Preparation, application and electrochemical detection device of gold electrode

Abstract

The present invention discloses a preparation, application and electrochemical detection device of a gold electrode. The preparation method of the modified gold electrode is as follows: a polished bare gold electrode is activated with nitric acid and immersed in a deoxygenated cysteamine (Cyst) solution for 2 hours; the electrode is washed with double distilled water and immersed for about 12 hours to remove physically adsorbed Cyst to obtain a Cyst-modified gold electrode; the Cyst-modified gold electrode is immersed in a nanogold solution for 18 hours, taken out and dried to obtain a gold glue-Cyst modified gold electrode; finally, the gold glue-Cyst modified gold electrode is immersed in Cyst for 2 hours, taken out and dried to obtain a target modified gold electrode. The present invention combines the modified gold electrode prepared by this method with a platinum wire electrode and a silver-silver chloride electrode to form a three-electrode system. The modified gold electrode in the three-electrode system has good electrochemical catalytic oxidation function for uric acid, and the peak current is linearly related to the uric acid content. The system can be directly used for uric acid detection in urine.

Description

Technical Field

[0001] The present invention relates to an electrochemical detection electrode and its application and an electrochemical detection device, and in particular to the preparation, application and electrochemical detection device of a gold electrode for detecting uric acid. Background Art

[0002] Uric acid test samples usually include blood samples and urine samples. Clinically, serum uric acid determination is mainly used to assist in disease diagnosis. The determination of urine uric acid can be used as a means to assess the health status of sub-healthy people and can assist in health management. Common uric acid detection methods include phosphotungstic acid reduction method, chromatography, spectrophotometry, electrochemical method, enzymatic method, etc. These methods each have their own advantages and disadvantages. Among them, electrochemical analysis has the characteristics of simple instrumentation, convenient testing, high sensitivity, high accuracy, and strong practicality, and has gradually become a hot field for uric acid detection. At present, research on electrochemical uric acid detection is mainly concentrated in the field of blood uric acid detection, and there is less research on urine uric acid detection. This may be because the former is more suitable for clinical diagnosis, while the role of routine urine uric acid detection in daily health monitoring and health management guidance has been ignored.

[0003] Electrochemical detection of uric acid has been reported. For example, Li Jianwen et al. prepared copper oxide (CuO) nanorods and carboxylated carbon nanosheets (cCNSs) and modified them on the surface of glassy carbon electrode (GCE) by drop coating to construct an electrochemical sensor for detecting uric acid (UA); Zhao Weiwei et al. synthesized the metal organic framework (MOF) material MIL-101(Cr) by hydrothermal method and characterized the material by X-ray diffraction (XRD) and scanning electron microscopy (SEM); MIL-101(Cr) was coated on the surface of glassy carbon electrode (GCE) by drop coating to prepare the modified electrode MIL-101(Cr) / GCE, and the feasibility of MIL-101(Cr)-based bioelectrochemical sensor for quantitative detection of uric acid was verified by cyclic voltammetry (CV) and differential pulse voltammetry (DPV); Yang Li synthesized nitrogen-doped carbon-based nanomaterials and used them for electrochemical detection of uric acid; Du J et al. developed a graphene-modified carbon fiber electrode (GE / CFE); Wu BW et al. developed a dendritic CeO2 / rGO composite-modified glassy carbon electrode and successfully detected UA in serum samples. Zheng et al. prepared a molecularly imprinted polymer / reduced graphene oxide composite for the electrochemical detection of uric acid. Huang et al. coupled a graphene foam carbon nanotube composite with gold nanoparticles to create an electrochemical sensor for the electrochemical detection of uric acid. Boitumelo et al. studied the electrochemical behavior of ITO electrodes modified with graphene films doped with different elements and applied them to the detection of uric acid. However, these methods suffer from the drawbacks of cumbersome preparation steps and difficult operation of the modified electrodes.

