An Electrochemical Method for Detecting Copper Ions by a Mesoporous Foam Hybrid Material

Abstract

The present invention discloses an electrochemical method for detecting copper ions by a mesoporous foam hybrid material, and the operation steps are as follows: (1) Preparation of a pyrene formaldehyde hydrazone mesoporous foam hybrid material; (2) Preparation of mesoporous foam; (3) Preparation of the mesoporous foam hybrid material; (4) Preparation of a carbon paste electrode modified with the mesoporous foam hybrid material; (5) Preparation of a standard solution; (6) Plotting of a standard curve. The present invention modifies the mesoporous foam to obtain a mesoporous foam hybrid material for highly selective, highly sensitive, low-cost and rapid detection of copper ions.

Description

Technical Field

[0001] The present invention relates to a method for detecting copper ions, and particularly to an electrochemical method for detecting copper ions using a mesoporous foam hybrid material. Background Art

[0002] Copper is widely used in light industry, electrical engineering, machinery manufacturing, national defense and other fields. At the same time, copper is also the third most essential trace element in organisms, playing an important role in electron transfer reactions involving the oxidation of various organic substrates, and playing a key role in the growth, development and maintenance of bones, connective tissues, the brain, the heart and many other body organs. However, excessive accumulation of copper ions in organisms can cause a series of diseases, such as Menkes disease, Alzheimer's disease, Wilson's disease and prion disease, etc. Therefore, how to quickly and accurately detect copper ions is an important task.

[0003] Existing methods for determining copper ions include inductively coupled plasma mass spectrometry, atomic absorption method, flow injection method, etc., but the instrument purchase and use costs are high, the operation is cumbersome, and the use and maintenance require strong technical skills, making it difficult to detect quickly at low cost. The electrochemical method for determining copper ions has become a reliable means for low-cost and rapid detection of copper ions due to its simple operation, low cost, fast response, short reaction time, good reproducibility and other characteristics. Since mesoporous silica has a large specific surface area and mesoporous channel structure, it provides the possibility for improving the analysis and detection sensitivity of pre-concentration, and is used to prepare chemically modified electrodes, which are widely used in the electrochemical detection of metal ions to improve the detection sensitivity. However, the selectivity of detecting copper ions using mesoporous silica is poor and the sensitivity needs to be improved. Therefore, it is very necessary to establish an electrochemical detection method for copper ions with good selectivity and high sensitivity.

[0004] The information disclosed in this background art section is only intended to enhance the overall understanding of the present invention and should not be regarded as an admission or any form of suggestion that this information constitutes prior art already known to those of ordinary skill in the art. Summary of the Invention

[0005] In view of the above technical problems, the present invention provides an electrochemical method for detecting copper ions using a mesoporous foam hybrid material, aiming to obtain a method for simply, low-cost, highly selective, highly sensitive and rapid detection of copper ions.

[0006] To achieve the above object, the technical solution provided by the present invention is as follows:

[0007] An electrochemical method for detecting copper ions using a mesoporous foam hybrid material, comprising the following operating steps:

[0008] (1) Preparation of pyrene-formaldehyde hydrazone mesoporous foam hybrid material: Dissolve 1-pyrene formaldehyde in tetrahydrofuran, stir at room temperature until completely dissolved, then add hydrazine hydrate solution, stir at room temperature, filter the product obtained by reaction under reduced pressure, wash it with ether, and dry to obtain pyrene-formaldehyde hydrazone;

[0009] (2) Preparation of mesoporous foam: At a temperature of 30 - 40 °C, mix the polyoxypropylene-polyoxyethylene copolymer solution and hydrochloric acid solution and stir until clear, then add cyclohexane, continue stirring, slowly dropwise add tetraethyl orthosilicate and stir. Transfer the mixture to a polytetrafluoroethylene bottle and then place it in an oven for aging. After the obtained product is filtered, washed, and air-dried at room temperature, mesoporous foam MCF is obtained;

