Electrode, three-electrode assembly and preparation method and application of three-electrode assembly

Abstract

The invention provides an electrode, a three-electrode assembly and a preparation method and application of the three-electrode assembly. The electrode comprises a base body and a functional layer arranged on the surface of the base body. The functional layer comprises a copper-carbon base material and nano stainless steel particles contained in the copper-carbon base material; the mass ratio of copper to carbon in the copper-carbon matrix material is (0.8-1.0): 1. The electrode has good sensitivity and sensing effect on heavy metal lead ions, cadmium ions and mercury ions, has the advantages of strong specificity, high sensitivity and good accuracy, and has wide application prospects in detection of cadmium, lead and mercury in food.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of detection, in particular to an electrode, a three-electrode assembly and a preparation method and application thereof. BACKGROUND

[0002] Currently, the commonly used metal ion detection methods include atomic emission spectrometry (AES), atomic absorption spectrometry (AAS), inductively coupled plasma-mass spectrometry (ICP-MS), etc. However, these methods are difficult to realize on-site monitoring due to the reasons such as complex operation, expensive instruments, and inconvenience for carrying. The electrochemical method has the advantages of high sensitivity, good selectivity, and short response time, and is widely used in the fields of medical detection, environmental monitoring and control, agricultural detection of drug residues, etc.

[0003] However, the three electrodes generally used in the existing metal electrochemical detection instrument are column electrodes, which generally need a tedious polishing and polishing pretreatment process before use, and cannot meet the needs of rapid detection.

[0004] CN109273588A discloses a thin film sensor, which comprises a first substrate, a second substrate, and a conductive part for bonding the first substrate and the second substrate. The first substrate comprises a thin film transistor; the second substrate comprises a sensor device, and the thin film transistor and the sensor device are electrically connected through the conductive part; but the thin film sensor cannot be used to detect the concentration of metal ions.

[0005] CN103424456A discloses a three-electrode electrochemical sensor, which comprises a working electrode, a reference electrode, and a counter electrode, all of which are in contact with a liquid electrolyte and form ion conduction through the electrolyte. The working electrode is composed of a porous electronic conductor layer; the electronic conductor layer contains an active substance; the active substance is selected from one or more combinations of manganese compounds, cobalt compounds, or chromium compounds. The electrochemical sensor is used for detecting toxic gases or amines, but cannot quantitatively detect the content of metal ions.

[0006] Therefore, it is urgent to develop an electrochemical workstation capable of accurately and rapidly detecting lead ions, cadmium ions, and mercury ions in food. SUMMARY

[0007] In view of the deficiencies in the prior art, the purpose of the present application is to provide an electrode, a three-electrode assembly, and a preparation method and application thereof, which can be used to simultaneously detect trace amounts of lead ions, cadmium ions, and mercury ions in food, and is a highly efficient and rapid metal ion detection electrode with wide application prospects.

[0008] To achieve this purpose, the present application adopts the following technical solutions:

[0009] In a first aspect, the present application provides an electrode, comprising a substrate and a functional layer arranged on the surface of the substrate; the functional layer comprises a copper-carbon substrate material and nano stainless steel particles contained in the copper-carbon substrate material; the mass ratio of copper to carbon in the copper-carbon substrate material is (0.8-1.0):1.

[0010] The functional layer of the present application contains copper, which can form an alloy with lead and mercury in the working electrode area, making the detection more sensitive.

[0011] Specifically, the mass ratio of copper to carbon in the copper-carbon substrate material is (0.8-1.0):1, for example, it can be 0.8:1, 0.82:1, 0.83:1, 0.85:1, 0.88:1, 0.9:1, 0.92:1, 0.93:1, 0.95:1, 0.98:1, 0.99:1 or 1:1, etc.

[0012] Preferably, the particle size of the nano stainless steel particles is in the range of 400-800 nm, for example, it can be 400 nm, 445 nm, 489 nm, 534 nm, 578 nm, 623 nm, 667 nm, 712 nm, 756 nm or 800 nm, etc.

[0013] Preferably, the mass percentage of the nano stainless steel particles in the functional layer is 0.1-1.2wt%, for example, it can be 0.1wt%, 0.3wt%, 0.4wt%, 0.5wt%, 0.6wt%, 0.8wt%, 0.9wt%, 1wt%, 1.1wt% or 1.2wt%, etc.

