Working electrode for detecting micro-plastic and method for detecting micro-plastic through electrochemical sensing

Abstract

The working electrode is characterized in that the working electrode is obtained by dispensing ferroferric oxide and lauric acid on the surface of a glassy carbon electrode. A working electrode for detecting the micro-plastic is a working electrode, an Ag / AgCl electrode is a reference electrode, and platinum is an auxiliary electrode; preparing a series of concentrations of micro-plastic standard sample solutions, preparing a ferrocene solution and an electrolyte, firstly putting a working electrode, a reference electrode and an auxiliary electrode into the standard sample solutions, incubating to reach adsorption equilibrium, then taking out the three electrodes, putting the three electrodes into the ferrocene solution, and incubating; and finally, taking out the three-electrode system, putting the three-electrode system into electrolyte, and carrying out DPV detection. A simple and low-cost electrochemical sensing detection method is established by utilizing the reaction of the micro-plastic reinforced ferrocene signal molecules. The method is rapid, simple and low in cost, and can effectively detect the micro-plastics in a wide range and maintain good sensitivity.

Description

Technical Field

[0001] The present invention relates to the technical field of pollutant detection, and in particular to a working electrode for detecting microplastics and a method for detecting microplastics by electrochemical sensing. Background Art

[0002] Plastic products are widely used in many industries, such as packaging, automobiles, construction, electronics and agriculture. Plastics have provided great convenience for modern people's lives, but due to the large-scale use of plastic products, the safety issues they bring cannot be ignored. In 2004, Thompson, a scientist at the University of Plymouth in the UK, first proposed the concept of "microplastics" in the journal Science. He defined microplastics as plastic fragments and particles with a diameter of less than 5 mm. The environmental pollution caused by microplastics has attracted the attention of researchers around the world.

[0003] The distribution, migration, toxicity and ecological effects of microplastics in aquatic environments are all important contents of microplastic research, and the establishment of accurate and efficient microplastic detection technology and analysis methods provides important tools and methodological support for microplastic research. At present, the commonly used identification methods for microplastics include visual method, microscopy, scanning electron microscopy, infrared spectroscopy, Raman spectroscopy, thermogravimetric differential scanning calorimetry, pyrolysis gas chromatography-mass spectrometry and thermal extraction thermal desorption gas chromatography-mass spectrometry. However, these methods require the use of large instruments and professional training for operators, and cannot achieve rapid, immediate and low-cost detection; on the other hand, these methods require time-consuming and complex pre-treatment of samples, which also increases the difficulty of microplastic detection. Summary of the invention

[0004] In view of the above technical problems, the first purpose of the present invention is to provide a working electrode for detecting microplastics, and the second purpose is to provide a method for detecting microplastics by electrochemical sensing. Microplastics are detected using electrochemical technology, namely differential pulse voltammetry (DPV). Microplastics are used to enhance the reaction of ferrocene signal molecules to establish a simple and low-cost electrochemical sensing detection method. It is fast, simple, and low-cost, and can effectively detect microplastics in a wide range and maintain good sensitivity.

[0005] In order to achieve the above-mentioned first purpose, the present invention provides a working electrode for detecting microplastics, characterized in that it is obtained by drop-coating ferrosoferric oxide and lauric acid on the surface of a glassy carbon electrode.

[0006] In the above scheme, the preparation is carried out according to the following method: (1) ultrasonically cleaning the magnetic nano-Fe with dilute hydrochloric acid solution 3 O 4Particles, remove surface pollutants, then use acetone to clean the oily impurities on the surface, and finally use ultrapure ethanol to clean the acid solution and acetone remaining on the surface, and dry for use;

[0007] (2) The magnetic nano-Fe 3 O 4 The particles were dispersed in ethanol, and lauric acid was added, stirred for reaction, and the solid was taken out, rinsed with ethanol and dried to obtain Fe 3 O 4 @C 12 ;

[0008] (3) Take the above Fe 3 O 4 @C 12 Put it into the ball mill, sieve it, and remove Fe 3 O 4 @C 12 The nafion solution was uniformly dispersed in ethanol, and the uniform ink formed by ultrasound was recorded as ink A;

[0009] (4) Polishing the surface of the glassy carbon electrode to remove impurities on the surface of the glassy carbon electrode, giving the surface of the glassy carbon electrode a mirror effect, applying a drop of ink A on the surface of the glassy carbon electrode, and after drying, the preparation of the working electrode is completed.