[0004] Chinese patent CN114019003A discloses an electrochemical sensor for uric acid detection by regulating nanointerfaces through molecular wires, as well as its preparation and application. However, this patent relies on the modification of molecular wires with special chemical structures and the modification of Ni3(HHTP)2 to produce an electrochemical sensor for detecting uric acid in the brain. The modification steps are cumbersome and complex, and the sensor only detects uric acid in the brain. It is unknown whether it can work normally in other samples, nor whether its detection limit can meet the detection requirements of other samples. Summary of the Invention

[0005] Objectives of the invention: The present invention aims to provide a method for preparing a gold electrode, thereby solving the problem of how to prepare a gold electrode for detecting uric acid. Another objective of the present invention is to propose the use of a gold electrode prepared by the above-mentioned preparation method in the electrochemical detection of uric acid, thereby solving the problem of how to use the modified gold electrode to detect uric acid concentration. A third objective of the present invention is to provide an electrochemical detection device for detecting uric acid concentration.

[0006] Technical solution: The method for preparing a gold electrode according to the present invention comprises the following steps:

[0007] (1) Immerse the bare gold electrode activated by nitric acid in a cysteamine aqueous solution, take it out and dry it to obtain a Cyst-modified electrode;

[0008] (2) Immerse the Cyst-modified electrode in a gold colloid solution, take it out and dry it to obtain a gold colloid-modified electrode;

[0009] (3) Immerse the gold colloid-modified electrode in a cysteamine aqueous solution, take it out and dry it to obtain a Cyst-nano-gold colloid-Cyst-modified gold electrode.

[0010] In the modification process of cysteamine-nano-gold colloid-cysteamine modified gold electrode in the present invention, cysteamine contains sulfhydryl (-SH) and amino (-NH2), and the sulfhydryl group binds to the surface of the gold electrode to form an S-Au bond. The -SH and -NH2 in cysteamine easily form S-Au and N-Au bonds with the nano-gold colloid. Therefore, the -NH2 in the first modified cysteamine forms an N-Au bond with the nano-gold colloid, and then the nano-gold colloid combines with the -SH of the second modified cysteamine to form an S-Au bond (see Figure 1 The electrode did not show obvious oxidation peaks and reduction peaks in pH 7.4 PBS buffer solution, but in pH 7.4 PBS buffer solution with a certain amount of uric acid added, a clear reduction peak appeared in the cyclic voltammogram (see Figure 2 The principle is that when a pulse voltage is applied to the working electrode and the potential is scanned toward the cathode, uric acid is reduced on the electrode, losing electrons and generating a reduction peak. When the potential is scanned toward the anode, the uric acid is not strongly oxidizable on the electrode and no oxidation peak is generated.

[0011] Preferably, in steps (1) and (3), the concentration of the cysteamine aqueous solution is 5-100 mmol / L; in step (2), the diameter of the gold colloid in the gold colloid solution is 13-60 nm.

[0012] Preferably, in step (2), the method for preparing the gold glue solution comprises the following steps:

[0013] (11) Use sub-boiling distilled water to rinse the preparation container, and then prepare the chloroauric acid aqueous solution and sodium citrate aqueous solution respectively;

[0014] (12) Add the chloroauric acid aqueous solution to sub-boiling distilled water, heat to boiling, add the sodium citrate aqueous solution while stirring rapidly, make up to volume with sub-boiling distilled water, and mix thoroughly to obtain the gold glue solution.

[0015] Sub-boiling distilled water is double-distilled water, which is purer than pure water. It removes more impurities and pollutants, avoids secondary contamination, and ensures the results of the experiment.

[0016] Furthermore, the molar ratio of chloroauric acid to sodium citrate in the gold colloid solution is 0.30-1.51.

[0017] Furthermore, in step (12), the concentration of the chloroauric acid aqueous solution is 0.5-1.5 wt %, and the volume is fixed to 100 times the volume of the chloroauric acid aqueous solution using sub-boiling distilled water.

[0018] Preferably, in step (1), the bare gold electrode activated with nitric acid is prepared as follows:

[0019] The gold electrode was polished with alumina and felt in turn, and then immersed in quartz sub-boiling water and ethanol solution for ultrasonic cleaning in turn. The treated electrode was subjected to cyclic voltammetry scanning in a mixed solution of K3Fe(CN)6 and KNO3 to make ΔE p ≤65mV; etch the treated bare gold electrode with HNO3, take it out, rinse it with water, take it out and place it in sub-boiling water for later use.

