CN111781258A - Sensor capable of rapidly detecting antibiotics in water environment and detection method - Google Patents

Abstract

The invention relates to the technical field of water quality detection, in particular to a sensor capable of quickly detecting antibiotics in a water environment, which comprises the following preparation steps of grinding and polishing, cleaning and blow-drying, and nitrogen plasma modification, wherein a nitrogen plasma modified electrode is adopted in the preparation process of the sensor, the hydrophilicity is improved, the resistance is reduced, the electron transfer capability is improved, the interface electrical activity of the electrode is further improved by increasing the types and the number of active functional groups on the surface of the electrode, and the high-sensitivity and high-selectivity detection and analysis on Ciprofloxacin (CFX) can be realized^‑7～1×10^‑5mol·L^‑1、1×10^‑5～1×10^‑4mol·L^‑1The detection limit is 8 × 10^‑9mol L^‑1And has good stability and reproducibility.

Description

Sensor capable of rapidly detecting antibiotics in water environment and detection method

Technical Field

The invention relates to the technical field of water quality detection, in particular to a sensor capable of quickly detecting antibiotics in a water environment and a detection method using the sensor.

Background

Ciprofloxacin (CFX), an artificially synthesized third-generation fluoroquinolone antibiotic, is one of the most widely used fluoroquinolone antibiotics at present because of its characteristics of broad-spectrum antibacterial activity, good bioavailability, few side effects, good tissue penetration and distribution in biological fluids. Ciprofloxacin enters water environments through domestic sewage, production and discharge of pharmaceutical factories, waste of solid wastes, livestock excrement, leaching of garbage fields and the like, and is frequently detected in various water environments.

With the aggravation of the problem of ciprofloxacin pollution in water environment, the detection method of ciprofloxacin is receiving more and more attention. So far, various detection means for ciprofloxacin have been available, and high performance liquid chromatography, immunoassay and spectrophotometry are commonly used. These methods have high sensitivity and low detection limit, and thus are widely used. However, these methods also have the disadvantages of high cost, complicated operation, long time consumption, etc., so that it is more necessary to develop a more convenient, rapid and accurate detection method. The electrochemical sensor detection method has the advantages of simplicity, portability, high sensitivity and low cost. Therefore, the development of a simple, rapid and good-selectivity method for detecting the antibiotics in the water environment has certain research significance.

In the future, the electrochemical analysis detection method has the advantages of simplicity, rapidness, high sensitivity, low consumption and in-situ online detection capability, and is also applied to the field of water quality detection. Typically, researchers functionalize different electrodes to increase the sensitivity and detection limit of the target analyte. Graphene and multi-walled carbon nanotubes have been widely used for modifying electrodes and detecting CFX due to their high conductivity, high chemical and mechanical stability and high specific surface area. On the basis, a plurality of researchers also use the research of compounding and doping with carbon materials, such as PAR/EGR/GCE, NiONPs-GO-CTS, EPH/GCE, g-CN/BiOCl, porous-Nafion-MWCNT/BDD, CNT-V2O5-CS/SPCE and the like. Some researchers have also applied electrochemical biosensors to the detection of CFX. In addition, a relatively small number of researchers have applied molecular imprinting techniques as well as screen printing techniques to the study of detecting CFX. Although the above sensors have been successful in detecting CFX in aqueous environments, they still require complex modification materials and modification methods, and in addition, the modification process is time-consuming. Therefore, there is a need to establish a simple, fast and convenient modification method to effectively detect the residual CFX in the water environment.

Disclosure of Invention

The embodiment of the invention aims to provide a sensor capable of quickly detecting antibiotics in a water environment, and the sensor has the advantages of simple preparation method, high sensitivity and low detection limit.

In order to achieve the above object, an embodiment of the present invention provides a sensor capable of rapidly detecting antibiotics in an aqueous environment, which is characterized in that the sensor is prepared by the following steps:

polishing, namely polishing the bare glassy carbon electrode on a polishing device attached with a polishing agent;

cleaning and blow-drying, namely cleaning and blow-drying the polished glassy carbon electrode for later use;

and step three, plasma modification, namely placing the dried glassy carbon electrode on a plasma cleaning machine CPC-A, wherein the modification power is 100W-180W, and the plasma modification time is 0.5 min-10 min.

