A preparation process of L-fucose

Abstract

The present invention provides a preparation process of L-fucose, and relates to the technical field of electrolytic production of organic compounds. The preparation process uses brown algae as raw material, hydrolyzes it with a mixed acid solution of concentrated hydrochloric acid and concentrated phosphoric acid, adjusts the pH value, electrolyzes the hydrolyzate, uses a graphite electrode as an anode, and a silver electrode with a surface modified with thiol-β-cyclodextrin as a cathode. After the electrolysis is completed, L-fucose is eluted, and column chromatography separation and recrystallization are performed. The method described in the present invention improves the extraction rate and extraction efficiency of L-fucose relative to the prior art, simplifies the operation steps, and is conducive to industrial large-scale acquisition of L-fucose.

Description

Technical Field

[0001] The invention relates to the technical field of electrolytic production of organic compounds, and relates to a process for preparing L-fucose, which is classified as C25B. Background Art

[0002] Fucose, also known as 6-deoxygalactose, is a six-carbon monosaccharide. It is widely present in nature and is an important component of many oligosaccharides. It can be found in plants and animals as well as some invertebrates such as sea urchins. Fucose is also one of the main components of human breast milk oligosaccharides (HMOs) and is considered to be one of the eight sugar substances required by the body. In nature, natural fucose is mainly in the L-configuration, while the D-configuration fucose is very rare. In 1890, scientists first reported the isolation of L-fucose from the hydrolysis product of a polysaccharide. The structural formula of L-fucose is as follows: .

[0003] Fucose is involved in many biological processes, including cell-to-cell recognition, signal transduction, and immune response. In addition, fucose is also related to the occurrence and development of some diseases. For example, abnormal fucosylation is often found on the surface of tumor cells, which may affect the growth and metastasis of cancer cells. Therefore, the study of fucose is of great significance for understanding the complex glycobiological mechanisms in organisms and developing new treatments.

[0004] There are mainly the following methods for producing L-fucose: natural extraction, microbial fermentation, enzyme-catalyzed synthesis and chemical synthesis.

[0005] As for natural extraction, currently the main method is to separate the corresponding oligosaccharides from algae and other plants rich in fucose, obtain fucose and its derivatives through hydrolysis, separation and other means, and then obtain fucose through separation and purification means.

[0006] Black(Black,WAP;ETDewar,ET;Woodward,FNManufacture of algalchemicals.IV-

[0007] laboratory-scale isolation of fucoidin from brown marine algae.) and others optimized the extraction method of fucoidan and investigated the effects of pH, temperature, extraction time and the ratio of extractant to algae weight on the extraction effect. Since the exact fucose content of fucoidan is unknown, the L-fucose content of these algae and the obtained extracts were used to calculate the extraction efficiency. The highest yield was obtained by extraction with hydrochloric acid at 70°C for 1 hour. This process produced about 50% L-fucose.

[0008] On this basis, Schwerger (Schweiger, RG Preparation of alpha-L-fucosides and L-fucose from fucoidan.) optimized the hydrolysis procedure of fucoidan to obtain free L-fucose. Fucoidan was dissolved in methanol and treated with hydrochloric acid. The filter agent was neutralized by an ion exchange column, and then methyl-L-fucoside was converted into L-fucose by sulfuric acid treatment, decolorized with activated carbon and concentrated. L-fucose was then obtained by adding ethanol to the concentrated solution. Finally, 4.2g of L-fucose was obtained from 500g (solid content 55.5g) of algae with a purity of 98.7%.

[0009] At present, domestic and foreign methods mainly use acid-base treatment, enzyme extraction, solvent extraction and other methods to obtain fucose from natural substances. The extraction steps are cumbersome, the extraction rate is low, and the extraction cost is high, which is not conducive to the industrial large-scale acquisition of L-fucose.

[0010] A Chinese invention patent with announcement number CN110387555B and classification number C25B3 / 00 discloses a method for preparing plant starch glucan by weak electrolysis, which comprises preparing plant starch into a plant starch solution and adding the solution into an electrolytic cell for electrolysis, using direct current electrolysis, a voltage of 15 to 45 V, an initial electrolysis temperature of 25° C., an electrolysis time of 1 to 6 h, and an inorganic salt electrolyte concentration of 1 to 5% (wt); after electrolysis, adjusting the solution pH to 6 to 7, and then precipitating, collecting the precipitate, washing with alcohol, and drying to obtain plant starch glucan.

