A method of treating a graphite electrode

Abstract

The present application relates to the technical field of electrochemical analysis detection, and particularly relates to a treatment method of a graphite electrode. The present application utilizes plasma to treat the graphite electrode, so as to realize that the oxidation peak potential of uric acid is obviously reduced, the uric acid can be oxidized on the surface of the graphite electrode at a lower potential, the oxidation of other reducing substances in blood is avoided, and the anti-interference ability during the uric acid test is improved.

Description

Technical Field

[0001] This invention relates to the field of electrochemical analysis and detection technology, and in particular to a method for processing graphite electrodes. Background Technology

[0002] In recent years, the prevalence of hyperuricemia and gout in China has increased dramatically. Hyperuricemia has shown a significant upward trend and a younger age of onset. Meta-analysis shows that the overall prevalence of hyperuricemia in China is 13.3% (approximately 186 million based on a population of 1.4 billion), and the prevalence of gout is 1.1% (approximately 15 million based on a population of 1.4 billion). It has become another common metabolic disease after diabetes.

[0003] Clinically, uric acid is the end product of purine metabolism. Disorders of purine metabolism, abnormal energy metabolism, and impaired renal excretion of uric acid can all lead to elevated plasma uric acid concentrations (hyperuricemia). The main characteristic of gout is high uric acid. Long-term high uric acid can cause kidney damage such as gouty acute arthritis, tophi deposition, tophaceous chronic arthritis, and joint deformities, posing a significant threat to health. Furthermore, much evidence suggests that hyperuricemia and gout are independent risk factors for chronic kidney disease, hypertension, cardiovascular disease, and diabetes. The "Chinese Guidelines for the Diagnosis and Treatment of Hyperuricemia and Gout (2019)" states that the management of hyperuricemia and gout should be a continuous process, requiring long-term, even lifelong, monitoring and management. It recommends that all patients with hyperuricemia and gout be aware of and monitor their blood uric acid levels throughout their lives, always keeping them within the ideal range. Therefore, uric acid testing will gradually develop into a testing indicator with huge market potential.

[0004] Currently, many methods for determining uric acid have been reported, mainly including high-performance liquid chromatography (HPLC), electrochemical methods, enzymatic methods, and chemical-optical methods. Among these methods, electrochemical methods have the advantages of being rapid, simple, and highly sensitive. However, compared with enzymatic methods, these methods suffer from low specificity and weak anti-interference ability. At a specific voltage, any substance in the blood that exhibits redox properties may be oxidized during the test, generating interfering signals. Moreover, the higher the voltage, the more substances are oxidized, and the stronger the interference signal. Therefore, this invention uses a special method to treat the surface of a graphite electrode, which can significantly reduce the oxidation peak potential of uric acid, allowing uric acid to be oxidized at a very low voltage while avoiding the oxidation of other substances in the blood, thus greatly improving the anti-interference ability of uric acid determination. Summary of the Invention

[0005] In view of this, the present invention provides a method for processing a graphite electrode. This method can significantly reduce the oxidation peak potential of uric acid, and uric acid is oxidized at a lower potential on the surface of the processed graphite electrode, effectively avoiding the oxidation of other reducing substances in the blood, thereby improving the anti-interference ability during uric acid detection.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] A method for processing graphite electrodes involves sequentially performing a first plasma treatment and a second plasma treatment on the graphite electrode using a plasma gun.

[0008] The flow rate of the ion gas in the first plasma treatment is 5-10 SLM, and the treatment speed is 20-40 mm / min;

[0009] The ion gas flow rate for the second plasma treatment is 10-20 SLM, and the treatment speed is 40-60 mm / min.

[0010] In some embodiments, the processing gas in the plasma gun is one of air, oxygen, nitrogen, or carbon dioxide. Specifically, the working gas used in the first plasma treatment is one of air, oxygen, nitrogen, or carbon dioxide; the working gas used in the second treatment is air.