As an improvement of the technical proposal, in the step one, the polishing agent is Al₂O₃Polishing powder paste.

As an improvement of the technical proposal, in the step one, the bare glassy carbon electrodes are sequentially arranged at 1 μm, 0.3 μm and 0.05 μm Al₂O₃Polishing the polishing cloth pasted with the polishing powder slurry.

As an improvement of the above technical scheme, in the second step, the polished glassy carbon electrode is put into secondary distilled water or absolute ethyl alcohol for ultrasonic cleaning.

As an improvement of the above technical scheme, in the second step, the polished glassy carbon electrode is subjected to ultrasonic cleaning in secondary distilled water, absolute ethyl alcohol and secondary distilled water in sequence.

In the second step, the cleaned glassy carbon electrode is dried by nitrogen.

As an improvement of the technical scheme, in the third step, the modification power is 120W-160W, and the modification time is 4 min-10 min.

The sensor adopts the nitrogen plasma to modify the electrode in the preparation process, improves the hydrophilicity, reduces the resistance and improves the electron transfer capacity by increasing the types and the number of active functional groups on the surface of the electrode, further improves the interfacial electrical activity of the electrode, and can realize the high-sensitivity and high-selectivity electrochemical detection and analysis of CFX.

The embodiment of the invention also provides a detection method of the sensor capable of quickly detecting the antibiotics in the water environment, and the detection method detects the water to be detected, which contains the ciprofloxacin, through the sensor modified on the surface of the nitrogen plasma.

As an improvement of the technical scheme, the PH of the water containing ciprofloxacin to be detected is adjusted to 4.5-8 by a buffer solution.

As an improvement of the technical scheme, the PH of the water containing ciprofloxacin to be detected is adjusted to 4.5-6 by a buffer solution.

The detection method can accurately detect CFX in a water environment containing multiple antibiotic components, has good anti-interference performance, improves the oxidation peak current value during CFX electrochemical analysis by preferably adjusting the pH value of the environmental aqueous solution, and has the linear response range of the CFX concentration on the modified electrode of 2.5 × 10^-7～1×10^-5mol·L^-1、1×10^-5～1×10^-4mol·L^-1The detection limit is 8 × 10^-9mol L^-1And has good stability, reproducibility and practicability.

Drawings

FIG. 1 is an AFM image of an electrode before and after nitrogen plasma modification, wherein (A) is an AFM image of a bare GCE; FIG. B is an AFM view of the NP-GCE electrode.

FIG. 2 is a schematic diagram showing the contact angle and XPS interface characterization before and after nitrogen plasma modification of an electrode, wherein (A), (C) and (E) are the interface characterization of a naked GCE, and (B), (D) and (F) are the interface characterization of an NP-GCE electrode.

Fig. 3 (a): alternating current impedance spectrograms before and after electrode plasma modification and under different modification powers; fig. 3 (B): k₃[Fe(CN)₆]Electrochemical behavior on different modified electrodes, i.e. 5mM K in 1M KCl solution₃[Fe(CN)₆]Cyclic voltammograms at different electrodes, sweep rate of 100mV s^-1FIG. 3C shows a composition containing 7 × 10^-5Differential voltammetric pulse profiles of M CFX PBS buffer on different electrodes.

Fig. 4 is a schematic representation of the electrochemical behavior of CFX on a modified electrode under different modification and experimental conditions. FIGS. 4(A) and (B) are schematic diagrams of CFX current versus modified power parameter and time; FIGS. 4(C) and (D) are schematic diagrams of pH effect on electrochemical behavior of CFX, wherein FIG. 4(C) is a cyclic voltammogram of CFX at different pH on NP-GCE electrode (pH values: 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8 in order), FIG. 4(D) is an effect of pH on CFX peak current and potential; FIG. 4(E) is a schematic representation of the effect of different sweep rates on CFX electrochemical behavior; FIG. 4(F) is a schematic representation of the effect of different resting times on the electrochemical behavior of CFX.

