Benzothiadiazole-based conjugated microporous polymer-coated graphene heterojunction material, photoelectrochemical sensor and levodopa detection method

Abstract

The present invention belongs to the technical field of electrochemical sensors, and provides a benzothiadiazolyl-based conjugated microporous polymer-coated graphene heterojunction material, a photoelectrochemical sensor, and a method for detecting levodopa. The benzothiadiazolyl-based conjugated microporous polymer-coated graphene heterojunction material CMP-rGO is obtained by reacting bromine-functionalized reduced graphene oxide with 1,3,5-triethynylbenzene, 4,7-dibromo-2,1,3-benzothiadiazole, tetrakis(triphenylphosphine)palladium, and cuprous iodide in a closed environment. The preparation of the photoelectrochemical sensor is to modify the CMP-rGO dispersion on an ITO electrode. The detection of levodopa is to first obtain a linear relationship between the photocurrent and the logarithm of the levodopa concentration, then test the sample, bring the photocurrent value into the linear relationship, and obtain the levodopa concentration. The detection method of the present invention has the advantages of simple operation, miniaturization of the device, low cost, rapid detection, and high sensitivity recognition.

Description

Technical Field

[0001] The present invention relates to the technical field of levodopa detection, and in particular to a benzothiadiazolyl-based conjugated microporous polymer-coated graphene heterojunction material, a photoelectrochemical sensor, a preparation method thereof, and a levodopa detection method. Background Art

[0002] Levodopa (LDA), whose chemical name is L-3,4-dihydroxyphenylalanine, has a molecular formula of C9H 11 NO4, the structural formula is as follows:

[0003]

[0004] Levodopa is a white or off-white crystalline powder, odorless. As a natural compound, Levodopa is often found in plants. Levodopa has been listed as the gold standard for the treatment of Parkinson's disease since the 1960s. Unlike dopamine, levodopa can cross the blood-brain barrier and be converted into dopamine by L-aromatic amino acid decarboxylase, thereby achieving the effect of treating Parkinson's disease. However, long-term use of levodopa can also cause some side effects, such as hypotension, nausea, arrhythmia, etc. Therefore, the detection of levodopa is very necessary for evaluating the patient's condition and preventing side effects.

[0005] At present, the main methods for detecting levodopa are fluorescence spectroscopy, high performance liquid chromatography, flow injection method and ultraviolet spectrophotometry. These methods can realize the detection of levodopa samples, but these methods require expensive instruments, complicated operations and skilled technicians. For example, the invention patent with publication number CN103364512A discloses a detection method for levodopa methyl ester and levodopa concentration in plasma, which discloses a detection method using UPLC / MS / MS coupling, which requires expensive equipment. The invention patent with publication number CN112179876A discloses a method for detecting levodopa and tyrosinase by in-situ formation of fluorescent copolymers, which requires the use of a fluorescence spectrometer. Therefore. It is of great significance to develop a new method for detecting levodopa. At present, photoelectrochemical sensors have the advantages of fast response, high sensitivity and simple operation. The present invention synthesizes a new type of conjugated microporous polymer-coated graphene heterojunction material for the first time, and uses it to construct a photoelectrochemical sensor to realize the rapid detection of levodopa. To date, there is no report on the photoelectrochemical detection of L-DOPA on benzothiadiazolyl-based conjugated microporous polymer-coated graphene heterojunctions. Summary of the invention

[0006] The purpose of the present invention is to provide a benzothiadiazolyl-based conjugated microporous polymer-coated graphene heterojunction material, a photoelectrochemical sensor, a preparation method thereof and a method for detecting levodopa in view of the above-mentioned problems. The present invention is a new method for detecting levodopa by photoelectrochemically modifying an electrode using a benzothiadiazolyl-based conjugated microporous polymer-coated graphene heterojunction material. The method is simple to operate, has a miniaturized device, is low in cost, and has a rapid detection speed, and can highly sensitively identify levodopa in a solution.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0008] A benzothiadiazolyl-based conjugated microporous polymer-coated graphene heterojunction material, wherein the structural formula of the benzothiadiazolyl-based conjugated microporous polymer-coated graphene heterojunction material is:

[0009]

[0010] The method for preparing the above-mentioned benzothiadiazolyl-based conjugated microporous polymer-coated graphene heterojunction material comprises the following steps:

[0011] Bromine-functionalized reduced graphene oxide rGBr and dry DMF are added to a reaction container and mixed, and then triethylamine is added, and nitrogen is switched multiple times in a closed environment, and the reactants are deoxygenated under nitrogen protection; then 1,3,5-triethynylbenzene, 4,7-dibromo-2,1,3-benzothiadiazole, tetrakis(triphenylphosphine)palladium and cuprous iodide are added, and nitrogen is switched multiple times in a closed environment; then, under nitrogen protection, the mixture is stirred at 90-100° C. in the dark for a certain period of time to obtain a crude product; the crude product is filtered, and the obtained product is washed several times with chloroform, distilled water and acetone in turn; then, Soxhlet extraction is performed with acetone; and after drying, a benzothiadiazole-based conjugated microporous polymer-coated graphene heterojunction material CMP-rGO is obtained.

[0012] Preferably, the bromine-functionalized reduced graphene oxide rGBr, DMF, and triethylamine are calculated in a g / ml / m1 ratio of 0.1-0.5:72-144:6-12. More preferably, the 1,3,5-triethynylbenzene, 4,7-dibromo-2,1,3-benzothiadiazole, tetrakis(triphenylphosphine)palladium, and cuprous iodide are calculated in a molar ratio of 1:1.5:0.01:0.024, and the bromine-functionalized reduced graphene oxide rGBr and 3,5-triethynylbenzene are calculated in a g / mmo1 ratio of 0.1-0.5:1.8.

[0013] Preferably, the bromine-functionalized reduced graphene oxide rGBr and DMF are mixed by ultrasound.

[0014] Preferably, the drying refers to vacuum drying at 60°C.

[0015] Preferably, the Soxhlet extraction time is 36-48 hours.

[0016] The method for preparing a photoelectrochemical sensor using the above-mentioned benzothiadiazolyl-based conjugated microporous polymer-coated graphene heterojunction material comprises the following steps: ultrasonically dispersing the benzothiadiazolyl-based conjugated microporous polymer-coated graphene heterojunction material CMP-rGO in N,N-dimethylformamide to form a dispersion; pipetting and applying the dispersion droplets to the conductive surface of the ITO electrode to prepare a CMP-rGO modified electrode CMP-rGO / ITO, and drying it at room temperature for use.

[0017] Preferably, the concentration of the benzothiadiazolyl-based conjugated microporous polymer-coated graphene heterojunction material dispersed in N,N-dimethylformamide is 2 mg / mL.

[0018] The method for detecting levodopa using the photoelectrochemical sensor prepared by the above method comprises the following steps:

[0019] (1) Establishing a linear relationship: Prepare L-dopa standard solutions of different concentrations; Use phosphate buffer solution as electrolyte, CMP-rGO modified electrode CMP-rGO / ITO as working electrode, calomel electrode as reference electrode, and platinum electrode as auxiliary electrode to form a three-electrode system; Add L-dopa standard solution to the electrolyte, and use chronoamperometry to detect L-dopa standard solutions of different concentrations, so as to obtain a linear relationship between photocurrent and the logarithm of L-dopa concentration;

[0020] (2) Detection: In a phosphate buffer solution, the concentration of L-DOPA in the sample to be tested is detected by the standard addition method, and the L-DOPA content in the sample is determined based on the linear relationship between the photocurrent and the concentration obtained in step (1).

[0021] Preferably, the concentration of the phosphate buffer solution used in steps (1) and (2) is 0.2 mol / L and the pH value is 6.0.

[0022] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0023] 1. The present invention prepares a new type of benzothiadiazolyl-based conjugated microporous polymer-coated graphene heterojunction material (CMP-rGO), and uses it to construct a photoelectrochemical sensor to detect levodopa, which belongs to the technical field of levodopa detection. The present invention uses a drop coating method to drop CMP-rGO onto an indium tin oxide (ITO) electrode to prepare a CMP-rGO modified electrode, and constructs a three-electrode system with a platinum electrode and a calomel electrode, and uses a chronoamperometry method to detect levodopa. The results show that within the range of 0.005 to 40 μmol / L, the photocurrent of levodopa and the logarithm of the levodopa concentration have two good linear relationships, with correlation coefficients of 0.9974 and 0.9920, respectively, and a detection limit of 0.0027 μmol / L. The determination method of the present invention provides a new idea for the detection of levodopa and broadens the application field of conjugated microporous polymers. The detection method provided by the present invention is simple, fast, highly sensitive, and has good stability.

