阅读说明：本技术 一种聚合物膜修饰电极及其制备方法与应用 (Polymer film modified electrode and preparation method and application thereof ) 是由 王红宁 闫建康 孙俊宝 张生智 于 2020-12-07 设计创作，主要内容包括：本发明属于电分析化学技术领域,本发明公开了一种铋膜/聚二溴荧光素修饰电极的制备及测定农田灌溉水中Cd～(2+)浓度的方法。修饰电极制备过程：通过循环伏安法,将二溴荧光素分子电化学聚合到玻碳电极表面制得聚二溴荧光素膜化学修饰电极(记为Poly(DBF)/GCE),然后在加入适量的铋离子通过吸附作用制的铋膜/聚二溴荧光素膜修饰电极(Bi/Poly(DBF)/GCE)。利用该修饰电极,通过阳极溶出微分脉冲伏安法,建立了一种新颖、灵敏、准确、简单的电化学方法来测定水样中的痕量Cd～(2+)。(The invention belongs to the technical field of electroanalytical chemistry, and discloses preparation of a bismuth film/polydibromofluorescein modified electrode and determination of Cd in farmland irrigation water 2+ And (3) concentration method. The preparation process of the modified electrode comprises the following steps: electrochemically polymerizing dibromofluorescein molecules to the surface of a glassy carbon electrode by cyclic voltammetry to obtain a polydibromofluorescein membrane chemically-modified electrode (marked as Poly (DBF)/GCE), and adding a proper amount of bismuth ions to prepare the bismuth membrane/polydibromofluorescein membrane chemically-modified electrode (Bi/Poly (DBF)/GCE) through adsorption. By utilizing the modified electrode and through anodic stripping differential pulse voltammetry, a novel, sensitive, accurate and simple electrochemical method is established for measuring trace Cd in a water sample 2+ 。)

1. A preparation method of a polymer membrane modified electrode is characterized by comprising the following steps:

(1) al for glassy carbon electrode₂O₃Polishing the polished powder into a mirror surface, and sequentially using HNO with the volume ratio of 1:1₃Respectively ultrasonically cleaning the solution, absolute ethyl alcohol and secondary distilled water;

(2) putting the electrode cleaned in the step (1) in 0.5-1.0mol/L H₂SO₄Performing cyclic voltammetry scanning until a stable cyclic voltammogram is obtained;

(3) taking the glassy carbon electrode pretreated in the step (2) as a working electrode, taking a saturated calomel electrode as a reference electrode and a platinum wire as a counter electrode, placing a three-electrode system in a phosphate buffer solution with the pH value of 4.0-6.0, then adding 0.5-1.5 mmol/L dibromofluorescein, circularly scanning at the scanning rate of 100mV/s within the range of-0.42-1.82V to prepare a polydibromofluorescein modified electrode, cleaning the polydibromofluorescein modified electrode with secondary distilled water, and storing the polydibromofluorescein modified electrode in a phosphate buffer solution with the pH value of 4.0-6.0 for later use;

(4) adding Bi into the electrolytic cell³⁺Standard solution, Cd²⁺Standard solution and HAc-NaAc buffer solution, and Bi in the obtained mixed solution³⁺The concentration is 3.5X 10^-6mol/L，Cd²⁺The concentration is 2.0 × 10^-7mol/L, pH 5.0-6.0, magnetic stirring and enriching for 300-400 s under-1.3V potential, standing for 50-70 s,and preparing the polymer membrane modified electrode.

2. The method for preparing a polymer film modified electrode according to claim 1, wherein in the step (1), the glassy carbon electrode Φ is 3mm, and Al is added₂O₃The grain size of the polishing powder is 0.04-0.06 mu m.

3. The method for preparing the polymer membrane modified electrode according to claim 1, wherein in the step (1), the ultrasonic cleaning time is 4-6 min.

4. The method for preparing the polymer film modified electrode according to claim 1, wherein in the step (2), cyclic voltammetry scanning is performed within a range of-0.4 to 1.8V.

