CN107576716A - A kind of acupuncture needle base working electrode electrochemical sensor for detecting trace heavy metal - Google Patents

Abstract

The invention relates to the field of electrochemical sensors, in particular to an acupuncture needle-based working electrode electrochemical sensor for detecting trace heavy metals. It specifically includes an acupuncture needle-based working electrode, a reference electrode and an auxiliary electrode; the working electrode is composed of a stainless steel acupuncture needle, and the needle shaft part of the acupuncture needle is insulated with a polyvinyl chloride tube, and the polyvinyl chloride tube and the needle are insulated with silicone rubber. The bonding part of the rod is sealed, and the needle tip of the acupuncture needle is used as the sensing surface, and the surface of the needle tip is covered with metal nanoparticles and a cation exchange membrane on the surface of the metal nanoparticles. The detection method is to insert an acupuncture needle-based working electrode, together with a reference electrode and an auxiliary electrode, into the sample to be tested, and use anodic stripping voltammetry to detect the concentration of heavy metal ions in the sample to be tested. The acupuncture needle-based working electrode electrochemical sensor prepared by the invention has the advantages of simple process, low cost, high sensitivity, good selectivity and stability, and can be widely used in the detection of trace heavy metals.

Description

An Acupuncture Needle-Based Working Electrode Electrochemical Sensor for Detecting Trace Heavy Metals

technical field

The invention relates to the field of electrochemical sensors, in particular to an acupuncture needle-based working electrode electrochemical sensor for detecting trace heavy metals.

Background technique

With the rapid development of modern industry and agriculture and the improvement of people's living standards, the problem of heavy metal pollution in the environment has become increasingly serious, which has seriously affected human health and safety. Heavy metals in the environment come from a wide range of sources, such as metal electroplating, mining operations, leather industry, fertilizer industry, paper industry, pesticide production and other processes will produce a large amount of heavy metals. Heavy metals are discharged into the environment, which can cause changes in the structure and function of the ecosystem through the transfer and accumulation on the food chain. Heavy metals are highly toxic, difficult to decompose, easy to be bioaccumulated and biomagnified, etc. They enter the human body through the food chain and can accumulate in the human body, causing anemia, nervous dysfunction, kidney damage, and even cancer. Diseases are a serious threat to human life and health. As people become more and more aware of the hazards of heavy metals, all countries have adopted various measures to reduce the pollution of heavy metals. Therefore, accurate, rapid and effective determination of heavy metal content has become an important content in the research of analytical methods in recent years.

At present, the detection methods of heavy metals mainly include atomic spectroscopy, inductively coupled plasma mass spectrometry, neutron activation and electrochemical analysis. Each approach has its unique advantages, as well as its limitations. Spectrometry is an important method for the determination of heavy metals and has been widely used as a standard method. However, this method has many steps, long time and high cost. However, inductively coupled plasma mass spectrometry and neutron activation require expensive large-scale instruments and high analysis costs, which limit their application range. The electrochemical analysis method has simple instruments, is easy to automate and continuous analysis, and has always been a common method for heavy metal analysis. However, the working electrode of the electrochemical sensor commonly used to detect heavy metals by electrochemical methods is a mercury electrode, and mercury is a highly toxic substance in the environment, and requires specific equipment for storage. With the strengthening of environmental awareness and the deepening of research, mercury has been banned in many countries. Therefore, electrode materials that are cheap, environmentally friendly, and can replace mercury have received more and more attention.

Contents of the invention

Stainless steel acupuncture needles are the core device of acupuncture medicine. They have the advantages of low price and easy operation. In addition to the medical field, they are also widely used in environmental protection, chemical and other fields. In view of its unique advantages, the present invention prepares it as the core component of the electrochemical sensor—the working electrode, and overcomes the defect that the stainless steel acupuncture needle electrode has low detection sensitivity of the analyte and cannot meet the requirements of heavy metal detection in actual samples.

To achieve the above object, the technical solution adopted in the present invention is:

An acupuncture needle-based working electrode electrochemical sensor for detecting trace heavy metals, comprising a working electrode, a reference electrode and an auxiliary electrode, wherein the working electrode is an acupuncture needle-based electrode made of stainless steel acupuncture needles.

One end of the acupuncture needle-based working electrode, reference electrode and auxiliary electrode is inserted into the electrolytic cell with a stirrer, and the other ends are respectively connected to the electrochemical workstation through wires.

