An electrochemical method and system for the detection of capsaicin

Abstract

The present application relates to a kind of electrochemical detection method and system for capsaicin, detection method includes: providing three electrode system;Configuration electrolyte solution and dissolve capsaicin standard sample or sample to be measured;Electrochemical detection is carried out using three electrode system to obtain oxidation peak current signal;Based on the corresponding relationship between oxidation peak current and capsaicin concentration determines the capsaicin content in sample to be measured.Detection system includes three electrode system, battery module, power module, MCU module, electrochemical detection circuit, signal conditioning circuit and communication module, can realize the rapid, sensitive detection of capsaicin.The present application improves the detection sensitivity by carbon nanocomposite modified carbon cloth electrode, combined with portable hardware circuit design, get rid of the dependence on large instrument, applicable to the on-site rapid detection of capsaicin in food industry, provide scientific, objective technical means for hot degree quantification.

Description

Technical Field

[0001] This invention relates to the field of capsaicin detection technology, and specifically to an electrochemical detection method and system for capsaicin. Background Technology

[0002] Chili peppers, as an important economic crop, have wide applications in food processing, cooking, seasoning, and medicine. Capsaicin, the most unique component, is the main active substance responsible for spiciness, and its content directly determines the intensity of the heat. Besides affecting flavor, capsaicin has also been shown to have potential applications in anti-tumor activity, regulating gastrointestinal function, and weight control.

[0003] With the rapid development of the market for casual braised and spicy foods, the lack of a unified standard for spiciness labeling has become increasingly prominent. Currently, most products still use highly subjective descriptions such as "mild," "medium," and "extra spicy," which not only fails to guarantee a consistent consumer experience but also easily leads to commercial disputes. Establishing a scientific, objective, and quantifiable method for evaluating spiciness has become an urgent need for the development of the food industry.

[0004] Currently, the quantitative detection of capsaicin mainly relies on large analytical instruments such as liquid chromatography, gas chromatography, mass spectrometry, and nuclear magnetic resonance. Although these techniques offer high accuracy and sensitivity, the equipment is expensive, the operation is complex, the detection cycle is long, and the requirements for the environment and personnel are high, making them unsuitable for routine use by food companies, especially small and medium-sized enterprises. On the other hand, some existing rapid detection methods have significant shortcomings in terms of sensitivity, selectivity, and result stability, making it difficult to meet the needs of on-site testing.

[0005] Electrochemical sensing technology, due to its advantages such as simple equipment, low cost, fast detection speed, high sensitivity, and ease of miniaturization, is gradually becoming a potential alternative for capsaicin detection. Carbon-based nanomaterials, especially graphene and carbon nanotubes, have been widely studied for sensor construction due to their good conductivity and large specific surface area. However, traditional carbon-based materials still have limitations in terms of dispersibility and electrocatalytic activity, affecting their performance in capsaicin detection.

[0006] Existing electrochemical detection schemes based on carbon nanomaterials still have some shortcomings. First, they are highly dependent on the detection equipment, typically employing large electrochemical workstations such as the CHI660E. These devices are bulky, heavy, and reliant on a laboratory environment, hindering portability and rapid on-site detection, thus failing to meet the needs of on-site food testing, portable applications, and industrialization. Second, the detection current is relatively low. Glassy carbon electrodes are commonly used as working electrodes. Due to their small specific surface area and limited electrochemical active sites, the response current generated during detection is weak, typically only in the microampere range. This microampere-level current also increases the difficulty of designing subsequent hardware processing circuits. Furthermore, glassy carbon electrodes often require complex pretreatment processes during detection, adding inconvenience to experimental operations.