5. The method for preparing the polymer membrane modified electrode according to claim 1, wherein the step (3) is performed by scanning at a scanning rate of 100mV/s for 20-40 weeks in a cyclic manner.

6. The method for preparing the polymer membrane modified electrode according to claim 1, wherein the concentration of the phosphate buffer solution is 0.1 mol/L.

7. A polymer film modified electrode prepared by the method for preparing a polymer film modified electrode according to any one of claims 1 to 6.

8. A method of determining Cd in farmland irrigation water using the polymer membrane modified electrode of claim 7²⁺The use of concentration.

9. The method for determining Cd in farmland irrigation water by using polymer film modified electrode according to claim 8²⁺The concentration application is characterized in that differential pulse voltammetry scanning is carried out within the range of-1.2-0.15V, and cadmium ions are quantitatively divided according to the magnitude of peak currentAnd (6) analyzing.

Technical Field

The invention belongs to the technical field of electroanalytical chemistry, and discloses preparation of a bismuth film/polydibromofluorescein modified electrode and determination of Cd in farmland irrigation water²⁺And (3) concentration method.

Background

With the rapid development of economy in China, environmental problems have become significant problems affecting human survival and development. The random discharge of heavy metal ions is one of the main pollution sources of the current environmental pollution. The heavy metal cadmium is widely applied to the fields of electroplating industry, chemical industry and the like, and is discharged into the environment through waste water to cause pollution. The cadmium metal can not be biodegraded and is easy to be enriched in human bodies, thus seriously harming human health.

At present, the detection means of cadmium ions include neutron activity analysis, atomic absorption spectrometry, X-ray fluorescence spectrometry, inductively coupled plasma mass spectrometry, atomic emission spectrometry and the like, and the analysis methods use expensive instruments and equipment, have high maintenance cost and are complex to operate; the polymer membrane modified electrode has the advantages of low equipment price, high analysis speed, high sensitivity, good selectivity and the like, and is a feasible and effective analysis method for measuring cadmium ions.

Therefore, how to select a proper polymer and prepare the polymer into a polymer film modified electrode for improving Cd²⁺The sensitivity of detection becomes an issue that those skilled in the art need to solve.

Disclosure of Invention

The invention aims to provide a preparation method of a polymer film modified electrode, which can prevent the surface of a bismuth film from being abraded and enhance the modified electrode pair Cd²⁺In response to (2).

In order to achieve the purpose, the technical scheme of the invention is as follows:

a preparation method of a polymer membrane modified electrode comprises the following steps:

(1) al for glassy carbon electrode₂O₃Polishing the polished powder into a mirror surface, and sequentially using HNO with the volume ratio of 1:1₃Ultrasonically cleaning the solution, absolute ethyl alcohol and secondary distilled water;

(2) placing the electrode cleaned in the step 1 in 0.5-1.0mol/L H₂SO₄Performing cyclic voltammetry scanning until a stable cyclic voltammogram is obtained;

(3) taking the glassy carbon electrode pretreated in the step (2) as a working electrode, taking a saturated calomel electrode as a reference electrode and a platinum wire as a counter electrode, placing a three-electrode system in a phosphate buffer solution with the pH value of 4.0-6.0, then adding 0.5-1.5 mmol/L dibromofluorescein, circularly scanning at the scanning rate of 100mV/s within the range of-0.42-1.82V to prepare a polydibromofluorescein modified electrode, cleaning the polydibromofluorescein modified electrode with secondary distilled water, and storing the polydibromofluorescein modified electrode in a phosphate buffer solution with the pH value of 4.0-6.0 for later use;

(4) adding Bi into the electrolytic cell³⁺Standard solution, Cd²⁺Standard solution and HAc-NaAc buffer solution, and Bi in the obtained mixed solution³⁺The concentration is 3.5X 10^-6mol/L，Cd²⁺The concentration is 2.0 × 10^-7And (3) mol/L, wherein the pH value is 5.0-6.0, the mixture is magnetically stirred and enriched for 300-400 s under the potential of-1.3V, and the mixture is kept stand for 50-70 s to prepare the polymer membrane modified electrode.