The acupuncture needle-based working electrode is composed of stainless steel acupuncture needles, the needle shaft of the acupuncture needles has an insulating layer, the surface of the needle tip of the acupuncture needles is covered with a modified material, and the needle handle of the acupuncture needles is used as an electrode wire.

The insulating layer of the needle shaft of the acupuncture needle is a polyvinyl chloride tube, and the junction between the nozzles at both ends of the polyvinyl chloride tube and the needle shaft of the acupuncture needle is sealed by silicon rubber.

The modification material on the surface of the acupuncture needle tip is metal nanoparticles and a cation exchange membrane covered on the surface of the metal nanoparticles.

The metal nanoparticles are one of gold, platinum, palladium or bismuth.

The acupuncture needle electrode with the needle tip washed as the working electrode, the platinum sheet as the auxiliary electrode, the Ag/AgCl as the reference electrode, the precursor solution of metal nanoparticles as the electrolyte, and the constant potential technology is used to deposit metal on the needle tip of the acupuncture needle. Nanoparticle finishing layer.

The cation-exchange membrane is Nafion. The needle tip of the acupuncture needle electrode covered with metal nanoparticles is immersed in the cation-exchange membrane solution for a certain period of time, taken out and dried, and covered with the cation-exchange membrane on the metal nanoparticle modification layer of the needle tip.

The electrochemical sensor can be used for detection of trace heavy metals copper, cadmium and lead.

The acupuncture needle-based working electrode is composed of stainless steel acupuncture needles, the needle shaft of the acupuncture needle has an insulating layer, the surface of the acupuncture needle tip is covered with a modification material, and the needle handle of the acupuncture needle is used as an electrode wire. Contains the following preparation steps:

(1) Preparation of acupuncture needle electrodes: Cover the needle shaft of the acupuncture needle with insulating material, the needle tip is the electrode sensing surface, and the needle handle is the electrode wire.

(2) Pretreatment of the acupuncture needle electrode: the needle tip of the acupuncture needle electrode was cleaned with ethanol and ultrapure water in sequence, and dried with nitrogen gas for later use.

(3) Modification of metal particles: Acupuncture needle electrode with needle tip washed as working electrode, platinum sheet as auxiliary electrode, Ag/AgCl as reference electrode, metal nanoparticle precursor solution as electrolyte, using constant potential technology , depositing a modified layer of metal nanoparticles on the needle tip of acupuncture needles.

(4) Modification of the cation-exchange membrane: the needle tip of the acupuncture needle electrode covered with metal nanoparticles on the surface is immersed in the cation-exchange membrane solution for a certain period of time, taken out and dried, and covered with the cation-exchange membrane on the metal nanoparticle modification layer of the needle tip. Acupuncture needle-based working electrodes modified with metal nanoparticles and cation exchange membranes were obtained.

The insulating material in the preparation step (1) is a polyvinyl chloride tube, and the junction between the nozzles at both ends of the polyvinyl chloride tube and the needle shaft of the acupuncture needle is sealed by silicon rubber.

The metal nanoparticles in the preparation step (3) are gold, platinum, palladium, bismuth, the electrolytes are respectively chloroauric acid, chloroplatinic acid, sodium chloropalladate and bismuth nitrate, and the deposition potential is -0.2--0.5V, The deposition time is 90-180s.

The cation exchange membrane in the preparation step (4) is Nafion, and the needle tip of the acupuncture needle electrode whose surface is covered with metal nanoparticles is immersed in it for 3s.

The trace heavy metals measured by the acupuncture needle-based working electrode electrochemical sensor are Cu, Cd, and Pb in samples such as fresh water, sea water, and food.

Beneficial effects of the present invention:

The present invention uses stainless steel acupuncture needles as the matrix, combines metal nanoparticles and cation exchange membranes to make acupuncture needle-based working electrodes, and constructs electrochemical sensors. It is used in the detection of trace heavy metals Cu, Cd, and Pb in safety and clinical fields.

In the present invention, after covering and sealing the needle shaft part except the needle point and handle of the acupuncture needle with an insulating layer, a layer of metal nanoparticles is electrochemically modified on the surface of the needle point of the stainless steel acupuncture needle, and then the metal nanoparticle on the surface of the needle point A layer of cation-exchange membrane is modified on the nanoparticles to obtain an acupuncture needle-based working electrode to construct an electrochemical sensor. Metal nanoparticles have a very good catalytic effect on the electrochemical detection of heavy metals, and the cation exchange membrane Nafion has a very good enrichment performance on heavy metal cations. Through the synergistic effect of the two, the sensitivity of heavy metal detection is greatly improved. At the same time, due to the excellent film-forming performance of Nafion, metal nanoparticles can be firmly fixed on the needle tip of the acupuncture needle electrode, and the combination is very stable, which greatly improves the stability and reproducibility of the electrochemical sensor of the acupuncture needle-based working electrode.