FIG. 5 is a calibration curve of CFX, in which (A) a differential pulse voltammogram of CFX at different concentrations has a concentration distribution of 2.5 × 10^-7，7×10^-7，1×10^-6，4×10^-6，7×10^-6，1×10^-5，2.5×10^-5，4×10^-5，5.5×10^-5，7×10^-5，8.5×10^-5，1×10^-4mol L^-1(ii) a FIG. B is a standard curve diagram of CFX.

FIG. 6 shows the effect of different antibiotics and inorganic ions on CFX peak current, in (A) (a)1 × 10^-5mol L^-1CFX，(b)1×10^-5mol L^-1Sulfapyridine, (c)1 × 10^-5mol L^-1Moxifloxacin (Moxifloxacin), (d)1 × 10^-5mol L^-1Doxycycline (Doxymycin), (e)2 × 10^-5mol L^-1Tetracycline (Teracycline), FIG. (B) (a)1 × 10^-5mol L^-1CFX，(b)0.2M Ca²⁺,(c)0.2M K⁺,(d)0.2M Mg²⁺,(e)0.2M Na⁺,(f)0.2M Cl^-。

Detailed Description

The embodiments of the present invention are described below by way of examples, and other advantages and effects of the present invention will be readily apparent to those skilled in the art from the disclosure of the present specification.

Example one

Modifying a glassy carbon electrode using a plasma cleaner by:

polishing, namely sequentially placing a bare glassy carbon electrode on a substrate with Al of 1 micron, 0.3 micron and 0.05 micron₂O₃Polishing the polishing cloth with the polishing powder paste, wherein Al is₂O₃The polishing powder paste is a polishing agent;

cleaning and blow-drying, namely, after ultrasonic cleaning is carried out for 5min in secondary distilled water, absolute ethyl alcohol and secondary distilled water in sequence, taking out the electrode, and blow-drying the electrode in the atmosphere protected by nitrogen for later use;

and step three, nitrogen plasma modification, namely placing the blow-dried glassy carbon electrode on a plasma cleaning machine table, marking an electrode modification area on the table to ensure that the electrode modification is in the same position every time, wherein the plasma modification power is 100W-180W, the modification time is 0.5 min-10 min, and the electrode (NP-GCE) modified by the plasma is sealed and stored for subsequent detection.

Glassy carbon electrode (diameter 2mm) in this example (Tianjin Eda science and technology Heng Cheng science and technology development, Inc.), three-electrode system: a bare Glassy Carbon Electrode (GCE) or a nitrogen plasma modified electrode (NP-GCE) is used as a working electrode, an Ag/AgCl electrode is used as a reference electrode, and a platinum wire electrode is used as a counter electrode; plasma modification was performed on the glassy carbon electrode using a plasma cleaner CPC-a (CIF International Group co., Ltd).

The performance of the modified glassy carbon electrode and the related sensor is mainly characterized by the following devices: AFM interface characterization of naked GCE and NP-GCE modified electrodes is respectively carried out by using a German Bruk Dimension Icon atomic force microscope to research the change of the roughness of the interface of the electrodes; the method comprises the following steps of (1) carrying out quantitative analysis and characterization on the types and the numbers of oxygen functional groups at the interfaces of naked GCE and NP-GCE electrodes by using a U.S. thermoelectric Thermo escalab 250XI X-ray photoelectron spectrometer; and (3) performing electrochemical impedance spectrum characterization of different modified electrodes by using an ivium electrochemical workstation to research the change of the electron transfer resistance.

Water sample treatment: groundwater and tap water from the university of geology of china (beijing) were selected as actual samples, all samples were first filtered through a 0.45 μm teflon membrane to remove physical impurities, and all samples were diluted with 0.2MPBS (pH 5). Then CFX standard solutions with different concentrations are added in sequence, and the subsequent CFX detection is the same as that of the CFX in the buffer solution.