[0011] In some implementations, the nozzle diameter of the plasma gun is 0.5mm-2mm; in some specific embodiments, it can be 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1.0mm, 1.1mm, 1.2mm, 1.3mm, 1.4mm, 1.5mm, 1.6mm, 1.7mm, 1.8mm, 1.9mm or 2.0mm.

[0012] In some implementation schemes, during the first plasma treatment, the distance between the plasma gun tip and the graphite electrode is 8 to 13 cm, specifically 8 cm, 9 cm, 10 cm, 10.5 cm, 11 cm, 12 cm, or 13 cm.

[0013] In some implementations, during the first plasma treatment, the power of the plasma gun is 200-300W, specifically 200W, 220W, 250W, 280W or 300W.

[0014] In some implementations, during the second plasma treatment, the distance between the plasma gun tip and the graphite electrode is 5-7 cm, specifically 5 cm, 5.5 cm, 6 cm, 6 cm, 6.5 cm, or 10 cm.

[0015] In some implementations, the power of the plasma gun in the second plasma treatment is 400-600W, specifically 400W, 450W, 500W, 550W or 600W.

[0016] The present invention also provides a graphite electrode obtained by the aforementioned processing method.

[0017] The present invention also provides the application of the graphite electrode obtained by the above-described processing method as a test strip electrode in the preparation of electrochemical sensors.

[0018] The present invention also provides an electrochemical sensor, wherein a graphite electrode obtained by the aforementioned processing method is used as a test strip electrode.

[0019] The present invention has the following beneficial effects:

[0020] 1. The method of the present invention can reduce the peak potential of uric acid oxidation by treating the surface of the carbon electrode;

[0021] This method utilizes plasma to treat the surface of a graphite electrode, increasing the number of fresh carbon atoms on the surface and altering its structure. By doping with nitrogen and oxygen, graphitic nitrogen and graphitic oxygen are formed, increasing the number of catalytic sites and making the electrode more reactive, thus improving the reaction rate. This allows uric acid to be oxidized at a lower potential on the treated graphite electrode surface (see...). Figure 3 ).

[0022] 2. The carbon electrode treated by this method can improve the anti-interference ability of uric acid testing;

[0023] Human blood contains a complex array of substances, many of which are easily oxidized. However, the carbon electrode processed using this method prevents easily oxidized substances such as acetaminophen, dopamine, and bilirubin from interfering with the uric acid test in blood samples. This is mainly because the electrode processed using plasma technology can oxidize uric acid at a lower potential, while other substances cannot be oxidized at that potential, thus eliminating interference from acetaminophen, dopamine, bilirubin, and other substances.

[0024] 3. This method is simple to operate, has high processing efficiency, and is easy to apply in industrial applications;

[0025] The main processing equipment used in this method is plasma. Plasma is simple to operate and does not produce biochemical waste after treatment. Common surface treatment methods, such as strong acid and strong alkali treatment, will produce highly corrosive wastewater. At the same time, plasma treatment is highly efficient, and it can process 400 test strips in about 120 seconds, which is conducive to large-scale industrial production. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the uric acid oxidation peak potential of the electrode after plasma treatment.

[0027] Figure 2 Schematic diagram of the uric acid oxidation peak potential of the electrode without plasma treatment.

[0028] Figure 3 This is a schematic diagram of the uric acid oxidation peak potential of electrodes after and without plasma treatment. Detailed Implementation

[0029] This invention provides a method for processing graphite electrodes. Those skilled in the art can refer to this document and appropriately modify the process parameters to achieve the desired result. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included in this invention. The methods and applications of this invention have been described through preferred embodiments, and those skilled in the art can clearly modify or appropriately change and combine the methods and applications described herein without departing from the content, spirit, and scope of this invention to implement and apply the technology of this invention.

[0030] The test materials used in this invention are all common commercial products and can be purchased on the market.

[0031] The present invention will be further illustrated below with reference to the embodiments:

[0032] Example 1

[0033] First, graphite electrodes and reference electrodes are screen-printed onto PET using screen printing technology. Then, the screen-printed substrate is placed on a plasma device, and the surface of the graphite electrodes on the substrate is treated using the following method: The plasma is generated by a plasma gun.