Description of drawings

Fig. 1 is a schematic diagram of an acupuncture needle-based working electrode electrochemical sensor provided by an embodiment of the present invention.

Figure 2 is a schematic diagram of the acupuncture needle-based working electrode provided by the embodiment of the present invention

Fig. 3 is the stripping voltammogram of the acupuncture needle-based working electrode provided by the embodiment of the present invention, the bare acupuncture needle electrode and the acupuncture needle electrode modified with gold nanoparticles for the same concentration of Cu.

Fig. 4 is the stripping voltammogram of the acupuncture needle-based working electrode electrochemical sensor with different concentrations of heavy metal Cu ²⁺ provided by the embodiment of the present invention and the corresponding working curve.

detailed description

The content of the invention of the present invention will be further described below in conjunction with the accompanying drawings and embodiments.

Example 1

Using gold as metal nanoparticles to construct acupuncture needle-based electrochemical sensors:

The sensor shown in Figures 1 and 2: the working electrode 1, the reference electrode 2 and the auxiliary electrode 3 are inserted into the electrolytic cell 4 filled with the detection solution. There is a magnetic stirrer 5 in the electrolytic cell 4, and a magnetic stirrer is provided under the electrolytic cell. ; The working electrode 1, the reference electrode 2 and the auxiliary electrode 3 are respectively connected to the electrochemical workstation 6 by wires.

The auxiliary electrode is a platinum sheet electrode, the reference electrode is an Ag/AgCl electrode, and the electrochemical workstation measures the current response value.

The gold is used as the acupuncture needle-based working electrode of metal nanoparticles, the needle handle 7 is used as a wire, the surface of the needle rod 9 is insulated by a polyvinyl chloride tube 10, and the joint between the needle rod 9 and the polyvinyl chloride tube 10 is made of silicon rubber 8. For sealing, the surface of the needle tip 13 is covered by gold nanoparticles 11 , and the surface of the gold nanoparticles 11 is covered by a cation exchange membrane (Nafion) 12 . Its preparation steps are as follows:

(1) Preparation of acupuncture needle electrodes: Cover the needle shaft part of the acupuncture needle with polyvinyl chloride tube 10, seal the junction between the needle shaft 9 and the polyvinyl chloride tube 10 with silicone rubber 8, and use the needle tip 13 as the electrode transmission. On the sensitive side, the needle handle 7 is an electrode wire.

(2) Pretreatment of the acupuncture needle electrode: the needle tip 13 of the acupuncture needle electrode is washed with ethanol and ultrapure water in sequence, and dried with nitrogen gas for later use.

(3) Modification of gold nanoparticles: the acupuncture needle electrode with the needle tip 13 after washing treatment is used as the working electrode, the Ag/AgCl electrode is used as the reference electrode 2, the platinum sheet is used as the auxiliary electrode 3, 1mM chloroauric acid solution (0.5MH ₂ SO ₄ diluted) as the electrolyte, using the constant potential technique, deposited at -0.3V for 120s under stirring conditions, and obtained acupuncture needle electrodes 13 covered with gold nanoparticles 11 .

(4) Modification of the cation-exchange membrane: the needle tip of the acupuncture needle electrode covered with gold nanoparticles on the surface is immersed in the cation-exchange membrane (Nafion) solution for 3 seconds, taken out and dried to obtain gold nanoparticles 11 and cation-exchange membrane 12 modified Acupuncture needle-based working electrodes.

Example 2

Using platinum as metal nanoparticles to construct acupuncture needle-based electrochemical sensors:

The difference from Example 1 is that the metal nanoparticles 11 on the surface of the needle tip 13 are platinum nanoparticles.

Acupuncture needle electrode with needle tip 13 after washing treatment was used as working electrode, Ag/AgCl electrode was used as reference electrode 2, platinum sheet was used as auxiliary electrode ₃ , 2mM chloroplatinic acid solution (diluted with _0.5MH2SO4 ) was used as electrolyte, and constant Potential technique, deposition at -0.25V for 100s under stirring condition, to obtain acupuncture needle electrode with needle tip 13 covered with platinum nanoparticles 11 .