[0014] In the present application, the content of nano stainless steel particles is controlled in the above range, and the obtained electrode has good stability and responsiveness. When the mass percentage of nano stainless steel particles is too low, the stability and responsiveness will be reduced; when the mass percentage of nano stainless steel particles is too high, it will have a greater impact on the resistance, thereby affecting the responsiveness of the current.

[0015] Preferably, the material of the nano stainless steel particles is 316L and / or 304.

[0016] Preferably, the substrate of the electrode comprises a silver-carbon mixture.

[0017] Preferably, the molar ratio of carbon to silver in the silver-carbon mixture is 1:(1.5-2.5), for example, it can be 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9, 1:2.0, 1:2.2, 1:2.3, 1:2.4 or 1:2.5, etc.

[0018] The molar ratio of carbon and silver in the conductive layer is 1: (1.5-2.5), which has a good conductive effect; when the molar ratio of the two is too high or too low, the electrode resistance will change, thereby affecting the conductive effect, further affecting the conduction effect and the detection sensitivity.

[0019] In a second aspect, the application provides a three-electrode assembly, which comprises a working electrode, a counter electrode and a reference electrode, and the working electrode is the electrode of the first aspect.

[0020] The three-electrode assembly has high test stability, can reduce solution pollution, has the advantages of strong specificity, high sensitivity and good accuracy, and can further reduce the amount of detection sample by setting the cofferdam film. On the premise of ensuring high sensitivity and accuracy, only a very small amount of sample is needed.

[0021] Preferably, the surface of the conductive area of the counter electrode and the reference electrode is provided with a second conductive layer.

[0022] Preferably, the conductive substance in the second conductive layer comprises a silver-carbon mixture.

[0023] Preferably, the molar ratio of carbon and silver in the second conductive layer is 1: (1-10), for example, it can be 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, 1:6, 1:7, 1:8, 1:9 or 1:10, etc.

[0024] Preferably, the counter electrode further comprises a carbon layer arranged on the surface of the second conductive layer.

[0025] Preferably, the reference electrode further comprises a silver chloride layer arranged on the surface of the second conductive layer.

[0026] In a third aspect, the application provides a preparation method of the three-electrode assembly of the second aspect, which comprises:

[0027] (1) printing carbon-silver mixed slurry on the surface of the conductive area of the three-electrode assembly on the substrate, drying to obtain a first electrode assembly with a conductive layer.

[0028] (2) printing copper-carbon slurry containing nano stainless steel particles on the working area of the working electrode of the first electrode assembly in step (1), drying to obtain a second electrode assembly.

[0029] (3) printing carbon slurry on the surface of the counter electrode of the second electrode assembly, drying; printing silver chloride slurry on the surface of the reference electrode of the second electrode assembly, drying to obtain the three-electrode assembly.

[0030] In a fourth aspect, the present application provides an application of the three-electrode assembly of the second aspect in heavy metal ion detection.

[0031] Preferably, the heavy metal ions include lead ions, cadmium ions and mercury ions.

[0032] Preferably, the heavy metal ions are heavy metal ions in food or in the environment.

[0033] Preferably, the method for detecting heavy metal ions comprises:

[0034] (1) The sample to be measured is subjected to acid extraction and solid-liquid separation, and the obtained solution is subjected to constant volume to obtain a solution to be measured.

[0035] (2) The solution to be measured is placed in an electrochemical workstation containing a three-electrode assembly for electrochemical detection to obtain current intensity, and the content of heavy metal ions in the sample to be measured is calculated according to a standard curve.

[0036] Preferably, the acid used in the acid extraction includes any one or a combination of at least two of sulfuric acid, hydrochloric acid, perchloric acid or nitric acid.

[0037] Preferably, the concentration of the acid used in the acid extraction is 0.5-5 mol / L, for example, it can be 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L, 4 mol / L, 4.5 mol / L or 5 mol / L, etc.

[0038] Preferably, when measuring cadmium ions, pH adjustment is further performed before constant volume. Preferably, the pH range for the pH adjustment is 3-5, for example, it can be 3, 3.3, 3.5, 3.7, 3.9, 4.2, 4.4, 4.6, 4.8 or 5, etc.

[0039] Preferably, the pH adjustment is performed using a sodium hydroxide solution.

[0040] Preferably, the constant volume is performed using a buffer solution.