[0034] 1) Place the screen-printed substrate into the fixture of the plasma equipment and secure it.

[0035] 2) Use a plasma gun to perform plasma treatment on the graphite electrode area; the gas used for plasma processing can be air or oxygen; the nozzle diameter of the plasma gun should be 1.2 mm;

[0036] 3) First treatment. Adjust the height of the plasma gun tip and the graphite electrode area to 10.5 cm, set the plasma gun power to 250 W, adjust the ion gas flow rate to 7.5 SLM (L / min), and move the plasma gun at a speed of 30 mm / min. This treatment can remove stains and organic matter (such as resin) from the surface of the graphite electrode, exposing fresh carbon atoms as active sites to catalyze the oxidation of uric acid, promote electron transfer, and accelerate the reaction rate.

[0037] 4) Second treatment. After the first treatment, the height of the plasma gun head and the working electrode area was readjusted to 6 cm, the plasma gun power was set to 500 W, the ion gas flow rate was adjusted to 15 SLM (L / min), and the plasma gun was moved at a speed of 50 mm / min. This treatment increased the intensity of the treatment based on the first treatment, which can further change the carbon atom structure of the graphite electrode and dope the structure with nitrogen and oxygen to form graphite nitrogen and graphite oxygen, increase more catalytic sites, make the electrode more active, make uric acid molecules easier to oxidize, and increase the electron transfer rate, so that the reaction can occur at a lower potential.

[0038] 5) Apply enzyme to the substrate after the second plasma treatment, add enzyme to the treated substrate, create a sample aspiration channel, and cut it into individual test strips.

[0039] Venous blood samples with different concentrations of uric acid were prepared as test samples, and the plasma-treated and untreated test strips were tested using linear cyclic voltammetry (LSV) on an electrochemical workstation.

[0040] The results showed that the peak potential of uric acid oxidation after plasma treatment according to the present invention was between 200mV and 300mV (see [reference]). Figure 1 , 3 The uric acid oxidation peak potential without plasma treatment is 400mV-500mV (see...). Figure 2 , 3 This indicates that the processing method of the present invention can significantly reduce the oxidation peak potential of uric acid on the graphite electrode surface, allowing uric acid to be oxidized at a lower potential on the graphite electrode surface, avoiding oxidation by other reducing substances in the blood, thereby improving the anti-interference ability during uric acid testing (see Table 1).

[0041] Table 1 Anti-interference test

[0042]

[0043] Example 2

[0044] First, graphite electrodes and reference electrodes are screen-printed onto PET using screen printing technology. Then, the screen-printed substrate is placed on a plasma device, and the surface of the graphite electrodes on the substrate is treated using the following method: The plasma is generated by a plasma gun.

[0045] 1) Place the screen-printed substrate into the fixture of the plasma equipment and secure it.

[0046] 2) Use a plasma gun to perform plasma treatment on the graphite electrode area; the gas used for plasma processing can be air or oxygen; the nozzle diameter of the plasma gun should be 0.5 mm;

[0047] 3) First treatment. Adjust the height of the plasma gun tip and the graphite electrode area to 13cm, set the plasma gun power to 200W, adjust the ion gas flow rate to 10SLM (L / min), and move the plasma gun at a speed of 20mm / min. This treatment can remove stains and organic matter (such as resin) from the graphite electrode surface, exposing fresh carbon atoms as active sites to catalyze the oxidation of uric acid, promote electron transfer, and accelerate the reaction rate.

[0048] 4) Second treatment. After the first treatment, the height of the plasma gun head and the working electrode area is readjusted to 7cm, the power of the plasma gun is set to 400W, the ion gas flow rate is adjusted to 10-20 SLM (L / min), and the plasma gun is moved at a speed of 40mm / min. This treatment increases the intensity of the treatment based on the first treatment, which can further change the carbon atom structure of the graphite electrode and dope the structure with nitrogen and oxygen to form graphite nitrogen and graphite oxygen, increase more catalytic sites, make the electrode more active, make uric acid molecules easier to oxidize, and increase the electron transfer rate, so that the reaction can occur at a lower potential.