[0024] 2. The method of the present invention is used to prepare CMP-rGO, and the synthesis method is simple and easy to synthesize. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Scanning electron microscopy image of CMP-rGO;

[0026] Figure 2 Transmission electron microscopy image of CMP-rGO;

[0027] Figure 3 FT-IR images of CMP-rGO and 1,3,5-triethynylbenzene;

[0028] Figure 4 Solid-state NMR image of CMP-rGO;

[0029] Figure 5 Photocurrent diagram of different concentrations of L-dopa; the concentration of L-dopa is 5×10 -9 ,1.25×10 -8 , 2.5×10 -8 ,1.0×10 -7 ,3.75×10 -7 ,1.5×10 -6 ,4×10 -6 ,5×10 -6 ,7.5×10 -6 ,1×10 -5 ,1.5×10 -5 ,3×10 -5 ,4×10 -5 mol / L.

[0030] Figure 6Standard curve of the L-DOPA photocurrent versus the logarithm of the L-DOPA concentration. DETAILED DESCRIPTION

[0031] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. 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.

[0032] The present invention provides a benzothiadiazolyl-based conjugated microporous polymer-coated graphene heterojunction material, the general structural formula of which is:

[0033]

[0034] 1. Preparation Example of CMP-rGO

[0035] The preparation route of benzothiadiazolyl-based conjugated microporous polymer-coated graphene heterojunction material CMP is as follows:

[0036]

[0037] Graphene oxide and bromine-functionalized reduced graphene oxide can be purchased through commercial channels or synthesized in the laboratory. The method for synthesizing relevant raw materials in the laboratory can refer to the following method.

[0038] (1) Synthesis of GO

[0039] Accurately weigh 1.0010g of graphite powder and 0.5010g of sodium nitrate, stir in 25ml 98% H2SO4 in an ice bath for 2 hours to obtain a mixed solution. Weigh 3.0069g of potassium permanganate, add 0.1g of each batch in batches and add the above solution once every 5 minutes, while keeping the temperature below 20°C. Then warm the mixed solution to 35°C and stir at 35°C for 2 hours, and dilute the resulting solution by adding 45ml of distilled water under vigorous stirring. Raise the temperature to 98°C, react for 15 minutes, and then cool naturally. Pour the above solution into a mixed solution of 10ml 30% hydrogen peroxide and 150ml distilled water, remove excess potassium permanganate, and the solution appears bright yellow. Pickle three times with 5% hydrochloric acid, wash with distilled water until neutral, and freeze-dry for 48 hours to obtain graphene oxide (GO).

[0040] (2) Synthesis of RGO

[0041] 0.9611 g of GO was accurately weighed and added to 300 ml of 1 wt% sodium dodecyl sulfate (SDS) solution. The solution was gently stirred for 1 hour, and then the solution was ultrasonicated for 10 minutes. The solution was then centrifuged and the precipitate was transferred to a 500 ml round-bottom flask. 0.5 ml of NH4OH and 0.5 ml of N2H4:H2O were added. The reactants were then heated to 95°C for 1 hour (without stirring), and the product was cooled to room temperature after the reaction was completed.

[0042] (3) Synthesis of diazonium salt

[0043] Take 4-bromoaniline as the raw material, accurately weigh 4.8186g (0.02801mol) 4-bromoaniline, dissolve it in 200ml distilled water, add the minimum amount of concentrated hydrochloric acid to dissolve it, then put the beaker in a salt ice bath to keep the solution at 0℃, add 2.0872g sodium nitrite (0.03025mmol, sodium nitrite is dissolved in the minimum amount of water beforehand) and 24ml 20% hydrochloric acid dropwise under stirring, and keep the solution at 0℃ and stir for 45 minutes. Due to the formation of diazonium salt, the color of the solution changes from colorless to yellow.