Preparing a CFX standard stock solution: the 1mM CFX solution is prepared by accurately measuring CFX standard substance and fixing volume with secondary distilled water, and is sealed and stored in a refrigerator at 4 ℃. Phosphate Buffered Solutions (PBS) of different pH values were each 0.2mol L^-1Disodium hydrogen phosphate (Na)₂HPO₄) And 0.2mol L^-1Sodium dihydrogen phosphate (NaH)₂PO₄) Prepared from 1mol of L^-1Phosphoric acid (H)₃PO₄) And (5) adjusting. Other reagents are domestic analytical purifiers, all reagents are not pretreated before use, experimental water is secondary distilled water, and all experiments are carried out at room temperature.

And (3) detection process: in the test, 0.2M PBS (pH 5) was used as a supporting electrolyte in the CFX detection process. The scanning potential of Cyclic Voltammetry (CV) is 0.4-1.4V, after each measurement, the three-electrode system is placed in a blank solution, and the CV is used for scanning for 3 times to remove pollutants adsorbed on the surface of the electrode. Respectively optimizing the pH value and the CV sweeping speed of the PBS buffer solution according to the operations, and carrying out CFX quantitative analysis by adopting a Differential Pulse Voltammetry (DPV) under the optimal condition, wherein the parameters of the DPV are set as follows: the potential interval is 0.4-1.4V, the potential increment is 0.004V, the pulse amplitude is 0.05V, the pulse period is 0.5s, the sampling width is 0.0167s, and the rest time is 2 s. The electrochemical AC impedance test was conducted in the presence of 5mM potassium ferricyanide (K)₃[Fe(CN)₆) And potassium ferrocyanide (K)₄[Fe(CN)₆]) In 1M potassium chloride (KCl).

The performance result of the glassy carbon electrode modified by plasma etching is characterized in that:

1. the Atomic Force Microscope (AFM) image is shown in FIG. 1, wherein images (A) and (B) are AFM images before and after electrode modification (naked GCE, NP-GCE), respectively. The changes in the chemical and physical properties of the electrode interface before and after modification were determined by AFM characterization of GCE and NP-GCE, and the results of the AFM image of GCE showed a roughness Ra in the 5 μm interface range₁8.3 nm. FIG. B shows an AFM image of NP-GCE, roughness Ra in the range of 5 μm interface₂The roughness of the electrode is not obviously increased before and after modification, the increase of background current is effectively controlled, the specific surface area of the electrode is increased, and the adsorption and electrochemical reaction of pollutants on an electrode interface are facilitated.

2. Contact angle and XPS interface characterization are shown in fig. 2, where graph (a) is a contact angle image of GCE with a contact angle θ of 80 °, graph (B) is a contact angle image of NP-GCE with a modification power P of 140W, θ of 27 °, indicating that the modified electrode (NP-GCE) is more hydrophilic due to the introduction of some reactive functional groups. Panels (C) and (D) are XPS characterization of GCE versus NP-GCE showing C, O two elements present in GCE, C, N, O three elements present in NP-GCE, and increased O/C, indicating the presence of N elements due to N plasma modification. The XPS spectrum of high resolution C1s in fig. 4(E) can be decomposed into four dominant peaks, C ═ C at 284.6eV, C — N at 285.3eV, C ═ N at 286.5eV, and C ═ O at 288.3eV, respectively. Peak at 284.6eV with C ═ C, mainly sp corresponding to carbon²Hybridization indicates that most of the carbon atoms are in a conjugated honeycomb lattice. The peaks corresponding to C-N and C ═ N demonstrate the presence of the N element and the presence of different binding forms of the N element. In the XPS spectrum of high resolution N1s of FIG. 4(F), the N1s peak can be decomposed into three components, with peak positions of 398.6eV, 399.8eV and 401.4eV for pyridine N, pyrrole N and graphite N atoms, respectively. Wherein, the content of pyrrole N is the maximum, the content of graphite N is intermediate, and the content of pyridine N is the minimum. This shows that pyrrole N and graphite N are the main active functional groups and play an important role in the process of improving the electrochemical performance of the electrode.