[0011] A Chinese invention patent with publication number CN118207549A and classification number C25B3 / 05 discloses a method for preparing cytarabine hydrochloride, which prepares cytarabine hydrochloride by ring-opening cyclocytidine hydrochloride using an electrochemical method.

[0012] The Chinese invention patent with publication number CN110079819A and classification number C25B3 / 00 discloses a process and application of preparing amino oligosaccharides by electrochemical method, wherein chitosan is used as raw material, dissolved in HAc-NaAc buffer, the temperature of the electrolyte is set at 40-60°C, and the current density is controlled at 0.06-0.2A / cm 2 After electrochemical degradation, the amino oligosaccharides are obtained by cooling, washing, filtering and drying.

[0013] Therefore, there is an urgent need for a method for preparing L-fucose with simple process, cost saving and high extraction efficiency. Summary of the invention

[0014] The purpose of the present invention is to provide a preparation process of L-fucose, which has simple process steps, low cost and high extraction efficiency.

[0015] In order to achieve the above object, the present invention provides the following technical solutions:

[0016] A process for preparing L-fucose comprises the following steps:

[0017] (1) Clean the brown algae, dry it, and crush it into particles;

[0018] (2) placing the crushed brown algae into a reaction bottle, adding a mixed acid solution of hydrochloric acid and phosphoric acid, sealing the reaction bottle and performing hydrolysis. After the hydrolysis is completed, taking out the reaction bottle and cooling it to room temperature;

[0019] (3) Adjust the pH value of the hydrolyzate to 7.5-8.5;

[0020] (4) adding NaCl to the hydrolyzate, and then placing the hydrolyzate in an electrolytic cell for electrolysis, wherein the anode of the electrolytic cell is a graphite electrode, and the cathode is a silver electrode surface-modified with thiol-β-cyclodextrin;

[0021] (5) After the electrolysis treatment, the silver electrode is eluted with deionized water, and the eluate is combined, filtered, and concentrated;

[0022] (6) separating the concentrated solution by column chromatography to obtain an L-fucose eluate, and concentrating the eluate;

[0023] (7) Anhydrous ethanol is added to the concentrated solution to crystallize and obtain L-fucose.

[0024] The present invention adopts the mixed acid solution of hydrochloric acid and phosphoric acid to carry out hydrolysis, provides stronger acidic environment, can accelerate the process of hydrolysis reaction, and helps to more thoroughly decompose polysaccharide macromolecules, improves the extraction efficiency of target product. Using mixed acid can also make hydrolysis reaction carry out at a lower temperature, and reduces the reaction time, is conducive to improving production efficiency, and is particularly important for large-scale production. By adjusting the ratio and concentration of mixed acid, the selectivity of hydrolysis can be optimized, hydrochloric acid is very effective for the hydrolysis of glycosidic bond, and phosphoric acid then has certain buffering effect, can help control pH value, reduce the side reaction caused by over-acidification, reduce the generation of by-products, and improve the purity of product.

[0025] The present invention adopts an electrolysis method to significantly improve the extraction rate of L-fucose. The surface of the silver electrode is modified with thiol-β-cyclodextrin, and β-cyclodextrin has a hydrophobic inner cavity, which can selectively adsorb L-fucose, and a stable inclusion complex is formed between the two through hydrogen bonds. After the electrolysis is completed, the silver electrode is eluted with deionized water for multiple times, and the eluate is collected, and the eluate contains L-fucose desorbed from the surface of the silver electrode. This process not only improves the purity of the target product, but also simplifies the subsequent separation and purification steps. In addition, adding NaCl to the hydrolyzate can significantly improve the conductivity of the solution, thereby improving the electrolysis efficiency.

[0026] As a preferred solution, in step (2), the concentration of the hydrochloric acid is 37 wt %, the concentration of the phosphoric acid is 85 wt %, and the volume ratio of the hydrochloric acid to the phosphoric acid is 1.5-2.5:1.

[0027] The present invention requires precise control of the volume ratio of hydrochloric acid and phosphoric acid. A high proportion of hydrochloric acid may lead to excessive hydrolysis, generate unwanted by-products, and even destroy the structure of the target product; a high proportion of phosphoric acid may affect the selectivity of hydrolysis, lead to product complexity, and increase the difficulty of subsequent purification. In addition, improper ratios may also induce unnecessary side reactions, such as dehydration, rearrangement, etc., thereby generating a variety of by-products and reducing the purity of the target product.