The needle tip of the acupuncture needle electrode covered with platinum nanoparticles was immersed in the cation exchange membrane (Nafion) solution for 3 seconds, and then dried in the air to obtain the acupuncture needle-based working electrode modified with platinum nanoparticles 11 and cation exchange membrane 12 .

Example 3

Using palladium as metal nanoparticles to construct acupuncture needle-based electrochemical sensors:

The difference from Example 1 is that the metal nanoparticles 11 on the surface of the needle tip 13 are palladium nanoparticles.

Acupuncture needle electrode with needle tip 13 after washing treatment was used as working electrode, Ag/AgCl was used as reference electrode 2, platinum sheet was used as auxiliary electrode 3, 1mM sodium chloropalladate solution (diluted with 0.5MH ₂ SO ₄ ) was used as electrolyte, and constant Potential technique, deposition at -0.3V for 90s under stirring condition, to obtain acupuncture needle electrode with needle tip 13 covered with palladium nanoparticles 11 .

Immerse the tip of the acupuncture needle electrode covered with palladium nanoparticles in the cation exchange membrane (Nafion) solution for 3 seconds, take it out and dry it to obtain the acupuncture needle-based working electrode modified with palladium nanoparticles 11 and cation exchange membrane 12.

Example 4

Using bismuth as metal nanoparticles to construct an acupuncture needle-based electrochemical sensor:

The difference from Example 1 is that the metal nanoparticles 11 on the surface of the needle tip 13 are bismuth nanoparticles.

Acupuncture needle electrode with needle tip 13 after washing treatment is used as working electrode, Ag/AgCl is used as reference electrode 2, platinum sheet is used as auxiliary electrode 3, 10mM bismuth nitrate solution (diluted in HAc-NaAc buffer solution) is used as electrolyte, and cyclic voltammetry is used method, deposited at -0.5V for 180s under stirring conditions, and obtained acupuncture needle electrodes 13 covered with bismuth nanoparticles 11 .

The needle tip of the acupuncture needle electrode covered with bismuth nanoparticles was immersed in the cation exchange membrane (Nafion) solution for 3 seconds, taken out and dried to obtain the acupuncture needle-based working electrode modified with palladium bismuth rice particles 11 and cation exchange membrane 12.

Application example 1

Using the acupuncture needle-based working electrode electrochemical sensor described in Example 1 to detect Cu:

Using the sensor described in Example 1, the above-mentioned acupuncture needle-based working electrode was washed with ethanol and ultrapure water successively, and then in the buffer solution containing 0.1M HAc-NaAc (pH4.5), by controlling the electrochemical workstation at -0.4 Perform cyclic voltammetry linear scan in the range from V to 0.6V until the cyclic voltammetry curves overlap well, that is, the purpose of activating the electrode is achieved, which can be used for the detection of Cu.

Using the above electrochemical sensor, insert it into the electrolytic cell filled with HAc-NaAc (10mL, 0.1M, pH4.5) buffer solution, enrich at -0.3V for 240s under the condition of magnetic stirring, and enrich at -0.2V to 0.7V The stripping scan is carried out within the range, and the electrochemical stripping current signal of Cu is obtained.

In order to investigate the influence of different modified materials on the performance of the acupuncture needle-based working electrode for electrochemical detection of Cu, square wave stripping voltammetry was used to test the effect of the acupuncture needle-based working electrode, the bare acupuncture needle electrode and the acupuncture needle electrode modified with gold nanoparticles on Cu. Electrochemical response signal (see Figure 3, in the figure a: bare acupuncture needle electrode, b: acupuncture needle electrode modified with gold nanoparticles, c: acupuncture needle-based working electrode). From the stripping voltammetry test in Figure 3, it can be clearly seen that the constructed acupuncture needle-based electrode has the best effect on the electrochemical detection of Cu under the condition of functional modification of gold nanoparticles and cation exchange membrane. Cu standard solutions with different concentrations were measured respectively, and the working curve of Cu response was drawn through the magnitude of the dissolution peak-peak current of Cu with different concentrations (see FIG. 4 ). Wherein: the concentration of the Cu standard solution is 0.05, 0.07, 0.1, 0.3, 0.5, 0.7, 1, 3, 5, 7, 10 nM from the bottom to the top. It can be seen from Figure 4 that the acupuncture needle-based working electrode electrochemical sensor of the present invention has a good linear response to Cu ions in the concentration range of 0.05-1nM, has high detection sensitivity, and the detection limit is as low as 0.01nM, and can be applied to Cu in seawater. determination.