[0020] Preferably, in step (1), the method of immersing the bare gold electrode in the cysteamine aqueous solution is: placing the bare gold electrode in the cysteamine aqueous solution and soaking it for 1-3 hours, while deoxygenating it for 10-20 minutes, taking out the electrode and soaking it in the cysteamine aqueous solution for 12-18 hours to obtain a Cyst-modified electrode;

[0021] In step (2), the Cyst-modified electrode is immersed in the gold colloid solution for 10-14 h;

[0022] In step (3), the method for immersing the gold colloid modified electrode in the cysteamine aqueous solution is as follows: the gold colloid modified electrode is placed in the cysteamine aqueous solution and immersed for 1-3 hours, while deoxygenating for 10-20 minutes, and the gold colloid modified electrode is taken out and immersed in the cysteamine aqueous solution for 12-18 hours before being taken out.

[0023] The present invention further applies the gold electrode prepared by the above preparation method to the electrochemical detection of uric acid.

[0024] The method for detecting uric acid using the gold electrode prepared by the above preparation method comprises the following steps:

[0025] (1) A gold electrode was used as the working electrode, a platinum wire electrode was used as the counter electrode, and a silver-silver chloride electrode was used as the reference electrode to form a three-electrode system. The three-electrode system and an electrochemical workstation constituted a uric acid electrochemical detection device.

[0026] (2) Gradual dilution of uric acid solutions of known concentrations with phosphate buffer was performed, and cyclic voltammetry was used to electrochemically detect uric acid solutions of different concentrations using a uric acid electrochemical detection device to obtain a fitting standard curve of uric acid concentration and electrical signal;

[0027] (3) Using phosphate buffer as the supporting electrolyte to dilute the sample to obtain the test solution, the electrochemical signal of uric acid in the test solution is obtained by cyclic voltammetry using a uric acid electrochemical detection device. The concentration of uric acid in the test solution is calculated according to the standard curve, and then multiplied by the dilution factor to obtain the uric acid concentration in the sample.

[0028] The present invention further discloses an electrochemical detection device, comprising a gold electrode, a platinum wire electrode and a silver-silver chloride electrode prepared by the above preparation method.

[0029] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0030] (1) The gold electrode for uric acid detection in the present invention has the advantages of high conductivity, high catalytic site activity, rich and uniformly dispersed catalytic sites, and long-lasting use. It has high sensitivity and a low detection limit, which can be as low as 0.001 μmol / L. The present invention can be used for the precise detection of uric acid in urine samples and has strong anti-interference ability.

[0031] (2) The present invention only uses cysteamine and gold colloid for modification operation. The raw materials are simple and easy to obtain and the amount used is small. The operation process is simple, and the modified gold electrode has high sensitivity, good stability and good reproducibility.

[0032] (3) The modified materials of the gold electrode are environmentally friendly and do not cause secondary pollution: the gold colloid is stable and does not easily change, and amino acids are biological materials and will not cause pollution. The electrode of the present invention will not pose a biosafety hazard to users during daily testing. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The schematic diagram of the preparation of cysteamine-nano-gold colloid-cysteamine modified gold electrode;

[0034] Figure 2 Comparison of cyclic voltammetry of modified electrode No. 3 under conditions without and with uric acid;

[0035] Figure 3 Cyclic voltammograms of gold electrodes modified with different modifiers at a concentration of 23.6 μmol / L uric acid;

[0036] Figure 4 This is a cyclic voltammetric comparison of the anti-interference ability of gold electrodes modified differently under the conditions of uric acid concentration of 23.6μmol / L and vitamin C concentration of 5μmol / L;

[0037] Figure 5 The cyclic voltammetry comparison of the anti-interference ability of different modified gold electrodes under the conditions of uric acid concentration of 23.6μmol / L, vitamin C concentration of 5μmol / L, and dopamine concentration of 240μmol / L;

