene oxide/gold nanoparticles/beta-cyclodextrin GO/AuNPs/beta-CD modified GCE sensor, and placing the sensor in a solution containing an imidacloprid sample to detect a current response signal of the imidacloprid.
As shown in fig. 6, the method for detecting imidacloprid by using an electrochemical sensor according to the embodiment of the present invention includes:
s101, preparing a GO/AuNPs/beta-CD modified GCE sensor;
s102, carrying out electrochemical detection;
and S103, preparing a sample.
The preparation of the GO/Au NPs/beta-CD modified GCE sensor in the step S101 provided by the embodiment of the invention comprises the following steps:
(1) adding 3mg GE, 6 mu LAuNPs, 3mg beta-CD and 5mL of secondary water into a 10.0mL test tube, uniformly mixing, and performing ultrasonic treatment for 30 min;
(2) preparing a GO/Au NPs/beta-CD film on the surface of the treated clean GCE by a cyclic voltammetry method, wherein the polymerization potential is-0.2-1.0V, the scanning speed is 0.1V/s, the GE is oxidized into GO in the polymerization process, and the GO/AuNPs/beta-CD modified electrode is obtained by drying after film polymerization;
(3) scanning a GO/AuNPs/beta-CD modified electrode in a PBS (phosphate buffer solution) with the concentration of 0.1 mol/LpH-7.0 for 5 circles from 0 to-1.7V by adopting a cyclic voltammetry method to perform electrochemical reduction; and the scanning speed is 0.1V/s, and finally the graphene oxide modified electrode oxidized and reduced by the electrochemical method is obtained.
The electrochemical detection in step S102 provided in the embodiment of the present invention includes:
(1) putting the prepared sensor in 10mLB-R buffer solution to carry out Differential Pulse Voltammetry (DPV) to obtain different response signals of imidacloprid on the electrodes;
(2) the scanning direction of the differential pulse voltammetry DPV is from 0V to-1.4V, and the scanning rate is 0.050V/s; and analyzing the preparation process and the performance of the sensor by adopting an electrochemical method.
The buffer solution B-R provided by the embodiment of the invention has the pH value of 5.02 and contains 10mL of imidacloprid with different concentrations.
The electrochemical method provided by the embodiment of the invention comprises cyclic voltammetry CV and alternating impedance EIS.
The CV scanning range provided by the embodiment of the invention is 0V to-1.4V, and the scanning rate is 0.050V/s; EIS detection at 3X 10 -4 mol/L of K 3 [Fe(CN) 6 ]/K 4 [Fe(CN) 6 ]The process is carried out in solution, the potential is set to be 0.15V, the amplitude is 5mV, and the frequency range is 100 mHz-100 kHz; wherein, K 3 [Fe(CN) 6 ]/K 4 [Fe(CN) 6 ]The solution contained 0.5 mol/LKCl.
The sample preparation in step S103 provided in the embodiment of the present invention includes:
(1) respectively taking 20g of smashed banana, mango and Chinese cabbage samples, adding 40mL of acetonitrile solution, homogenizing at high speed for 2min, filtering to a measuring cylinder with a plug containing 10g of sodium chloride, mixing uniformly, and standing for 30 min;
(2) taking 10mL of the lower acetonitrile solution into a 50mL rotary evaporation bottle, and carrying out vacuum rotary evaporation at 35 ℃ in a water bath until the solution is nearly dry; the resulting solution was dissolved in a 10ml of a B-R solution having a pH of 5.02 and assayed.
Second, the application embodiment. In order to prove the creativity and the technical value of the technical scheme of the invention, the part is the application example of the technical scheme of the claims on specific products or related technologies.
According to the invention, the graphene oxide, gold nanoparticles and beta-cyclodextrin are introduced for the first time to prepare the modified electrochemical sensor, so that the imidacloprid electrochemical sensor with multiple amplified detection signals is obtained, and the ultra-sensitive detection of imidacloprid is realized. Firstly, polymerizing graphene, gold nanoparticles and beta-cyclodextrin to the surface of a Glassy Carbon Electrode (GCE) by a cyclic voltammetry method, and then electrically reducing the graphene to prepare the graphene oxide/gold nanoparticles/beta-cyclodextrin (GO/AuNPs/beta-CD) modified GCE sensor. The sensor was placed in a solution containing an imidacloprid sample to detect the current response signal of imidacloprid. Due to the existence of multiple amplification effects, the sensitivity of the sensor is greatly improved.