[0041] Preferably, the buffer solution includes a phosphate buffer solution and / or an acetate buffer solution.

[0042] Preferably, when measuring cadmium ions, an auxiliary agent is further added to the solution to be measured in step (2).

[0043] Preferably, the auxiliary agent includes bismuth ions.

[0044] Preferably, the auxiliary agent includes a bismuth nitrate solution.

[0045] Preferably, the volume ratio of the auxiliary agent to the to-be-tested liquid is (1.2~2.2):1, for example, it can be 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.8:1, 1.85:1, 1.89:1, 1.94:1, 1.98:1, 2.03:1, 2.07:1, 2.12:1, 2.16:1 or 2.2:1, etc.

[0046] Preferably, the concentration of bismuth nitrate in the auxiliary agent is 80~120mg / L, for example, it can be 80mg / L, 85mg / L, 89mg / L, 94mg / L, 98mg / L, 103mg / L, 107mg / L, 112mg / L, 116mg / L or 120mg / L, etc.

[0047] Preferably, when measuring cadmium ions, the mixing in step (2) further adds an acetic acid-sodium acetate buffer solution.

[0048] Preferably, the pH of the acetic acid-sodium acetate buffer solution is 4.2~4.8, for example, it can be 4.2, 4.3, 4.4, 4.5, 4.6, 4.7 or 4.8, etc.

[0049] Preferably, when measuring cadmium ions, the mixing in step (2) further adds a pH regulator to adjust the pH to 4.2~4.8, for example, it can be 4.2, 4.3, 4.4, 4.5, 4.6, 4.7 or 4.8, etc.

[0050] Preferably, the pH regulator comprises sodium hydroxide.

[0051] Preferably, the enrichment potential of the electrochemical detection is -1.0~-2.0V.

[0052] Preferably, the enrichment time of the electrochemical detection is 250~600s.

[0053] Compared with the prior art, the present application has at least the following beneficial effects:

[0054] (1) The electrode provided by the present application has excellent conductivity, which can increase the conduction effect and the sensitivity of detection; the electrochemical sensor has high testing accuracy, can reduce solution pollution, has the advantages of strong specificity, high sensitivity and good accuracy, and the relative standard deviation is less than 5%;

[0055] (2) The preparation method of the three-electrode assembly provided by the present application is simple, the raw materials are easy to obtain and low in price, easy to realize, and convenient for industrial large-scale application; the electrochemical workstation can be used for detecting the content of lead ions, cadmium ions and mercury ions in food by converting electrical signals into chemical signals, and has wide application prospect. DETAILED DESCRIPTION

[0056] For the convenience of understanding the present application, the present application lists the following examples. Those skilled in the art should understand that the examples are only to help understand the present application, and should not be regarded as specific limitations of the present application.

[0057] For the convenience of test, the following three-electrode assemblies are prepared by the following preparation method.

[0058] The preparation method comprises:

[0059] (1) printing carbon-silver mixed paste on the surface of the conductive area of the three-electrode assembly on the substrate, drying to obtain a first electrode assembly with a conductive layer;

[0060] (2) printing copper-carbon paste containing nano stainless steel particles on the working area of the working electrode of the first electrode assembly in step (1), drying to obtain a second electrode assembly;

[0061] (3) printing carbon paste on the surface of the counter electrode of the second electrode assembly, drying; printing silver chloride paste on the surface of the reference electrode of the second electrode assembly, drying to obtain the three-electrode assembly.

[0062] Example 1

[0063] The present example provides an electrode, which comprises a substrate and a functional layer arranged on the surface of the substrate.

[0064] The functional layer comprises copper-carbon base material and nano stainless steel particles contained in the copper-carbon base material; the mass ratio of copper to carbon in the copper-carbon base material is 0.9:1. The particle size range of the nano stainless steel particles is 500-600 nm; the mass percentage content of the nano stainless steel particles in the functional layer is 0.8 wt%. The material of the nano stainless steel particles is 316L.

[0065] The substrate of the electrode comprises silver-carbon mixture; the molar ratio of carbon to silver in the silver-carbon mixture is 1:2.0.

[0066] Example 2

[0067] The present example provides an electrode, which comprises a substrate and a functional layer arranged on the surface of the substrate.