[0038] Figure 6 Cyclic voltammograms of modified electrode No. 3 detecting different concentrations of uric acid;

[0039] Figure 7 This is the linear fitting diagram of the reduction peak current of the modified electrode in different concentrations of uric acid. DETAILED DESCRIPTION

[0040] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0041] Example 1: A method for preparing a gold electrode, comprising the following steps:

[0042] (1) The unmodified gold disk working electrode with a diameter of 2 mm was polished with coarse sand, fine sand, slurry (particle size 0.30 μm) alumina powder and felt in sequence, and ultrasonically cleaned. -3 mol / LK3Fe(CN)6+0.1 mol / LKNO3 solution and perform cyclic voltammetry scanning to make ΔE p ≤65mV. Etch the treated bare gold electrode with 1:1 (v / v) HNO3 for 1 minute, remove it, rinse it twice with water, remove the gold electrode and place it in sub-boiling water for later use, thus obtaining a bare gold electrode. Soak the bare gold electrode in a 0.1 mol / L cysteamine aqueous solution for 2 hours, while deoxygenating it with nitrogen for 15 minutes. Remove the electrode and soak it in a 0.1 mol / L cysteamine aqueous solution for 15 hours to obtain a Cyst-modified electrode.

[0043] (2) Preparation of gold colloid solution: Rinse the preparation container with sub-boiling distilled water, then prepare a 1.0 wt% AuCl3•HCl•4H2O aqueous solution and a trisodium citrate aqueous solution, respectively. Filter both solutions through 0.22 μm filter paper and set aside. Add 1.0 mL of the AuCl3•HCl•4H2O aqueous solution to 50 mL of sub-boiling distilled water, with a molar ratio of AuCl3•HCl•4H2O to trisodium citrate of 0.5. Heat to a boil, add an appropriate amount of trisodium citrate aqueous solution while stirring rapidly, and then add sub-boiling distilled water to a constant volume of 100 mL and mix thoroughly to obtain the gold colloid solution. Transmission electron microscopy (TEM) was used to characterize the colloidal particle size, and the diameter of the gold colloid was found to be 31 ± 2.5 nm. Store the gold colloid at 4°C until used.

[0044] The Cyst modified electrode was immersed in the gold colloid solution for 12 hours, and then taken out and dried to obtain the gold colloid modified electrode;

[0045] (3) The gold colloid-modified electrode was placed in a 0.1 mol / L cysteamine aqueous solution and soaked for 2 h, while deoxygenating for 15 min. The gold colloid-modified electrode was taken out and soaked in a 0.1 mol / L cysteamine aqueous solution for 15 h, then taken out and dried to obtain the target gold electrode, i.e., modified electrode sample No. 3.

[0046] Example 2: A method for preparing a gold electrode, comprising the following steps:

[0047] (1) An unmodified 2mm diameter gold disk working electrode was polished with alumina and felt in turn. The gold electrode was then immersed in quartz sub-boiling water and ethanol solution for ultrasonic cleaning for 5 minutes. The gold electrode was removed and placed in sub-boiling water for later use to obtain a bare gold electrode. The bare gold electrode was immersed in a 0.005mol / L cysteamine aqueous solution for 3 hours, while nitrogen was passed through to deoxygenate for 10 minutes. The electrode was removed and immersed in a 0.005mol / L cysteamine aqueous solution for 12 hours to obtain a Cyst-modified electrode.

[0048] (2) Preparation of gold colloid solution: Rinse the preparation container with sub-boiling distilled water, then prepare a 0.5 wt% AuCl3•HCl•4H2O aqueous solution and a sodium citrate aqueous solution, respectively. Filter both solutions through 0.22 μm filter paper and set aside. Add 0.5 mL of the AuCl3•HCl•4H2O aqueous solution to 50 mL of sub-boiling distilled water, with a molar ratio of AuCl3•HCl•4H2O to sodium citrate of 0.30. Heat to a boil, add an appropriate amount of sodium citrate aqueous solution with rapid stirring, and then dilute to 100 mL with sub-boiling distilled water. Mix thoroughly to obtain the gold colloid solution. Transmission electron microscopy (TEM) was used to characterize the colloidal particle size, and the diameter of the gold colloid was found to be 16 ± 2.3 nm. Store the gold colloid at 4°C until used.