[0010] (3) Preparation of mesoporous foam hybrid material: Add toluene to the mesoporous foam MCF obtained in step (2), stir at room temperature to disperse it evenly, then add 3-chloropropyltriethoxysilane, reflux and stir for a certain time, wash it with chloroform and centrifuge 5 times, dry at room temperature to obtain chlorinated mesoporous foam; Dissolve the pyrene-formaldehyde hydrazone obtained in step (1) in tetrahydrofuran, add triethylamine, stir at room temperature to disperse it evenly, then add the chlorinated mesoporous foam, reflux, wash the product with chloroform and centrifuge 5 times to remove the excess pyrene-formaldehyde hydrazone, and finally dry at room temperature to obtain the mesoporous foam hybrid material;

[0011] (4) Preparation of mesoporous foam hybrid material modified carbon paste electrode: Place the mesoporous foam hybrid material obtained in step (3) and graphite powder in a mortar, grind and mix them evenly, then add paraffin oil to the mixture and grind it into a uniform paste. Press the obtained uniform paste into the carbon paste electrode shell connected to a copper wire, and polish it on a clean weighing paper to obtain the mesoporous foam hybrid material modified carbon paste electrode (MCF-P / CPE);

[0012] (5) Preparation of standard solution: Weigh copper chloride solid to prepare a copper ion stock solution, respectively measure a certain amount of the copper ion stock solution and add it to an acetic acid-sodium acetate buffer solution, and make up the volume to obtain a series of copper ion standard solutions to be measured with different concentrations;

[0013] (6) Plotting of the standard curve: Insert a three-electrode system, namely a three-electrode system composed of a carbon paste electrode modified with a mesoporous foam hybrid material as the working electrode, a saturated calomel electrode as the reference electrode, and a platinum wire electrode as the counter electrode, into an electrolytic cell containing a copper ion standard solution. Enrich it under stirring conditions and perform differential pulse voltammetry (DPV) scanning in the range of -0.3 - 0.1 V. Record the oxidation peak current value at -0.1 ± 0.02 V, plot the standard curve based on the corresponding copper ion concentration value, and then obtain the corresponding linear equation; Replace the above copper ion standard solution with the sample to be tested, and according to the same operation, substitute the measured oxidation peak current value at -0.1 ± 0.02 V into the obtained linear equation to calculate the content of copper ions in the sample to be tested;

[0014] In the range of 0.005 - 0.1 μmol / L, the linear equation is: ip = 38.5602C1 - 0.2442 (R 2 = 0.9942). In the range of 0.1 - 1.0 μmol / L, the linear equation is ip = 5.7077C2 + 3.3928 (R 2 = 0.9940); where ip is the oxidation peak current (μA), and C is the concentration of copper ions (μmol / L); The detection limit is: 0.005 μmol / L.

[0015] Preferably, in step (1): The concentration of the hydrazine hydrate solution is 25%; The molar ratio of 1-pyrenecarboxaldehyde to hydrazine hydrate is 1:10; The dosage of 1-pyrenecarboxaldehyde and tetrahydrofuran is that for every 1 mmol of 1-pyrenecarboxaldehyde, it is dissolved in 5 mL of tetrahydrofuran; After adding the hydrazine hydrate solution, stir at room temperature for 12 h.

[0016] Preferably, in step (2), at a temperature of 35 °C, mix the polyoxypropylene polyoxyethylene copolymer solution and the hydrochloric acid solution and stir until clear; The addition amount of the polyoxypropylene polyoxyethylene copolymer solution is 1 g; The concentration of the hydrochloric acid solution is 2 mol / L, and the addition amount of the hydrochloric acid solution is 35 mL; The addition amount of cyclohexane is 4.8 g; The addition amount of tetraethyl orthosilicate is 2.1 g. After adding tetraethyl orthosilicate, stir for 24 h; The temperature of the oven is set at 120 °C, and the aging time is 24 h.

[0017] Preferably, in step (3): The dosage of mesoporous foam MCF is 0.5 g, the dosage of toluene is 20 mL, the dosage of 3-chloropropyltriethoxysilane is 1.204 g. After adding 3-chloropropyltriethoxysilane, reflux and stir at 110 °C for 12 h; The dosage of pyrenecarboxaldehyde hydrazone is 0.2441 g, the dosage of tetrahydrofuran is 20 mL, the dosage of triethylamine is 0.5 mL. After adding triethylamine, stir at room temperature for 0.5 h; The dosage of chlorinated mesoporous foam is 0.5 g. After adding chlorinated mesoporous foam, reflux at 66 °C for 24 h.