[0007] In summary, existing technologies are insufficient to meet the detection requirements of capsaicin, which demand high sensitivity, rapid response, and portability. Therefore, developing a high-performance electrochemical sensing system based on modified carbon materials, combined with miniaturized detection circuits, to construct a capsaicin detection method and system that combines high sensitivity with field applicability is an urgent problem to be solved. This has significant practical implications for promoting quality standardization in the food industry and improving detection efficiency. Summary of the Invention

[0008] In view of the technical problems existing in the prior art, the first objective of the present invention is to provide an electrochemical detection method for capsaicin, which achieves highly sensitive and rapid detection of capsaicin.

[0009] The second objective of this invention is to provide an electrochemical detection system for capsaicin that is miniaturized, low-cost, and easy to apply and promote.

[0010] To achieve the above objectives, the present invention adopts the following technical solution:

[0011] An electrochemical detection method for capsaicin includes the following steps:

[0012] (1) A three-electrode system is provided, the three-electrode system including a working electrode, an auxiliary electrode and a reference electrode; wherein the working electrode is a carbon cloth electrode with a surface modified with carbon nanocomposite material, the carbon nanocomposite material including graphene derivatives, carbon nanotube derivatives and cyclodextrin;

[0013] (2) Prepare an electrolyte solution by dissolving the standard sample or the sample to be tested containing capsaicin in the electrolyte solution;

[0014] (3) The solution from step (2) is electrochemically detected using the three-electrode system to obtain the oxidation peak current signal;

[0015] (4) Based on the correspondence between the oxidation peak current signal and the capsaicin concentration, the capsaicin content in the sample to be tested is determined.

[0016] According to one example, the graphene derivative is sulfonated reduced graphene oxide, the carbon nanotube derivative is carboxylated multi-walled carbon nanotubes, and the cyclodextrin is β-cyclodextrin.

[0017] According to one example, the method for preparing the carbon nanocomposite material includes the following steps:

[0018] The graphene derivative, the carbon nanotube derivative, and the cyclodextrin were dispersed in water at a mass ratio of (1-2):(0.5-1):(1-2), and the dispersion was obtained by ultrasonic treatment. Preferably, sulfonated reduced graphene oxide, carboxylated multi-walled carbon nanotubes, and β-cyclodextrin were dispersed in water at a mass ratio of 2:1:2, and the dispersion was obtained by ultrasonic treatment for 30 min.

[0019] The composite material of sulfonated reduced graphene oxide (SRGO) and carboxylated multi-walled carbon nanotubes (CNT-COOH) was dispersed using β-cyclodextrin (β-CD). The carbon nanocomposite material exhibits the following characteristics: sulfonated reduced graphene oxide (SRGO), through sulfonation modification, introduces sulfonic acid groups onto the graphene surface, improving its hydrophilicity and dispersibility, preventing material aggregation, and providing additional charge transport channels, thus enhancing the material's conductivity and electrochemical activity. The material itself possesses a large specific surface area, providing ample space for subsequent carbon nanotube loading, which is conducive to forming a stable composite structure. Carboxylation modification of the CNT-COOH surface enhances the dispersibility of carbon nanotubes and their interfacial bonding with graphene. The carboxyl groups provide potential binding sites, forming non-covalent interactions with β-cyclodextrin and the target molecule (capsaicin), which is beneficial for improving sensor selectivity. β-Cyclodextrin (β-CD) stabilizes the SRGO / CNT-COOH composite material through inclusion complexation, preventing agglomeration, improving material dispersibility, and enabling the two materials to be mixed and dispersed uniformly.

[0020] According to one example, the method for preparing the working electrode includes the following steps:

[0021] After cleaning and surface activation treatment of the carbon cloth, a dispersion of the carbon nanocomposite material is coated onto the surface of the carbon cloth, and after drying, a modification layer is formed. The carbon cloth electrode possesses a large specific surface area and abundant active sites, enabling it to load more modification materials, thereby significantly enhancing catalytic efficiency and response current, and improving the sensitivity and stability of capsaicin detection. Simultaneously, the carbon cloth electrode exhibits good flexibility and low cost, making it suitable for widespread application.