[0049] The Cyst modified electrode was immersed in the gold colloid solution for 10 h, taken out and dried to obtain the gold colloid modified electrode;

[0050] (3) Soak the gold colloid-modified electrode in a 0.005 mol / L cysteamine aqueous solution for 3 h, deoxygenate for 20 min, take out the gold colloid-modified electrode, soak it in a 0.005 mol / L cysteamine aqueous solution for 12 h, take it out, take it out and dry it to obtain the target gold electrode.

[0051] Example 3: A method for preparing a gold electrode, comprising the following steps:

[0052] (1) An unmodified 2mm diameter gold disk working electrode was polished with alumina and felt in turn. The gold electrode was then immersed in quartz sub-boiling water and ethanol solution for ultrasonic cleaning for 5 minutes. The gold electrode was removed and placed in sub-boiling water for later use to obtain a bare gold electrode. The bare gold electrode was immersed in a 0.02mol / L cysteamine aqueous solution for 1 hour, while nitrogen was passed through to deoxygenate for 20 minutes. The electrode was removed and immersed in a 0.02mol / L cysteamine aqueous solution for 18 hours to obtain a Cyst-modified electrode.

[0053] (2) Preparation of gold colloid solution: Rinse the preparation container with sub-boiling distilled water, then prepare a 1.5 wt% AuCl3•HCl•4H2O aqueous solution and a sodium citrate aqueous solution, respectively. Filter both solutions through 0.22 μm filter paper and set aside. Add 1.5 mL of the AuCl3•HCl•4H2O aqueous solution to 25 mL of sub-boiling distilled water, with a molar ratio of AuCl3•HCl•4H2O to sodium citrate of 1.51. Heat to a boil, add an appropriate amount of sodium citrate aqueous solution with rapid stirring, and then dilute to 100 mL with sub-boiling distilled water. Mix thoroughly to obtain the gold colloid solution. Transmission electron microscopy (TEM) was used to characterize the colloidal particle size, and the diameter of the gold colloid was 52 ± 5.1 nm. Store the gold colloid at 4°C until used.

[0054] The Cyst modified electrode was immersed in a gold colloid solution for 14 h, taken out and dried to obtain a gold colloid modified electrode;

[0055] (3) Soak the gold colloid-modified electrode in a 0.02 mol / L cysteamine aqueous solution for 1 hour, deoxygenate for 10 minutes, take out the gold colloid-modified electrode and soak it in a 0.02 mol / L cysteamine aqueous solution for 18 hours, then take it out and dry it to obtain the target gold electrode.

[0056] Example 4: The rest is the same as Example 1, except that:

[0057] In step (2), the molar ratio of AuCl3•HCl•4H2O to sodium citrate was 0.75. The colloidal particle size was characterized by transmission electron microscopy (TEM), and the diameter of the gold colloid was 24±2.1 nm.

[0058] Example 5: The rest is the same as Example 1, except that:

[0059] In step (2), the molar ratio of AuCl3•HCl•4H2O to sodium citrate was 1.00. The colloidal particle size was characterized by transmission electron microscopy (TEM), and the diameter of the gold colloid was 42±2.6 nm.

[0060] Comparative Example 1: The rest are the same as Example 1, except that:

[0061] Without performing step (3), the gold colloid modified electrode prepared in step (2) is directly used as modified electrode sample No. 2 for subsequent detection.

[0062] Comparative Example 2: All other aspects are the same as Example 1, except that:

[0063] The gold colloid solution in step (2) was replaced with chloroauric acid solution.

[0064] Comparative Example 3: The rest is the same as Example 1, except that:

[0065] In steps (1) and (3), no deoxygenation step is performed, and the cysteamine aqueous solution is directly and continuously immersed.

[0066] Comparative Example 4: The rest is the same as Example 1, except that:

[0067] In step (2), when the Cyst modified electrode is immersed in the gold colloid solution, the Cyst modified electrode is scanned for 2 cycles at a scanning rate of 50 mV / s in the potential range of -0.2 V to +0.6 V using cyclic voltammetry.

