CN112697859B - Electrochemical Sensing Analysis Method of Environmental Hormone p-Nitrophenol - Google Patents

Abstract

The invention discloses an electrochemical sensing analysis method of environmental hormone 4-NP, which is implemented by mixing WO _2.9 /g‑C ₃ N ₄ Ultrasonically dispersing the stepped heterojunction in deionized water to obtain a dispersion liquid, wherein the concentration of the obtained dispersion liquid is 0.0002-0.01 g/mL; adding 1-10 mu L of WO on a clean and impurity-free bare glassy carbon electrode _2.9 /g‑C ₃ N ₄ Modifying the dispersion liquid, and then baking for 3-10 min under an infrared lamp to obtain a modified electrode; placing the modified electrode in liquid to be tested for DPV test; if an obvious oxidation peak appears in the range of 0.8-1.2V, the liquid to be detected is qualitatively detected according to the oxidation peak. When the concentration is in the range of 0.4-100 mu mol/L, the oxidation peak current value and the concentration have good linear relation, the detection limit is 0.13 mu mol/L, and the method has good stability and reproducibility and can be applied to the detection of the environmental hormone 4-NP in an actual water sample.

Description

Electrochemical Sensing Analysis Method of Environmental Hormone p-Nitrophenol

technical field

The invention belongs to the technical field of electrochemical sensing, and in particular relates to an electrochemical sensing analysis method for environmental hormone p-nitrophenol.

Background technique

Environmental hormones refer to chemical substances that exogenously interfere with the endocrine of organisms. These substances are similar to hormones and bind to hormone receptors in the human body, affecting the amount of original hormones in the organism, causing normal hormone imbalance, interfering with the metabolic balance in the organism, and then affecting normal physiological functions of living organisms. Among them, phenolic environmental hormones have received the most attention. With the development of industrialization and the intensification of environmental pollution, the residues of phenolic environmental hormones in the environment are increasing day by day. They have mutagenic, cytotoxic and phytotoxic effects, and are considered to be industrial wastewater. major priority pollutants in According to statistics, p-nitrophenol (4-NP) is one of the most harmful and toxic phenolic environmental hormones. It is widely used in the production of pesticides, herbicides, and synthetic dyes. The environmental hormone 4-NP can cause headache, drowsiness, nausea and cyanosis, and finally cause serious harm to human health and the environment. At present, the residual environmental hormone 4-NP in the environment is mainly detected by highly professional and expensive analytical instruments such as liquid chromatography-mass spectrometer and inductively coupled plasma mass spectrometer. Therefore, it is urgent to develop a fast, sensitive and real-time analytical method for detecting the environmental hormone 4-NP.

gC ₃ N ₄ has the advantages of high hardness, low density, high chemical stability, strong wear resistance, good biocompatibility, non-toxicity, rich sources of synthetic precursors, easy functionalization of the surface, etc., and gC ₃ N ₄ has graphite The similar structure of alkenes can form π-π stacking interactions with aromatic environmental hormone molecules, which will accelerate the enrichment of environmental hormone analytes on the surface of gC ₃ N ₄ . However, due to its wide band gap, severe carrier recombination, lack of surface active sites, thick sheets, and small specific surface area, its application in photoelectrocatalysis and other fields is limited.

Contents of the invention

The object of the present invention is to provide an electrochemical sensing analysis method for efficiently detecting the environmental hormone 4-NP, which has low production cost, simple operation, high efficiency and sensitivity, and can be successfully applied to the detection of 4-NP in actual water samples.

In order to achieve the above purpose, the following technical solutions are adopted:

The electrochemical sensing analysis method of environmental hormone 4-NP, comprises the following steps:

Ultrasonic dispersion of WO _2.9 /gC ₃ N ₄ stepped heterojunction in deionized water to obtain a dispersion, the concentration of the obtained dispersion is 0.0002-0.01g/mL;

Add 1-10 μL of WO _2.9 /gC ₃ N ₄ dispersion solution to a clean and impurity-free bare glassy carbon electrode for modification, and then bake it under an infrared lamp for 3-10 minutes to obtain a modified electrode;

Put the modified electrode in the liquid to be tested for differential pulse voltammetry (DPV) test;

If there is an obvious oxidation peak in the range of 0.8-1.2V, it is inferred that the liquid to be tested contains the environmental hormone 4-NP; based on this, the liquid to be tested is qualitatively detected.