[0010] In the above scheme, in step (2), the concentration of the ethanol dispersion solution of ferrosoferric oxide is 0.025 g / mL, and the concentration of lauric acid is 0.1 g / mL.

[0011] In the above scheme, after adding lauric acid in step (2), the reaction is stirred at 80-90° C. for 1-2 hours.

[0012] In the above scheme, in step (1) and step (2), the drying temperature is 80-90°C.

[0013] In the above scheme, in step (3), the sieve is 200 mesh, Fe 3 O 4 @C 12 The ratio of nafion solution to ethanol is 4 mg:10 μL:2 mL.

[0014] The second object of the present invention is achieved as follows: a method for electrochemical sensing detection of microplastics, using a working electrode for detecting microplastics as a working electrode, an Ag / AgCl electrode as a reference electrode, and platinum as an auxiliary electrode; preparing a series of microplastic standard sample solutions of concentrations, preparing a ferrocene solution and an electrolyte, first placing the working electrode, the reference electrode, and the auxiliary electrode in the standard sample solution, incubating to reach adsorption equilibrium, then taking out the three electrodes, and placing them in the ferrocene solution, and incubating; finally taking out the three-electrode system and placing it in the electrolyte, performing DPV detection, establishing a linear relationship between the DPV current y and the logarithm of the concentration x, and obtaining the corresponding regression equation; and detecting the sample solution in the same way.

[0015] In the above scheme, the concentrations of microplastics in a series of standard sample solutions were 0, 1 μg / L, 3.16 μg / L, 10 μg / L, 31.6 μg / L, and 100 μg / L.

[0016] In the above scheme, the concentration of the ferrocene solution is 0.1 mM / L to 1 mM / L, and the electrolyte is a 0.1 m / L KCl solution. The electrolyte may also be other electrolytes.

[0017] In the above scheme, the DPV detection parameters are potential range 0-0.4V, pulse height 25mV / s, step height 2mV / s, pulse width 25ms, and step width 75ms.

[0018] The present invention uses Fe 3 O 4 @C 12 The modified glassy carbon electrode (GCE) was used as the working electrode and incubated in the pollutant and signal substance solutions respectively. Finally, differential pulse voltammetry was used in the electrolyte solution to detect microplastics in the water sample.

[0019] The present invention uses Fe 3 O 4 @C 12 The modified glassy carbon electrode (GCE) is used as the working electrode, and a charged external probe molecule is used as the electrochemical signal molecule (ferrocene). When there are no microplastics in the water sample, the working electrode adsorbs the charged external probe molecule, which can indirectly indicate the current of the circuit through redox and generate an electrochemical signal; when there are microplastics in the water sample, Fe 3 O 4 @C 12The adsorption of microplastics, the combination of the two through electrostatic interaction, van der Waals force and other possible chemical bonds, affects the redox of the subsequently adsorbed charged exoprobe molecules, and finally the electrochemical detection of trace microplastics in water is achieved by recording the changes in the electrochemical signals of the exoprobe molecules. A linear relationship between the electrochemical signal and the concentration of microplastics is established, and the corresponding linear regression equation is obtained.

[0020] The beneficial effects of the present invention are as follows: the present invention utilizes electrical signal excitation to generate electrochemical signals. It utilizes relatively safe ferrocene as a charged probe molecule to react to the current of the circuit. 3 O 4 @C 12 The combination with microplastics affects the conductivity of the circuit and thus affects the electrochemical signal. The detection of microplastics is achieved through electrochemical signals. The higher the concentration of microplastics, the greater the circuit current, and the stronger the intensity of the electrochemical signal generated. Based on this, a correlation between microplastics and the intensity of the electrochemical signal is established. The detection method of the present invention is used to quickly detect microplastics in water, which is safe, accurate, effective and simple. The linear detection range of microplastics in this detection method is 1μg / L to 100μg / L, the detection limit is 0.36μg / L, the detection linear range is wide, the sensitivity is high, and it has good reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is an electrochemical diagram showing the variation of electrochemical signal intensity with microplastic concentration in Example 1 of the present invention.