In order to further improve the sensitivity of the electrochemical direct detection method, the introduction of the catalytic amplification nano material is the key for preparing the high-sensitivity electrochemical sensor. The invention provides a novel strategy for preparing an electrochemical sensor with a multiple amplification strategy. Graphene (GE), gold nano (Au NPs) and beta-cyclodextrin (beta-CD) are introduced to the surface of a glassy carbon electrode, and the GO/AuNPs/beta-CD film modified electrode sensor is prepared while the GE is reduced into Graphene Oxide (GO) by adopting a cyclic voltammetry method. Due to the multiple amplification effect of GO/Au NPs/beta-CD, the sensor effectively catalyzes and amplifies the reduction current of imidacloprid in B-R buffer solution with the pH value of 5.02, and the reduction electric response and the imidacloprid concentration are 5 multiplied by 10 -10 ～3000×10 -10 A good linear relation is formed in the concentration range of mol/L, so that a new method for detecting imidacloprid by an electrochemical sensor is established. The detection limit of the method reaches 1.33 multiplied by 10 -10 And mol/L, the recovery rate is 92.0-110.0% when the method is applied to detection of actual samples.
And thirdly, evidence of relevant effects of the embodiment. The embodiment of the invention achieves some positive effects in the process of research and development or use, and has great advantages compared with the prior art, and the following contents are described by combining data, diagrams and the like in the test process.
1. Experimental part
1.1 reagents and instruments
Graphene (GE ≥ 98%), water-soluble gold nanoparticles (30nm, 0.03mg/mL, solvent: ultrapure water) and beta-cyclodextrin are all purchased from Aladdin reagent GmbH (Shanghai). Imidacloprid, thiamethoxam, clothianidin, acetamiprid, nitenpyram, imidaclothiz, aldicarb, carbofuran, carbaryl, isoprocarb, fenobucarbCarbaryl standard substance purchased from J&K Bailingwei reagent Inc.; the B-R buffer at pH 5.02 was prepared as follows: in 100mL of a triacid mixed solution (phosphoric acid, acetic acid and boric acid, the concentration is 0.04mol/L), the pH value is adjusted to 5.02 by 0.2mol/L NaOH. 3X 10 -4 mol/L of K 3 [Fe(CN) 6 ]/K 4 [Fe(CN) 6 ]Solution (containing 0.5 mol/LKCl). Except for special instructions, all reagents were analytically pure except for special instructions. The experimental water is ultrapure water.
The electrochemical performance of the sensor was analyzed using a CHI660E electrochemical workstation (shanghai chenhua instruments), including Differential Pulse Voltammetry (DPV), Cyclic Voltammetry (CV), and alternating current impedance method (EIS). Three-electrode system: the working electrode is a GO/AuNPs/beta-CD modified glassy carbon electrode (GCE, d is 2 mm); reference electrode: Ag/AgCl (saturated KCl); auxiliary electrode: a platinum wire electrode. The morphology of the nanomaterials and graphene was analyzed using an Ultima IV X-ray powder diffractometer (XRD, japan chem), a Tecnai 30F transmission electron microscope (TEM, Philips-FEI, netherlands).
1.2 GO/AuNPs/beta-CD modified GCE sensor preparation
3mg of GE, 6 mu of LAuNPs, 3mg of beta-CD and 5mL of secondary water are added into a 10.0mL test tube to be uniformly mixed, and ultrasonic treatment is carried out for 30 minutes. Preparing a GO/Au NPs/beta-CD film on the surface of the treated clean GCE by a cyclic voltammetry method, wherein the polymerization potential is-0.2-1.0V, the scanning speed is 0.1V/s, the GE is oxidized into GO in the polymerization process, and the GO/Au NPs/beta-CD modified electrode is obtained by drying after film polymerization. And then scanning the GO/Au NPs/beta-CD modified electrode in a PBS (phosphate buffer solution) with the concentration of 0.1 mol/LpH-7.0 for 5 circles (electrochemical reduction process) from 0 to-1.7V by adopting a cyclic voltammetry at the scanning speed of 0.1V/s, and finally obtaining the graphene oxide modified electrode oxidized and reduced by the electrochemical method.