[0028] As a preferred solution, the amount of the mixed acid solution added in step (2) is 10-15 mL of the mixed acid solution per gram of dry weight of brown algae.

[0029] As a preferred solution, the hydrolysis temperature in step (2) is 30-60° C., more preferably 40-50° C.; the hydrolysis time is 1-5 hours, more preferably 2-3 hours.

[0030] As a preferred solution, in step (3), sodium hydroxide, potassium hydroxide, aqueous ammonia, sodium carbonate or sodium bicarbonate is used to adjust the pH value of the hydrolyzate.

[0031] As a preferred solution, the concentration of NaCl after addition in step (4) is 0.1~1 M.

[0032] As a preferred solution, the voltage of the electrolytic cell in step (4) is 8-10 V, and the electrolysis time is 20-40 minutes.

[0033] As a preferred solution, the preparation method of the silver electrode with surface modified with mercapto-β-cyclodextrin in step (4) is as follows:

[0034] 1) Clean the silver electrode;

[0035] 2) dissolving thiol-β-cyclodextrin in ethanol to prepare a thiol-β-cyclodextrin solution;

[0036] 3) Immerse the cleaned silver electrode in the thiol-β-cyclodextrin solution and let it stand for 12 to 24 hours;

[0037] 4) The silver electrode is taken out, rinsed with deionized water, and dried to obtain a silver electrode with surface modified with mercapto-β-cyclodextrin.

[0038] The present invention uses thiol-β-cyclodextrin to modify the silver electrode. There is a strong covalent bond or coordination bond between the thiol (-SH) and the silver surface, which enables β-cyclodextrin to be firmly fixed on the surface of the silver electrode and not easy to fall off. β-cyclodextrin has a unique hydrophobic inner cavity and a hydrophilic outer wall, and can form a stable inclusion complex with L-fucose. Through the modification of thiol-β-cyclodextrin, the surface of the silver electrode can selectively bind to the target molecule, while other impurities will not be adsorbed or adsorb less.

[0039] As a preferred solution, the mercapto-β-cyclodextrin can be directly a commercially available product, or can be prepared by reacting β-cyclodextrin with cysteamine hydrochloride.

[0040] As a preferred solution, the filler of the column chromatography in step (6) is Sephadex G-10, and the mobile phase is deionized water.

[0041] Compared with the prior art, the advantages and beneficial effects of the present invention are:

[0042] 1. The present invention adopts a mixed acid solution of concentrated hydrochloric acid and concentrated phosphoric acid to hydrolyze brown algae, and controls a suitable ratio of the two, which significantly improves the extraction efficiency and extraction rate of L-fucose, reduces the generation of by-products, and improves the purity of the product.

[0043] 2. The present invention electrolyzes the extract and uses a thiol-β-cyclodextrin-modified silver electrode as a cathode, so that the surface of the silver electrode can selectively bind to the target molecule, simplifying the difficulty of subsequent purification and improving the extraction rate and purity of the target product.

[0044] 3. The method of the present invention has simple operation steps, reduces the reaction temperature and shortens the time compared with the prior art, and is conducive to industrial large-scale acquisition of L-fucose. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 This is the HPLC spectrum of L-fucose prepared in Example 1;

[0046] Figure 2 This is the HPLC spectrum of L-fucose prepared in Example 2;

[0047] Figure 3 This is the HPLC spectrum of L-fucose prepared in Example 3. DETAILED DESCRIPTION

[0048] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0049] Example 1

[0050] This embodiment provides a process for preparing L-fucose, comprising the following steps:

[0051] (1) Clean the fresh brown algae, place it in an oven and dry it at 60°C for 6 hours, and then use a grinder to crush the brown algae into small particles;

[0052] (2) Weigh 500 g of crushed brown algae and put it into a reaction bottle, add 5000 mL of a mixed acid solution of 37 wt% hydrochloric acid and 85 wt% phosphoric acid (the volume ratio of hydrochloric acid to phosphoric acid is 2.5:1), seal the reaction bottle, and hydrolyze at 50 °C for 5 h. After the hydrolysis is completed, take out the reaction bottle and cool it to room temperature;

