CN104267086B - Chemically modified carbon paste electrode as well as preparation method and application thereof - Google Patents

Abstract

The invention discloses a chemically modified carbon paste electrode, which comprises an electrode shell, carbon paste filled in the electrode shell, and electrode leads which are in contact with the carbon paste and drawn out from the electrode shell. The carbon paste includes Conductive carbon material, binder and composite modifier, the composite modifier includes bismuth-containing solid powder and a chelating agent; the bismuth-containing solid powder is a water-insoluble solid bismuth-containing substance; the chelating agent is hydrophobic and can interact with lead ions An organic reagent that forms a chelate with at least one ion in , cadmium ion and zinc ion. The detection limits of the chemically modified carbon paste electrode for the detection of lead ions, cadmium ions and zinc ions all reached 1.0×10 ^-12 M, which is 1 to 3 times lower than that of the existing chemically modified carbon paste electrodes. On the basis of the existing chemically modified carbon paste electrode, its detection performance has been significantly improved.

Description

A chemically modified carbon paste electrode and its preparation method and application

technical field

The invention relates to the field of electrochemical analysis, in particular to a chemically modified carbon paste electrode and its preparation method and application.

Background technique

In the daily environment, lead ions, cadmium ions and zinc ions are the main heavy metal pollutants, which have obvious biological toxicity and cannot be degraded. As long as there are heavy metal ions such as lead, cadmium and zinc in the environment, they can produce toxic effects, which not only cause environmental pollution, but also harm the normal growth and development of the human body after entering the biological chain, and become important pollutants with potential hazards in the environment. The detection of heavy metal ions such as lead and cadmium is of great significance.

The traditional analytical methods for detecting lead ions, cadmium ions and zinc ions mainly include atomic absorption spectrometry, X-ray fluorescence spectrometry, ultraviolet-visible spectrometry, atomic emission spectrometry, etc. However, compared with traditional analysis methods, the electrochemical method has relatively simple equipment, easy automation, and portability, and has the advantages of high sensitivity, high accuracy, and good selectivity, so it is widely used in the analysis of lead ions, cadmium ions, and zinc ions , and stripping voltammetry of chemically modified carbon paste electrodes is a very commonly used method. The stripping voltammetry of chemically modified carbon paste electrodes has attracted more and more attention and attention due to its advantages of low environmental toxicity, excellent electrochemical performance, and good stability. However, the stripping voltammetry of most chemically modified carbon paste electrodes The detection limits for the detection of lead ions, cadmium ions, and zinc ions are still not low enough to meet the requirements of surface water quality monitoring, which hinders the commercial development of carbon paste electrodes for heavy metal ions. For example, Samo B. Hocevar et al. published in Electrochimica Acta 2005, 51, 706-710 papers reported a carbon paste electrode called bismuth powder, the detection limits of cadmium and lead ions were 1.2 and 0.9ppb (ie 1 × 10 ^-8 M and 6×10 ^-9 M); Xu Yanxia et al. published a paper in "Food Science and Technology and Economics", 2014, 39, 39-42, reporting a carbon paste electrode modified with ethylenediaminetetraacetic acid (EDTA) and used in For the detection of cadmium ions, under the optimal detection conditions, the detection limit of cadmium ions is 1×10 ^-8 mol/L (signal-to-noise ratio is 3). Wu Hua et al. published a review article "Research Progress on Chemically Modified Carbon Paste Electrodes" published in "Applied Chemical Industry", 2012, 41, 880-883. The detection limits of various chemically modified carbon paste electrodes for detecting heavy metal ions are also lower Mostly between 10 ^-8 M and 10 ^-10 M. Therefore, chemically modified carbon paste electrodes cannot be used to monitor heavy metals in surface water, and further improvement of their detection performance has become an urgent problem for researchers in this field.

Contents of the invention

In order to solve the above problems, the present invention provides a chemically modified carbon paste electrode, the carbon paste of the chemically modified carbon paste electrode is combined by adding bismuth-containing solid powder and a chelating agent, as the chemically modified carbon paste electrode Composite modifier, so that the detection limit of the chemically modified carbon paste electrode for detecting lead ions, cadmium ions and zinc ions is significantly reduced, compared with the detection limit of the existing chemically modified carbon paste electrode using a single modifier, it reduces 1 to 3 orders of magnitude, on the basis of the existing chemically modified carbon paste electrodes, its detection performance has been significantly improved; the invention also provides a preparation method of chemically modified carbon paste electrodes and the detection of lead ions, Application of cadmium ion and zinc ion.

In a first aspect, the present invention provides a chemically modified carbon paste electrode, including an electrode shell, a carbon paste filled in the electrode shell, and a carbon paste that is in contact with the carbon paste and drawn out from the electrode shell. The electrode lead, the carbon paste includes a conductive carbon material, a binder and a composite modifier, and the composite modifier includes a bismuth-containing solid powder and a chelating agent; the bismuth-containing solid powder is a water-insoluble solid bismuth-containing substance; The chelating agent is a hydrophobic agent capable of forming a chelate with at least one of lead ions, cadmium ions and zinc ions.

The chelating agent adopted in the present invention is a hydrophobic, insoluble organic small molecular compound or an insoluble macromolecular compound that has a chelating effect on at least one ion in lead ions, cadmium ions and zinc ions; the adhesive used is Hydrophobic viscous substances such as methyl silicone oil, paraffin oil, mineral oil, vaseline, dibutyl nitrate, silicone rubber or epoxy resin; the conductive carbon materials used are graphite powder, mesoporous carbon, fullerene or carbon nanotubes Conductive carbon materials commonly used in the prior art; the bismuth-containing solid powders used are powders of various particle sizes, such as micron-scale and nano-scale powders, and powders of various microscopic shapes, such as rod-shaped, needle-shaped, granular , flower shape, etc.

Preferably, the carbon paste includes the conductive carbon material, the binder and the composite modifier uniformly mixed.

Preferably, the composite modifier includes the chelating agent and the bismuth-containing solid powder mixed uniformly.

Preferably, the bismuth-containing solid powder is bismuth powder, bismuth oxide powder or bismuth hydroxide powder.

Wherein, the bismuth powder is the powder of metal bismuth.

Preferably, the chelating agent is 8-hydroxyquinoline, benzoin oxime, dimethylglyoxime or dithizone.

Preferably, the mass ratio of the conductive carbon material, the bismuth-containing solid powder, the chelating agent to the binder in the carbon paste is (20～90):(0.5～50):(0.5～ 30): (10-50).

Preferably, the mass ratio of the conductive carbon material, the bismuth-containing solid powder, the chelating agent to the binder in the carbon paste is (60-80): (0.5-10): (0.5- 5): (10-30).

Preferably, the mass ratio of the conductive carbon material, the bismuth-containing solid powder, the chelating agent to the binder in the carbon paste is 70:2:2:30.