1.3 electrochemical detection method
The prepared sensor is placed in 10mL of B-R buffer (pH is 5.02, and 10mL of imidacloprid with different concentrations) to be subjected to Differential Pulse Voltammetry (DPV), so that different response signals of the imidacloprid on the electrodes are obtained. Differential Pulse Voltammetry (DPV) scans from 0V to-1.4V at a rate of 0.050V/s. Using Cyclic Voltammetry (CV)) And an electrochemical method such as an alternating current impedance method (EIS) and the like are used for analyzing the preparation process and the performance of the sensor. The CV scanning range is 0V to-1.4V, and the scanning speed is 0.050V/s. EIS detection at 3X 10 -4 mol/L of K 3 [Fe(CN) 6 ]/K 4 [Fe(CN) 6 ]In a solution (containing 0.5mol/L KCl), the potential is set to 0.15V, the amplitude is 5mV, and the frequency range is 100 mHz-100 kHz.
1.4 sample preparation
Respectively taking 20g of smashed banana, mango and Chinese cabbage samples, adding 40mL of acetonitrile solution, homogenizing at high speed for 2min, filtering to a measuring cylinder with a plug containing 10g of sodium chloride, mixing uniformly, and standing for 30 min. The lower acetonitrile solution 10mL was taken in a 50mL rotary evaporation flask and rotary evaporated to near dryness under vacuum in a 35 ℃ water bath. The resulting solution was dissolved in a 10ml of a B-R solution having a pH of 5.02 and assayed.
2. Results
2.1 GO/AuNPs/beta-CD modified electrode characterization
And analyzing the morphology and components of the GO/AuNPs/beta-CD modified electrode by adopting TEM and XRD. As shown in fig. 1A, the gold nanoparticles dispersed individually are in a spherical state, and the particle size is about 30 nm; graphene exhibits a sheet-like structure (fig. 1B). When GO/AuNPs/beta-CD is polymerized to the surface of GCE, gold nano-particles are distributed on the surface of GO (figure 1C). The XRD pattern (FIG. 1D) shows that GO/AuNPs/beta-CD has a relatively broad (002) amorphous peak, which is the characteristic XRD pattern of GO; and the characteristic peaks of the crystal plane of Au (111) Au (200) Au (220) Au (311) of the gold nanometer appear at 35.4 °, 43.0 °, 62.8 ° and 74.1 °, respectively. And further analyzing the resistances of the GO/Au NPs/beta-CD before and after the electrode is modified by adopting alternating-current impedance. As can be seen from fig. 1E, after GO/AuNPs/β -CD is modified on the surface of the electrode, the resistance of the electrode is slightly increased (curve a to curve b), because although GO and gold nanoparticles have excellent electron conductivity, the conductivity of β -CD is poor, and when β -CD covers the GO/AuNPs surface, the conductivity of the electrode is reduced, and the sensor resistance is increased. The above results indicate that GO/AuNPs/beta-CD has been successfully modified onto the surface of GCE electrodes.