[0053] (3) Add NaOH to adjust the pH value of the hydrolyzate to 7.8;

[0054] (4) adding 50 g of NaCl to the hydrolyzate, and then placing the hydrolyzate in an electrolytic cell for electrolysis, wherein the anode of the electrolytic cell is a graphite electrode, the cathode is a silver electrode surface-modified with thiol-β-cyclodextrin, the voltage is 10 V, and the electrolysis time is 40 min;

[0055] (5) After the electrolysis treatment is completed, the silver electrode is washed with deionized water for 5 times, the eluates are combined, filtered to remove the residue, and the eluates are concentrated using a rotary evaporator to obtain a concentrated solution;

[0056] (6) The concentrated liquid is subjected to column chromatography separation, the filler is Sephadex G-10, the mobile phase is deionized water, the sample in the column is gradually eluted, the effluent is collected, and the sugar content in the eluate is monitored by high performance liquid chromatography. When the L-fucose peak is detected, the eluate containing L-fucose is collected, and the L-fucose eluate is concentrated after being obtained;

[0057] (7) Transfer the concentrated solution to a beaker and slowly add anhydrous ethanol to allow L-fucose to crystallize.

[0058] The preparation method of the silver electrode with surface modified with mercapto-β-cyclodextrin is as follows:

[0059] 1) Clean the silver electrode;

[0060] 2) dissolving thiol-β-cyclodextrin in ethanol to prepare a thiol-β-cyclodextrin solution;

[0061] 3) Immerse the cleaned silver electrode in the thiol-β-cyclodextrin solution and let it stand for 20 hours;

[0062] 4) The silver electrode is taken out, rinsed with deionized water, and dried to obtain a silver electrode with surface modified with mercapto-β-cyclodextrin.

[0063] This example finally obtained 52.8 g of L-fucose with a purity of 99.977%. The HPLC spectrum is shown in Figure 1 shown.

[0064] Example 2

[0065] This embodiment provides a process for preparing L-fucose, comprising the following steps:

[0066] (1) Clean the fresh brown algae, place it in an oven and dry it at 60°C for 6 hours, and then use a grinder to crush the brown algae into small particles;

[0067] (2) Weigh 500 g of crushed brown algae and put it into a reaction bottle, add 5000 mL of a mixed acid solution of 37 wt% hydrochloric acid and 85 wt% phosphoric acid (the volume ratio of hydrochloric acid to phosphoric acid is 2:1), seal the reaction bottle, and hydrolyze at 40 °C for 3 h. After the hydrolysis is completed, take out the reaction bottle and cool it to room temperature;

[0068] (3) Add NaOH to adjust the pH value of the hydrolyzate to 8;

[0069] (4) adding 50 g of NaCl to the hydrolyzate, and then placing the hydrolyzate in an electrolytic cell for electrolysis, wherein the anode of the electrolytic cell is a graphite electrode, the cathode is a silver electrode surface-modified with thiol-β-cyclodextrin, the voltage is 10 V, and the electrolysis time is 20 min;

[0070] (5) After the electrolysis treatment is completed, the silver electrode is washed with deionized water for 5 times, the eluates are combined, filtered to remove the residue, and the eluates are concentrated using a rotary evaporator to obtain a concentrated solution;

[0071] (6) The concentrated liquid is subjected to column chromatography separation, the filler is Sephadex G-10, the mobile phase is deionized water, the sample in the column is gradually eluted, the effluent is collected, and the sugar content in the eluate is monitored by high performance liquid chromatography. When the L-fucose peak is detected, the eluate containing L-fucose is collected, and the L-fucose eluate is concentrated after being obtained;

[0072] (7) Transfer the concentrated solution to a beaker and slowly add anhydrous ethanol to allow L-fucose to crystallize.

[0073] The preparation method of the silver electrode with surface modified with mercapto-β-cyclodextrin is the same as that in Example 1.

[0074] This example finally obtained 49.6 g of L-fucose with a purity of 99.999%. The HPLC spectrum is as follows Figure 2 shown.