In a second aspect, the present invention provides a method for preparing a chemically modified carbon paste electrode, comprising the steps of:

(1) Mix conductive carbon material, binder and composite modifier, said composite modifier includes bismuth-containing solid powder and chelating agent to obtain carbon paste; said bismuth-containing solid powder is a water-insoluble solid bismuth-containing substance ; The chelating agent is hydrophobic, and can form a chelate reagent with at least one ion in lead ions, cadmium ions and zinc ions;

(2) filling the carbon paste into the electrode shell;

(3) Install one end of the electrode lead inside the electrode shell and connect it to the carbon paste, and lead the other end of the electrode lead out from the inside of the electrode shell to obtain the chemically modified carbon paste electrode.

Using the chemically modified carbon paste electrode prepared by the present invention, the user only needs a piece of high-grade sandpaper or polishing cloth, polishing paper, and the old electrode can be reused after taking out and polishing, without other operations such as bismuth plating, which is very convenient to use, especially For users of automated lead, cadmium, and zinc detection instruments, electrode updates are very convenient, and the operating procedures of further automated instruments can also be simplified, and the types of liquids it carries will also be greatly reduced, thereby reducing volume and cost.

Various chelating agents, bismuth-containing solid powders, conductive carbon materials and adhesives used in the present invention can be directly purchased from the market or directly prepared by prior art. The electrode shell used in the present invention is an insulating tube commonly used in the prior art such as a polytetrafluoroethylene tube, a glass tube or a plastic tube; the electrode lead wire used is a conductive wire commonly used in the prior art such as a copper wire or a silver wire.

Preferably, in step (1), the conductive carbon material, the binder and the composite modifier are uniformly mixed.

Preferably, in step (1), the composite modifier includes uniformly mixed bismuth-containing solid powder and a chelating agent.

Preferably, in step (1), the bismuth-containing solid powder is bismuth powder, bismuth oxide powder or bismuth hydroxide powder.

Preferably, in step (1), the chelating agent is 8-hydroxyquinoline, benzoin oxime, dimethylglyoxime or dithizone.

Preferably, the mass ratio of the conductive carbon material, the bismuth-containing solid powder, the chelating agent to the binder in the carbon paste in step (1) is (20-90): (0.5-50 ):(0.5～30):(10～50).

Preferably, the mass ratio of the conductive carbon material, the bismuth-containing solid powder, the chelating agent to the binder in the carbon paste in step (1) is (60-80): (0.5-10 ):(0.5～5):(10～30).

Preferably, the mass ratio of the conductive carbon material, the bismuth-containing solid powder, the chelating agent to the binder in the carbon paste in step (1) is 70:2:2:30.

In a third aspect, the present invention also provides the application of the chemically modified carbon paste electrode described in the first aspect in detecting lead ions, cadmium ions and zinc ions in the environment, including the following steps:

(1) firstly add supporting electrolyte in the liquid to be tested containing lead ion, cadmium ion and zinc ion, form the system to be tested, then set the pH value of the system to be tested;

(2) The above-mentioned chemically modified carbon paste electrode is used as the three-electrode system composed of the working electrode, and stripping voltammetry is applied to detect lead ions, cadmium ions and zinc ions in the system to be tested.

In the carbon paste of the chemically modified carbon paste electrode provided by the present invention, the bismuth-containing solid powder and the chelating agent are combined together as a composite modifier of the chemically modified carbon paste electrode. When the chemically modified carbon paste electrode obtained by mixing conductive carbon materials, binders and composite modifiers detects lead ions, cadmium ions and zinc ions, the chelating agent on the surface of the carbon paste first chelates the lead ions in the solution of the system to be measured , cadmium ions and zinc ions, making it enriched near the surface of the bismuth-containing solid powder particles on the surface of the carbon paste, which makes the concentration of lead ions, cadmium ions and zinc ions near the surface of the bismuth-containing solid powder particles much higher than that of the bulk solution Concentrations of lead ions, cadmium ions and zinc ions in the The following stripping voltammetry is the same as the carbon paste electrode of conventional bismuth-containing solid powder, but because the surface of the bismuth-containing solid powder particles of the present invention has enriched higher concentrations of lead ions, cadmium ions and zinc ions through a chelating agent, thus Its detection current increases obviously. That is to say, for the same concentration of lead ions, cadmium ions and zinc ions, the current signal of the chemically modified carbon paste electrode provided by the present invention is large; Lower concentrations of cadmium ions and zinc ions provide significantly improved detection performance.

The reagents used in the present invention are all analytically pure, and the water is double distilled water.

Preferably, the application of the chemically modified carbon paste electrode in detecting lead ions, cadmium ions and zinc ions in the environment includes the following steps:

(1) first add supporting electrolyte acetic acid-sodium acetate, phosphate, acetate or citrate in the liquid to be tested that contains lead ion, cadmium ion and zinc ion, form the system to be tested, in the system to be tested The concentration of the supporting electrolyte phosphate, acetate or citrate is 0.001mol/L-0.5mol/L, and then the pH value of the system to be tested is set to 2-7;

(2) The above-mentioned chemically modified carbon paste electrode is used as a three-electrode system composed of working electrodes, and differential pulse anode stripping voltammetry is used to detect lead ions, cadmium ions and zinc ions in the system to be tested;

That is, first insert the three-electrode system into the system to be tested, then stir and enrich at the enrichment potential of -1.4V to -1.2V for 0.5min to 20min, and after standing still, set the potential range to -1.3V to -0.45 V, the potential increment is 1mV～20mV, the pulse amplitude is 1mV～100mV, the pulse width is 0.001s～1s, the pulse period is 0.002s～2s, do anodization scanning, and record the anodic stripping voltammetry curve.

Compared with the prior art, the present invention has the following beneficial effects:

1. The carbon paste of a chemically modified carbon paste electrode provided by the present invention is combined by adding bismuth-containing solid powder and a chelating agent, as a composite modifier of the chemically modified carbon paste electrode, so that the chemically modified The detection limit of lead ion, cadmium ion and zinc ion by carbon paste electrode reached 1.0×10 ^-12 M. Compared with the chemically modified electrode using the compound modifier, the detection limit of The detection limit is reduced by 1 to 3 orders of magnitude, and its detection performance is obviously improved on the basis of the existing chemically modified carbon paste electrode.

2. The chemically modified carbon paste electrode provided by the present invention is easy to update, that is, it can be put into use again only by updating the surface of the electrode through grinding operation, which further simplifies the operation procedure of the automatic instrument and greatly reduces the types of liquids it carries , thereby reducing the size of the automated instrument and reducing the cost.

3. The chemically modified carbon paste electrode provided by the present invention can conveniently, quickly and sensitively realize the electrochemical determination of lead, cadmium and zinc in samples such as tap water, lake water and snow water; its potential window is wide and the operation is simple. It has extremely high detection sensitivity, which is conducive to the simultaneous determination of lead, cadmium and zinc; further, by designing a chelating agent that selectively adsorbs lead, cadmium and zinc, it can also be used for specific lead ions, cadmium ions and zinc ions. Selective detection.

Description of drawings

Fig. 1 is the anodic stripping voltammogram of lead ions, cadmium ions and zinc ions in the solution of test system 1 to test system 6 using the electrode of Example 1, wherein the insets are the stripping of lead ions, cadmium ions and zinc ions respectively The linear relationship between the peak current i _p and the concentrations of lead ions, cadmium ions and zinc ions.