3. The alternating current impedance spectrogram of the electrode before and after nitrogen plasma modification is shown in FIG. 3(A). Electrochemical impedance is the most effective characterization tool for studying surface interface properties before and after electrode modification. The AC impedance curve is composed of a high frequency region and a low frequency region, and the semi-circle diameter of the curve represents the electron transfer impedance (R) of the electrode surface_et) Different modified electrodes (naked GCE and NP-GCE) in the presence of 50mM [ Fe (CN)₆]^4-/3-Electrochemical impedance diagram in 1M KCl solution. Wherein the frequency ranges from 1Hz to 100KHz and the amplitude is 5 mV. EIS diagram of bare GCE shows a large semicircle (Rct 1900. OMEGA.) for Fe (CN) dissolved in electrolyte solution₆ ^3-Has a high resistance. EIS plots of NP-GCE showed smaller semicircles compared to GCE. Indicating that the NP-GCE surface has lower resistance and excellent capability of transferring electrons. The results of the NP-GCE with different power modifications show that Rct (100W)<Rct(140W)<Rct (180W). The Rct (140W) is approximately equal to 200 omega, the optimal electron transfer is realized, and the physical and chemical properties of the electrode are optimal under the optimal plasma power modification condition.

4. The electrochemical behavior at the different modified electrodes is shown in FIGS. 3(B) and (C). Wherein the picture (B) is 5mMK in 1M KCl solution₃[Fe(CN)₆]Cyclic voltammograms at different electrodes, sweep rate of 100mV s^-1(ii) a Panel (C) is the electrochemical curve of CFX at different electrodes. To assess the change in electrochemical activity of the NP-GCE, different electrodes were scanned using Cyclic Voltammetry (CV). As shown in FIG. B, Fe [ (CN) is observed in the CV curve of the original GCE₆]^3-The redox peak potential difference (. DELTA.Ep) of the pair of redox peaks of (2) was 138 mV. In contrast, Δ Ep of NP-GCE was reduced to 70mV, which means that the reversibility of the electrode was significantly improved and that NP-GCE was able to perform faster electron transfer than the original GCE. Panel (C) is a DPV plot of CFX at different electrodes. Under the condition of detecting the same concentration of CFX, the peak current response of the original GCE is 0.484. mu.A, while the peak current response of the NP-GCE is remarkably increased to 1.393. mu.A, and the oxidation peak potential is negatively shifted from 1.088 to 1.064V. Further proves that the electron transfer capability of the electrode can be effectively enhanced by plasma modification, and the electrochemical performance of the electrode is improved.

Example two

The embodiment is mainly used for researching the influence of two parameters of power and time modified by nitrogen plasma on the structure of the modified glassy carbon electrode. The CFX current versus power parameter versus time is shown in fig. 4(a) and (B).

As can be seen from fig. 4(a) and (B), the modification power has a great influence on the change of the glassy carbon electrode structure, the oxidation peak current value of CFX gradually increases when the plasma power increases from 100W to 140W, the oxidation peak current value of CFX significantly decreases when the plasma power increases from 140W to 180W, and the oxidation peak current value is the highest when the plasma power is 140W. This is because when the modification power is increased from 100W to 140W, the strength of the plasma acting on the GCE surface increases, which promotes the number of active functional groups on the GCE surface to increase, so that the activity of the electrode increases, more CFX is oxidized, and as the power of the plasma continues to increase, the power is too high, the modification on the electrode surface is too strong, which may cause the structure of the electrode surface to be damaged. Therefore, 140W was chosen as the optimum power for this experiment. As shown in fig. 4(B), at the optimum power, the oxidation peak current of CFX gradually increases with time, and when the action time is 8min, the oxidation peak current of CFX reaches the maximum, the action time increases again, and the peak current decreases to some extent. This is due to the increased duration of action, which contributes to an increased number of active functional groups on the GCE surface, but too long a duration of action can lead to damage to the electrode surface. Thus, a modification power of 140W and an action time of 8min were determined to be optimal in this experiment.