[0075] Example 3

[0076] This embodiment provides a process for preparing L-fucose, comprising the following steps:

[0077] (1) Clean the fresh brown algae, place it in an oven and dry it at 60°C for 6 hours, and then use a grinder to crush the brown algae into small particles;

[0078] (2) Weigh 500 g of crushed brown algae and put it into a reaction bottle, add 5000 mL of a mixed acid solution of 37 wt% hydrochloric acid and 85 wt% phosphoric acid (the volume ratio of hydrochloric acid to phosphoric acid is 1.5:1), seal the reaction bottle, and hydrolyze at 50 °C for 2 h. After the hydrolysis is completed, take out the reaction bottle and cool it to room temperature;

[0079] (3) Add NaOH to adjust the pH value of the hydrolyzate to 7.8;

[0080] (4) adding 50 g of NaCl to the hydrolyzate, and then placing the hydrolyzate in an electrolytic cell for electrolysis, wherein the anode of the electrolytic cell is a graphite electrode, the cathode is a silver electrode surface-modified with thiol-β-cyclodextrin, the voltage is 10 V, and the electrolysis time is 20 min;

[0081] (5) After the electrolysis treatment is completed, the silver electrode is washed with deionized water for 5 times, the eluates are combined, filtered to remove the residue, and the eluates are concentrated using a rotary evaporator to obtain a concentrated solution;

[0082] (6) The concentrated liquid is subjected to column chromatography separation, the filler is Sephadex G-10, the mobile phase is deionized water, the sample in the column is gradually eluted, the effluent is collected, and the sugar content in the eluate is monitored by high performance liquid chromatography. When the L-fucose peak is detected, the eluate containing L-fucose is collected, and the L-fucose eluate is concentrated after being obtained;

[0083] (7) Transfer the concentrated solution to a beaker and slowly add anhydrous ethanol to allow L-fucose to crystallize.

[0084] The preparation method of the silver electrode with surface modified with mercapto-β-cyclodextrin is the same as that in Example 1.

[0085] This example finally obtained 48.7 g of L-fucose with a purity of 99.997%. The HPLC spectrum is as follows Figure 3 shown.

[0086] Comparative Example 1

[0087] This comparative example provides a process for preparing L-fucose, which differs from Example 1 only in that 5000 mL of 37 wt % hydrochloric acid is added in step (2).

[0088] This comparative example finally obtained 41.3 g of L-fucose with a purity of 98.703%.

[0089] Comparative Example 2

[0090] This comparative example provides a process for preparing L-fucose, which differs from Example 1 only in that in step (2), 5000 mL of a mixed acid solution of 37 wt % hydrochloric acid and 85 wt % phosphoric acid (the volume ratio of hydrochloric acid to phosphoric acid is 1:1) is added.

[0091] This comparative example finally obtained 35.9 g of L-fucose with a purity of 98.815%.

[0092] Comparative Example 3

[0093] This comparative example provides a process for preparing L-fucose, which differs from Example 1 only in that in step (2), 5000 mL of a mixed acid solution of 37 wt % hydrochloric acid and 85 wt % phosphoric acid (the volume ratio of hydrochloric acid to phosphoric acid is 3:1) is added.

[0094] This comparative example finally obtained 42.0 g of L-fucose with a purity of 98.672%.

[0095] Comparative Example 4

[0096] This comparative example provides a preparation process of L-fucose, comprising the following steps:

[0097] (1) Clean the fresh brown algae, place it in an oven and dry it at 60°C for 6 hours, and then use a grinder to crush the brown algae into small particles;

[0098] (2) Weigh 500 g of crushed brown algae and put it into a reaction bottle, add 5000 mL of a mixed acid solution of 37 wt% hydrochloric acid and 85 wt% phosphoric acid (the volume ratio of hydrochloric acid to phosphoric acid is 2.5:1), seal the reaction bottle, and hydrolyze at 50 °C for 5 h. After the hydrolysis is completed, take out the reaction bottle and cool it to room temperature;

[0099] (3) Add NaOH to adjust the pH value of the hydrolyzate to neutral;

[0100] (4) filtering the hydrolyzate to remove insoluble impurities, and concentrating to obtain a concentrated solution;

[0101] (6) The concentrated liquid is subjected to column chromatography separation, the filler is Sephadex G-10, the mobile phase is deionized water, the sample in the column is gradually eluted, the effluent is collected, and the sugar content in the eluate is monitored by high performance liquid chromatography. When the L-fucose peak is detected, the eluate containing L-fucose is collected, and the L-fucose eluate is concentrated after being obtained;

[0102] (7) Transfer the concentrated solution to a beaker and slowly add anhydrous ethanol to allow L-fucose to crystallize.