Application example 2

Using the acupuncture needle-based working electrode electrochemical sensor described in Example 1 to detect Cd or Pb:

Using the sensor described in Example 1, the above-mentioned acupuncture needle-based working electrode was washed with ethanol and ultrapure water successively, and then in the buffer solution containing 0.1M HAc-NaAc (pH4.5), by controlling the electrochemical workstation at -0.4 Perform cyclic voltammetry linear scan in the range from V to 0.6V until the cyclic voltammetry curves overlap well, that is, the purpose of activating the electrode is achieved, which can be used for the detection of Cd or Pb.

Add 5 μL of 10 ⁻² M Cd or Pb standard solution to 10 mL of 0.1 M HAc-NaAc (pH 4.5) buffer solution with the above electrode under magnetic stirring. Insert the sensor into the measurement pool, and measure the electrochemical stripping signal of Cd or Pb by square wave stripping voltammetry. Compared with the stripping signal measured by the bare acupuncture needle electrode and the acupuncture needle electrode modified with gold nanoparticles, the acupuncture needle electrode of the present invention The current signal measured by the needle-based working electrode was significantly enhanced. The electrochemical sensor adopting the acupuncture needle-based working electrode of the present invention also has good response to the detection of heavy metal Cd or Pb.

Claims (9)

1. An acupuncture needle-based working electrode electrochemical sensor for detecting trace heavy metals, comprising a working electrode, a reference electrode and an auxiliary electrode, characterized in that: the working electrode is an acupuncture needle-based electrode made of stainless steel acupuncture needles. 2. A kind of acupuncture needle base working electrode electrochemical sensor for detecting trace heavy metals according to claim 1, characterized in that: one end of acupuncture needle base working electrode, reference electrode and auxiliary electrode is inserted in the electrolytic cell with stirrer , and the other ends are respectively connected to the electrochemical workstation through wires. 3. An acupuncture needle-based working electrode electrochemical sensor for detecting trace heavy metals according to claim 1 or 2, characterized in that: the acupuncture needle-based working electrode is made of stainless steel acupuncture needles, and the needles of the acupuncture needles The rod part has an insulating layer, the surface of the needle point of the acupuncture needle is covered with a modification material, and the needle handle of the acupuncture needle is used as an electrode wire. 4. A kind of acupuncture needle base working electrode electrochemical sensor for detecting trace heavy metals according to claim 3, characterized in that: the insulating layer of the needle shaft part of the acupuncture needle is a polyvinyl chloride tube, and the polyvinyl chloride The junction between the nozzles at both ends of the tube and the needle shaft of the acupuncture needle is sealed by silicon rubber. 5. A kind of acupuncture needle-based working electrode electrochemical sensor for detecting trace heavy metals according to claim 3, characterized in that: the modification material on the surface of the needle tip of the acupuncture needle is metal nanoparticles and cations covered on the surface of metal nanoparticles exchange membrane. 6. An acupuncture needle-based working electrode electrochemical sensor for detecting trace heavy metals according to claim 5, wherein the metal nanoparticles are one of gold, platinum, palladium or bismuth. 7. a kind of acupuncture needle-based working electrode electrochemical sensor for detecting trace heavy metals according to claim 6 is characterized in that: the acupuncture needle electrode through washing treatment with the needle point is used as the working electrode, the platinum sheet is the auxiliary electrode, and the Ag/ AgCl is used as a reference electrode, and the precursor solution of metal nanoparticles is an electrolyte. A constant potential technique is used to deposit a metal nanoparticle modification layer on the needle tip of an acupuncture needle. 8. A kind of acupuncture needle-based working electrode electrochemical sensor for detecting trace heavy metals according to claim 5, characterized in that: the cation exchange membrane is Nafion, and the surface is covered with the needle tip of the acupuncture needle electrode of metal nanoparticles Immerse in the cation exchange membrane solution for a certain period of time, take it out and dry it, and cover the cation exchange membrane on the needlepoint metal nano particle modification layer. 9. An acupuncture needle-based working electrode electrochemical sensor for detecting trace heavy metals according to claim 2, characterized in that: said electrochemical sensor can be used for the detection of trace heavy metals copper, cadmium and lead.