[0022] Figure 2 This is the standard curve of the electrochemical signal intensity in Example 1 as it changes with the microplastic concentration.

[0023] Figure 3 This is an electrochemical diagram showing the variation of electrochemical signal intensity with microplastic concentration in Example 2 of the present invention.

[0024] Figure 4 This is the standard curve of the electrochemical signal intensity in Example 2 as it changes with the microplastic concentration. DETAILED DESCRIPTION

[0025] The present invention will be further described below by way of embodiments and in conjunction with the accompanying drawings:

[0026] Example 1

[0027] With dilute hydrochloric acid solution (V HCl :V water =1:20) Ultrasonic cleaning of magnetic nano-Fe 3 O 4 The particles were cleaned to remove the pollutants on the surface. Then the oily impurities on the surface were cleaned with acetone, and finally the acid solution and acetone remaining on the surface were cleaned with ultrapure ethanol.3 O 4 Dry at 80-90°C. Take the above 0.5g Fe 3 O 4 Disperse in 20 mL of anhydrous ethanol, add 2 g of lauric acid, and stir at 80-90 °C for 1-2 h. Then, take out the solid and rinse with ethanol to obtain Fe 3 O 4 @C 12 Dry at 80-90°C.

[0028] Take the above Fe 3 O 4 @C 12 Put it into the ball mill and grind it for 30 minutes, and then pass it through a 200-mesh screen. Weigh 4 mg of Fe 3 O 4 @C 12 10 μL of nafion solution was uniformly dispersed in 2 mL of ethanol by ultrasound to form a uniform ink, which was recorded as Ink A.

[0029] The surface of the glassy carbon electrode was polished with 0.3μm and 0.05μm alumina powders in turn. The impurities on the surface of the glassy carbon electrode were removed by polishing, giving the surface of the glassy carbon electrode a mirror effect. 10μL of ink A was dropped on the surface of the glassy carbon electrode (the glassy carbon electrode is a cylinder, the drop-coating area is at the bottom of the cylinder, and the effective diameter is 5mm). After drying, the preparation of the working electrode was completed.

[0030] The detection method is as follows:

[0031] Take three groups of solutions, A, B, and C, where A is a water sample contaminated with microplastics, with a concentration gradient of 0, 1 μg / L, 3.16 μg / L, 10 μg / L, 31.6 μg / L, and 100 μg / L, B is a 0.1 m / L ferrocene solution, and C is a 0.1 m / L KCl electrolyte. Assemble the three-electrode system with Fe 3 O 4 @C 12 The three-electrode system was placed in solution A and incubated at 200 rpm for 40 min to achieve adsorption equilibrium. The three-electrode system was then taken out and placed in solution B, which was also incubated at 200 rpm for 40 min. Finally, the three-electrode system was taken out and placed in solution C for DPV detection.

[0032] The DPV parameters are potential range 0-0.4V, pulse height 25mV / s, step height 2mV / s, pulse width 25ms, and step width 75ms. The results are as follows Figure 1 It should be noted that the results have been baseline subtracted and Gaussian smoothed.

[0033] like Figure 2 The standard curve of electrochemical signal and microplastic concentration. The linear relationship between DPV current y and concentration logarithm x was established, and the corresponding regression equation y = 4.32 + 0.69x, R 2 =0.9932. According to the detection limit calculation formula in is the slope of the standard curve in the low concentration range, and s is the standard deviation of the blank sample. In the linear detection range of 1μg / L to 100μg / L, the detection limit was calculated to be 0.36μg / L.

[0034] Example 2

[0035] The other conditions were the same as in Example 1, except that the concentration of the ferrocene solution was 1 mM / L, and the microplastic concentration gradient was 0, 1 μg / L, 10 μg / L, 100 μg / L, and 1000 μg / L.