[0103] This comparative example finally obtained 30.9 g of L-fucose with a purity of 96.571%.

[0104] The above results show that the preparation method provided by the present invention significantly improves the extraction rate and purity of L-fucose. Comparative Examples 1-3 respectively use concentrated hydrochloric acid, a mixed acid solution of concentrated hydrochloric acid and concentrated phosphoric acid with a volume ratio of 1:1, and a mixed acid solution of concentrated hydrochloric acid and concentrated phosphoric acid with a volume ratio of 3:1 to hydrolyze brown algae, and the quality of L-fucose finally obtained decreases. The inventor speculates that when only concentrated hydrochloric acid is used, or when the proportion of concentrated hydrochloric acid is too high, it may lead to excessive hydrolysis, generate unwanted by-products, and even destroy the structure of the target product, so that the content of by-products in the extract increases and the content of the target product decreases; when the proportion of concentrated phosphoric acid is too high, it may affect the selectivity of hydrolysis, resulting in product complexity, and it is difficult to efficiently separate the target product during subsequent column chromatography separation, resulting in a reduction in the final target product and a reduction in purity. Comparative Example 4 did not perform electrolysis, and the by-products in the hydrolyzate were difficult to separate from the target product during subsequent column chromatography separation and purification, resulting in a reduction in the final target product, and the purity was still not high after recrystallization.

[0105] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A process for preparing L-fucose, comprising the following steps: (1) Clean the brown algae, dry it, and crush it into particles; (2) placing the crushed brown algae into a reaction bottle, adding a mixed acid solution of hydrochloric acid and phosphoric acid, sealing the reaction bottle and performing hydrolysis. After the hydrolysis is completed, taking out the reaction bottle and cooling it to room temperature; (3) Adjust the pH value of the hydrolyzate to 7.5-8.5; (4) adding NaCl to the hydrolyzate, and then placing the solution in an electrolytic cell for electrolysis, wherein the anode of the electrolytic cell is a graphite electrode, and the cathode is a silver electrode surface-modified with thiol-β-cyclodextrin; (5) After the electrolysis treatment, the silver electrode is eluted with deionized water, and the eluate is combined, filtered, and concentrated; (6) separating the concentrated solution by column chromatography to obtain an L-fucose eluate, and concentrating the eluate; (7) adding anhydrous ethanol to the concentrated solution for crystallization to obtain L-fucose; In step (2), the concentration of the hydrochloric acid is 37 wt %, the concentration of the phosphoric acid is 85 wt %, and the volume ratio of the hydrochloric acid to the phosphoric acid is 1.5-2.5:

1.

2. The preparation process according to claim 1, characterized in that: The amount of the mixed acid solution added in step (2) is 10-15 mL of the mixed acid solution per gram of dry weight of brown algae.

3. The preparation process according to claim 1, characterized in that: The hydrolysis temperature in step (2) is 30-60° C., and the hydrolysis time is 1-5 hours.

4. The preparation process according to claim 3, characterized in that: The hydrolysis temperature in step (2) is 40-50° C. and the hydrolysis time is 2-3 hours.

5. The preparation process according to claim 1, characterized in that: In step (3), sodium hydroxide, potassium hydroxide, aqueous ammonia, sodium carbonate or sodium bicarbonate is used to adjust the pH value of the hydrolyzate.

6. The preparation process according to claim 1, characterized in that: The concentration of NaCl after addition in step (4) is 0.1~1 M.

7. The preparation process according to claim 1, characterized in that: The voltage of the electrolytic cell in step (4) is 8-10 V, and the electrolysis time is 20-40 minutes.

8. The preparation process according to claim 1, characterized in that: The preparation method of the silver electrode with surface modified with mercapto-β-cyclodextrin in step (4) is as follows: 1) Clean the silver electrode; 2) dissolving thiol-β-cyclodextrin in ethanol to prepare a thiol-β-cyclodextrin solution; 3) Immerse the cleaned silver electrode in the thiol-β-cyclodextrin solution and let it stand for 12 to 24 hours; 4) The silver electrode is taken out, rinsed with deionized water, and dried to obtain a silver electrode with surface modified with mercapto-β-cyclodextrin.

9. The preparation process according to claim 1, characterized in that: The filler of the column chromatography in step (6) is Sephadex G-10, and the mobile phase is deionized water.

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