A detection electrode, a preparation method and a detection method for trace arsenic in water
By modifying a carbon paper electrode with chitosan and catechol derivatives and combining it with a ferrocene indicator, a simple and rapid electrochemical detection electrode was prepared, solving the problems of dependence on large equipment and in-situ detection, and realizing low-cost and high-sensitivity detection of trivalent arsenic in water.
Patent Information
- Application Number
- CN202310153500.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-02-22
- Publication Date
- 2026-08-25
- Estimated Expiration
- 2043-02-22
AI Technical Summary
Existing arsenic detection methods require large equipment, are costly, and cannot achieve simple and rapid in-situ detection, especially in the case of sudden water pollution incidents in remote rural areas where accurate arsenic concentration information cannot be obtained in a timely manner.
A carbon paper electrode was modified with chitosan and catechol and their derivatives, and a detection electrode was prepared by electrochemical method. Combined with ferrocene as an indicator, trace trivalent arsenic in water was detected by cyclic voltammetry.
It achieves low-cost, simple and rapid in-situ detection of trace trivalent arsenic in water, with a detection limit of less than 10 μg L⁻¹, which meets the standards for drinking water. Furthermore, the materials used are renewable biomass resources, making it environmentally friendly.
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Figure CN116256409B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of heavy metal detection technology, and relates to an arsenic detection technology. Specifically, it relates to a detection electrode, a preparation method, and a method for detecting trace trivalent arsenic in water. It is a technology for detecting heavy metal ion concentration by modifying a carbon paper electrode with natural polymer functional materials. Background Technology
[0002] Arsenic detection methods mainly include atomic absorption spectrometry, inductively coupled plasma atomic emission spectrometry, atomic fluorescence spectrometry, and spectrophotometry. These methods offer advantages such as high sensitivity and specificity, but their drawbacks include high maintenance costs of large-scale equipment, the need for specialized personnel, and complex sample pretreatment, limiting their application. In some sudden water pollution incidents occurring in remote rural areas contaminated with arsenic, the limitations of these detection methods prevented the timely acquisition of accurate arsenic concentration information. In-situ detection refers to real-time detection at the pollution site, requiring the determination of the concentration level of the analyte within a short time. Methods used for in-situ detection need to have characteristics such as small sample volumes, high accuracy and sensitivity, simple and rapid operation, and portable instruments. Summary of the Invention
[0003] To address the problems existing in the prior art, this invention provides a detection electrode, a preparation method, and a method for detecting trace trivalent arsenic in water. This method solves the problems of relying on large instruments and high costs for trivalent arsenic detection, as well as the inability to perform simple, rapid, and in-situ detection.
[0004] The technical solution provided by this invention is as follows:
[0005] This invention provides a method for preparing a detection electrode for the electrochemical detection of trace trivalent arsenic in water, comprising the following steps:
[0006] Step 1: Add chitosan powder to an acidic aqueous solution and stir until the chitosan powder is completely dissolved to obtain an acidic aqueous solution of chitosan.
[0007] Step 2: Immerse the conductive carbon paper in the acidic aqueous solution of chitosan obtained in Step 1; Under a two-electrode system, with the conductive carbon paper as the working electrode and the platinum wire as the counter electrode, electrodeposit a chitosan film on the conductive carbon paper by means of chronopotential method.
[0008] Step 3: Place the conductive carbon paper with the chitosan film deposited in Step 2 into deionized water to wash away the undeposited chitosan solution, and obtain the conductive carbon paper-chitosan film electrode.
[0009] Step 4: In a three-electrode system, using the conductive carbon paper-chitosan film electrode obtained in Step 3 as the working electrode, the silver / silver chloride electrode as the reference electrode, and the platinum wire as the counter electrode, the catechol and its derivatives are oxidized and grafted onto the chitosan film in a solution of catechol and its derivatives by a time-coulometric method.
[0010] Step 5: Place the working electrode, which was deposited in step 4 and grafted with catechol and its derivatives, in deionized water to wash away the free catechol and its derivatives in the film, and obtain the detection electrode.
[0011] Preferably, in step 1, the acidic aqueous solution is hydrochloric acid or acetic acid.
[0012] Preferably, in step 1, the concentration of the chitosan solution in the acidic aqueous solution is 1-5 wt%.
[0013] Preferably, in step 2, the conductive carbon paper is commercially available conductive carbon paper or a laboratory-made carbon-based conductive material.
[0014] Preferably, in step 2, the current density of the chronopotential method is 0.5-2 A / m. 2 .
[0015] Preferably, in step 2, the running time of the timing potentiometric method is 30s-1200s.
[0016] Preferably, in step 3, the rinsing time in deionized water is 300s-1800s.
[0017] Preferably, in step 4, the concentration of the catechol and its derivative solution is 1-10 mM (millimoles per liter).