[0068] The functional layer comprises copper-carbon base material and nano stainless steel particles contained in the copper-carbon base material; the mass ratio of copper to carbon in the copper-carbon base material is 0.8:1. The particle size range of the nano stainless steel particles is 500-800 nm; the mass percentage content of the nano stainless steel particles in the functional layer is 0.5 wt%. The material of the nano stainless steel particles is 316L.

[0069] The base body of the electrode comprises a silver-carbon mixture; the molar ratio of carbon to silver in the silver-carbon mixture is 1:1.5.

[0070] Embodiment 3

[0071] The embodiment provides an electrode, which comprises a base body and a functional layer arranged on the surface of the base body.

[0072] The functional layer comprises a copper-carbon base material and nano stainless steel particles contained in the copper-carbon base material; the mass ratio of copper to carbon in the copper-carbon base material is 1.0:1. The particle size of the nano stainless steel particles ranges from 400nm to 700nm; the mass percentage of the nano stainless steel particles in the functional layer is 1.2wt%. The material of the nano stainless steel particles is 316L.

[0073] The base body of the electrode comprises a silver-carbon mixture; the molar ratio of carbon to silver in the silver-carbon mixture is 1:2.5.

[0074] Application Example 1

[0075] The application example provides an electrochemical workstation, which comprises a three-electrode assembly, the three-electrode assembly comprises a working electrode, a counter electrode and a reference electrode, and the working electrode is the electrode described in Embodiment 1. The electrochemical workstation is used for detecting the concentration of cadmium ions in rice, and the detection method is as follows:

[0076] (1) 1.0g of the rice sample to be detected is weighed and placed in 5mL of 2mol / L nitric acid, shaken for 3min, and after centrifugation, a pretreated sample is obtained;

[0077] (2) 300ul of the pretreated sample is taken and placed in a stirring cup, 500ul of 100mg / L Bi 2+ , 100ul of pH4.5 acetic acid-sodium acetate buffer is added, the pH is adjusted to 4.5 with NaOH, the detection parameters are set by the electrochemical workstation, the enrichment potential is-1.4V, and the enrichment time is 300s.

[0078] The supernatant of the blank rice matrix extraction (without cadmium ions) is taken, different concentrations of 1ug / L, 5ug / L, 10ug / L, 20ug / L, 40ug / L and 100ug / L of cadmium ions are added, the current intensity is detected, and a standard curve for matrix calibration is established.

[0079] According to the standard curve, the concentration of cadmium ions in the rice sample to be detected is tested, and the test result is that the concentration of cadmium ions in the sample to be detected is 1.68mg / kg.

[0080] The cadmium ion in the to-be-tested rice sample is determined by ICP, and the cadmium ion concentration in the to-be-tested rice sample is 1.72 mg / kg; the relative error of the cadmium ion detection result of the embodiment and the ICP detection result is 2.32%, proving that the test method is accurate and reliable.

[0081] Application Example 2

[0082] The embodiment also provides an electrochemical workstation, which comprises a three-electrode assembly, the three-electrode assembly comprises a working electrode, a counter electrode and a reference electrode, and the working electrode is the electrode described in the embodiment 2. The electrochemical workstation is used for detecting the mercury ion concentration in rice, and the detection method is as follows:

[0083] (1) 1.0 g of the to-be-tested rice sample is weighed and placed in 5 mL of hydrochloric acid with a concentration of 5 mol / L, shaken for 5 min, and after centrifugation, 300 μL of supernatant is taken and added to 600 μL of 0.4 M NaCl solution in a stirring cup, and the detection parameters of the electrochemical workstation are set as an enrichment potential of -1.0 V and an enrichment time of 600 s.

[0084] (2) The blank rice matrix extraction supernatant (without mercury ions) is taken, and different concentrations of 1 μg / L, 5 μg / L, 10 μg / L, 20 μg / L, 40 μg / L and 100 μg / L of mercury ions are added, and the current intensity is detected to establish a standard curve for matrix calibration.

[0085] (3) The standard curve is used as the basis to test the mercury ion concentration in the to-be-tested rice sample. GBW (E) 100560 (0.021 mg / kg) and GBW (E) 100561 (0.061 mg / kg) are tested respectively, and the results are 0.020 mg / kg and 0.063 mg / kg respectively, proving that the test method is accurate and reliable.