Fig. 2 is the anodic stripping voltammogram of lead ion, cadmium ion and zinc ion in the solution of the electrode detection test system 1 to test system 6 of the application example 2, wherein the insets are lead ion, cadmium ion and zinc ion stripping respectively The linear relationship between the peak current i _p and the concentrations of lead ions, cadmium ions and zinc ions.

Fig. 3 is the anodic stripping voltammogram of lead ions, cadmium ions and zinc ions in the solutions of test system 1 to test system 6 using the electrode of Example 3, wherein the insets are the stripping of lead ions, cadmium ions and zinc ions respectively The linear relationship between the peak current i _p and the concentrations of lead ions, cadmium ions and zinc ions.

Fig. 4 is the anodic stripping voltammogram of lead ions, cadmium ions and zinc ions in the solution of system 1 to system 6 to be tested using the electrode of Example 4, wherein the insets are the stripping of lead ions, cadmium ions and zinc ions respectively The linear relationship between the peak current i _p and the concentrations of lead ions, cadmium ions and zinc ions.

Fig. 5 is the anodic stripping voltammogram in the same concentrations of lead ions, cadmium ions and zinc ions in the comparative examples 1 to 4 of the present invention.

detailed description

In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and preferred embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

The preparation equipment used is an ultrasonic oscillator and a mortar.

Example 1:

A method for preparing a chemically modified carbon paste electrode, comprising the steps of:

(1) First, take a 100mL mortar, and then add 10.0mg of bismuth oxide powder into the mortar;

(2) Measure 1 mL of ethanol and add it to the mortar, wherein the 1 mL of ethanol contains 5 mg of dimethylglyoxime, and stir the bismuth oxide powder and dimethylglyoxime in the grinding body to form a paste to obtain a composite modifier;

(3) After the ethanol is completely volatilized, add 60 mg of graphite powder in the mortar and stir evenly; then add 10 mg of methyl silicone oil and stir to obtain the required carbon paste;

(4) Take a polytetrafluoroethylene tube with an inner diameter of 2mm, an outer diameter of 5mm, and a length of 40mm as the electrode shell, and polish both ends on sandpaper, clean it by ultrasonic cleaning, dry it, and set it aside;

(5) The carbon paste that step (3) is made tightly fills in the cleaned polytetrafluoroethylene electrode shell, inserts the copper wire that diameter is 2mm, length is 50mm at one end of electrode nozzle, makes 20mm copper wire Expose outside the electrode shell as a lead to obtain the desired chemically modified carbon paste electrode.

Example 2:

A method for preparing a chemically modified carbon paste electrode, comprising the steps of:

(1) First, take a 100mL mortar, and then add 2mg of bismuth oxide powder into the mortar;

(2) Measure 2 mL of benzene and add it to the mortar, wherein the 2 mL of benzene contains 2 mg of dithizone, and stir the bismuth oxide powder and dithizone in the grinding body to form a paste to obtain a composite modifier;

(3) After the benzene is completely volatilized, add 70 mg of mesoporous carbon powder in the mortar and stir evenly; then add 30 mg of paraffin oil and stir to obtain the required carbon paste;

(4) Take a glass tube with an inner diameter of 2 mm, an outer diameter of 4 mm, and a length of 40 mm as the electrode shell, and smooth both ends on sandpaper, clean it with ultrasonic waves, dry it, and set aside;

(5) Fill the carbon paste prepared in step (3) tightly into the cleaned glass electrode shell, insert a copper wire with a diameter of 2 mm and a length of 50 mm at one end of the electrode nozzle, so that the 20 mm copper wire is exposed to the electrode. The outside of the shell is used as a lead to obtain the desired chemically modified carbon paste electrode.

Example 3:

A method for preparing a chemically modified carbon paste electrode, comprising the steps of:

(1) First, take a 25mL mortar, and then add 50mg of bismuth hydroxide powder, 30mg of benzoin oxime and 20mg of fullerene into the mortar, and stir well, wherein the bismuth hydroxide powder and benzoin oxime Composition of composite modifiers;

(2) Add 50mg of mineral oil in the beaker, stir evenly, and make the required carbon paste;

(3) Take a plastic tube with an inner diameter of 2 mm, an outer diameter of 5 mm, and a length of 40 mm as the electrode shell, and smooth both ends on sandpaper, clean it with ultrasonic waves, dry it, and set aside;

(4) Fill the carbon paste prepared in step (2) tightly into the cleaned plastic electrode shell, insert a copper wire with a diameter of 2 mm and a length of 50 mm at one end of the electrode nozzle, so that the 20 mm copper wire is exposed to the electrode. The outside of the shell is used as a lead to obtain the desired chemically modified carbon paste electrode.

Example 4:

A method for preparing a chemically modified carbon paste electrode, comprising the steps of:

(1) First, take a 25mL mortar, then add 0.5mg of bismuth powder, 0.5mg of 8-hydroxyquinoline, 80mg of carbon nanotubes and 10mg of epoxy resin in the beaker, and grind to make Bismuth powder, 8-hydroxyquinoline, and carbon nanotubes are uniformly dispersed to prepare the required carbon paste, wherein bismuth powder and 8-hydroxyquinoline form a composite modifier;

(2) Take a polytetrafluoroethylene tube with an inner diameter of 2 mm, an outer diameter of 3 mm, and a length of 40 mm as the electrode shell, and smooth both ends on sandpaper, clean it with ultrasonic waves, dry it, and set aside;

(3) Fill the carbon paste prepared in step (1) tightly into the cleaned polytetrafluoroethylene electrode shell, insert a diameter of 2mm at one end of the electrode nozzle, and a copper wire with a length of 50mm to make the 20mm copper wire Expose outside the electrode shell as a lead to obtain the desired chemically modified carbon paste electrode.

Example 5:

A method for preparing a chemically modified carbon paste electrode, comprising the steps of:

(1) First, take a 100mL mortar, and then add 2mg of bismuth oxide powder into the mortar;

(2) Measure 2 mL of benzene and add it to the mortar, wherein the 2 mL of benzene contains 2 mg of dithizone, and stir the bismuth oxide powder and dithizone in the grinding body to form a paste to obtain a composite modifier;

(3) After the benzene is completely volatilized, add 90 mg of mesoporous carbon powder in the mortar and stir evenly; then add 30 mg of paraffin oil and stir to obtain the required carbon paste;

(4) Take a glass tube with an inner diameter of 2 mm, an outer diameter of 4 mm, and a length of 40 mm as the electrode shell, and smooth both ends on sandpaper, clean it with ultrasonic waves, dry it, and set aside;

(5) Fill the carbon paste prepared in step (3) tightly into the cleaned glass electrode shell, insert a copper wire with a diameter of 2 mm and a length of 50 mm at one end of the electrode nozzle, so that the 20 mm copper wire is exposed to the electrode. The outside of the shell is used as a lead to obtain the desired chemically modified carbon paste electrode.