Preferably, in the step (1), the glassy carbon electrode Φ is 3mm, and Al is₂O₃The particle size of the polishing powder was 0.05. mu.m.

Preferably, in the step (1), the ultrasonic cleaning time in the step (1) is 4-6 min.

Preferably, in the step (2), cyclic voltammetry scanning is performed in a range of-0.4 to 1.8V.

Preferably, the step (3) is carried out for 20-40 weeks at a scanning rate of 100mV/s in a circulating manner.

Preferably, in the step (3), the concentration of the phosphate buffer solution is 0.1 mol/L.

The second purpose of the invention is to provide a polymer membrane modified electrode.

The third purpose of the invention is to provide a method for determining Cd in farmland irrigation water by using a polymer film modified electrode²⁺The use of (1).

Preferably, Cd in the farmland irrigation water is determined²⁺And scanning by differential pulse voltammetry within the range of-1.2-0.15V, and quantitatively analyzing cadmium ions according to the magnitude of peak current.

According to the technical scheme, compared with the prior art, the invention has the following beneficial effects:

1. the method comprises the steps of electrochemically polymerizing dibromofluorescein molecules onto the surface of a glassy carbon electrode by cyclic voltammetry to obtain a polydibromofluorescein membrane chemically modified electrode (marked as Poly (DBF)/GCE), and adding a proper amount of bismuth ions to prepare a bismuth membrane/polydibromofluorescein membrane through adsorptionFluorescein membrane modified electrode (Bi/Poly (DBF)/GCE). By utilizing the modified electrode and through anodic stripping differential pulse voltammetry, a novel, sensitive, accurate and simple electrochemical method is established for measuring trace Cd in a water sample²⁺。

2. The invention firstly prepares the bismuth film/polydibromofluorescein film modified electrode to be applied to the determination of trace metal cadmium ions in farmland irrigation water. The result shows that the polydibromofluorescein film can prevent the abrasion of the surface of the bismuth film and the adsorption of active compounds, and meanwhile, the sensitivity of the modified electrode is enhanced. The modified electrode has the advantages of simple preparation, good reproducibility and high sensitivity, and has a certain application prospect in water environment monitoring.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.

FIG. 1 is a diagram of ATR-FTIR of a polydibromofluorescein membrane chemically modified electrode;

FIG. 2 shows different electrode pairs Cd²⁺Wherein A is a bare glassy carbon electrode, B is a polydibromofluorescein film modified electrode, C is a bismuth film modified electrode, and D is a bismuth film/polydibromofluorescein modified glassy carbon electrode;

FIG. 3 shows different Cd²⁺Differential pulse voltammogram of concentration.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example 1

(1) Will be provided with0.05 μm Al for glassy carbon electrode (. phi.: 3mm)₂O₃Polishing the polished powder into a mirror surface, and sequentially using HNO with the volume ratio of 1:1₃And respectively ultrasonically cleaning with absolute ethyl alcohol and secondary distilled water for 4 min.

(2) Placing the electrode cleaned in the step (1) in 1.0mol/L H₂SO₄Performing cyclic voltammetry scanning within a range of-0.40-1.80V until a stable cyclic voltammogram is obtained.

(3) And (3) taking the glassy carbon electrode pretreated in the step (2) as a working electrode, taking a saturated calomel electrode as a reference electrode and a platinum wire as a counter electrode, putting the three-electrode system into phosphate buffer solution with the pH value of 4.0, then adding 0.5mmol/L dibromofluorescein, wherein the concentration of phosphate in the mixed solution is 0.1mol/L, and circularly scanning at the scanning rate of 100mV/s for 20 weeks within the range of-0.42-1.82V to prepare the polydibromofluorescein modified electrode (Poly (DBF)/GCE). The polymerized electrode was washed with double distilled water and stored in 0.1mol/L phosphate buffer solution of pH 4.0.