[0022] According to one example, the electrolyte solution is an acidic mixed solution comprising 0.005-0.02M hydrochloric acid and 0.05-0.2M soluble chloride, with a pH of 1-3. The soluble chloride is selected from potassium chloride (KCl) or sodium chloride (NaCl). Preferably, the electrolyte solution is 0.01 mol·L⁻¹ HCl and 0.1 mol·L⁻¹ KCl, with a pH of 2.

[0023] According to one example, in step (3), cyclic voltammetry is used for detection, with a scanning potential range of -0.8V to +1.0V and a scanning rate of 10-100mV / s.

[0024] According to one example, the correspondence in step (4) is a linear equation with a linear correlation coefficient R²≥0.99 in the concentration range of 1~30μM and a linear correlation coefficient R²≥0.99 in the concentration range of 30~340μM. The detection limit is 1.67μM and S / N=3.

[0025] According to one example, in step (2), the method for preparing the standard sample containing capsaicin is as follows: the capsaicin solid is dissolved in ethanol solvent to prepare a standard capsaicin stock solution with a concentration of 50 mM; in subsequent detection, the capsaicin standard detection solution of different concentrations can be prepared by diluting the stock solution into the electrolyte solution in proportion; the sample to be tested containing capsaicin needs to be dissolved or extracted in ethanol and then diluted into the electrolyte solution for detection.

[0026] An electrochemical detection system for capsaicin, used to implement the above-mentioned detection method, comprising:

[0027] A three-electrode system, which includes a working electrode, an auxiliary electrode, and a reference electrode;

[0028] The battery module is used to provide initial electrical energy to the system;

[0029] A power module, which is connected to the battery module, is used to convert and regulate the electrical energy output by the battery module in order to provide the voltage required by the system.

[0030] The MCU module is used to generate electrochemical scan voltages and acquire processed signals.

[0031] An electrochemical detection circuit, which is connected to the MCU module and the three-electrode system respectively, is used to apply the scanning voltage generated by the MCU module to the three-electrode system and acquire the current signal generated by the reaction;

[0032] The signal conditioning circuit has its input terminal connected to the electrochemical detection circuit and its output terminal connected to the MCU module, and is used to convert, amplify and filter the current signal;

[0033] A communication module, which is connected to the MCU module, is used to transmit the data collected by the MCU module to the host computer.

[0034] According to one example, the power module includes a positive voltage generation unit, a negative voltage generation unit, a working voltage generation unit, and a high-precision reference voltage generation unit, used to provide matching voltages for each module of the system; the battery module is a rechargeable battery that provides power to the system.

[0035] According to one example, the signal conditioning circuit includes a transimpedance conversion module, a differential amplifier module, and a filter module; the transimpedance conversion module is used to convert a microampere-level reactive current into a voltage signal; the differential amplifier module is used to amplify the converted voltage signal; the filter module is used to filter the amplified voltage signal to remove mid- and high-frequency interference; and the communication module supports at least one wired or wireless data transmission method.

[0036] The present invention has the following advantages:

[0037] The SRGO / CNT-COOH / β-CD composite material provided by this invention reduces graphene oxide to reduced graphene oxide via sulfonation, resulting in higher conductivity and hydrophilicity. Subsequently, utilizing the excellent catalytic synergy between reduced graphene oxide and carboxylated multi-walled carbon nanotubes, an SRGO / CNT-COOH carbon nanomaterial catalyst was prepared. Since both have the same electrode polarity, β-cyclodextrin was added as a dispersant. Its ring structure, with a hydrophobic interior and a hydrophilic exterior, effectively improves the dispersibility and adhesion between the two. After being fabricated into an electrochemical sensor for capsaicin detection, the SRGO sheets and CNT-COOH tubular structures intertwine to form a three-dimensional conductive network, significantly increasing the electrochemical active surface area of ​​the electrode and effectively exposing more capsaicin molecule recognition and catalytic sites. Simultaneously, the synergistic effect between SRGO and CNT-COOH accelerates the electron transfer rate, further enhancing the electrocatalytic performance of the electrode. The introduction of β-cyclodextrin, through its unique structure of hydrophobic inner cavity and hydrophilic outer surface, not only improves the dispersibility and stability of the composite material, but also promotes the efficient enrichment and fixation of capsaicin molecules, thereby enabling the modified electrode to exhibit excellent performance in terms of detection sensitivity, selectivity and response speed.