EXAMPLE III

The embodiment provides a sensor which is prepared by the technical scheme and can be used for rapidly detecting antibiotics in water environment, the sensor is used for a detection method for detecting ciprofloxacin in water environment, and 0.2M Na is utilized₂HPO₄And 0.2M NaH₂PO₄The solutions are mixed according to different volume ratios to prepare PBS buffer solution with the pH range of 4.5-8.0, and after sampling the water environment to be detected, the PBS buffer solution is used for adjusting the pH of the sample to be detected.

The effect of different pH on CFX oxidation peak current is shown in FIGS. 4(C) and (D), where (C) is the differential pulse voltammogram of CFX at different pH on NP-GCE electrode (pH values: 4.5, 5, 5.5, 6, 6.5,7, 7.5, 8) and (D) the effect of pH on the CFX peak current and potential at a CFX concentration of 1 × 10^-4mol L^-1The electrochemical response of the CFX oxidation peak is gradually increased when the pH is increased from 4.5 to 5, and the electrochemical response value of the CFX oxidation peak is sharply reduced when the pH is increased from 5 to 8 in the solution with different pH values. Indicating that during oxidation of CFX, there may be H⁺Participates in the reaction. Therefore, PBS buffer at pH 5 was selected as the best supporting electrolyte for the experiment. Meanwhile, as shown in graph (D), the oxidation peak potential of CFX is shifted negatively in the range of 4.5 to 8.0 as the pH is increased. This is because the progress of the oxidation process is hindered as the proton concentration decreases. The linear regression equation between oxidation potential (Ep) and pH is: epa (V) -1.293 (V) -0.045pH (correlation coefficient, R)²0.9932) with a slope of-45.0 mV/pH, approaching the theoretical value of-59 mV/pH, indicating that the oxidation reaction at the modified electrode involves protons and that the reaction process is an equi-proton, etc. electronic reaction.

The effect of different sweep rates on CFX electrochemical behavior is shown in FIG. 4(E), which is a cyclic voltammogram of CFX at different sweep rates, with the inset showing the effect of sweep rate on CFX peak current. As shown in graph (E), the peak current value gradually increases with an increase in the scanning rate, while the background current also significantly increases. When the scanning speed is too fast, the charging current is too large, and the accuracy of the experiment is influenced; when the scanning speed is too slow, the current decreases and the sensitivity of detection deteriorates. In view of the above, the optimal scan rate is selected to be 100mV · s^-1. As shown in the inset of graph (E), the relationship between peak current (Ipa) and scan rate can be expressed as follows: ipa (μ a) ═ 0.2734v (mV · s)^-1) +1.2735 (correlation coefficient, R)²0.9836), the results show that the oxidation process of CFX on NP-GCE is an adsorption controlled process. Furthermore, no reduction peak of CFX was observed in the cyclic voltammetry reverse scan, indicating that the reaction of CFX on NP-GCE was completely irreversible.

The influence of different resting time on the electrochemical behavior of CFX is shown in fig. 4(F), and in 2s to 350s, the peak current continuously increases with the extension of the enrichment time, while the increase value of the peak current tends to decrease, and the peak current tends to be stable when the enrichment time is 200s, presumably because the reaction of CFX on the surface of the electrode has adsorption characteristics and reaches adsorption saturation at 200 s. It was thus determined that the optimum enrichment time employed was 200 s.

Example four

The group of embodiments is used for verifying the linear range and stability of the nitrogen plasma modified electrode