2.2 electrochemical and catalytic amplification of Imidacloprid on GO/AuNPs/beta-CD modified electrodes
The electrochemical behavior of imidacloprid in a B-R buffer solution (pH 5.02) under different electrode conditions is analyzed. As shown in FIG. 2A, in the B-R free buffer solution, a reduction peak was observed for imidacloprid at around-1.1V on the bare GCE electrode, which corresponds to the reduction of the nitro group in the imidacloprid molecule (curve a). This indicates that the electrode process is an irreversible reduction process. And the reduction peak of the imidacloprid with the same concentration on GO/Au NPs/beta-CD modified GCE is further enhanced (curve b), which shows that the GO/Au NPs/beta-CD modified GCE electrode has stronger catalytic action on the imidacloprid. DPV is adopted to detect the magnitude of the reduction peak current of the imidacloprid so as to further investigate the catalytic amplification behavior of the sensor. As shown in fig. 2B, the weaker reduction current of imidacloprid in the B-R solution (curve a) can be catalytically amplified by gold nanoparticles (curve B) and graphene (curve c), respectively; this is due to their excellent electron conductivity and large specific surface area. When the gold nano-particles and the graphene are simultaneously modified on the surface of the GCE, the current is further amplified (curve d). The beta-CD does not have the capability of catalytically amplifying the reduction current of the imidacloprid, but when the beta-CD and the gold nanoparticles are simultaneously modified on the surface of the electrode, the reduction current of the imidacloprid is further catalytically amplified (curve e); similarly, when the beta-CD and the graphene are simultaneously modified on the surface of the electrode, the reduction current of the imidacloprid is further catalytically amplified (curve f); it is believed that the hydrophobic groups of imidacloprid, such as-Cl, can be recognized by the hydrophobic cavity of β -CD and immobilized on the electrode surface to enhance the reduction current. And when GO/AuNPs/beta-CD is completely modified on the surface of the electrode, the weaker reduction current of imidacloprid in the B-R solution is amplified by more than 20 times due to the catalytic superposition effect (curve g). The results show that GO/AuNPs/beta-CD can effectively amplify the electroreduction current of imidacloprid, thereby greatly improving the detection sensitivity of the sensor.
2.3 optimization of the Experimental conditions
The invention analyzes various influencing factors influencing the DPV signal intensity of the imidacloprid detected by the sensor, including the dosage of graphene, gold nano and beta-CD and the pH value of PBS buffer solution, so as to determine the optimal experimental conditions. As shown in fig. 3, graphene, gold nano-particles and β -CD play a role in catalytic amplification of current in the sensor, and when the amount of the graphene, gold nano-particles and β -CD is increased from low to high, the amount of materials polymerized on the surface of the electrode is increased, the catalytic effect is more obvious, and the DPV response is increased. However, when the graphene dosage exceeds 3mg, the gold nano dosage exceeds 6 mu L, and the beta-CD dosage exceeds 3mg, the DPV is reduced. Therefore, considering together, 3mg graphene (fig. 3A), 6 μ L gold nanoparticles (fig. 3B) and 3mg β -CD (fig. 3C) were selected as the optimal amounts to prepare the modified electrode. The pH of the B-R buffer had a large effect on the DPV response of the sensor to detect imidacloprid, and therefore the effect of the buffer with a pH value from 4 to 10 on the detection signal was examined. The results are shown in fig. 3D, where the sensor gave the best DPV response signal in a pH 5.0 buffer, and therefore all subsequent experiments used a pH 5.0 buffer.
2.4 calibration Curve
Under optimized conditions, the sensors were placed in B-R solutions containing imidacloprid at different concentrations, and different DPV response signal intensities were measured. As shown in FIG. 4A, the DPV intensity response signal intensity increased with increasing imidacloprid concentration at 5X 10 -10 ～3000×10 -10 The DPV intensity response signal intensity (I) is well linear with imidacloprid concentration (c) over the concentration range of mol/L (FIG. 4B). The linear regression equation is that I is 0.023c (10) -10 mol/L) +5.96, correlation coefficient r ═ 0.997. The detection limit is 1.33 multiplied by 10 -10 mol/L(DL＝KSb/a，K＝3)。
2.5 sensor Selective analysis
The ability to specifically recognize target molecules in the presence of coexisting compounds is very important to sensor performance. Therefore, 11 neonicotinoid pesticides with structures similar to imidacloprid and carbamate pesticides (thiamethoxam, clothianidin, acetamiprid, nitenpyram, imidaclothiz, aldicarb, carbofuran, carbaryl, isoprocarb, fenobucarb and carbaryl) are selected as interference compounds, and the analysis sensor pair is 1.0 × 10 -8 The selective detection capability of the imidacloprid in mol/L. At 1.0X 10 -6 Detection in the presence of mol/L of interfering compounds at 1.0X 10 -8 DPV response intensity of imidacloprid on the sensor in mol/L. The current values (I respectively) before and after addition of the interfering compound were recorded 0 And I), and calculating the current change (I-I) 0 ) And relative deviation (I-I) 0 )/I 0 X 100%. As shown in fig. 5, after imidacloprid and other organophosphate pesticides were mixed at 100 times higher concentration, the DPV strength of the sensor did not change significantly (relative deviation was less than 5.0%). This indicates that the sensor has good specificity for imidacloprid.