[0044] (4) RGBr synthesis

[0045] Add acetone that does not cover the precipitate to the RGO cooled to room temperature, stir rapidly to form an RGO dispersion, put it in a salt ice bath for precooling, and add the prepared diazonium salt solution to the rapidly stirred RGO dispersion with a pipette after the temperature drops below 3°C. The reaction mixture is kept at 0°C in the ice bath and stirred for 2 hours. After that, remove the ice bath and stir the reaction at room temperature for 6 hours. The solution is dark green. After the reaction is completed, pour the mixture into 100 ml of acetone, let it stand for half an hour, filter it, and filter and wash it three times with distilled water, acetone, and DMF respectively. The solid is vacuum dried at room temperature for 24 hours to obtain RGBr.

[0046] Example 1 Preparation of CMP-rGO

[0047] The preparation method of a benzothiadiazolyl-based conjugated microporous polymer-coated graphene heterojunction material comprises the following steps:

[0048] 0.1000g of bromine-functionalized reduced graphene oxide (rGBr) and 100mL of dry DMF were added to a round-bottom flask and ultrasonicated for 20 minutes; then, 8mL of triethylamine was added, nitrogen was switched three times in a closed environment, and the reactants were deoxygenated for 15 minutes under nitrogen protection; then 0.2722g of 1,3,5-triethynylbenzene, 0.8005g of 4,7-dibromo-2,1,3-benzothiadiazole, 0.0210g of tetrakis(triphenylphosphine)palladium and 0.0084g of cuprous iodide were added, and nitrogen was switched three times in a closed environment; then, under nitrogen protection, stirred at 95°C in the dark for 72 hours to obtain a crude product; the product was filtered, and the obtained product was washed several times with chloroform, distilled water, and acetone in turn. Subsequently, Soxhlet extraction was performed with acetone for 36 hours, and dried in a vacuum oven at 60°C for 10 hours to obtain CMP-rGO.

[0049] Example 2 Preparation of CMP-rGO

[0050] The preparation method of a benzothiadiazolyl-based conjugated microporous polymer-coated graphene heterojunction material comprises the following steps:

[0051] 0.3000g of bromine-functionalized reduced graphene oxide (rGBr) and 72mL of dry DMF were added to a round-bottom flask and ultrasonicated for 20 minutes; then, 6mL of triethylamine was added, nitrogen was switched three times in a closed environment, and the reactants were deoxygenated under nitrogen protection for 15 minutes; then 0.2722g of 1,3,5-triethynylbenzene, 0.8005g of 4,7-dibromo-2,1,3-benzothiadiazole, 0.0210g of tetrakis(triphenylphosphine)palladium and 0.0084g of cuprous iodide were added, and nitrogen was switched three times in a closed environment; then, under nitrogen protection, stirred at 95°C in the dark for 72 hours to obtain a crude product; the product was filtered, and the obtained product was washed several times with chloroform, distilled water, and acetone in turn. Subsequently, Soxhlet extraction was performed with acetone for 42 hours, and dried in a vacuum oven at 60°C for 12 hours to obtain CMP-rGO.

[0052] Example 3 Preparation of CMP-rGO

[0053] The preparation method of a benzothiadiazolyl-based conjugated microporous polymer-coated graphene heterojunction material comprises the following steps:

[0054] 0.5000g of bromine-functionalized reduced graphene oxide (rGBr) and 144mL of dry DMF were added to a round-bottom flask and ultrasonicated for 30 minutes; then, 12mL of triethylamine was added, nitrogen was switched three times in a closed environment, and the reactants were deoxygenated under nitrogen protection for 15 minutes; then 0.2722g of 1,3,5-triethynylbenzene, 0.8005g of 4,7-dibromo-2,1,3-benzothiadiazole, 0.0210g of tetrakis(triphenylphosphine)palladium and 0.0084g of cuprous iodide were added, and nitrogen was switched three times in a closed environment; then, under nitrogen protection, stirred at 100℃ in the dark for 72 hours to obtain a crude product; the product was filtered, and the obtained product was washed several times with chloroform, distilled water and acetone in turn. Subsequently, Soxhlet extraction was performed with acetone for 48 hours, and dried in a vacuum oven at 60℃ for 12 hours to obtain CMP-rGO.