1. The linear range and detection limit of CFX are detected.

The calibration curve of CFX is shown in FIG. 5, in which (A) the differential pulse voltammograms of CFX with different concentrations are 2.5 × 10^-7，7×10^-7，1×10^-6，4×10^-6，7×10^-6，1×10^-5，2.5×10^-5，4×10^-5，5.5×10^-5，7×10^-5，8.5×10^-5，1×10^-4mol L^-1Comparing both cyclic voltammetry and differential pulse voltammetry, differential pulse voltammetry was found to be more sensitive for determining CFX, so this experiment used differential pulse voltammetry to determine a range of standard CFX solutions of different concentrations, as shown in the figure at 2.5 × 10^-7～1×10^{- 5}mol·L^-1、1×10^-5～1×10^-4mol·L^-1Within the concentration range of (2), the peak current of CFX and the concentration of CFX have a good linear relation, and the corresponding linear regression equation is as follows: i is_p，a1(μA)＝0.0135C_CFX(μM)+0.2951(R²＝0.993)、I_p，a2(μA)＝0.038C_CFX(μM)-0.0024(R²0.998), detection limit of 8 × 10^-9mol L^-1。

The performance of the different methods for detecting CFX is shown in table 1. Compared with other working electrodes, the nitrogen plasma modified electrode provided by the embodiment of the invention has a wider linear range, lower background response and stronger sensitivity, and a test result can show that the nitrogen plasma modified electrode is a promising electrochemical sensor for detecting CFX.

TABLE 1 Performance of OFLs tested by different methods

2. Selectivity of nitrogen plasma modified electrode

To evaluate the selectivity of NP-GCE for CFX, organic components and inorganic ions were separately selected to investigate their effect on CFX detection. The organic component selects different classes of moxifloxacin, sulfapyridine, doxycycline and tetracycline in antibiotics, and the inorganic ion selects K⁺、Ca²⁺、Na⁺、Mg²⁺、Cl^-As shown in FIG. 6, (a)1 × 10 in FIG. A^-5mol L^-1CFX，(b)1×10^-5mol L^-1Sulfapyridine, (c)1 × 10^-5mol L^-1Moxifloxacin (Moxifloxacin), (d)1 × 10^-5mol L^-1Doxycycline (Doxymycin), (e)2 × 10^-5mol L^-1Tetracycline (Teracycline), FIG. (B) (a)1 × 10^-5mol L^-1CFX，(b)0.2M Ca²⁺,(c)0.2M K⁺,(d)0.2M Mg²⁺,(e)0.2M Na⁺,(f)0.2M Cl^-. As shown in fig. (a), the current changes caused by the addition of these 4 antibiotics to CFX peak current are 12.2%, 15.2%, 7.7%, and 6.2% of the original peak current, respectively, wherein moxifloxacin has the greatest effect on the detection of CFX, probably because moxifloxacin and ciprofloxacin are both quinolone antibiotics, and the similar structure causes the impact on the detection of CFX. As shown in FIG. 6(B), the current changes caused to the CFX peak current after the inorganic ion was added as an interfering ion were 7.0%, 4.2%, 3.8%, 2.2%, respectively, of the original peak current, where Ca was present²⁺The effect of detection of CFX may be due to Ca^{2 +}The complex is generated with CFX, and the adsorption of CFX on the interface is influenced. In general, other antibiotics and interfering ions have less influence on the detection of CFX by NP-GCE, and the detection of CFX by NP-GCE shows better selectivity.

3. Stability and reproducibility of nitrogen plasma modified electrodes

To examine the reproducibility of the modified electrode, 10 replicates of assay 1 × 10 were performed with the same electrode^-4mol L^-1The relative standard deviation (R.S.D.) of the differential pulse voltammetric current of CFX is 4.29%, and the result shows that the electrode has high repeatability, meanwhile, in order to verify the reproducibility of the electrode, 5-branch nitrogen plasma modified glassy carbon electrodes are prepared by the same method and the same conditions, and the 5-branch electrode pair 1 × 10 is tested^-4mol L^-1The R.S.D. of the current response value is 4.59% as a result of experiments of the magnitude of the differential pulse voltammetric current of CFX, and the results show that the sensor prepared by the nitrogen plasma modified electrode has higher repeatability. Regarding the stability of the electrode, a single NP-GCE detects CFX, the CFX is stored at 25 ℃, the same CFX is detected every 2 days, and the response current value of the CFX detection after six days is 89% of the initial current, so that the good stability is shown.