2.6 sensor reproducibility and stability analysis
Using 5 sensors prepared under the same conditions, 1.0X 10 measurements were made -8 And (3) recording 5 times of DPV detection results by mol/L imidacloprid, and calculating the relative standard deviation of the 5 times of detection results to be 1.28%. In addition, the same sensor pair is used, 1.0 × 10 -8 The relative standard deviation obtained after 10 DPV measurements of mol/L imidacloprid was 2.124%. The above results show that the sensor has good reproducibility. To ensure stability, the sensor was stored in a refrigerator at 4 ℃ when not in use, and used periodically at 1.0X 10 -8 The DPV response signal was tested with mol/L imidacloprid. After 10 days, there was no significant decrease in DPV response signal intensity, about 1.6%. After 20 days, the DPV response signal intensity decreased by about 7.4%, and after 1 month, by about 14.3% compared to the initial DPV response signal. This indicates that the sensor has good stability.
2.7 application of sensor to detection and analysis of actual sample
The prepared sensor is applied to detection of an actual sample, so that the application effect of the sensor is inspected. And (3) selecting the banana, mango and Chinese cabbage samples prepared by the method of 2.4 to detect and performing a labeling recovery test. As shown in Table 1, the recovery rate of the process was 92.0 to 110.0%, and the results were satisfactory.
TABLE 1 actual sample detection and recovery with standard experiment
The invention introduces a multiple amplification strategy in the process of preparing the modified electrode sensor. Simultaneously introducing the gold nano-particles and graphene with the effect of catalyzing imidacloprid reduction current into the preparation process of the GCE modified electrode, and simultaneously adding the synergistic enhancement of the beta-CD to the catalytic effect, so that the detection signal of the prepared modified electrode sensor to the target molecule imidacloprid is catalytically amplified. Due to the GO/AuNPs/beta-CD multiple amplification strategy, the sensitivity of the sensor applied to imidacloprid residue detection in samples of agricultural products such as bananas is effectively improved.
The above description is only for the purpose of illustrating the present invention and the appended claims are not to be construed as limiting the scope of the invention, which is intended to cover all modifications, equivalents and improvements that are within the spirit and scope of the invention as defined by the appended claims.
Claims (10)
1. A method for detecting imidacloprid by an electrochemical sensor, which is characterized by comprising the following steps: introducing graphene GE, gold nano Au NPs and beta-cyclodextrin beta-CD on the surface of a glassy carbon electrode, reducing the GE into graphene oxide GO by adopting a cyclic voltammetry method, preparing a GO/Au NPs/beta-CD film modified electrode sensor, and establishing a new method for detecting imidacloprid by using an electrochemical sensor.
2. The method for detecting imidacloprid by the electrochemical sensor as claimed in claim 1, wherein the method for detecting imidacloprid by the electrochemical sensor further comprises: polymerizing graphene, gold nanoparticles and beta-cyclodextrin to the surface of a glassy carbon electrode GCE by cyclic voltammetry, electrically reducing the graphene to prepare a graphene oxide/gold nanoparticles/beta-cyclodextrin GO/Au NPs/beta-CD modified GCE sensor, and placing the sensor in a solution containing an imidacloprid sample to detect a current response signal of the imidacloprid.
3. The method for detecting imidacloprid by using the electrochemical sensor as claimed in claim 1, wherein the method for detecting imidacloprid by using the electrochemical sensor comprises the following steps:
step one, preparing a GO/Au NPs/beta-CD modified GCE sensor;
step two, carrying out electrochemical detection;
and step three, preparing a sample.