[0018] Furthermore, the derivatives of the catechol include 4-tert-butylcatechol and chloroacetylcatechol.
[0019] Preferably, in step 4, the potential of the time coulomb method is 0.4-0.8V.
[0020] Preferably, in step 4, the amount of charge transferred by the chrono-coulomb method is 50-200 mC.
[0021] Preferably, in step 5, the washing time in deionized water is 2-12 hours.
[0022] The present invention also provides a method for detecting trace trivalent arsenic in water using the above-mentioned detection electrode, comprising the following steps:
[0023] Step 6: Add ferrocene to the trivalent arsenic solution to obtain the test solution. Place the detection electrode obtained in step 5 into the test solution and use cyclic voltammetry to detect the arsenic concentration in the solution.
[0024] Preferably, in step 6, the ferrocene concentration is 0.1-1 mM.
[0025] Preferably, in step 6, the concentration of trivalent arsenic is 1-1000 μg / L. -1 .
[0026] Preferably, in step 6, the scanning range of the cyclic voltammetry is -0.5 to 0.5 V.
[0027] Preferably, in step 6, the scan rate of the cyclic voltammetry is 50-100 mM / s.
[0028] Prior to detection, in step 6, trivalent arsenic standard solutions of different concentrations are prepared. Ferrocene is added to the standard solutions to obtain a detection solution containing ferrocene and trivalent arsenic. Then, using the detection electrode as the working electrode, a standard curve is obtained by scanning with cyclic voltammetry to obtain the relationship between the peak value of the oxidation current and different concentrations of trivalent arsenic. The concentration of trivalent arsenic solution is detected using the standard curve.
[0029] The principle of this invention is as follows:
[0030] Under the influence of the cathode current, hydroxide ions are generated near the conductive carbon paper, causing the nearby chitosan to deprotonate and deposit into a gel state. Catechol (and its derivatives) are oxidized to benzoquinone at the electrode. The abundant amino groups on the chitosan can undergo Macaddition or Schiff base reactions with the benzoquinone to complete the grafting process. Catechol / quinone exhibits excellent redox activity; its electron-accepting and losing behavior can be controlled by adjusting the voltage. In the presence of the redox medium ferrocene, electrical signal amplification can be achieved. Due to the specific redox potential of trivalent arsenic, it can significantly affect the above process, resulting in a significant decrease in the amplified signal current. Therefore, a correlation between arsenic concentration and signal current can be established, enabling the determination of arsenic. Attached Figure Description
[0031] Figure 1 This is a schematic diagram illustrating the preparation process of the conductive carbon paper-chitosan-catechol electrode of this invention and its arsenic detection process.
[0032] Figure 2 These are the peak oxidation current values corresponding to different concentrations of trivalent arsenic in Example 1, and the slant lines obtained after mathematical fitting.
[0033] Figure labels: 1. Electrochemical workstation; 2. Conductive carbon paper; 3. Platinum wire electrode; 4. Conductive carbon paper-chitosan film electrode; 5. Silver / silver chloride electrode; 6. Catechol solution; 7. Conductive carbon paper-chitosan-catechol electrode; 8. Detection solution for ferrocene and trivalent arsenic; 9. Chitosan solution. Detailed Implementation
[0034] The present invention is further illustrated below by way of examples. It should be understood that the examples of the present invention are for illustrative purposes and not for limiting the present invention. Simple modifications made to the present invention based on the essence of the present invention are all within the scope of protection claimed by the present invention.
[0035] Example 1
[0036] Weigh 5g of chitosan powder into a 1000mL beaker, add 495mL of deionized water and 5mL of hydrochloric acid, and stir until the chitosan is completely dissolved. Then, immerse a 1cm×1cm piece of commercially available conductive carbon paper into 20mL of the chitosan solution. Using the conductive carbon paper as the working electrode and a platinum wire as the counter electrode, set the current density to 2A / m using a chronopotentiometric method. 2 Electrodeposition was performed for 300 seconds, followed by washing in deionized water for 600 seconds to obtain a conductive carbon paper-chitosan thin film electrode. The conductive carbon paper-chitosan thin film electrode was then immersed in 20 mL of water. In a 5 mM catechol solution, under a three-electrode system, using a conductive carbon paper-chitosan film electrode as the working electrode, a silver / silver chloride electrode as the reference electrode, and a platinum wire as the counter electrode, a chronocoulometric method was used with a voltage of 0.6 V and a charge transfer of 50 mC. The electrode was then washed in deionized water for 12 h to obtain the conductive carbon paper-chitosan-catechol electrode, which serves as the detection electrode. Ferrocene was added to a trivalent arsenic solution to prepare a detection solution containing 0.1 mM ferrocene. Using the conductive carbon paper-chitosan-catechol electrode as the working electrode, a silver / silver chloride electrode as the reference electrode, and a platinum wire as the counter electrode, cyclic voltammetry (scan range -0.5 V to 0.5 V, scan rate 50 mV / s) was employed to detect trivalent arsenic in solutions containing different concentrations of trivalent arsenic (1-1000 μg / L). -1 The detection was performed in the test solution, and the results showed that the detection limit was 5.18 μg / L. -1 Simultaneously, by utilizing the detection results of test solutions containing different concentrations of trivalent arsenic, a standard curve can be generated to show the relationship between the peak oxidation current and different concentrations of trivalent arsenic. This standard curve can then be used to detect the concentration of trivalent arsenic solutions with unknown concentrations.