[0018] Preferably, in step (4), the mass ratio of the mesoporous foam hybrid material to the graphite powder is 0.05:1, and the ratio of the mixture to the paraffin oil is 1.0 g∶20 μL.

[0019] Preferably, in step (5), the concentration of the acetic acid-sodium acetate buffer solution is 0.1 mol / L, and pH = 3.6.

[0020] Preferably, in step (6), during differential pulse voltammetry (DPV) scanning, the deposition potential is -0.6 V, and the enrichment time is 210 seconds.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] By modifying the mesoporous foam, the present invention obtains a mesoporous foam hybrid material for highly selective, highly sensitive, low-cost, and rapid detection of copper ions. Description of the Drawings

[0023] Figure 1 It is a scanning electron microscope image of the mesoporous foam hybrid material prepared by the present invention.

[0024] Figure 2 It is a DPV curve graph of different electrodes in a 0.1 μmol / L copper ion solution; among them, curve a is the control bare carbon paste electrode (CPE), curve b is the mesoporous foam modified carbon paste electrode (MCF / CPE), and curve c is the mesoporous foam hybrid material modified carbon paste electrode (MCF-P / CPE) prepared by the present invention.

[0025] Figure 3 A is the DPV response graph of the mesoporous foam hybrid material modified carbon paste electrode (MCF-P / CPE) prepared by the present invention for recording standard copper ion solutions with different concentrations; Figure 3 B is the standard curve graph of the copper ion concentration and its oxidation peak current. Specific Embodiments

[0026] The following is a detailed description in combination with the specific embodiments of the drawings, but it should be understood that the protection scope of the present invention is not limited by the specific embodiments. The electrochemical workstation used in the examples is PalmSens4C, and the parameters of differential pulse voltammetry are: the potential increment is 4 mV, the amplitude is 50 mV, the pulse time is 0.05 s, and the deposition potential is -0.6 V; all the chemical substances used are commercially available.

[0027] Example 1

[0028] The electrochemical method for detecting copper ions using the mesoporous foam hybrid material has the following operating steps:

[0029] (1) Preparation of pyrene - formaldehyde hydrazone mesoporous foam hybrid material: Dissolve 0.4605 g (2.0 mmol) of 1 - pyrene - formaldehyde in 10 mL of tetrahydrofuran, stir at room temperature until completely dissolved, then add 3.85 mL (20 mmol) of 25% hydrazine hydrate solution, stir at room temperature for 12 h. Filter the product obtained from the reaction under reduced pressure, wash it with ether, and dry it to obtain pyrene - formaldehyde hydrazone;

[0030] (2) Preparation of mesoporous foam: At a temperature of 35 °C, mix 1.0 g of polyoxypropylene - polyoxyethylene copolymer solution and 35 mL of 2 mol / L hydrochloric acid solution and stir until clear. Then add 4.8 g of cyclohexane, continue stirring, and slowly add 2.1 g of tetraethyl orthosilicate while stirring. Transfer the mixture to a polytetrafluoroethylene bottle and place it in an oven at 120 °C for aging for 24 h. After the obtained product is filtered, washed, and air - dried at room temperature, mesoporous foam MCF is obtained;

[0031] (3) Preparation of mesoporous foam hybrid material: Weigh 0.5 g of the mesoporous foam MCF obtained in step (2), add 20 mL of toluene, stir at room temperature to disperse it evenly, then add 1.204 g of 3 - chloropropyltriethoxysilane, reflux and stir at 110 °C for 12 h, wash it with chloroform and centrifuge 5 times, and dry at room temperature to obtain chlorinated mesoporous foam; Weigh 0.2441 g of the pyrene - formaldehyde hydrazone obtained in step (1), dissolve it in 20 mL of tetrahydrofuran, add 0.5 mL of triethylamine, stir at room temperature to disperse it evenly, then add 0.5 g of chlorinated mesoporous foam, reflux at 66 °C for 24 h. Wash the product with chloroform and centrifuge 5 times to remove the excess pyrene - formaldehyde hydrazone, and finally dry at room temperature to obtain the mesoporous foam hybrid material. The scanning electron micrograph of this mesoporous foam hybrid material is shown in Figure 1 ;