[0055] 2. Characterization of CMP-rGO

[0056] The morphology of the synthesized CMP-rGO was characterized by scanning electron microscopy (SEM). Figure 1 As shown in the SEM image, it can be seen that CMP-rGO is a stacked sheet structure with a rough surface. Transmission electron microscopy further proves that the synthesized CMP-rGO is a sheet structure, as shown in Figure 2 The structures of CMP-rGO and 1,3,5-triethynylbenzene were characterized by spectrum 65 Fourier transform infrared spectrometer, see Figure 3 As shown. 1382-1626cm -1 The absorption peak of CMP-rGO is the skeleton vibration of the benzene ring. Compared with 1,3,5-triethynylbenzene, the absorption peak of CMP-rGO is 1382-1626cm -1 The absorption peak at 3472cm -1 The absorption peak at 2200 cm-1 is the stretching vibration of -OH, which may be due to the moisture absorption of the sample. -1 There is a weak absorption peak at , which is attributed to C≡C. The formation of the expected bond indicates that the coupling reaction is successful. In addition, CMP-rGO is characterized by solid-state NMR. Figure 4 There are two low-intensity peaks at 88.34 and 95.36 ppm, which are attributed to C≡C; the peaks at 116.68-154.79 ppm are attributed to the carbon atoms on the benzene ring.

[0057] 3. Preparation of Photoelectrochemical Sensor

[0058] Example 4 Preparation of Photoelectrochemical Sensor

[0059] The method for preparing a photoelectrochemical sensor using the benzothiadiazolyl-based conjugated microporous polymer-coated graphene heterojunction material of the present invention comprises the following steps: ultrasonically dispersing 2 mg of the benzothiadiazolyl-based conjugated microporous polymer-coated graphene heterojunction material in 1 mL of N,N-dimethylformamide to form a 2 mg / mL CMP-rGO dispersion; pipetting 15 μL of the dispersion droplets onto the conductive surface of an ITO electrode to prepare a CMP-rGO modified electrode CMP-rGO / ITO, and drying at room temperature for later use.

[0060] 4. Levodopa detection method

[0061] Example 5 Detection method of levodopa

[0062] The photoelectrochemical sensor prepared in Example 4 is used to detect levodopa, comprising the following steps:

[0063] (1) Establishing a linear relationship: Prepare L-DOPA standard solutions of different concentrations, with a specific concentration of 5 × 10 -9 ,1.25×10 -8 , 2.5×10 -8 ,1.0×10 -7 ,3.75×10 -7 ,1.5×10 -6 ,4×10 -6 ,5×10 -6 ,7.5×10 -6 ,1×10 -5 ,1.5×10 -5 ,3×10 -5 ,4×10 -5 mol / L. A three-electrode system was constructed with CMP-rGO / ITO as the working electrode, calomel electrode as the reference electrode, and platinum electrode as the auxiliary electrode; 0.2 mol / L, pH 6.0 PBS buffer solution was used as the electrolyte, and levodopa standard solution was added to the electrolyte. The chronoamperometry was used to detect different concentrations of levodopa standard solution. The relationship between the logarithm of levodopa and the photocurrent is shown in Figure 6 As shown in Figure 2, the photocurrent increases with the increase of L-dopa concentration. The photocurrent of L-dopa and the logarithm of L-dopa concentration show two good linear relationships. The linear equations are I1=0.1194lgC+0.5788(R 2 =0.9974), I2=0.5535lgC+0.2898(R 2 =0.9920), and the detection limit was 0.0027 μmol / L.

[0064] (2) Detection: In a phosphate buffer solution, the concentration of levodopa in the sample to be tested is detected by the standard addition method, and the content of levodopa in the sample is determined based on the linear relationship between the photocurrent and the concentration obtained in step (1). The sample can be a human serum or urine sample.

[0065] 5. Reproducibility, stability, and selectivity

[0066] The reproducibility of the CMP-rGO / ITO sensor was further investigated. Under the same experimental conditions, 5 CMP-rGO / ITO were modified and the same concentration of L-DOPA was detected. The relative standard deviation of the peak current value was 1.55%, indicating that the sensor has good reproducibility. At the same time, a CMP-rGO / ITO was prepared and stored at room temperature. After 10 days, it was measured under the same conditions. The peak current values ​​were 98.22% of the first detection current, and the relative standard deviation was 0.92%, indicating that the sensor has good stability.