In order to effectively prove the detection performance of the chemically modified carbon paste electrodes disclosed in the present invention, the chemically modified carbon paste electrodes prepared in Examples 1 to 4 of the present invention were used to detect lead ions, cadmium ions in the system to be tested by differential pulse anodic stripping voltammetry ions and zinc ions. The instrument used is a CHI660D electrochemical workstation (Shanghai Chenhua Instrument Co., Ltd.): a three-electrode system (the working electrode is the chemically modified carbon paste electrode prepared in Examples 1 to 4, the reference electrode is a saturated calomel electrode, and the counter electrode Platinum electrode); the reagents used are all analytically pure, and the water is double distilled water; the reagents used are all analytically pure, and the water is double distilled water.

Effect Example 1

A method for chemically modifying carbon paste electrodes to detect lead ions, cadmium ions and zinc ions in the environment, comprising the steps of:

(1) At first, add supporting electrolyte acetic acid-sodium acetate in the liquid to be tested containing lead ion, cadmium ion and zinc ion, form the system to be tested, the concentration of the supporting electrolyte acetic acid-sodium acetate in this system to be tested is 0.5mol/ L, then the pH value of the system to be tested is set to 2;

(2) First, the prepared three-electrode system (the working electrode is the chemically modified carbon paste electrode prepared in Example 1, the reference electrode is a saturated calomel electrode, and the counter electrode is a platinum electrode) is inserted into the system to be tested, and the differential Pulse anode stripping voltammetry to detect lead ions, cadmium ions and zinc ions in the system to be tested;

That is, first insert the prepared three-electrode system into the system to be tested, then stir and enrich at the enrichment potential of -1.2V for 6 minutes, after resting, set the potential range from -1.2V to -0.45V, and the potential increment is 4mV , the pulse amplitude is 50mV, the pulse width is 0.2s, the pulse period is 0.5s, do anodization scanning, and record the anodic stripping voltammetry curve.

Under the above experimental conditions, the chemically modified carbon paste electrode prepared in Example 1 was used to detect 6 systems to be tested (the concentrations of lead ions, cadmium ions and zinc ions in system 1 to be tested were respectively 1.0×10 ^-8 mol/L , 1.0×10 ^-8 mol/L and 1.0×10 ^-8 mol/L; the concentrations of lead ions, cadmium ions and zinc ions in system 2 to be tested are 7.0×10 ^-9 mol/L and 7.0×10 ^-9 mol respectively /L and 7.0×10 ^-9 mol/L; the concentrations of lead ions, cadmium ions and zinc ions in system 3 to be tested are 5.0×10 ^-9 mol/L, 5.0×10 ^-9 mol/L and 5.0×10 ^{- 9} mol/L; the concentrations of lead ions, cadmium ions and zinc ions in system 4 to be tested are 1.0×10 ^-9 mol/L, 1.0×10 ^-9 mol/L and 1.0×10 ^-9 mol/L respectively; The concentrations of lead ions, cadmium ions and zinc ions in system 5 were 5.0×10 ^-10 mol/L, 5.0×10 ^-10 mol/L and 5.0×10 ^-10 mol/L respectively; ion and zinc ion concentrations were 2.0×10 ^-10 mol/L, 2.0×10 ^-10 mol/L and 2.0×10 ^-10 mol/L), the relative standard deviation (RSD ) are 0.9%, 1.1% and 1.1% respectively (wherein n (lead)=n (zinc)=n (cadmium)=6); Explain that this chemically modified carbon paste electrode has the detection ability to lead ion, cadmium ion and zinc ion good linearity.

Fig. 1 is the anodic stripping voltammogram of lead ion, cadmium ion and zinc ion in the solution of the electrode detection test system 1 to test system 6 of the application example 1; wherein the insets are lead ion, cadmium ion and zinc ion stripping respectively The linear relationship between the peak current i _p and the concentrations of lead ions, cadmium ions and zinc ions. As shown in Figure 1, in the anodic stripping voltammogram, six curves from low to high represent successively that the concentrations of zinc ions, cadmium ions and lead ions are all 2.0× ^10-10 mol/L (system 6 to be tested), 5.0 ×10 ^-10 mol/L (measurement system 5), 1.0×10 ^-9 mol/L (measurement system 4), 5.0×10 ^-9 mol/L (measurement system 3), 7.0×10 ^-9 mol /L (system 2 to be tested), or 1.0×10 ^-8 mol/L (system 1 to be tested), the anodic stripping voltammetry curve; from -1.2V to -0.45V, as the voltage increases, each Three peaks appear in the curve in turn, which are the stripping current peaks of zinc ions, cadmium ions and lead ions respectively. The inner inserts in the figure are the linear relationship graphs of the stripping peak current i _p of lead ion, cadmium ion and zinc ion and the concentration of lead ion, cadmium ion and zinc ion respectively, that is, the stripping current peaks of zinc ion, cadmium ion and lead ion are taken respectively The peak is the ordinate, the corresponding ion concentration is the abscissa, and the current-concentration curve is drawn. Through linear fitting, it can be known that the dissolution peak current i _p of lead ion, cadmium ion and zinc ion and the concentration of lead ion, cadmium ion and zinc ion in the system to be tested are between 2.0×10 ^-10 mol/L～1.0×10 ^-8 mol In the range of /L, there is a linear relationship. The linear regression equation corresponding to the lead ion is: i _p =0.246+0.154c (R=0.999); the linear regression equation corresponding to the cadmium ion is: i _p =0.566+0.116c (R=0.999); the linear regression equation corresponding to the zinc ion is: i _p =1.725+0.176c (R=0.998). Among them, the unit of dissolution peak current i _p is μA, and the unit of concentration c is 10 ^-10 mol/L. According to the general standard of signal-to-noise ratio equal to 3, the calculated detection limits of lead ion, cadmium ion and zinc ion are 1.5×10 ^-12 mol/L, 1.9×10 ^-12 mol/L and 1.3×10 ^-12 respectively mol/L.

Under the above experimental conditions, the same batch of chemically modified carbon paste electrode pairs prepared in Example 1 contained lead ions, cadmium ions, and zinc ions at concentrations of 5.0×10 ^-9 mol/L and 5.0×10 ^-9 mol/L, respectively. /L and 5.0×10 ^-9 mol/L of the system 7 to be tested (since the chemically modified carbon paste electrode used was prepared in the same batch, so its structure is exactly the same and it is only used once and discarded), its relative standard The differences (RSD) are 1.8%, 1.2% and 1.6% (where n(lead)=n(cadmium)=n(zinc)=5), indicating that the chemically modified carbon paste electrode has good preparation repeatability.

Under the above experimental conditions, the concentrations of lead ions, cadmium ions and zinc ions in system 8 to be tested are 5.0×10 ^-9 mol/L, 5.0×10 ^-9 mol/L and 5.0×10 ^-9 mol/L respectively, When the relative error is less than ±5%, the influence of interfering substances on the detection is investigated. The results show that: 1500 times the concentration of aluminum ions, manganese ions, nickel ions, sodium ions, calcium ions, magnesium ions, potassium ions, nitrate ions And sulfate ions, 500 times the concentration of iron ions, bismuth ions and ammonium ions, 200 times the concentration of ferrous ions, arsenic ions, mercury ions and chromium ions have no effect on the detection.