[0032] (4) Preparation of mesoporous foam hybrid material - modified carbon paste electrode: Place the mesoporous foam hybrid material MCF - P obtained in step (3) and graphite powder in an agate mortar according to a mass ratio of 0.05:1, grind and mix them thoroughly. Then add paraffin oil to the mixture, and the ratio of the mixture to paraffin oil is 1.0 g∶20 μL. Grind it into a uniform paste, press the obtained uniform paste into the carbon paste electrode shell connected to a copper wire, and polish it flat on a clean weighing paper to obtain the mesoporous foam hybrid material - modified carbon paste electrode (MCF - P / CPE);

[0033] (5) Preparation of standard solution: Weigh 0.0135 g of copper chloride solid, dissolve it with pure water, dilute it, and make the volume up to 100 mL in a volumetric flask to prepare a 1.0×10 -3Copper ion stock solution at mol / L; 0.10 mL and 1.00 mL of the copper ion stock solution were respectively pipetted into 100 mL volumetric flasks, and acetic acid-sodium acetate buffer solution (0.1 mol / L, pH = 3.6) was added to make up to the mark and shaken well to prepare copper ion standard working solutions with concentrations of 1 μmol / L and 10 μmol / L respectively; 0.50 mL, 1.00 mL, 2.00 mL, 3.00 mL, 5.00 mL, 6.00 mL, 8.00 mL, 10.00 mL of the copper ion standard working solution with a concentration of 1 μmol / L were respectively pipetted into 100 mL volumetric flasks, and acetic acid-sodium acetate buffer solution (0.1 mol / L, pH = 3.6) was added to make up to the mark and shaken well to obtain copper ion standard solutions to be measured with concentrations of 0.005 μmol / L, 0.01 μmol / L, 0.02 μmol / L, 0.03 μmol / L, 0.05 μmol / L, 0.06 μmol / L, 0.08 μmol / L, 0.1 μmol / L respectively; 2.00 mL, 5.00 mL, 8.00 mL, 10.00 mL of the copper ion standard working solution with a concentration of 10 μmol / L were respectively pipetted into 100 mL volumetric flasks, and acetic acid-sodium acetate buffer solution (0.1 mol / L, pH = 3.6) was added to make up to the mark and shaken well to obtain copper ion standard solutions to be measured with concentrations of 0.2 μmol / L, 0.5 μmol / L, 0.08 μmol / L, 1.0 μmol / L respectively;

[0034] (6) Plotting of the standard curve: The three-electrode system, that is, a three-electrode system composed of a mesoporous foam hybrid material modified carbon paste electrode as the working electrode, a saturated calomel electrode as the reference electrode, and a platinum wire electrode as the counter electrode, was respectively inserted into the electrolytic cell containing 10 mL of the copper ion standard solution. After stirring and enriching for 210 s at a deposition potential of -0.6 V, differential pulse voltammetric scanning was carried out in the range of -0.3 - 0.1 V, and the oxidation peak current value at -0.1 ± 0.02 V was recorded. The standard curve was plotted according to the corresponding copper ion concentration value, and then the corresponding linear equation was obtained; in the range of 0.005 - 0.1 μmol / L, the linear equation was: ip = 38.5602C1 - 0.2442 (R 2 = 0.9942), and in the range of 0.1 - 1.0 μmol / L, the linear equation was ip = 5.7077C2 + 3.3928 (R 2 = 0.9940); where ip is the oxidation peak current (μA), and C is the concentration of copper ions (μmol / L); the detection limit is: 0.005 μmol / L; during detection, the above copper ion standard solution was replaced with the sample to be measured, and according to the same operation, the oxidation peak current value at -0.1 ± 0.02 V was brought into the obtained linear equation to calculate the content of copper ions in the sample to be measured;

[0035] Figure 1 This is the SEM image of the mesoporous foam hybrid material prepared in the present invention. It can be seen from Figure 1 that the material presents a uniform and ordered foam-like structure.

[0036] Figure 2 These are the DPV curves of different electrodes in a 0.1 μmol / L copper ion solution. Among them, curve a is the control bare carbon paste electrode (CPE), curve b is the mesoporous foam modified carbon paste electrode (MCF / CPE), and curve c is the mesoporous foam hybrid material modified carbon paste electrode (MCF-P / CPE) prepared in the present invention. It can be seen from Figure 2 that the response current of MCF-P / CPE in a 0.1 μmol / L copper ion solution is significantly greater than that of MCF / CPE and CPE, indicating that the MCF-P / CPE of the present invention significantly improves the intensity of the catalytic current signal and enhances the sensitivity of the analytical method.