(4) Adding Bi into the electrolytic cell³⁺Standard solution, Cd²⁺Standard solution and HAc-NaAc buffer solution, and Bi in the obtained mixed solution³⁺The concentration is 3.5X 10^-6mol/L，Cd²⁺The concentration is 2.0 × 10^-7mol/L, pH 5.0, magnetic stirring and enriching for 300s under-1.3V potential, standing for 50s, and obtaining the bismuth membrane/polydibromofluorescein modified electrode (Bi/Poly (DBF)/GCE).

Example 2

(1) 0.05 μm of Al was used for a glassy carbon electrode (. phi.: 3mm)₂O₃Polishing the polished powder into a mirror surface, and sequentially using HNO with the volume ratio of 1:1₃And respectively ultrasonically cleaning the mixture by absolute ethyl alcohol and secondary distilled water for 5 min.

(2) Placing the electrode cleaned in the step (1) in 0.5mol/L H₂SO₄Performing cyclic voltammetry scanning within a range of-0.4-1.8V until a stable cyclic voltammogram is obtained.

(3) And (3) taking the glassy carbon electrode pretreated in the step (2) as a working electrode, taking a saturated calomel electrode as a reference electrode and a platinum wire as a counter electrode, putting a three-electrode system into phosphate buffer solution with the pH value of 5.0, then adding 1.0mmol/L dibromofluorescein, wherein the concentration of phosphate in the mixed solution is 0.1mol/L, and circularly scanning at the scanning rate of 100mV/s for 30 weeks within the range of-0.42-1.82V to prepare the polydibromofluorescein modified electrode (Poly (DBF)/GCE). The polymerized electrode was washed with redistilled water and stored in 0.1mol/L phosphate buffer solution with pH 5.0.

(4) Adding Bi into the electrolytic cell³⁺Standard solution, Cd²⁺Standard solution and HAc-NaAc buffer solution, and Bi in the obtained mixed solution³⁺The concentration is 3.5X 10^-6mol/L，Cd²⁺The concentration is 2.0 × 10^-7mol/L, pH 5.5, magnetic stirring and enriching for 300s under-1.3V potential, standing for 50s, and obtaining the bismuth membrane/polydibromofluorescein modified electrode (Bi/Poly (DBF)/GCE).

Example 3

(1) 0.05 μm of Al was used for a glassy carbon electrode (. phi.: 3mm)₂O₃Polishing the polished powder into a mirror surface, and sequentially using HNO with the volume ratio of 1:1₃And respectively ultrasonically cleaning the absolute ethyl alcohol and the secondary distilled water for 6 min.

(2) Placing the electrode cleaned in the step (1) in 1.5mol/L H₂SO₄Performing cyclic voltammetry scanning within a range of-0.4-1.8V until a stable cyclic voltammogram is obtained.

(3) And (3) taking the glassy carbon electrode pretreated in the step (2) as a working electrode, taking a saturated calomel electrode as a reference electrode and a platinum wire as a counter electrode, putting a three-electrode system into phosphate buffer solution with the pH value of 6.0, then adding 1.5mmol/L dibromofluorescein, wherein the concentration of phosphate in the mixed solution is 0.1mol/L, and circularly scanning at the scanning rate of 100mV/s for 40 weeks within the range of-0.42-1.82V to prepare the polydibromofluorescein modified electrode (Poly (DBF)/GCE). The polymerized electrode was washed with redistilled water and stored in 0.1mol/L phosphate buffer solution with pH 6.0.

(4) Adding Bi into the electrolytic cell³⁺Standard solution, Cd²⁺Standard solution and HAc-NaAc buffer solution, and Bi in the obtained mixed solution³⁺The concentration is 3.5X 10^-6mol/L，Cd²⁺The concentration is 2.0 × 10^-7mol/L, pH 6.0, at-1.3And (3) enriching for 300s by magnetic stirring at the potential V, and standing for 50s to prepare the bismuth membrane/polydibromofluorescein modified electrode (Bi/Poly (DBF)/GCE).