[0086] Application Example 3

[0087] The embodiment also provides an electrochemical workstation, which comprises a three-electrode assembly, the three-electrode assembly comprises a working electrode, a counter electrode and a reference electrode, and the working electrode is the electrode described in the embodiment 3. The electrochemical workstation is used for detecting the lead ion concentration in rice, and the detection method is as follows:

[0088] (1) 1.0 g of the to-be-tested rice sample is weighed and placed in 5 mL of hydrochloric acid with a concentration of 0.5 mol / L, shaken for 5 min, and after centrifugation, 200 μL of supernatant is taken and added to 800 μL of 1.0 M NaCl solution in a stirring cup, and the detection parameters of the electrochemical workstation are set as an enrichment potential of -1.2 V and an enrichment time of 300 s.

[0089] (2) Take the blank brown rice matrix extraction supernatant (without lead ions), add different concentrations of 2 μg / L, 5 μg / L, 10 μg / L, 20 μg / L, 40 μg / L, 100 μg / L lead ions, detect the current intensity, and establish the standard curve of matrix calibration.

[0090] (3) According to the standard curve, the lead ion concentration in the brown rice sample to be tested is tested. GBW (E) 100377 (0.22 mg / kg) is tested, and the results are 0.20 mg / kg, proving that the test method of the present application is accurate and reliable.

[0091] The above embodiments are used to illustrate the detailed features of the present application, but the present application is not limited to the above detailed features, that is, it does not mean that the present application must rely on the above detailed features to be implemented. Those skilled in the art should understand that any improvement of the present application, equivalent replacement of the technical features selected by the present application, addition of auxiliary technical features, selection of specific modes, etc. fall within the protection scope and disclosure scope of the present application.

Claims

1. An electrode, characterized in that, The electrode includes a substrate and a functional layer disposed on the surface of the substrate; The functional layer includes a copper-carbon matrix material and nano-stainless steel particles contained in the copper-carbon matrix material. The mass ratio of copper to carbon in the copper-carbon matrix material is (0.8~1.0):

1.

2. The electrode according to claim 1, characterized in that, The particle size range of the nano-stainless steel particles is 400~800nm; And / or, the mass percentage of nano-stainless steel particles in the functional layer is 0.1~1.2wt%.

3. The electrode according to claim 1 or 2, characterized in that, The nano-stainless steel particles are made of 316L and / or 304 stainless steel.

4. The electrode according to any one of claims 1 to 3, characterized in that, The electrode substrate comprises a silver-carbon mixture; Preferably, the molar ratio of carbon to silver in the silver-carbon mixture is 1:(1.5~2.5).

5. A three-electrode assembly, characterized in that, The three-electrode assembly includes a working electrode, a counter electrode, and a reference electrode, wherein the working electrode is the electrode described in any one of claims 1 to 4.

6. A method for preparing the three-electrode assembly according to claim 5, characterized in that, The preparation method includes: (1) A carbon-silver mixed paste is printed on the conductive area surface of the three-electrode assembly on the substrate and dried to obtain a first electrode assembly with a conductive layer. (2) In step (1), a copper-carbon paste containing nano-stainless steel particles is printed on the working area of ​​the working electrode in the first electrode assembly, and dried to obtain the second electrode assembly. (3) Print carbon paste on the surface of the electrode in the second electrode assembly and dry it; print silver chloride paste on the surface of the reference electrode in the second electrode assembly and dry it to obtain the three-electrode assembly.

7. The application of the three-electrode assembly according to claim 5 in the detection of heavy metal ions.

8. The application according to claim 7, characterized in that, The heavy metal ions include lead ions, cadmium ions, and mercury ions; Preferably, the heavy metal ions are heavy metal ions found in food or in the environment.

9. The application according to claim 8, characterized in that, The method for detecting heavy metal ions includes: (1) The sample to be tested is subjected to acid extraction and solid-liquid separation, and the resulting solution is diluted to volume to obtain the test solution; (2) The test solution is placed in an electrochemical workstation with a three-electrode assembly for electrochemical detection to obtain the current intensity, and the content of heavy metal ions in the test sample is calculated according to the standard curve.

10. The application according to claim 9, characterized in that, The acid used for acid extraction includes any one or a combination of at least two of sulfuric acid, hydrochloric acid, perchloric acid, or nitric acid. Preferably, the concentration of acid in the acid extraction is 0.5~5 mol / L.