[0037] Figure 3 A is the DPV response diagram of the mesoporous foam hybrid material modified carbon paste electrode (MCF-P / CPE) prepared in the present invention for recording standard copper ion solutions with different concentrations; Figure 3 B is the standard curve diagram of copper ion concentration versus its oxidation peak current. It can be seen from Figure 3 A that the response current of MCF-P / CPE increases with the increase of copper ion concentration; Figure 3 B shows that there is a good linear relationship between the response current value and the copper ion concentration in the range of 0.005 - 1.0 μmol / L.

[0038] Determination of the sample in Example 2

[0039] Take 1 g of the GBW10043 reference material (Liaoning rice, copper content is 1.7 ± 0.1 mg / kg) sample and add 10 mL of nitric acid into a digestion tube. Digest it on an adjustable electric heating furnace (digest at 110 °C for 0.5 hours and at 160 °C for 3 hours) until white smoke appears. Take out the digestion tube, cool it, and then make the volume up to 10 mL with water. Take 0.2 mL of the above sample to be measured and add 9.8 mL of acetic acid - sodium acetate buffer solution (0.1 mol / L, pH = 3.6). Detect it according to the method of Example 1 and calculate its spike recovery rate. The results are shown in Table 1:

[0040] Table 1 Spike recovery determination results of copper ions in the GBW10043 reference material (Liaoning rice) sample

[0041]

[0042] As can be seen from Table 1, the determination results of the samples in the method of the present invention are consistent with those determined by graphite furnace atomic absorption spectrometry. Moreover, the spiked recoveries of the method of the present invention are 93.5%, 98.4% and 102.6% respectively, all above 90 - 105%, indicating that the electrochemical method for detecting copper ions by the mesoporous foam hybrid material proposed by the present invention has good practicability and accuracy.

[0043] The foregoing description of the specific exemplary embodiments of the present invention is for purposes of illustration and exemplification. These descriptions are not intended to limit the invention to the precise forms disclosed, and obviously, many changes and variations are possible in light of the above teaching. The purpose of selecting and describing the exemplary embodiments is to explain the specific principles of the present invention and its practical applications, so that those skilled in the art can implement and utilize the various different exemplary embodiments of the present invention, as well as various different selections and changes. The scope of the present invention is intended to be defined by the claims and their equivalents.