4. The method for detecting imidacloprid by using the electrochemical sensor as claimed in claim 3, wherein the preparation of the GO/Au NPs/beta-CD modified GCE sensor in the first step comprises the following steps:
(1) adding 3mg GE, 6 mu L Au NPs, 3mg beta-CD and 5mL secondary water into a 10.0mL test tube, uniformly mixing, and performing ultrasonic treatment for 30 min;
(2) preparing a GO/Au NPs/beta-CD film on the surface of the treated clean GCE by a cyclic voltammetry method, wherein the polymerization potential is-0.2-1.0V, the scanning speed is 0.1V/s, the GE is oxidized into GO in the polymerization process, and the GO/Au NPs/beta-CD modified electrode is obtained by drying after film polymerization;
(3) scanning a GO/Au NPs/beta-CD modified electrode in PBS (phosphate buffer solution) with the pH value of 7.0 at 0.1mol/L for 5 circles from 0 to-1.7V by adopting a cyclic voltammetry method, and carrying out electrochemical reduction; and the scanning speed is 0.1V/s, and finally the graphene oxide modified electrode oxidized and reduced by the electrochemical method is obtained.
5. The method for detecting imidacloprid by using the electrochemical sensor as claimed in claim 3, wherein the electrochemical detection in the second step comprises the following steps:
(1) putting the prepared sensor into 10mL of B-R buffer solution to carry out Differential Pulse Voltammetry (DPV) to obtain different response signals of imidacloprid on the electrodes;
(2) the scanning direction of the differential pulse voltammetry DPV is from 0V to-1.4V, and the scanning rate is 0.050V/s; and analyzing the preparation process and the performance of the sensor by adopting an electrochemical method.
6. The method for detecting imidacloprid by using the electrochemical sensor as claimed in claim 5, wherein the pH value of the B-R buffer solution is 5.02, and the B-R buffer solution contains 10mL of imidacloprid with different concentrations;
the electrochemical methods include cyclic voltammetry CV and alternating impedance EIS.
7. The method for detecting imidacloprid by using electrochemical sensor as claimed in claim 6, wherein the method comprises the step of detecting imidacloprid by using electrochemical sensorThen, the CV scanning range is 0V to-1.4V, and the scanning speed is 0.050V/s; EIS detection at 3X 10 -4 mol/L of K 3 [Fe(CN) 6 ]/K 4 [Fe(CN) 6 ]The process is carried out in solution, the potential is set to be 0.15V, the amplitude is 5mV, and the frequency range is 100 mHz-100 kHz; said K 3 [Fe(CN) 6 ]/K 4 [Fe(CN) 6 ]The solution contained 0.5mol/L KCl.
8. The method for detecting imidacloprid by using the electrochemical sensor as claimed in claim 3, wherein the sample preparation in the third step comprises the following steps:
(1) respectively taking the smashed banana, mango and Chinese cabbage samples, adding an acetonitrile solution, homogenizing at a high speed, filtering to a measuring cylinder with a plug containing sodium chloride, fully mixing uniformly, and standing;
(2) taking the lower acetonitrile solution in a rotary evaporation bottle, and carrying out vacuum rotary evaporation in a water bath until the solution is nearly dry; dissolving with B-R solution, and testing.
9. The method for detecting imidacloprid by using the electrochemical sensor as claimed in claim 8, wherein 20g of the samples of the broken bananas, mangoes and Chinese cabbages are respectively taken, added with 40mL of acetonitrile solution, homogenized at high speed for 2min, filtered to a measuring cylinder with a plug containing 10g of sodium chloride, fully mixed and stood for 30 min.
10. The method for detecting imidacloprid by using the electrochemical sensor as claimed in claim 8, wherein 10mL of the lower acetonitrile solution is taken out of a 50mL rotary evaporation bottle and is subjected to vacuum rotary evaporation to be nearly dry in a water bath at 35 ℃; the mixture was dissolved in 10mL of a B-R solution having a pH of 5.02 and assayed.
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| MING CHEN等: "β-Cyclodextrin polymer as a linker to fabricate ternary nanocomposites AuNPs/pATP-β-CDP/rGO and their electrochemical application", 《CARBOHYDRATE POLYMERS》, vol. 119, pages 26 - 34, XP029128097, DOI: 10.1016/j.carbpol.2014.11.022 * |
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| CN114839248B (en) | 2024-01-23 |
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