[0049] 5) Apply enzyme to the substrate after the second plasma treatment, add enzyme to the treated substrate, create a sample aspiration channel, and cut it into individual test strips.

[0050] Example 3

[0051] First, graphite electrodes and reference electrodes are screen-printed onto PET using screen printing technology. Then, the screen-printed substrate is placed on a plasma device, and the surface of the graphite electrodes on the substrate is treated using the following method: The plasma is generated by a plasma gun.

[0052] 1) Place the screen-printed substrate into the fixture of the plasma equipment and secure it.

[0053] 2) Use a plasma gun to perform plasma treatment on the graphite electrode area; the gas used for plasma processing can be air or oxygen; the nozzle diameter of the plasma gun should be 2mm.

[0054] 3) First treatment. Adjust the height of the plasma gun tip and the graphite electrode area to 8cm, set the plasma gun power to 300W, adjust the ion gas flow rate to 5SLM (L / min), and move the plasma gun at a speed of 40mm / min. This treatment can remove stains and organic matter (such as resin) from the graphite electrode surface, exposing fresh carbon atoms as active sites to catalyze the oxidation of uric acid, promote electron transfer, and accelerate the reaction rate.

[0055] 4) Second treatment. After the first treatment, the height of the plasma gun head and the working electrode area was readjusted to 5 cm, the power of the plasma gun was set to 600 W, the ion gas flow rate was adjusted to 10 SLM (L / min), and the plasma gun was moved at a speed of 60 mm / min. This treatment increased the intensity of the treatment based on the first treatment, which can further change the carbon atom structure of the graphite electrode and dope the structure with nitrogen and oxygen to form graphite nitrogen and graphite oxygen, increase more catalytic sites, make the electrode more active, make uric acid molecules easier to oxidize, and increase the electron transfer rate, so that the reaction can occur at a lower potential.

[0056] 5) Apply enzyme to the substrate after the second plasma treatment, add enzyme to the treated substrate, create a sample aspiration channel, and cut it into individual test strips.

[0057] The plasma-treated test strips of Examples 2 and 3 were tested according to the method of Example 1, and the results were very similar to those of Example 1, with only minor differences.

[0058] The above are merely preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method of treating a graphite electrode, characterized by, The graphite electrode is subjected to first and second plasma treatments in sequence by using a plasma gun; The ion gas flow rate of the first plasma treatment is 5-10 SLM, and the processing speed is 20-40 mm / min; The ion gas flow rate of the second plasma treatment is 10-20 SLM, and the processing speed is 40-60 mm / min; The processing gas in the plasma gun is one of air, oxygen, nitrogen or carbon dioxide.

2. The treatment method according to claim 1, characterized in that, The nozzle diameter of the plasma gun is 0.5-2 mm.

3. The treatment method of claim 1, wherein, In the first plasma treatment, the distance between the gun head of the plasma gun and the graphite electrode is 8-13 cm.

4. The treatment method of claim 1, wherein In the first plasma treatment, the power of the plasma gun is 200-300 W.

5. The treatment method of claim 1, wherein In the second plasma treatment, the distance between the gun head of the plasma gun and the graphite electrode is 5-7 cm.

6. The treatment method of claim 1, wherein In the second plasma treatment, the power of the plasma gun is 400-600 W.

7. A graphite electrode obtained by using the treatment method according to any one of claims 1-6.

8. Use of the graphite electrode obtained by using the treatment method according to any one of claims 1-6 or the graphite electrode according to claim 7 as a test strip electrode in preparation of an electrochemical sensor.

9. An electrochemical sensor, characterized in that The graphite electrode obtained by using the treatment method according to any one of claims 1-6 or the graphite electrode according to claim 7 as a test strip electrode.

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