Claims

1. An electrochemical method for detecting copper ions by a mesoporous foam hybrid material, characterized in that, It includes the following operation steps: (1) Preparation of pyrene formaldehyde hydrazone: Dissolve 1-pyrene formaldehyde in tetrahydrofuran, stir at room temperature until it is completely dissolved, then add hydrazine hydrate solution, stir at room temperature, filter the reaction product under reduced pressure, wash it with ether, and dry it to obtain pyrene formaldehyde hydrazone; (2) Preparation of mesoporous foam: At a temperature of 30-40 °C, mix the polyoxypropylene-polyoxyethylene copolymer solution and hydrochloric acid solution and stir until clear, then add cyclohexane, continue to stir, slowly dropwise add tetraethyl orthosilicate and stir, transfer the mixture to a polytetrafluoroethylene bottle and then place it in an oven for aging. After the obtained product is filtered, washed and air-dried at room temperature, mesoporous foam MCF is obtained; (3) Preparation of mesoporous foam hybrid material: Add toluene to the mesoporous foam MCF obtained in step (2), stir at room temperature to make it disperse evenly, then add 3-chloropropyltriethoxysilane, reflux and stir for a certain time, wash it with chloroform and centrifuge 5 times, dry at room temperature to obtain chlorinated mesoporous foam; Dissolve the pyrene formaldehyde hydrazone obtained in step (1) in tetrahydrofuran, add triethylamine, stir at room temperature to make it disperse evenly, then add chlorinated mesoporous foam, reflux, wash the product with chloroform and centrifuge 5 times to remove the excess pyrene formaldehyde hydrazone, and finally dry at room temperature to obtain mesoporous foam hybrid material; (4) Preparation of mesoporous foam hybrid material modified carbon paste electrode: Place the mesoporous foam hybrid material obtained in step (3) and graphite powder in a mortar, grind and mix them evenly, then add paraffin oil to the mixture and grind it into a uniform paste. Press the obtained uniform paste into the carbon paste electrode shell connected to a copper wire, and polish it on a clean weighing paper to obtain mesoporous foam hybrid material modified carbon paste electrode MCF-P / CPE; (5) Preparation of standard solution: Weigh copper chloride solid to prepare a copper ion stock solution, respectively measure a certain amount of copper ion stock solution and add it to acetic acid-sodium acetate buffer solution, and make up the volume to obtain a series of copper ion standard solutions to be measured with different concentrations; (6) Plotting of standard curve: Insert the three-electrode system, that is, the three-electrode system composed of a mesoporous foam hybrid material modified carbon paste electrode as the working electrode, a saturated calomel electrode as the reference electrode, and a platinum wire electrode as the counter electrode, into the electrolytic cell containing the copper ion standard solution, enrich it under stirring conditions, perform differential pulse voltammetry DPV scanning in the range of -0.3 - 0.1 V, record the oxidation peak current value at -0.1 ± 0.02 V, plot the standard curve according to the corresponding copper ion concentration value, and then obtain the corresponding linear equation; Replace the above copper ion standard solution with the sample to be measured, perform the same operation, measure the oxidation peak current value at -0.1 ± 0.02 V and substitute it into the obtained linear equation to calculate the content of copper ions in the sample to be measured; In the range of 0.005 - 0.1 μmol / L, the linear equation is: ip = 38.5602C1 - 0.2442, R 2 = 0.9942. In the range of 0.1 - 1.0 μmol / L, the linear equation is ip = 5.7077C2 + 3.3928, R 2 = 0.9940; where ip is the oxidation peak current in μA and C is the concentration of copper ions in μmol / L; the detection limit is: 0.005 μmol / L.

2. The electrochemical method according to claim 1, characterized in that, In step (1): The concentration of hydrazine hydrate solution is 25%; The molar ratio of 1-pyrene formaldehyde to hydrazine hydrate is 1:10; The dosage of 1-pyrene formaldehyde and tetrahydrofuran is that every 1 mmol of 1-pyrene formaldehyde is dissolved in 5 mL of tetrahydrofuran; After adding the hydrazine hydrate solution, stir at room temperature for 12 h.

3. The electrochemical method according to claim 1, wherein In step (2): at a temperature of 35 °C, mix the polyoxypropylene polyoxyethylene copolymer solution and the hydrochloric acid solution and stir until clear; the addition amount of the polyoxypropylene polyoxyethylene copolymer solution is 1 g; the concentration of the hydrochloric acid solution is 2 mol / L, and the addition amount of the hydrochloric acid solution is 35 mL; the addition amount of cyclohexane is 4.8 g; the addition amount of tetraethyl orthosilicate is 2.1 g, and stir for 24 h after adding tetraethyl orthosilicate; the temperature of the oven is set at 120 °C, and the aging time is 24 h.

4. The electrochemical method according to claim 1, characterized in that, In step (3): the amount of mesoporous foam MCF used is 0.5 g, the amount of toluene used is 20 mL, the amount of 3-chloropropyltriethoxysilane used is 1.204 g, and after adding 3-chloropropyltriethoxysilane, reflux and stir at 110 °C for 12 h; the amount of pyrene formaldehyde hydrazone used is 0.2441 g, the amount of tetrahydrofuran used is 20 mL, the amount of triethylamine used is 0.5 mL, and stir for 0.5 h at room temperature after adding triethylamine; the amount of chlorinated mesoporous foam used is 0.5 g, and reflux at 66 °C for 24 h after adding chlorinated mesoporous foam.

5. The electrochemical method according to claim 1, characterized in that, In step (4), the mass ratio of the mesoporous foam hybrid material to the graphite powder is 0.05:1, and the ratio of the mixture to the paraffin oil is 1.0 g∶20 μL.

6. The electrochemical method according to claim 1, characterized in that, In step (5), the concentration of the acetic acid-sodium acetate buffer solution is 0.1 mol / L and pH = 3.6.

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