According to the above scheme, the following steps are also included:

Prepare a 4-NP solution sample with a known concentration of 0.04-100 μmol/L, and perform a differential pulse voltammetry test on the 4-NP solution sample with a known concentration using the modified electrode. According to the magnitude of the oxidation peak current and the corresponding 4-NP The concentration is calculated by a linear equation: I _p =0.0491c+0.0908; c is the 4-NP concentration, μmol/L, I _p is the oxidation peak current, μA; based on this, the 4-NP concentration of the liquid to be tested is quantitatively detected.

According to the above scheme, the WO _2.9 /gC ₃ N ₄ stepped heterojunction is prepared in the following manner:

Heat melamine in a muffle furnace at a rate of 3-12°C/min to 500-600°C, keep the temperature constant for 3-10 hours, and obtain a pale yellow gC ₃ N ₄ block after cooling;

Put the obtained gC ₃ N ₄ block into a polytetrafluoroethylene-lined autoclave, add deionized water and mix to obtain a dispersion, and use a cell wall-breaking ultrasonic instrument to perform ultrasonic treatment on the dispersion of the gC ₃ N ₄ block; Take the supernatant and dilute it, place it in an ultrasonic cleaner to continue ultrasonic treatment, and let it stand to obtain a thin layer of gC ₃ N ₄ dispersion;

Prepare an absolute ethanol solution of WCl ₆ , transfer it to a polytetrafluoroethylene-lined stainless steel autoclave, seal it and heat it to 150-200°C for 10-15 hours; after natural cooling, rinse the substrate with absolute ethanol for 3-5 times, vacuum drying at 50-80°C to obtain WO _2.9 ;

Mix WO _2.9 and thin-layer gC ₃ N ₄ dispersion liquid in a vial, put it into an ultrasonic cleaning machine at 80-140W for ultrasonic treatment for 20-80 minutes, and obtain WO _2.9 /gC ₃ N ₄ stepped heterojunction.

According to the above scheme, the power of the ultrasonic treatment of the gC ₃ N ₄ block is 800-1500 W, the start/stop time ratio is 10:2, and the treatment time is 2-4 hours.

According to the above scheme, take the supernatant and dilute it to a concentration of 0.00001-0.0003 g/mL, and continue the ultrasonic treatment with a power of 80-140 W and a treatment time of 1-4 hours.

According to the above scheme, the concentration of WCl ₆ in absolute ethanol solution is 1-10 g/L.

According to the above scheme, the mass ratio of WO _2.9 to gC ₃ N ₄ is 1:(0.006～0.3).

The beneficial effects of the present invention are:

The invention prepares a WO _2.9 /gC ₃ N ₄ stepped heterojunction material with enhanced current signal modified on the surface of a glassy carbon electrode, and develops an electrochemical sensing and analysis method for efficiently detecting environmental hormones.

The invention utilizes the electrostatic self-assembly of WO _2.9 nanoparticles and gC ₃ N ₄ nanosheets to prepare a WO _2.9 /gC ₃ N ₄ oxygen vacancy-mediated ladder-shaped heterojunction, which is simple in synthesis and low in cost. Due to the recombination of WO _2.9 and gC ₃ N ₄ to form a ladder-shaped heterojunction mediated by oxygen vacancies, with the introduction of oxygen vacancies in WO _2.9 nanoparticles, excitons can be effectively dissociated into free charge carriers, thereby improving the compatibility with the charge carriers. Flow-dependent electrocatalytic activity. At the same time, the formation of stepped heterojunctions can suppress the recombination of useful electrons and holes on the heterointerface, thereby enhancing the electrocatalytic rate of the modified electrode surface.

In the present invention, when the concentration of the environmental hormone 4-NP is in the range of 0.4 to 100 μmol/L, its oxidation peak current value on the modified electrode has a good linear relationship with the concentration, and the detection limit is 0.13 μmol/L; WO _2.9 / The gC ₃ N ₄ modified electrode has good stability and reproducibility in the detection of environmental hormone 4-NP; in addition, this sensing analysis method has also been successfully applied to the detection of environmental hormone 4-NP in actual water samples.

Description of drawings

Figure 1: Differential pulse voltammograms of environmental hormone 4-NP on different modified electrodes.

Detailed ways

The following examples further illustrate the technical solutions of the present invention, but are not intended to limit the protection scope of the present invention.