[0037] Example 2
[0038] Weigh 5g of chitosan powder into a 1000mL beaker, add 495mL of deionized water and 5mL of hydrochloric acid, and stir until the chitosan is completely dissolved. Then, immerse a 1cm×1cm piece of commercially available conductive carbon paper into 20mL of the chitosan solution. Using the conductive carbon paper as the working electrode and a platinum wire as the counter electrode, set the current density to 2A / m using a chronopotentiometric method. 2Electrodeposition was performed for 300 s, followed by rinsing in deionized water for 600 s to obtain a conductive carbon paper-chitosan film electrode. This electrode was then immersed in 20 mL of 5 mM catechol solution. Using a three-electrode system with the conductive carbon paper-chitosan film electrode as the working electrode, a silver / silver chloride electrode as the reference electrode, and a platinum wire as the counter electrode, a chronocoulometric method was used with a voltage of 0.6 V and a transferred charge of 75 mC. After rinsing in deionized water for 12 h, a conductive carbon paper-chitosan-catechol electrode, i.e., the detection electrode, was obtained. Ferrocene was added to a trivalent arsenic solution to prepare a detection solution containing 0.1 mM ferrocene. Using the conductive carbon paper-chitosan-catechol electrode as the working electrode, a silver / silver chloride electrode as the reference electrode, and a platinum wire as the counter electrode, cyclic voltammetry (scan range -0.5 V to 0.5 V, scan rate 50 mV / s) was employed to detect trivalent arsenic in solutions containing different concentrations of trivalent arsenic (1-1000 μg). L -1 The detection was performed in the test solution, and the results showed that the detection limit was 7.49 μg / L. -1 .
[0039] Example 3
[0040] Weigh 5g of chitosan powder into a 1000mL beaker, add 495mL of deionized water and 5mL of hydrochloric acid, and stir until the chitosan is completely dissolved. Then, immerse a 1cm×1cm piece of commercially available conductive carbon paper into 20mL of the chitosan solution. Using the conductive carbon paper as the working electrode and a platinum wire as the counter electrode, set the current density to 2A / m using a chronopotentiometric method. 2 Electrodeposition was performed for 300 seconds, followed by washing in deionized water for 600 seconds to obtain a conductive carbon paper-chitosan thin film electrode. The conductive carbon paper-chitosan thin film electrode was then immersed in 20 mL of water. In a 5 mM catechol solution, under a three-electrode system, using a conductive carbon paper-chitosan film electrode as the working electrode, a silver / silver chloride electrode as the reference electrode, and a platinum wire as the counter electrode, a chronocoulometric method was used with a voltage of 0.6 V and a transfer charge of 100 mC. The electrode was then washed in deionized water for 12 h to obtain the conductive carbon paper-chitosan-catechol electrode, which serves as the detection electrode. Ferrocene was added to a trivalent arsenic solution to prepare a detection solution containing 0.1 mM ferrocene. Using the conductive carbon paper-chitosan-catechol electrode as the working electrode, a silver / silver chloride electrode as the reference electrode, and a platinum wire as the counter electrode, cyclic voltammetry (scan range -0.5 V to 0.5 V, scan rate 50 mV / s) was employed to detect trivalent arsenic in solutions containing different concentrations of trivalent arsenic (1-1000 μg / L). -1 The detection was performed in the test solution, and the results showed that the detection limit was 8.14 μg / L. -1 .