Effect Example 2

A method for chemically modifying carbon paste electrodes to detect lead ions, cadmium ions and zinc ions in the environment, comprising the steps of:

(1) First, in the test solution containing lead ion, cadmium ion and zinc ion, add supporting electrolyte phosphate buffer solution to form the system to be tested, the concentration of the supporting electrolyte phosphate buffer in the system to be tested is 0.001mol/ L, then the pH value of the system to be tested is set to 6;

(2) Insert the prepared three-electrode system (the working electrode is the chemically modified carbon paste electrode prepared in Example 2, the reference electrode is a saturated calomel electrode, and the counter electrode is a platinum electrode) into the system to be tested, and apply differential pulse Anodic stripping voltammetry to detect lead ions, cadmium ions and zinc ions in the system to be tested;

That is, first insert the prepared three-electrode system into the system to be tested, then stir and enrich at the enrichment potential of -1.4V for 20 minutes, and after resting, set the potential range from -1.2V to -0.45V, and the potential increment is 4mV , the pulse amplitude is 50mV, the pulse width is 0.2s, and the pulse period is 0.5s. Anodization scanning is performed, and the anodic stripping voltammetry curve is recorded.

Under the above experimental conditions, the chemically modified carbon paste electrode prepared in Example 2 was used to detect 6 systems to be tested (the concentrations of lead ions, cadmium ions and zinc ions in system 1 to be tested were respectively 1.0×10 ^-8 mol/L , 1.0×10 ^-8 mol/L and 1.0×10 ^-8 mol/L; the concentrations of lead ions, cadmium ions and zinc ions in system 2 to be tested are 7.0×10 ^-9 mol/L and 7.0×10 ^-9 mol respectively /L and 7.0×10 ^-9 mol/L; the concentrations of lead ions, cadmium ions and zinc ions in system 3 to be tested are 5.0×10 ^-9 mol/L, 5.0×10 ^-9 mol/L and 5.0×10 ^{- 9} mol/L; the concentrations of lead ions, cadmium ions and zinc ions in system 4 to be tested are 1.0×10 ^-9 mol/L, 1.0×10 ^-9 mol/L and 1.0×10 ^-9 mol/L respectively; The concentrations of lead ions, cadmium ions and zinc ions in system 5 were 5.0×10 ^-10 mol/L, 5.0×10 ^-10 mol/L and 5.0×10 ^-10 mol/L respectively; ion and zinc ion concentrations were 2.0×10 ^-10 mol/L, 2.0×10 ^-10 mol/L and 2.0×10 ^-10 mol/L), the relative standard deviation (RSD ) are 1.9%, 2.5% and 1.1% respectively (wherein n (lead)=n (cadmium)=n (zinc)=6); Explain that this chemically modified carbon paste electrode has the detection ability to lead ion, cadmium ion and zinc ion good precision.

Fig. 2 is the anodic stripping voltammogram of lead ion, cadmium ion and zinc ion in the solution of the electrode detection test system 1 to test system 6 using the electrode of Example 2; wherein the insets are lead ion, cadmium ion and zinc ion stripping respectively The linear relationship between the peak current i _p and the concentrations of lead ions, cadmium ions and zinc ions. As shown in Figure 2, in the anodic stripping voltammogram, six curves from low to high represent successively that the concentrations of zinc ions, cadmium ions and lead ions are all 2.0× ^10-10 mol/L (system 6 to be tested), 5.0 ×10 ^-10 mol/L (measurement system 5), 1.0×10 ^-9 mol/L (measurement system 4), 5.0×10 ^-9 mol/L (measurement system 3), 7.0×10 ^-9 mol /L (system 2 to be tested) or 1.0×10 ^-8 mol/L (system 1 to be tested), the anodic stripping voltammetry curve, from -1.2V to -0.45V, increases with the voltage, each Three peaks appear in the curve in turn, which are the stripping current peaks of zinc ions, cadmium ions and lead ions respectively. The inner inserts in the figure are the linear relationship graphs of the stripping peak current i _p of lead ion, cadmium ion and zinc ion and the concentration of lead ion, cadmium ion and zinc ion respectively, that is, the stripping current peaks of zinc ion, cadmium ion and lead ion are taken respectively The peak is the ordinate, the corresponding ion concentration is the abscissa, and the current-concentration curve is drawn. Through linear fitting, it can be known that the dissolution peak current i _p of lead ion, cadmium ion and zinc ion and the concentration of lead ion, cadmium ion and zinc ion in the system to be tested are between 2.0×10 ^-10 mol/L～1.0×10 ^-8 mol In the range of /L, there is a linear relationship. The linear regression equation corresponding to the lead ion is: i _p =0.380+0.311c (R=0.999); the linear regression equation corresponding to the cadmium ion is: i _p =1.250+0.235c (R=0.999); the linear regression equation corresponding to the zinc ion is: i _p =3.313+0.369c (R=0.998). Among them, the unit of dissolution peak current i _p is μA, and the unit of concentration c is 10 ^-10 mol/L. According to the general standard of signal-to-noise ratio equal to 3, the detection limits of lead ion, cadmium ion and zinc ion are 0.9×10 ^-12 mol/L, 1.2×10 ^-12 mol/L and 0.8×10 ^-12 mol respectively /L.

Under the above experimental conditions, the same batch of chemically modified carbon paste electrode pairs prepared in Example 2 contained lead ions, cadmium ions and zinc ions at concentrations of 1.0×10 ^-8 mol/L and 1.0×10 ^-8 mol /L and 1.0×10 ^-8 mol/L of the system 7 to be tested (since the chemically modified carbon paste electrode used was prepared in the same batch, so its structure is exactly the same and it is only used once and discarded), its relative standard The differences (RSD) are 2.5%, 1.3% and 1.6% (where n(lead)=n(cadmium)=n(zinc)=5), indicating that the chemically modified carbon paste electrode has good preparation repeatability.

Under the above experimental conditions, the concentrations of lead ions, cadmium ions and zinc ions in system 8 to be tested are 2.0×10 ^-10 mol/L, 2.0×10 ^-10 mol/L and 2.0×10 ^-10 mol/L, respectively, When the relative error is less than ±5%, the influence of interfering substances on the detection is investigated. The results show that: 1500 times the concentration of aluminum ions, manganese ions, nickel ions, sodium ions, calcium ions, magnesium ions, potassium ions, nitrate ions And sulfate ions, 500 times the concentration of iron ions, bismuth ions and ammonium ions, 200 times the concentration of ferrous ions, arsenic ions, mercury ions and chromium ions have no effect on the detection.

Effect Example 3

A method for chemically modifying carbon paste electrodes to detect lead ions, cadmium ions and zinc ions in the environment, comprising the steps of:

(1) at first in the liquid to be tested containing lead ion, cadmium ion and zinc ion, add supporting electrolyte acetate, form the system to be tested, the concentration of the supporting electrolyte acetate in this system to be tested is 0.05mol/L, Then the pH value of the system to be tested is set to 5;

(2) Insert the prepared three-electrode system (the working electrode is the chemically modified carbon paste electrode prepared in Example 3, the reference electrode is a saturated calomel electrode, and the counter electrode is a platinum electrode) into the system to be tested, and apply differential pulse Anodic stripping voltammetry to detect lead ions, cadmium ions and zinc ions in the system to be tested;

That is, first insert the prepared three-electrode system into the system to be tested, then stir and enrich at the enrichment potential of -1.2V for 6 minutes, after resting, set the potential range from -1.2V to -0.45V, and the potential increment is 4mV , the pulse amplitude is 50mV, the pulse width is 0.2s, the pulse period is 0.5s, do anodization scanning, and record the anodic stripping voltammetry curve.