[0068] The gold electrodes prepared in Examples 1-5 and Comparative Examples 1-4 were used to assemble an electrochemical detection device. The electrochemical detection device was electrically connected to an electrochemical workstation and used to measure the uric acid concentration in a urine sample. The test electrochemical workstation used was a Shanghai Chenhua electrochemical workstation [CHI760E]. The specific method is as follows:

[0069] (1) A three-electrode system was formed by using a gold electrode as the working electrode, a platinum wire electrode as the counter electrode, and a silver-silver chloride electrode as the reference electrode. The three-electrode system and an electrochemical workstation constituted a uric acid electrochemical detection system.

[0070] (2) Uric acid solutions of known concentrations were diluted with 0.1 mol / L pH 7.4 PBS. Cyclic voltammetry was used to electrochemically detect uric acid solutions of different concentrations in the potential range of +0.8 to -0.8 V using a uric acid electrochemical detection system. -5 ~1.4×10 -4 There is a linear relationship between uric acid concentration and oxidation peak current in the mol / L range, and the corresponding linear equation is established. Figure 6 and Figure 7 As shown;

[0071] (3) The urine sample was diluted with pH 7.4 phosphate buffer (1×PBS) as the supporting electrolyte to obtain the test solution. The electrochemical signal of uric acid in the test solution was obtained by cyclic voltammetry using a uric acid electrochemical detection system. The concentration of uric acid in the test solution was calculated based on the oxidation peak current and its corresponding linear equation, and then multiplied by the dilution factor to obtain the uric acid concentration in the sample.

[0072] The detection limits of each gold electrode can be obtained from the standard curve as follows:

[0073] Table 1 Detection limits of different gold electrodes

[0074]

[0075] As shown in Table 1, the gold colloid layer formed on the electrode surface by immersion alone in Comparative Example 1 exhibited a high uric acid detection limit and relatively low sensitivity. In Comparative Example 2, the electrode was unable to form a gold colloid layer capable of detection after immersion in chloroauric acid solution. Chloroauric acid solution relies on electrophoresis or cyclic voltammetry scanning to deposit gold nanoparticles on the electrode surface, thereby enabling the electrode to function as a detector. Soaking alone was unable to effectively deposit gold nanoparticles, and therefore, Comparative Example 2 lacked detection capability.

[0076] Comparative Example 3 shows that the deoxygenation step can significantly improve the detection sensitivity of the gold electrode.

[0077] Comparative Example 4 shows that an external electric field may cause the charged gold colloid particles in the gold colloid solution to aggregate due to electrophoresis, making it impossible to form a uniform gold colloid layer, thereby significantly reducing the sensitivity.

[0078] Example 6: The rest is the same as Example 1, except that:

[0079] Gold electrodes were prepared using the immersion time and concentration of the cysteamine aqueous solution in steps (1) and (3) as variables. The detection limits of each electrode sample were determined using the aforementioned uric acid detection method, and the results are as follows:

[0080] Table 2 Effects of immersion time and concentration of cysteamine aqueous solution on the performance of gold electrodes

[0081]

[0082] It can be seen from the results in Table 2 that when the immersion time and concentration of the cysteamine aqueous solution are too high or too low, the detection sensitivity of the gold electrode will be greatly reduced.

[0083] Example 7: The rest is the same as Example 1, except that:

[0084] Different gold electrodes were prepared by taking the particle size of gold colloid particles in the gold colloid solution as a variable.

[0085] The detection limits of the electrode samples were determined using the above uric acid detection method. The results are as follows:

[0086] Table 3 Effects of different gold colloid particle sizes on gold electrode performance

[0087]

[0088] As can be seen from Table 3, when the gold colloid particle size is too large or too small, the detection limit of the gold electrode increases significantly and the detection performance decreases.

[0089] Comparative Example 5: The rest is the same as Example 1, except that:

[0090] At room temperature, the modified electrode sample No. 3 prepared in Example 1 was immersed in a 100 μm / L histidine solution for 12 h, and then taken out and dried to obtain a modified electrode: gold electrode-Cyst-gold gel-Cyst-His, which is the modified electrode sample No. 4.