[0041] Example 4
[0042] Weigh 5g of chitosan powder into a 1000mL beaker, add 495mL of deionized water and 5mL of hydrochloric acid, and stir until the chitosan is completely dissolved. Then, immerse a 1cm×1cm piece of commercially available conductive carbon paper into 20mL of the chitosan solution. Using the conductive carbon paper as the working electrode and a platinum wire as the counter electrode, set the current density to 2A / m using a chronopotentiometric method. 2 Electrodeposition was performed for 300 seconds, followed by washing in deionized water for 600 seconds to obtain a conductive carbon paper-chitosan thin film electrode. The conductive carbon paper-chitosan thin film electrode was then immersed in 20 mL of water. In a 5 mM catechol solution, under a three-electrode system, using a conductive carbon paper-chitosan film electrode as the working electrode, a silver / silver chloride electrode as the reference electrode, and a platinum wire as the counter electrode, a chronocoulometric method was used with a voltage of 0.6 V and a charge transfer of 125 mC. The electrode was then washed in deionized water for 12 h to obtain the conductive carbon paper-chitosan-catechol electrode, which serves as the detection electrode. Ferrocene was added to a trivalent arsenic solution to prepare a detection solution containing 0.1 mM ferrocene. Using the conductive carbon paper-chitosan-catechol electrode as the working electrode, a silver / silver chloride electrode as the reference electrode, and a platinum wire as the counter electrode, cyclic voltammetry (scan range -0.5 V to 0.5 V, scan rate 50 mV / s) was employed to detect trivalent arsenic in solutions containing different concentrations of trivalent arsenic (1-1000 μg / L). -1 The detection was performed in the test solution, and the results showed that the detection limit was 6.75 μg / L. -1 .
[0043] Based on the above experimental results, the detection limits for trivalent arsenic in all four examples were below 10 μg / L. -1 This method meets the requirements of the "Standards for Drinking Water Quality" (GB 5749-2006). The materials used in the electrode preparation (carbon, chitosan, phenols) are all renewable biomass resources, environmentally friendly, and biodegradable. The electrochemical workstation is easy to miniaturize, simple to operate, and can quickly obtain data, well meeting the needs of in-situ measurement and enabling its widespread application in arsenic detection in the environment.
[0044] The above embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Although the invention has been described in detail with reference to the embodiments, those skilled in the art should understand that various combinations, modifications, or equivalent substitutions of the technical solutions of the invention do not depart from the spirit and scope of the invention and should be covered within the scope of the claims of the invention.
Claims
1. A paper-based electrochemical method for detecting trace amounts of trivalent arsenic in water, characterized in that, Includes the following steps: Step 1: Add chitosan powder to an acidic aqueous solution and stir until the chitosan powder is completely dissolved to obtain an acidic aqueous solution of chitosan. Step 2: Immerse the conductive carbon paper in the acidic aqueous solution of chitosan obtained in Step 1; Under a two-electrode system, with the conductive carbon paper as the working electrode and the platinum wire as the counter electrode, electrodeposit a chitosan film on the conductive carbon paper by means of chronopotential method. Step 3: Place the conductive carbon paper with the chitosan film deposited in Step 2 into deionized water to wash away the undeposited chitosan solution, and obtain the conductive carbon paper-chitosan film electrode. Step 4: In a three-electrode system, using the conductive carbon paper-chitosan film electrode obtained in Step 3 as the working electrode, the silver / silver chloride electrode as the reference electrode, and the platinum wire as the counter electrode, the catechol and its derivatives are oxidized and grafted onto the chitosan film in a solution of catechol and its derivatives by a time-coulometric method. Step 5: Place the working electrode, which was deposited in step 4 and grafted with catechol and its derivatives, in deionized water to wash away the free catechol and its derivatives in the film, and obtain the detection electrode. Step 6: Add ferrocene to the trivalent arsenic solution to obtain the test solution. Place the detection electrode obtained in step 5 into the test solution and use cyclic voltammetry to detect the arsenic concentration in the solution.
2. The paper-based electrochemical method for detecting trace amounts of trivalent arsenic in water according to claim 1, characterized in that: In step 1, the acidic aqueous solution is hydrochloric acid or acetic acid.
3. The paper-based electrochemical method for detecting trace amounts of trivalent arsenic in water according to claim 1, characterized in that: In the acidic aqueous solution of chitosan in step 1, the concentration of chitosan is 1~5 wt%.
4. The paper-based electrochemical method for detecting trace amounts of trivalent arsenic in water according to claim 1, characterized in that: In step 2, the current density of the chronopotential method is 0.5-2 A / m. 2 The running time is 30s-1200s.
5. The paper-based electrochemical method for detecting trace amounts of trivalent arsenic in water according to claim 1, characterized in that: In step 3, the washing time in deionized water is 300s-1800s.
6. The paper-based electrochemical method for detecting trace amounts of trivalent arsenic in water according to claim 1, characterized in that: In step 4, the concentration of the catechol and its derivative solutions is 1-10 mM.
7. The paper-based electrochemical method for detecting trace amounts of trivalent arsenic in water according to claim 1, characterized in that: In step 4, the potential of the time-coulomb method is 0.4-0.8V, and the amount of transferred charge is 50-200mC.
8. The paper-based electrochemical method for detecting trace amounts of trivalent arsenic in water according to claim 1, characterized in that: In step 5, the washing time in deionized water is 2-12 hours.