[0036] like Figure 3 and 4 Regression equation y = 15.01 + 1.608x, R 2 =0.9990

[0037] Within the linear detection range of 1μg / L to 1000μg / L, the detection limit was calculated to be 0.99μg / L.

[0038] The present invention is not limited to the above embodiments. For example, the concentration of the ferrocene solution may be other concentrations between 0.1 mM / L and 1 mM / L, and the electrolyte may be other electrolytes. Those skilled in the art will appreciate that various changes, modifications, substitutions and variations may be made to these embodiments without departing from the principles and purpose of the present invention. The scope of the present invention is defined by the claims and their equivalents.

Claims

1. A working electrode for detecting microplastics, characterized in that: It is obtained by drop-coating ferroferric oxide and lauric acid on the surface of glassy carbon electrode.

2. The working electrode for detecting microplastics according to claim 1, characterized in that: The preparation method is as follows: (1) using a dilute hydrochloric acid solution to ultrasonically clean the magnetic nano-Fe3O4 particles to remove surface pollutants, then using acetone to clean the oily impurities on the surface, and finally using ethanol to clean the acid solution and acetone remaining on the surface, and drying for later use; (2) The magnetic nano Fe3O4 particles are dispersed in ethanol, lauric acid is added, stirred for reaction, the solid is taken out, washed with ethanol and dried to obtain Fe3O4@C 12 ; (3) Take the above Fe3O4@C 12 Put it into the ball mill, sieve it, and Fe3O4@C 12 The nafion solution was uniformly dispersed in ethanol, and the uniform ink formed by ultrasound was recorded as ink A; (4) Polishing the surface of the glassy carbon electrode to remove impurities on the surface of the glassy carbon electrode, giving the surface of the glassy carbon electrode a mirror effect, applying a drop of ink A on the surface of the glassy carbon electrode, and after drying, the preparation of the working electrode is completed.

3. The working electrode for detecting microplastics according to claim 2, characterized in that: In step (2), the concentration of the ethanol dispersion solution of ferrosoferric oxide is 0.025 g / mL, and the concentration of lauric acid is 0.1 g / mL.

4. The working electrode for detecting microplastics according to claim 3, characterized in that: After adding lauric acid in step (2), stirring the reaction at 80-90° C. for 1-2 h.

5. The working electrode for detecting microplastics according to claim 4, characterized in that: In step (1) and step (2), the drying temperature is 80-90°C.

6. The working electrode for detecting microplastics according to claim 5, characterized in that: In step (3), the sieve is 200 mesh, Fe3O4@C 12 The ratio of nafion solution to ethanol is 4 mg:10 μL:2 mL.

7. A method for detecting microplastics by electrochemical sensing, characterized in that: The working electrode for detecting microplastics described in claims 1-6 is used as the working electrode, the Ag / AgCl electrode is used as the reference electrode, and platinum is used as the auxiliary electrode; a series of microplastic standard sample solutions of different concentrations are prepared, a ferrocene solution and an electrolyte are prepared, the working electrode, the reference electrode and the auxiliary electrode are first placed in the standard sample solution, incubated to reach adsorption equilibrium, and then the three electrodes are taken out and placed in the ferrocene solution for incubation; finally, the three-electrode system is taken out and placed in the electrolyte for DPV detection, a linear relationship between the DPV current y and the logarithm of the concentration x is established, and the corresponding regression equation is obtained; and the sample solution is detected in the same way.

8. The method for detecting microplastics by electrochemical sensing according to claim 7, characterized in that: The concentrations of microplastics in a series of standard sample solutions were 0, 1 μg / L, 3.16 μg / L, 10 μg / L, 31.6 μg / L, and 100 μg / L.

9. The method for detecting microplastics by electrochemical sensing according to claim 7, characterized in that: The concentration of the ferrocene solution is 0.1 mM / L to 1 mM / L, and the electrolyte is a 0.1 m / L KCl solution.

10. The method for detecting microplastics by electrochemical sensing according to claim 9, characterized in that: The DPV detection parameters are potential range 0-0.4V, pulse height 25mV / s, step height 2mV / s, pulse width 25ms, and step width 75ms.

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