[0038] The sheet-like structure of SRGO and the tubular structure of CNT-COOH form a three-dimensional conductive network. The hydrophobic lumen of β-cyclodextrin specifically binds capsaicin molecules through host-guest interactions. The three work synergistically to increase the electrochemical active surface area of ​​the electrode to 8.27 cm² (compared to only 1.55 cm² for the blank electrode) and increase the electron transfer rate by more than 3 times (according to EIS test, Rct decreased from 550.7 Ω to 5.7 Ω).

[0039] The electrochemical sensor for detecting capsaicin provided by this invention has a linear detection range of 1-340 μM for capsaicin, a low detection limit (1.67 μM), and good selectivity and anti-interference ability, thus achieving sensitive detection of capsaicin.

[0040] The detection system provided by this invention has a small size, specifically 8cm*10cm, which has a significant portability advantage compared to the traditional CHI660E electrochemical workstation. Attached Figure Description

[0041] Figure 1 This is a photograph of the SRGO / CNT-COOH / β-CD composite material dispersion prepared in Example 1 of the present invention.

[0042] Figure 2 These are scanning electron microscope (SEM) images of the relevant materials and electrodes in Embodiment 1 of the present invention, wherein, Figure 2 a is a SEM image of graphene oxide (GO) powder; Figure 2 b is a SEM image of sulfonated reduced graphene oxide (SRGO) powder; Figure 2 c is a SEM image of carboxylated multi-walled carbon nanotube (CNT-COOH) powder; Figure 2 d is the SEM image of blank carbon cloth (CC); Figure 2 e is a SEM image of a carbon cloth electrode modified with SRGO / CNT-COOH composite material; Figure 2 f is a SEM image of a carbon cloth electrode modified with SRGO / CNT-COOH / β-CD composite material.

[0043] Figure 3 These are diagrams showing the structure and characterization results of the relevant materials in Embodiment 1 of the present invention, wherein... Figure 3 a shows the X-ray diffraction (XRD) patterns of SRGO / CNT-COOH, CNT-COOH, SRGO, and GO; Figure 3 b is the full X-ray photoelectron spectroscopy (XPS) spectrum of SRGO and GO; Figure 3 c is the high-resolution XPS image of element C in GO; Figure 3 d is the high-resolution XPS image of C element in SRGO; Figure 3e is the high-resolution XPS image of element O in SRGO; Figure 3 f is the high-resolution XPS image of the S element of SRGO.

[0044] Figure 4 These are cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) results of different electrodes prepared in Example 1 and Comparative Examples 1-4 of this invention in potassium ferricyanide solution. Figure 4 a represents the cyclic voltammetry curves of the blank carbon cloth electrode (Blank CC), graphene oxide carbon cloth electrode (GO CC), sulfonated reduced graphene oxide carbon cloth electrode (SRGO CC), SRGO / CNT-COOH carbon cloth electrode, and SRGO / CNT-COOH / β-CD carbon cloth electrode. Figure 4 b represents the electrochemical impedance spectroscopy curves of the five electrodes under the same conditions; Figure 4 c represents the SRGO / CNT-COOH / β-CD CC electrode in a solution containing 5.0 mM [Fe(CN)6]³⁻ / 4 ⁻ Cyclic voltammetry curves in solutions containing 0.1 M KCl at different scan rates from 10 mV / s to 100 mV / s; Figure 4 d is a graph showing the linear relationship between the peak current and the square root of the scan rate for the SRGO / CNT-COOH / β-CD CC electrode at different scan rates.