Example 4

FIG. 1 is an ATR-FTIR spectrum of the polydibromofluorescein film formed on the surface of an electrode in example 2;

FIG. 1 shows infrared spectra of bromodibromofluorescein (curve A) and polydibromofluorescein (curve B) obtained by differential spectroscopy. Dibromofluorescein (curve A) is approximately 3330cm due to the effect of a hydrogen bond^-1Has a strong and broad absorption peak; polydibromofluorescein (curve B) at 3740cm^-1A strong and sharp absorption peak caused by the stretching vibration of hydroxyl groups is formed; at 1246cm^-1And 1093cm^-1An absorption peak caused by C-O-C stretching vibration generated by polymerization of dibromofluorescein is generated. The appearance of a new functional group in the spectrogram indicates that the polydibromofluorescein film is formed on the surface of the glassy carbon electrode.

FIG. 2 shows Cd in acetic acid buffer (pH 5.5)²⁺Response at each electrode:

a bare glassy carbon electrode

B polydibromofluorescein film modified electrode

C bismuth film modified electrode

And D, modifying the glassy carbon electrode by the bismuth film/polydibromofluorescein.

FIG. 2 shows 2.0X 10 in acetic acid buffer (pH 5.5)^-7mol/L Cd²⁺In a bare glassy carbon electrode (curve A), a polydibromofluorescein film modified electrode (curve B) and a bismuth film modified electrode (curve C) (containing 3.5 mu mol/L Bi³⁺) And an anodic stripping voltammetry curve of the bismuth film/polydibromofluorescein modified glassy carbon electrode (curve D). As can be seen from fig. 2, a broad and small peak was observed on the bare glassy carbon electrode, and the peak current was significantly enhanced on the bismuth film electrode due to the formation of a binary alloy of bismuth ions and metal ions. Cd on bismuth film/polydibromofluorescein film modified glassy carbon electrode²⁺The oxidation peak current of the electrode is obviously larger than the current on a bare glassy carbon electrode and a bismuth film modified electrode, the modified electrode can prevent the abrasion of the surface of the bismuth film, enhance the adsorption of active substances, and improve the sensitivity of the modified electrode on the detection of metal ions.

Example 5

The polymer film modified electrode polydibromofluorescein obtained in the embodiment 1-3 can form the surface of a glassy carbon electrode, has good reproducibility, and can accurately determine Cd in farmland irrigation water²⁺The polymer membrane modified electrode obtained in example 2 was characterized:

cd modification electrode pair obtained in example 2²⁺The current response values are measured continuously for 8 times, and the standard deviation RSD is less than 5%, which shows that the modified electrode obtained in the example 2 has good reproducibility.

FIG. 3 shows different Cd²⁺Differential pulse voltammogram of concentration.

Cd²⁺Peak current and its concentration of 2.5X 10^-8～1.5×10^-7And 1.5X 10^-7～6.0×10^-6The good linear relation exists in the mol/L range, and the correction curve equations are respectively as follows:

ipa/μA＝-0.22+33.27Ccd²⁺/μmol/L(r＝0.9974)

ipa/μA＝3.17+13.34Ccd²⁺/μmol/L(r＝0.9985)

the detection limit of the method is 8.0 multiplied by 10 when the signal-to-noise ratio is 3^-9mol/L。

Example 6

Application method

And (3) taking a proper amount of farmland irrigation water, performing suction filtration through microporous filter paper with the diameter of 0.45 mu m, and measuring the concentration of Cd2+ in the farmland water by adopting a standard addition method. The experimental result is shown in table 1, and the recovery rate is 98.00-102.40%.

TABLE 1 Cd in actual samples²⁺Analysis result of (n ═ 8)

In conclusion, the decorative electrode disclosed by the invention is simple to prepare, good in reproducibility and high in sensitivity, and has a certain application prospect in water environment monitoring.

The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.