Under the above experimental conditions, the chemically modified carbon paste electrode prepared in Example 3 was used to detect 6 systems to be tested (the concentrations of lead ions, cadmium ions and zinc ions in system 1 to be tested were respectively 1.0×10 ^-8 mol/L , 1.0×10 ^-8 mol/L and 1.0×10 ^-8 mol/L; the concentrations of lead ions, cadmium ions and zinc ions in system 2 to be tested are 7.0×10 ^-9 mol/L and 7.0×10 ^-9 mol respectively /L and 7.0×10 ^-9 mol/L; the concentrations of lead ions, cadmium ions and zinc ions in system 3 to be tested are 3.0×10 ^-9 mol/L, 3.0×10 ^-9 mol/L and 3.0×10 ^{- 9} mol/L; the concentrations of lead ions, cadmium ions and zinc ions in system 4 to be tested are 1.0×10 ^-9 mol/L, 1.0×10 ^-9 mol/L and 1.0×10 ^-9 mol/L respectively; The concentrations of lead ions, cadmium ions and zinc ions in system 5 were 5.0×10 ^-10 mol/L, 5.0×10 ^-10 mol/L and 5.0×10 ^-10 mol/L respectively; ion and zinc ion concentrations were 2.0×10 ^-10 mol/L, 2.0×10 ^-10 mol/L and 2.0×10 ^-10 mol/L), the relative standard deviation (RSD ) are 1.9%, 2.1% and 1.1% respectively (wherein n (lead)=n (cadmium)=n (zinc)=6); Explain that this chemically modified carbon paste electrode has the detection ability to lead ion, cadmium ion and zinc ion good precision.

Fig. 3 is the anodic stripping voltammogram of lead ion, cadmium ion and zinc ion in the solution of the electrode detection test system 1 to test system 6 using the electrode of Example 3; wherein the insets are lead ion, cadmium ion and zinc ion stripping respectively The linear relationship between the peak current i _p and the concentrations of lead ions, cadmium ions and zinc ions. As shown in Figure 3, in the anodic stripping voltammogram, six curves from low to high represent successively that the concentrations of zinc ions, cadmium ions and lead ions are all 2.0× ^10-10 mol/L (system 6 to be tested), 5.0 ×10 ^-10 mol/L (measurement system 5), 1.0×10 ^-9 mol/L (measurement system 4), 3.0×10 ^-9 mol/L (measurement system 3), 7.0×10 ^-9 mol /L (system 2 to be tested) or 1.0×10 ^-8 mol/L (system 1 to be tested), the anodic stripping voltammetry curve, from -1.2V to -0.45V, increases with the voltage, each Three peaks appear in the curve in turn, which are the stripping current peaks of zinc ions, cadmium ions and lead ions respectively. The inner inserts in the figure are the linear relationship graphs of the stripping peak current i _p of lead ion, cadmium ion and zinc ion and the concentration of lead ion, cadmium ion and zinc ion respectively, that is, the stripping current peaks of zinc ion, cadmium ion and lead ion are taken respectively The peak is the ordinate, the corresponding ion concentration is the abscissa, and the current-concentration curve is drawn. Through linear fitting, it can be known that the dissolution peak current i _p of lead ion, cadmium ion and zinc ion and the concentration of lead ion, cadmium ion and zinc ion in the system to be tested are between 2.0×10 ^-10 mol/L～1.0×10 ^-8 mol In the range of /L, there is a linear relationship. The linear regression equation corresponding to the lead ion is: i _p =0.597+0.063c (R=0.996); the linear regression equation corresponding to the cadmium ion is: i _p =0.952+0.0496c (R=0.999); the linear regression equation corresponding to the zinc ion is: i _p =0.353+0.097c (R=0.993). Wherein, the unit of dissolution peak current i _p is μA, and the unit of concentration c is 10 ^-10 . According to the general standard of signal-to-noise ratio equal to 3, the detection limits of lead ion, cadmium ion and zinc ion are 3.5×10 ^-12 mol/L, 4.2×10 ^-12 mol/L and 3.1×10 ^-12 mol respectively /L.

Under the above experimental conditions, five same batches of chemically modified carbon paste electrodes prepared in Example 3 were used to detect the test system 7 containing lead ions, cadmium ions and zinc ions at a concentration of 1.0×10 ^-8 mol/L (Because the chemically modified carbon paste electrodes used are prepared in the same batch, so their structures are exactly the same and they can be discarded after only one use), and their relative standard deviations (RSD) are 2.5%, 1.9% and 2.9% respectively (wherein n( lead)=n(cadmium)=n(zinc)=5), indicating that the chemically modified carbon paste electrode has good preparation repeatability.

Under the above experimental conditions, the concentrations of lead ions, cadmium ions and zinc ions in the system 8 to be tested are all 5.0×10 ^-10 mol/L, and the relative error is less than ±5%. The results show that: 1500 times the concentration of aluminum ions, manganese ions, nickel ions, sodium ions, calcium ions, magnesium ions, potassium ions, nitrate ions and sulfate ions, 500 times the concentration of iron ions, bismuth ions and ammonium ions ions, 200 times the concentration of ferrous ions, arsenic ions, mercury ions and chromium ions have no effect on the detection.

Effect Example 4

A method for chemically modifying carbon paste electrodes to detect lead ions, cadmium ions and zinc ions in the environment, comprising the steps of:

(1) first add supporting electrolyte citrate in the liquid to be tested containing lead ion, cadmium ion and zinc ion, form the system to be tested, the concentration of the supporting electrolyte citrate in this system to be tested is 0.4mol/L, Then the pH value of the system to be tested is set to 7;

(2) Insert the prepared three-electrode system (the working electrode is the chemically modified carbon paste electrode prepared in Example 4, the reference electrode is a saturated calomel electrode, and the counter electrode is a platinum electrode) into the system to be tested, and apply differential pulse Anodic stripping voltammetry to detect lead ions, cadmium ions and zinc ions in the system to be tested;

That is, first insert the prepared three-electrode system into the system to be tested, then stir and enrich at the enrichment potential of -1.2V for 6 minutes, after resting, set the potential range from -1.2V to -0.45V, and the potential increment is 4mV , the pulse amplitude is 50mV, the pulse width is 0.2s, the pulse period is 0.5s, do anodization scanning, and record the anodic stripping voltammetry curve.