[0045] Figure 5 These are the electrochemical performance test results of the electrodes prepared in Example 1 and Comparative Examples 1-4 of this invention in capsaicin detection, wherein... Figure 5 a shows the cyclic voltammetry curves of the blank carbon cloth electrode (Blank CC), graphene oxide carbon cloth electrode (GO CC), sulfonated reduced graphene oxide carbon cloth electrode (SRGO CC), SRGO / CNT-COOH carbon cloth electrode, and SRGO / CNT-COOH / β-CD carbon cloth electrode in 100 μM capsaicin solution (0.01 M HCl + 0.1 M KCl as electrolyte); Figure 5 b shows the cyclic voltammetry curves of the SRGO / CNT-COOH / β-CD CC electrode in capsaicin solution at different scan rates; Figure 5 c represents the cyclic voltammetry curves of the SRGO / CNT-COOH / β-CD CC electrode in 0.01 M HCl + 0.1 M KCl electrolyte solution with different concentrations of capsaicin (0 ~ 340 μM). Figure 5 d is the linear relationship between its peak current and capsaicin concentration; Figure 5e represents the anti-interference performance test results of the SRGO / CNT-COOH / β-CDCC electrode when detecting 50 μM capsaicin. The current is the peak current obtained by differential pulse voltammetry (DPV), n=3. The interfering substances added in sequence are: a, CaCl2 (500 μM); b, KCl (500 μM); c, KNO3 (500 μM); d, NaOH (500 μM); e, NaCl (500 μM); f, glucose (500 μM); g, sodium citrate (500 μM); h, NaNO2 (500 μM). Figure 5 f represents the response current results of six sets of electrodes prepared by the same method in capsaicin solution obtained by differential pulse voltammetry (DPV).

[0046] Figure 6 This is a flowchart of the electrochemical detection system for capsaicin according to the present invention.

[0047] Among them, 1 is the battery module, 2 is the power supply module, 3 is the MCU module, 4 is the electrochemical detection circuit, 5 is the signal conditioning circuit, and 6 is the communication module. Detailed Implementation

[0048] The present invention will be further described in detail below with reference to embodiments, but the embodiments of the present invention are not limited thereto. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in this technical field. The experimental methods in the following embodiments that do not specify specific experimental conditions are generally performed according to conventional experimental conditions. Unless otherwise specified, the reagents and raw materials used in the present invention are all commercially available. Among them, phenylhydrazine-4-sulfonic acid (PHPA), synthetic capsaicin, potassium ferricyanide, potassium ferrocyanide, β-cyclodextrin, sodium nitrite (NaNO2) and 0.1M phosphate buffer solution (PBS, pH 7.2–7.4) were purchased from Maclean's, graphene oxide (GO) powder was purchased from Suzhou Carbon-rich Graphene Technology Co., Ltd., and carboxylated multi-walled carbon nanotubes (MWCNT-COOH) were purchased from Xianfeng Nanotechnology Co., Ltd. Potassium chloride (KCl), glucose, sodium chloride (NaCl), calcium chloride (CaCl2), sodium hydroxide (NaOH), sodium citrate, and anhydrous ethanol (EtOH, 99.7%) were purchased from Shanghai Guoyao Chemical Reagent Co., Ltd. Potassium nitrate (KNO3) and concentrated hydrochloric acid (HCl, 12 M) were purchased from Guangzhou Chemical Reagent Factory (Guangdong, China). Standard potassium hydroxide solution (KOH) was purchased from Yida Technology Co., Ltd. (Quanzhou, China). All reagents were of analytical grade. Carbon cloth (CC) was purchased from Carbon Energy Technology Co., Ltd. Ultrapure water with a resistivity of 18.2 MΩ·cm was used in all experiments.