[0091] Comparative Example 6: The rest is the same as Example 1, except that:

[0092] At room temperature, the modified electrode sample No. 3 prepared in Example 1 was polymerized in 0.01 mol / L glycine (Gly) by cyclic voltammetry for 10 cycles, scanning the potential range from -0.5 to 1.8 V at a rate of 100 mV / s. The modified electrode was then washed three times with sub-boiling water and air-dried for later use. The resulting modified electrode was: gold electrode-Cyst-gold gel-Cyst-Gly, which is modified electrode sample No. 5.

[0093] The different electrode samples prepared in Example 1 and Comparative Examples 1, 5, and 6 were used to measure the cyclic voltammogram of 23.6 μmol / L uric acid solution. The results are as follows: Figure 3 shown.

[0094] Figure 3 The treatment method of modified electrode No. 1 is as follows: a bare gold disk working electrode with a diameter of 2 mm is polished with alumina and felt in turn, and then the gold electrode is immersed in pure water and sub-boiling water for cleaning three times in turn, and then ultrasonically cleaned in sub-boiling water for 5 minutes, and the gold electrode is placed in sub-boiling water for standby use.

[0095] from Figure 3 It can be seen that the cyclic voltammogram of uric acid is irreversible, with only a reduction peak appearing, and the potential Ep is between 0.4 and 0.6 V, while the peak current density i p The order of size is No. 3 < No. 2 < No. 5 < No. 4 < No. 1. No. 3 has stronger conductivity, and it is easier for uric acid to transfer electrons at No. 3 electrode, so No. 3 has higher sensitivity in detecting uric acid and a wider detection range.

[0096] Urine samples generally contain vitamin C (AA) and dopamine (DA), which can interfere with the detection of uric acid. The sensitivity and separation effect of modified electrode samples 1-5 after adding vitamin C to uric acid solution were investigated. Figure 4 As shown in the figure, the cyclic voltammograms of uric acid and vitamin C are irreversible, with only reduction peaks appearing. The potential E of uric acid is p Between 0.50 and 0.60 V, the potential of vitamin C is E p The peak current density i of each uric acid modified gold electrode was detected between 0.40 and 0.50 V. p The order of size is No. 1 < No. 3 < No. 2 < No. 4 < No. 5. The peak current density i of each vitamin C modified gold electrode is detected. p The order of size is No. 3 < No. 1 < No. 2 < No. 4 < No. 5. No. 1 has the highest sensitivity for detecting uric acid when vitamin C alone is present, but No. 3 is more effective in separating uric acid and vitamin C.

[0097] The sensitivity and separation effect of modified electrode samples No. 1-5 after adding vitamin C and dopamine to uric acid solution were investigated experimentally. Figure 5 As shown in the figure, the cyclic voltammograms of uric acid, vitamin C, and dopamine are all irreversible. The uric acid potential E p A reduction peak appeared between 0.50 and 0.60 V, and the potential of vitamin C was E p A reduction peak appeared between 0.40 and 0.50 V, and the dopamine potential E p The oxidation peak appeared between 0.00 and 0.20 V, and the peak current density i of each uric acid modified gold electrode was detected. p The order of size is No. 1 < No. 3 < No. 2 < No. 4 < No. 5. The peak current density i of each vitamin C modified gold electrode is detected. p The order of size is No. 1 < No. 3 < No. 4 < No. 2 < No. 5. The peak current density i of each modified gold electrode of dopamine is detected. p The order of size is No. 3 < No. 2 < No. 5 < No. 4 < No. 1. In the presence of vitamin C and dopamine, No. 1 has the highest sensitivity for detecting uric acid, but No. 3 is better at separating uric acid, vitamin C, and dopamine.

[0098] Overall, the modified electrode No. 3 is more effective in detecting uric acid in the presence of vitamin C and dopamine, and is more stable and has better separation effect.