Under the above experimental conditions, the chemically modified carbon paste electrode prepared in Example 4 was used to detect 6 systems to be tested (the concentrations of lead ions, cadmium ions and zinc ions in system 1 to be tested were respectively 1.0×10 ^-8 mol/L , 1.0×10 ^-8 mol/L and 1.0×10 ^-8 mol/L; the concentrations of lead ions, cadmium ions and zinc ions in system 2 to be tested are 7.0×10 ^-9 mol/L and 7.0×10 ^-9 mol respectively /L and 7.0×10 ^-9 mol/L; the concentrations of lead ions, cadmium ions and zinc ions in system 3 to be tested are 5.0×10 ^-9 mol/L, 5.0×10 ^-9 mol/L and 5.0×10 ^{- 9} mol/L; the concentrations of lead ions, cadmium ions and zinc ions in system 4 to be tested are 2.0×10 ^-9 mol/L, 2.0×10 ^-9 mol/L and 2.0×10 ^-9 mol/L respectively; The concentrations of lead ions, cadmium ions and zinc ions in system 5 were all 1.0×10 ^-9 mol/L; the concentrations of lead ions, cadmium ions and zinc ions in system 6 to be tested were 2.0×10 ^-10 mol/L, 2.0× 10 ^-10 mol/L and 2.0×10 ^-10 mol/L), the relative standard deviation (RSD) of detecting lead ion, cadmium ion and zinc ion is respectively 2.3%, 2.1% and 2.8% (wherein n (lead) = n(cadmium)=n(zinc)=6); indicating that the chemically modified carbon paste electrode has good precision for the detection of lead ions, cadmium ions and zinc ions.

Fig. 4 is the anodic stripping voltammogram of lead ion, cadmium ion and zinc ion in the solution of the electrode detection test system 1 to test system 6 using the electrode of Example 4; wherein the insets are lead ion, cadmium ion and zinc ion stripping respectively The linear relationship between the peak current i _p and the concentrations of lead ions, cadmium ions and zinc ions. As shown in Figure 4, in the anodic stripping voltammogram, six curves from low to high represent successively that the concentrations of zinc ions, cadmium ions and lead ions are all 2.0× ^10-10 mol/L (system 6 to be tested), 1.0 ×10 ^-9 mol/L (measurement system 5), 2.0×10 ^-9 mol/L (measurement system 4), 5.0×10 ^-9 mol/L (measurement system 3), 7.0×10 ^-9 mol /L (system 2 to be tested) or 1.0×10 ^-8 mol/L (system 1 to be tested), the anodic stripping voltammetry curve, from -1.2V to -0.45V, increases with the voltage, each Three peaks appear in the curve in turn, which are the stripping current peaks of zinc ions, cadmium ions and lead ions respectively. The inner inserts in the figure are the linear relationship graphs of the stripping peak current i _p of lead ion, cadmium ion and zinc ion and the concentration of lead ion, cadmium ion and zinc ion respectively, that is, the stripping current peaks of zinc ion, cadmium ion and lead ion are taken respectively The peak is the ordinate, the corresponding ion concentration is the abscissa, and the current-concentration curve is drawn. Through linear fitting, it can be known that the dissolution peak current i _p of lead ion, cadmium ion and zinc ion and the concentration of lead ion, cadmium ion and zinc ion in the system to be tested are between 2.0×10 ^-10 mol/L～1.0×10 ^-8 mol In the range of /L, there is a linear relationship. The linear regression equation corresponding to the lead ion is: i _p =0.258+0.114c (R=0.999); the linear regression equation corresponding to the cadmium ion is: i _p =0.887+0.0857c (R=0.988); the linear regression equation corresponding to the zinc ion is: i _p =2.75+0.106c (R=0.989). Among them, the unit of dissolution peak current i _p is μA, and the unit of concentration c is 10 ^-10 mol/L. According to the general standard of signal-to-noise ratio equal to 3, the detection limits of lead ion, cadmium ion and zinc ion are 9.2×10 ^-12 mol/L, 7.2×10 ^-12 mol/L and 8.1×10 ^-12 mol respectively /L.

Under the above experimental conditions, five same batches of chemically modified carbon paste electrodes prepared in Example 4 were used to detect the test system 7 containing lead ions, cadmium ions and zinc ions at concentrations of 2.0×10 ^-9 mol/L (Because the chemically modified carbon paste electrodes used are prepared in the same batch, so their structures are exactly the same and they can be discarded after only one use), and their relative standard deviations (RSD) are 1.8%, 1.3% and 2.3% respectively (where n( lead)=n(cadmium)=n(zinc)=5), indicating that the chemically modified carbon paste electrode has good preparation repeatability.

Under the above experimental conditions, the concentrations of lead ions, cadmium ions and zinc ions in system 8 to be tested are all 1.0×10 ^-9 mol/L, and the relative error is less than ±5%, the influence of interfering substances on the detection is investigated , the results show that: 1500 times the concentration of aluminum ions, manganese ions, nickel ions, sodium ions, calcium ions, magnesium ions, potassium ions, nitrate ions and sulfate ions, 500 times the concentration of iron ions, bismuth ions and ammonium ions , 200 times the concentration of ferrous ions, arsenic ions, mercury ions and chromium ions have no effect on the detection.

Comparative Example 1

A method for chemically modifying carbon paste electrodes to detect lead ions, cadmium ions and zinc ions in the environment, comprising the steps of:

(1) first add supporting electrolyte citrate in the liquid to be tested containing lead ion, cadmium ion and zinc ion, form the system to be tested, the concentration of the supporting electrolyte citrate in this system to be tested is 0.4mol/L, Then the pH value of the system to be tested is set to 5;

(2) First, the prepared three-electrode system (working electrode is compared with the chemically modified carbon paste electrode prepared in Example 2, lacks bismuth oxide powder component in the carbon paste, other components and components in the carbon paste The quality is the same, and the materials and specifications of the electrode shell and lead are the same, the reference electrode is a saturated calomel electrode, and the counter electrode is a platinum electrode) inserted into the system to be tested, suitable for differential pulse anode stripping voltammetry detection Lead ions, cadmium ions and zinc ions in the system to be measured;

That is, first insert the prepared three-electrode system into the system to be tested, then stir and enrich at the enrichment potential of -1.2V for 6 minutes, after resting, set the potential range from -1.2V to -0.45V, and the potential increment is 4mV , the pulse amplitude is 50mV, the pulse width is 0.2s, the pulse period is 0.5s, do anodization scanning, and record the anodic stripping voltammetry curve.

Comparative Example 2

A method for chemically modifying carbon paste electrodes to detect lead ions, cadmium ions and zinc ions in the environment, comprising the steps of:

(1) first add supporting electrolyte citrate in the liquid to be tested containing lead ion, cadmium ion and zinc ion, form the system to be tested, the concentration of the supporting electrolyte citrate in this system to be tested is 0.4mol/L, Then the pH value of the system to be tested is set to 5;

(2) First, the prepared three-electrode system (the working electrode is compared with the chemically modified carbon paste electrode prepared in Example 2, lacks dithizone components in the carbon paste, other components and components in the carbon paste The quality is the same, and the materials and specifications of the electrode shell and lead are the same, the reference electrode is a saturated calomel electrode, and the counter electrode is a platinum electrode) inserted into the system to be tested, suitable for differential pulse anode stripping voltammetry detection Lead ions, cadmium ions and zinc ions in the system to be measured;

That is, first insert the prepared three-electrode system into the system to be tested, then stir and enrich at the enrichment potential of -1.2V for 6 minutes, after resting, set the potential range from -1.2V to -0.45V, and the potential increment is 4mV , the pulse amplitude is 50mV, the pulse width is 0.2s, the pulse period is 0.5s, do anodization scanning, and record the anodic stripping voltammetry curve.