[0067] The above description is a detailed description of the preferred feasible embodiments of the present invention, but the embodiments are not intended to limit the scope of the patent application of the present invention. All equivalent changes or modified changes completed under the technical spirit suggested by the present invention should fall within the patent scope covered by the present invention.

Claims

1. A benzothiadiazolyl-based conjugated microporous polymer-coated graphene heterojunction material, characterized in that: The general structural formula of the benzothiadiazolyl-based conjugated microporous polymer-coated graphene heterojunction material CMP-rGO is:

2. The method for preparing the benzothiadiazolyl-based conjugated microporous polymer-coated graphene heterojunction material according to claim 1, characterized in that: The following steps are involved: Add bromine-functionalized reduced graphene oxide rGBr and dry DMF into a reaction container and mix them, then add triethylamine, switch nitrogen multiple times in a closed environment, and deoxygenate the reactants under nitrogen protection; then add 1,3,5-triethynylbenzene, 4,7-dibromo-2,1,3-benzothiadiazole, tetrakis(triphenylphosphine)palladium and cuprous iodide, switch nitrogen multiple times in a closed environment; then stir at 90-100° C. in the dark for a certain period of time under nitrogen protection to obtain a crude product; filter the crude product, and wash the obtained product with chloroform, distilled water and acetone for several times in sequence; Subsequently, Soxhlet extraction was performed with acetone; after drying, the benzothiadiazolyl-based conjugated microporous polymer-coated graphene heterojunction material CMP-rGO was obtained.

3. The preparation method according to claim 2, characterized in that: The bromine-functionalized reduced graphene oxide rGBr, DMF, and triethylamine are in a ratio of 0.1-0.5:72-144:6-12 in terms of g / ml / m1.

4. The preparation method according to claim 3, characterized in that: The molar ratio of 1,3,5-triethynylbenzene, 4,7-dibromo-2,1,3-benzothiadiazole, tetrakis(triphenylphosphine)palladium and cuprous iodide is 1:1.5:0.01:0.024, and the g / mmo1 ratio of the bromine-functionalized reduced graphene oxide rGBr to 3,5-triethynylbenzene is 0.1-0.5:1.

8.

5. The preparation method according to claim 2, characterized in that: The Soxhlet extraction time is 36-48 hours.

6. A photoelectrochemical sensor, characterized in that: The method is obtained by modifying the benzothiadiazole-based conjugated microporous polymer-coated graphene heterojunction material described in claim 1 on the conductive surface of an ITO electrode.

7. A method for preparing a photoelectrochemical sensor using the benzothiadiazolyl-based conjugated microporous polymer-coated graphene heterojunction material according to claim 1, characterized in that: The following steps are involved: The benzothiadiazolyl-based conjugated microporous polymer-coated graphene heterojunction material CMP-rGO is ultrasonically dispersed in N,N-dimethylformamide to form a dispersion; the dispersion is dropped onto the conductive surface of the ITO electrode to prepare a CMP-rGO modified electrode CMP-rGO / ITO, which is dried at room temperature for use.

8. The method according to claim 7, characterized in that: The concentration of the benzothiadiazolyl-based conjugated microporous polymer-coated graphene heterojunction material dispersed in N,N-dimethylformamide is 2 mg / mL.

9. A method for detecting levodopa using the photoelectrochemical sensor prepared by the method according to claim 7, characterized in that: The following steps are involved: (1) Establishing a linear relationship: Prepare L-dopa standard solutions of different concentrations; Use phosphate buffer solution as electrolyte, CMP-rGO modified electrode CMP-rGO / ITO as working electrode, calomel electrode as reference electrode, and platinum electrode as auxiliary electrode to form a three-electrode system; Add L-dopa standard solution to the electrolyte, and use chronoamperometry to detect L-dopa standard solutions of different concentrations, so as to obtain a linear relationship between photocurrent and the logarithm of L-dopa concentration; (2) Detection: In a phosphate buffer solution, the concentration of L-DOPA in the sample to be tested is detected by the standard addition method, and the L-DOPA content in the sample is determined based on the linear relationship between the photocurrent and the concentration obtained in step (1).

10. The method according to claim 9, characterized in that: The concentration of the phosphate buffer solution used in steps (1) and (2) is 0.2 mol / L, and the pH value is 6.0.

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