[0049] Example 1

[0050] Preparation of carbon nanocomposites

[0051] First, 500 mg of graphene oxide (GO) was weighed and added to a polytetrafluoroethylene (PTFE) liner containing 25 ml of pure water, and ultrasonically dispersed for 5 min. Then, 250 mg of phenylhydrazine-4-sulfonic acid (PHPA) was added, and the mixture was stirred at 700 rpm magnetically for 20 min to ensure thorough mixing. Next, the 100 ml PTFE liner was sealed and placed in a stainless steel autoclave, heated to 140°C in an oven, and subjected to a hydrothermal reaction for 8 h. After the reactants cooled to room temperature, they were collected in batches using centrifuge tubes and washed five times alternately with anhydrous ethanol and ultrapure water at 7000 rpm for 15 min each time. The washing continued until the supernatant changed from pale yellow to transparent. The bottom precipitate was then removed and dried overnight in a 60°C oven. The precipitate was then ground using an agate mortar and pestle to obtain sulfonated reduced graphene oxide (SRGO) powder. 10 mg of sulfonated reduced graphene oxide (SRGO) powder was weighed and placed in a beaker containing 2.5 mL of pure water. The mixture was ultrasonically dispersed for 5 min to obtain a sulfonated reduced graphene oxide (SRGO) suspension. 10 mg of sulfonated reduced graphene oxide (SRGO) powder and β-cyclodextrin were weighed and placed in 10 mL glass sample vials. Then, 5 mg of carboxylated multi-walled carbon nanotubes (CNT-COOH) were added, followed by 2.5 mL of pure water. The mixture was ultrasonically treated for 30 min using an ultrasonic material disperser to obtain an SRGO / CNT-COOH / β-CD dispersion. In this material, tubular CNT-COOH structures are attached to the surface of sheet-like SRGO, such as... Figure 1 As shown, the composite material with added β-CD exhibits significant mixing uniformity and dispersion.

[0052] Preparation of three-electrode system

[0053] The SRGO / CNT-COOH / β-CD composite material was drop-coated and dispersed on the clean carbon cloth electrode surface. The specific operation was as follows: the purchased carbon cloth substrate was cut into 1×1cm pieces. 2 The standard-sized carbon cloth was ultrasonically cleaned at least three times (ten minutes each time) with alternating ethanol and deionized water until no floating impurities remained on the surface of the pure water. After drying, the cleaned carbon cloth was placed in a plasma cleaner (50W, 80s) to enhance surface hydrophilicity. The treated carbon cloth was then placed in an oven for 1 hour. Subsequently, 50 μL of a prepared SRGO / CNT-COOH / β-CD dispersion suspension was evenly drop-coated onto the surface of the carbon cloth (CC) using a pipette, and dried in an oven at 60°C for 12 hours to obtain the SRGO / CNT-COOH / β-CD CC electrode, which served as the working electrode of the three-electrode system.

[0054] The electrolyte solution consists of a mixed solution of 0.01 MHCl and 0.1 MCl at pH 2.

[0055] A three-electrode system was constructed using a platinum electrode as the auxiliary electrode and Ag / AgCl as the reference electrode.

[0056] Reference Figure 2 The image shows SEM images of GO, SRGO, CNT-COOH powder, SRGO / CNT-COOH carbon cloth electrode, and SRGO / CNT-COOH / β-CD carbon cloth electrode. (Refer to...) Figure 2 a,GO powder exhibits a typical folded layered structure, with flat, smooth layers and a relatively loose stacking. (Reference) Figure 2 b. SRGO powder appears as individual flakes, with large, curled lamellae and increased surface roughness. This reflects enhanced lamellar interactions after the removal of oxygen-containing functional groups during reduction, leading to spontaneous curling and localized aggregation. (Ref.) Figure 2 c. CNT-COOH powder exhibits a one-dimensional tubular morphology with uniform diameter and relatively long length, displaying an interwoven network structure. Carboxylation treatment retains the multi-walled carbon nanotube structure and enhances surface activity and hydrophilicity, which is beneficial for subsequent composite processes. (Reference) Figure 2 d and Figure 2 e. After drop-coating the material onto blank carbon cloth, it can be seen that, compared to the smooth blank carbon cloth, the introduction of SRGO / CNT-COOH material results in a uniform multi-scale composite film covering the surface of the carbon cloth. The layers are bridged by carbon nanotubes to form a three-dimensional porous structure, which significantly improves conductivity and specific surface area. (Refer to...) Figure 5 f, after further introduction of β-CD, the surface attachments became more compact and the surface roughness increased, indicating that β-CD can effectively enhance the dispersibility between the two.