Comparative Example 3

A method for chemically modifying carbon paste electrodes to detect lead ions, cadmium ions and zinc ions in the environment, comprising the steps of:

(1) first add supporting electrolyte citrate in the liquid to be tested containing lead ion, cadmium ion and zinc ion, form the system to be tested, the concentration of the supporting electrolyte citrate in this system to be tested is 0.4mol/L, Then the pH value of the system to be tested is set to 5;

(2) First, the prepared three-electrode system (working electrode is compared with the chemically modified carbon paste electrode prepared in Example 2, lacks bismuth oxide powder component and dithizone component in the carbon paste, and other The components and the quality of the components are the same, and the materials and specifications of the electrode shell and lead are the same, the reference electrode is a saturated calomel electrode, and the counter electrode is a platinum electrode) inserted into the system to be tested, and it is suitable for differential pulse Anodic stripping voltammetry to detect lead ions, cadmium ions and zinc ions in the system to be tested;

That is, first insert the prepared three-electrode system into the system to be tested, then stir and enrich at the enrichment potential of -1.2V for 6 minutes, after resting, set the potential range from -1.2V to -0.45V, and the potential increment is 4mV , the pulse amplitude is 50mV, the pulse width is 0.2s, the pulse period is 0.5s, do anodization scanning, and record the anodic stripping voltammetry curve.

Comparative Example 4

A method for chemically modifying carbon paste electrodes to detect lead ions, cadmium ions and zinc ions in the environment, comprising the steps of:

(1) first add supporting electrolyte citrate in the liquid to be tested containing lead ion, cadmium ion and zinc ion, form the system to be tested, the concentration of the supporting electrolyte citrate in this system to be tested is 0.4mol/L, Then the pH value of the system to be tested is set to 5;

(2) First, the prepared three-electrode system (the working electrode is the chemically modified carbon paste electrode prepared in Example 2, the reference electrode is a saturated calomel electrode, and the counter electrode is a platinum electrode) is inserted into the system to be tested, and the differential Pulse anode stripping voltammetry to detect lead ions, cadmium ions and zinc ions in the system to be tested;

That is, first insert the prepared three-electrode system into the system to be tested, then stir and enrich at the enrichment potential of -1.2V for 6 minutes, after resting, set the potential range from -1.2V to -0.45V, and the potential increment is 4mV , the pulse amplitude is 50mV, the pulse width is 0.2s, the pulse period is 0.5s, do anodization scanning, and record the anodic stripping voltammetry curve.

Fig. 5 is the anodic stripping voltammogram in the same concentrations of lead ions, cadmium ions and zinc ions in the comparative examples 1 to 4 of the present invention. Wherein the modifier of the chemically modified carbon paste electrode used in Comparative Example 1 is dithizone, the modifier of the chemically modified carbon paste electrode used in Comparative Example 2 is bismuth oxide, and the carbon paste electrode used in Comparative Example 3 does not use any Modifier, the modifier of the chemically modified carbon paste electrode used in Comparative Example 4 is a composite modifier composed of bismuth oxide and dithizone. As shown in FIG. 5 , compared to the electrode in Example 3 which only has carbon paste without any modifier, there is almost no stripping peak in the solution, and lead, cadmium, and zinc at this concentration cannot be detected. The electrode using bismuth oxide as a modifier in Comparative Example 1, and the electrode using dithizone as a modifier in Comparative Example 2 have obvious stripping peaks, and can detect lead ions, cadmium ions and zinc ions at this concentration. ions, but the height of the peak is low and the lower limit of detection is high. In comparative example 4, the electrode using a composite modifier composed of bismuth oxide and dithizone, under the same conditions, its stripping peak significantly increased, indicating that the chemically modified carbon paste electrode used in the present invention is resistant to lead ions, cadmium ions and zinc ions. Compared with the existing electrodes, the detection ability of the method is significantly improved, and a lower detection limit can be obtained.

It should be understood that the above descriptions of the preferred embodiments of the present invention are relatively detailed, and should not be considered as limiting the scope of the patent protection of the present invention. The scope of protection of the patent protection of the present invention should be based on the appended claims.

Claims (10)

1. A chemically modified carbon paste electrode, comprising an electrode shell, the carbon paste filled in the electrode shell, and an electrode lead that is in contact with the carbon paste and drawn out from the electrode shell, the carbon The paste includes a conductive carbon material, an adhesive and a composite modifier, wherein the composite modifier includes a bismuth-containing solid powder and a chelating agent; the bismuth-containing solid powder is a water-insoluble solid bismuth-containing substance; the The chelating agent is a hydrophobic agent capable of forming a chelate with at least one of lead ions, cadmium ions and zinc ions. 2. The chemically modified carbon paste electrode according to claim 1, wherein the bismuth-containing solid powder is bismuth powder, bismuth oxide powder or bismuth hydroxide powder. 3. The chemically modified carbon paste electrode according to claim 1, wherein the chelating agent is 8-hydroxyquinoline, benzoin oxime, dimethylglyoxime or dithizone. 4. chemically modified carbon paste electrode according to claim 1, is characterized in that, the mass ratio of described conductive carbon material, described bismuth-containing solid powder, described chelating agent and described binding agent in described carbon paste It is (20-90): (0.5-50): (0.5-30): (10-50). 5. chemically modified carbon paste electrode according to claim 1, is characterized in that, the mass ratio of described conductive carbon material, described bismuth-containing solid powder, described chelating agent and described binding agent in described carbon paste It is (60-80): (0.5-10): (0.5-5): (10-30). 6. chemically modified carbon paste electrode according to claim 1, is characterized in that, the mass ratio of described conductive carbon material, described bismuth-containing solid powder, described chelating agent and described binding agent in described carbon paste For 70:2:2:30. 7. A preparation method for a chemically modified carbon paste electrode, characterized in that, comprising the steps: (1) Mix conductive carbon material, binder and composite modifier, said composite modifier includes bismuth-containing solid powder and chelating agent to obtain carbon paste; said bismuth-containing solid powder is a water-insoluble solid bismuth-containing substance ; The chelating agent is hydrophobic, and can form a chelate reagent with at least one ion in lead ions, cadmium ions and zinc ions; (2) filling the carbon paste into the electrode shell; (3) Install one end of the electrode lead inside the electrode shell and connect it to the carbon paste, and lead the other end of the electrode lead out from the inside of the electrode shell to obtain the chemically modified carbon paste electrode. 8. The method for preparing a chemically modified carbon paste electrode according to claim 7, characterized in that, in step (1), the bismuth-containing solid powder is bismuth powder, bismuth oxide powder or bismuth hydroxide powder. 9. the preparation method of chemically modified carbon paste electrode according to claim 7 is characterized in that, in step (1), described chelating agent is 8-hydroxyquinoline, benzoin oxime, dimethylglyoxime or dithizone . 10. the preparation method of chemical modification carbon paste electrode according to claim 7 is characterized in that, in step (1), in described carbon paste, described conductive carbon material, described bismuth-containing solid powder, described chelating agent The mass ratio to the binder is (20-90):(0.5-50):(0.5-30):(10-50).