Example 1:

Preparation of WO _2.9 /gC ₃ N ₄ stepped heterojunction:

Weigh 2-10g of melamine into a ceramic crucible, heat and stir evenly, put it into a muffle furnace for heating, the heating rate is 3-12°C/min, the heating temperature is 500-600°C, the constant temperature is 3-10h, and it is ready after cooling Pale yellow gC ₃ N ₄ powder. Then place gC ₃ N ₄ in a cell wall breaking apparatus for ultrasonication, the ultrasonic power is 800-1500W, the ultrasonic start:stop time ratio is 10:2, and the ultrasonic time is 2-4h. Take 2-10mL supernatant and dilute to 0.5-1.5L, ultrasonic treatment power is 80-140W, ultrasonic time is 1-4h, stand overnight to obtain a thin-layer gC ₃ N ₄ dispersion; add 0.05-0.20g of WCl ₆ Put it in 20-50mL of absolute ethanol, and ultrasonically dissolve it completely. The ultrasonic power is 80-140W, and the ultrasonic time is 3-10min. In the still, seal and heat to 150-200°C for 10-15h. After the reaction is over, cool down to room temperature naturally, rinse the substrate with absolute ethanol for 3-5 times, and dry it in a vacuum drying oven at 50-80°C. Dry to obtain WO _2.9 ; weigh 0.001-0.05g WO _2.9 and place it in a vial, then add 5-10ml of thin-layer gC ₃ N ₄ dispersion, put the vial in an ultrasonic cleaner for ultrasonication, the ultrasonic power is 80- 140W, the ultrasonic time is 20-80min, and the WO _2.9 /gC ₃ N ₄ ladder type heterojunction is prepared.

Preparation of modified electrodes:

Add WO _2.9 /gC ₃ N ₄ step-type heterojunction powder into deionized water, and disperse uniformly by ultrasonic. The ultrasonic power is 80-140W, and the ultrasonic time is 5-30min. At the same time, the glassy carbon electrode is polished to a mirror surface with 0.02-1 μm Al ₂ O ₃ polishing powder, and cleaned with deionized water. Pipette 1-10 μL _{of WO 2.9} /gC ₃ N ₄ dispersion, drop-coat it on the surface of the glassy carbon electrode, bake it under the infrared lamp for 3-10 minutes, and observe a layer of blue film on the surface of the electrode, and obtain WO _2.9 /gC ₃ N ₄ modified electrode.

The modified WO _2.9 /gC ₃ N ₄ electrode and the gC ₃ N ₄ electrode, WO _2.9 electrode, WO ₃ /gC ₃ N ₄ electrode, WO ₃ electrode, and bare electrode were respectively placed in the test solution containing the environmental hormone 4-NP. Perform DPV scanning in . It can be seen from Figure 1 that the environmental hormone 4-NP current measured by the WO _2.9 /gC ₃ N ₄ modified electrode is significantly higher than that of other electrodes. The buffer solution, pH value and other conditions were optimized to maximize the oxidation peak current of the environmental hormone 4-NP.

Example 2

Prepare the environmental hormone 4-NP sample with a known concentration of 0.04-100 μM, and perform DPV scanning on the WO _2.9 /gC ₃ N ₄ modified electrode in the environmental hormone 4-NP. According to the magnitude of the oxidation peak current and the corresponding environmental hormone 4-NP The concentration is calculated by a linear equation: I _p =0.0491c+0.0908 (R ² =0.9985); c is the concentration of the environmental hormone 4-NP (μmol/L), and I _p is the oxidation peak current (μA). According to this equation, the unknown concentration of environmental hormone 4-NP can be quantitatively detected.

Example 3

Referring to Example 1, the WO _2.9 /gC ₃ N ₄ modified electrode was prepared, and the modified electrode was placed in a sodium acetate-acetic acid buffer solution containing the analyte at a pH of 3 to 7 for DPV scanning. The current intensity corresponding to the catalytic oxidation peak was used to determine the content of the environmental hormone 4-NP. Its optimal pH value is 5, and the peak current is the largest. According to the relationship between pH and voltage to analyze the number of electron proton transfer, through the linear regression analysis of pH value and voltage to get E _pa (V)=-0.06019pH+1.376 (R ² =0.993), according to the formula: d _Epc /d _pH = 0.059m/n, where m is the number of protons, n is the number of electrons, dE _pc /d _pH = 0.06019, close to 0.059, so it can be drawn that m/n = 1, that is, in WO _2.9 /gC ₃ N ₄ On the electrode, the number of electrons transferred during the electrocatalytic oxidation of 4-NP is equal to the number of protons.

Example 4

Preparation of WO _2.9 /gC ₃ N ₄ modified electrode Referring to Example 1, the modified electrode was placed in the phosphate buffer system containing the analyte, and DPV scanning was performed to measure the current corresponding to the electrocatalytic oxidation peak of the environmental hormone 4-NP According to the linear equation in Example 2, the environmental hormone 4-NP content in this water sample can be obtained.