4. Application in actual water environment

To verify the application of the sensor in real water environment, we utilized nitrogen plasma modified electrodes to determine the CFX content in real tap water and groundwater. Results as shown in table 2 below, the recovery of the antibiotic was measured to be between 92.10% and 109.48% in both tap water and groundwater, with a relative standard deviation of less than 4.07%. The method shows good sensitivity and accuracy, so that the electrochemical method of the nitrogen plasma modified electrode is feasible for determining CFX in the water environment.

TABLE 2 detection of CFX in real water environment samples

The NP-GCE sensor which is easy to modify and novel is successfully developed through a nitrogen plasma process, active functional groups on the surface of the GCE are increased through nitrogen plasma modification, the hydrophilicity of an electrode is better, the surface has lower resistance and excellent electron transfer capability, a wider linear concentration range is shown for effective detection of CFX in water, and the detection limit is as low as 0.008 mu M. The detection of CFX by NP-GCE is facilitated under the condition that the pH value is 5. It is found that the oxidation process of CFX on NP-GCE is an adsorption control process, and the oxidation reaction of CFX on NP-GCE is an electronic reaction of equal proton and the like. Discloses a nitrogen plasma modified glassy carbon electrode interface element and a change mechanism of a functional group. The sensor has good anti-interference capability on non-target detection objects (such as moxifloxacin, sulfapyridine, doxycycline, tetracycline and other inorganic ions), and has good repeatability, stability and reproducibility, and the content of CFX in a real water environment can be determined.

Although the present invention has been described in considerable detail with reference to certain embodiments and examples, it will be apparent to one skilled in the art that many modifications and variations are possible in light of the above teaching. Accordingly, such modifications and improvements are intended to be within the scope of the invention as claimed.

Claims (10)

1. A sensor capable of rapidly detecting antibiotics in water environment is characterized by being prepared through the following steps:

polishing, namely polishing the bare glassy carbon electrode on a polishing device attached with a polishing agent;

cleaning and blow-drying, namely cleaning and blow-drying the polished glassy carbon electrode for later use;

and step three, plasma modification, namely placing the dried glassy carbon electrode on a CPC-A (CIFINertional Group Co., Ltd) of a plasma cleaning machine, wherein the modification power is 100W-180W, and the modification time is 0.5 min-10 min.

2. The sensor of claim 1, wherein in step one, the polishing agent is Al₂O₃Polishing powder paste.

3. The sensor for rapidly detecting antibiotics in water environment as claimed in claim 2, wherein in the step one, the bare glassy carbon electrodes are sequentially arranged at 1 μm, 0.3 μm and 0.05 μm Al₂O₃Of polishing powder pastesAnd (5) grinding and polishing the polishing cloth.

4. The sensor capable of rapidly detecting antibiotics in water environment according to claim 1, wherein in the second step, the polished glassy carbon electrode is placed in secondary distilled water or absolute ethyl alcohol for ultrasonic cleaning.

5. The sensor capable of rapidly detecting antibiotics in water environment according to claim 4, wherein in the second step, the polished glassy carbon electrode is sequentially subjected to ultrasonic cleaning in secondary distilled water, absolute ethyl alcohol and secondary distilled water.

6. The sensor capable of rapidly detecting antibiotics in water environment according to claim 5, wherein in the second step, the cleaned glassy carbon electrode is dried in a nitrogen protection atmosphere.

7. The sensor capable of rapidly detecting antibiotics in water environment according to claim 1, wherein in step three, the modification power is 120W-160W, and the modification time is 4 min-10 min.

8. The detection method of the sensor capable of rapidly detecting the antibiotics in the water environment according to any one of claims 1 to 7 is characterized in that the detection method detects ciprofloxacin-containing water to be detected through a nitrogen plasma surface modified sensor.

9. The detection method according to claim 8, wherein the ciprofloxacin-containing water to be detected is adjusted to pH 4.5 to 8 by a buffer solution.

10. The detection method according to claim 9, wherein the ciprofloxacin-containing water to be detected is adjusted to pH 4.5 to 6 by a buffer solution.

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