Claims

1. A method for preparing a gold electrode, characterized in that: The steps include: (1) Immerse the bare gold electrode activated by nitric acid in a cysteamine aqueous solution, take it out and dry it to obtain a Cyst-modified electrode; (2) Immerse the Cyst-modified electrode in a gold colloid solution, take it out and dry it to obtain a gold colloid-modified electrode; (3) Immerse the gold colloid-modified electrode in a cysteamine aqueous solution, take it out and dry it to obtain a Cyst-nano-gold colloid-Cyst-modified gold electrode; In step (2), the method for preparing the gold glue solution comprises the following steps: (11) Use sub-boiling distilled water to rinse the preparation container, and then prepare the chloroauric acid aqueous solution and sodium citrate aqueous solution respectively; (12) Add the chloroauric acid aqueous solution to sub-boiling distilled water, heat to boiling, add the sodium citrate aqueous solution under rapid stirring, adjust the volume with sub-boiling distilled water, and mix well to obtain a gold glue solution; The molar ratio of chloroauric acid to sodium citrate in the gold colloid solution is 0.30-1.51; In step (12), the concentration of the chloroauric acid aqueous solution is 0.5-1.5 wt %, and the volume is adjusted to 100 times the volume of the chloroauric acid aqueous solution using sub-boiling distilled water; In step (1), the method of immersing the bare gold electrode in the cysteamine aqueous solution is as follows: the bare gold electrode is placed in the cysteamine aqueous solution and immersed for 1-3 hours, while deoxygenating for 10-20 minutes, and the electrode is taken out and immersed in the cysteamine aqueous solution for 12-18 hours to obtain a Cyst-modified electrode; In step (2), the Cyst-modified electrode is immersed in the gold colloid solution for 10-14 h; In step (3), the method for immersing the gold colloid modified electrode in the cysteamine aqueous solution is as follows: the gold colloid modified electrode is placed in the cysteamine aqueous solution and immersed for 1-3 hours, while deoxygenating for 10-20 minutes, and the gold colloid modified electrode is taken out and immersed in the cysteamine aqueous solution for 12-18 hours before being taken out.

2. The method for preparing a gold electrode according to claim 1, wherein: In steps (1) and (3), the concentration of the cysteamine aqueous solution is 5-100 mmol / L; in step (2), the diameter of the gold colloid in the gold colloid solution is 13-60 nm.

3. The method for preparing a gold electrode according to claim 1, wherein: In step (1), the bare gold electrode is prepared as follows: The gold electrode was polished with alumina and felt in turn, and then immersed in quartz sub-boiling water and ethanol solution for ultrasonic cleaning in turn. The treated electrode was subjected to cyclic voltammetry scanning in a mixed solution of K3Fe(CN)6 and KNO3 to make ΔE p ≤65mV; etch the treated bare gold electrode with HNO3, take it out, rinse it with water, take it out and place it in sub-boiling water for later use.

4. Use of the gold electrode prepared according to the preparation method according to any one of claims 1 to 3 in electrochemical detection of uric acid.

5. The use according to claim 4, characterized in that The steps include: (1) A gold electrode was used as the working electrode, a platinum wire electrode was used as the counter electrode, and a silver-silver chloride electrode was used as the reference electrode to form a three-electrode system. The three-electrode system and an electrochemical workstation constituted a uric acid electrochemical detection device. (2) Gradual dilution of uric acid solutions of known concentrations with phosphate buffer was performed, and cyclic voltammetry was used to electrochemically detect uric acid solutions of different concentrations using a uric acid electrochemical detection device to obtain a fitting standard curve of uric acid concentration and electrical signal; (3) Using phosphate buffer as the supporting electrolyte to dilute the sample to obtain the test solution, the electrochemical signal of uric acid in the test solution is obtained by cyclic voltammetry using a uric acid electrochemical detection device. The concentration of uric acid in the test solution is calculated according to the standard curve, and then multiplied by the dilution factor to obtain the uric acid concentration in the sample.

6. An electrochemical detection device, characterized in that: The invention comprises a gold electrode, a platinum wire electrode and a silver-silver chloride electrode prepared by the preparation method according to any one of claims 1 to 3.

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