Example 5

This method was applied to water samples in the actual environment, and the water samples were filtered until clear to detect the environmental hormone 4-NP. Under optimal conditions, carry out differential pulse voltammetry test, adopt the standard addition method to calculate the concentration of 4-NP, according to the linear equation of the oxidation peak current size and corresponding environmental hormone 4-NP concentration that embodiment 2 obtains, calculate The results showed that the recovery rate was between 98.8% and 108.8%, and the relative standard deviation (RSD) was within 4.8%.

Example 6

Add 10-200 times of catechol, hydroquinone, Ca ²⁺ , Cu ²⁺ and 20-300 times of glucose, Na ²⁺ , Mg ²⁺ , K to the appropriate concentration of environmental hormone 4-NP solution ⁺ , Cl ^- , CO ^3- plasma were tested for interference, and it was found that these substances did not interfere with the detection of environmental hormone 4-NP, which indicated that the electrochemical sensing analysis method had good anti-interference ability.

Claims (6)

1. The electrochemical sensing analysis method of environmental hormone 4-NP is characterized in that comprising the following steps: Ultrasonic dispersion of WO _2.9 /gC ₃ N ₄ stepped heterojunction in deionized water to obtain a dispersion, the concentration of the obtained dispersion is 0.0002-0.01g/mL; Add 1-10 μL of WO _2.9 /gC ₃ N ₄ dispersion solution to a clean and impurity-free bare glassy carbon electrode for modification, and then bake it under an infrared lamp for 3-10 minutes to obtain a modified electrode; Put the modified electrode in the liquid to be tested for differential pulse voltammetry test; If there is an obvious oxidation peak in the range of 0.8 ~ 1.2V, it is inferred that the liquid to be tested contains the environmental hormone 4-NP; based on this, the liquid to be tested is qualitatively detected; The WO _2.9 /gC ₃ N ₄ stepped heterojunction is prepared in the following manner: (1) Heat melamine in a muffle furnace at a rate of 3-12°C/min to 500-600°C, keep the temperature constant for 3-10 hours, and obtain a light yellow gC ₃ N ₄ block after cooling; (2) Put the obtained gC ₃ N ₄ block into _a polytetrafluoroethylene-lined autoclave, add deionized water and mix to obtain a dispersion, _and use a cell wall-breaking ultrasonic instrument to conduct Ultrasonic treatment; take the supernatant and dilute it, put it in an ultrasonic cleaner to continue ultrasonic treatment, and let it stand to obtain a thin layer of gC ₃ N ₄ dispersion; (3) Prepare an absolute ethanol solution of WCl ₆ , transfer it to a polytetrafluoroethylene-lined stainless steel autoclave, seal it and heat it to 150-200°C for 10-15 hours; rinse the substrate with absolute ethanol after natural cooling 3-5 times, vacuum drying at 50-80°C to obtain WO _2.9 ; (4) Mix WO _2.9 and thin-layer gC ₃ N ₄ dispersion liquid in a vial, put it into an ultrasonic cleaner at 80-140W for 20-80 min, and obtain WO _2.9 /gC ₃ N ₄ stepped heterojunction. 2. the electrochemical sensing analysis method of environmental hormone 4-NP as claimed in claim 1, is characterized in that also comprising the following steps: Prepare a 4-NP solution sample with a known concentration of 0.04-100 μmol/L, and perform a differential pulse voltammetry test on the 4-NP solution sample with a known concentration using the modified electrode. According to the magnitude of the oxidation peak current and the corresponding 4-NP The concentration is calculated by a linear equation: I _p =0.0491c+0.0908; c is the 4-NP concentration, μmol/L, I _p is the oxidation peak current, μA; based on this, the 4-NP concentration of the liquid to be tested is quantitatively detected. 3. The electrochemical sensing analysis method of environmental hormone 4-NP as claimed in claim 1, is characterized in that in the step (2), the power of using a cell wall-breaking ultrasonic instrument to gC ₃ N ₄ blocks to carry out ultrasonic treatment is 800～ 1500W, start/stop time ratio is 10:2, processing time is 2~4h. 4. The electrochemical sensing analysis method of environmental hormone 4-NP as claimed in claim 1, is characterized in that in the step (2), after getting the supernatant diluted, the concentration is 0.00001～0.0003g/mL, and the power of continuing ultrasonic treatment is 80 ~ 140W treatment time is 1 ~ 4h. 5. The electrochemical sensing analysis method of environmental hormone 4-NP as claimed in claim 1, is characterized in that in step (3) _WCl The concentration in absolute ethanol solution is 1～10g/L. 6. The electrochemical sensing and analysis method of environmental hormone 4-NP according to claim 1, characterized in that the mass ratio of WO _2.9 to gC ₃ N ₄ in step (4) is 1:(0.006-0.3).

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