[0057] Reference Figure 3a. This paper shows the crystal structure characteristics and changes revealed during the preparation process through XRD analysis, including XRD images of GO, SRGO, CNT-COOH, and SRGO / CNT-COOH. For pure GO powder, a strong diffraction peak can be seen at 2θ = 10.68°, corresponding to the (001) crystal plane of GO. According to Bragg's law, its interlayer spacing is 0.827 nm. This is because oxygen-containing functional groups and water molecules are inserted into the graphite interlayer during the oxidation process of GO, causing the graphite interlayer to expand and significantly increasing the interlayer spacing. At the same time, a weak diffraction peak can be seen at 42.3°, which corresponds to the (100) crystal plane of the graphite standard card PDF#41-1487. This peak originates from the order of the sp² carbon atom hexagonal lattice in the graphite plane, reflecting that the carbon skeleton still partially retains the in-plane atomic arrangement structure during the oxidation process. After sulfonation reduction, the original (001) plane diffraction peak completely disappeared, and a wider (002) plane diffraction peak appeared at 2θ=24.6° with an interlayer spacing of 0.362 nm, accompanied by a (100) peak at 43.1°. This indicates that the oxygen-containing groups were removed, the interlayer spacing shrank, and the graphite sheets re-stacking π–π. GO was successfully sulfonated and reduced to SRGO, which is consistent with the curled and wrinkled morphology observed in SEM. Carboxylated multi-walled carbon nanotubes exhibited a high-intensity diffraction peak at 2θ=24.6°, corresponding to the (002) crystal plane (PDF#75-1621). The smaller diffraction peaks at 42.4° and 44.2° correspond to the (100) and (101) crystal planes, respectively, indicating a high degree of graphitization of the tube walls. The XRD pattern of the obtained composite material SRGO / CNT-COOH shows the superposition of the characteristic peaks of the two materials, with diffraction peaks at 25.9° and 43.02°, and the intensity of the diffraction peaks is between that of SRGO and CNT-COOH. This may be attributed to the strain caused by the interface and the damage to the crystal structure caused by the ultrasonic dispersion process.

[0058] Figure 3 b shows the XPS full spectra of SRGO and GO. Distinct C1s and O1s peaks are observed in both GO and SRGO. However, a new S2p peak appears in the SRGO full spectrum. The introduction of sulfur indicates that GO has been sulfonated and reduced to SRGO, and sulfur has been introduced into the graphene framework. To more clearly analyze the chemical state of each functional group, peak fitting was performed on the fine spectra of the samples.

[0059] Reference Figure 3 c shows the C1s spectrum of GO. The peak at 284.64 eV is related to the sp2 carbon atom of graphite, representing a C=C bond. The peaks at 286.89 eV and 288.7 eV represent CO and C=O bonds, respectively. The high intensity of CO bonds is a typical characteristic of the abundance of oxygen-containing functional groups in GO.

[0060] Reference Figure 3 d. For the C1s spectrum of SRGO, the main peak representing the CC bond is still around 284.74 eV, and the other three peaks are at 285.56 eV, 287.69 eV, and 289.98 eV, respectively, representing the CS, CO, and C=O bonds. Compared to GO, the CO peak of SRGO is significantly weakened, indicating that most oxygen-containing functional groups have been successfully removed. The new CS peak signal at 285.56 eV also provides strong evidence for the introduction of sulfonic acid groups.

[0061] Reference Figure 3 e. In the O1s spectrum, SRGO shows a new peak of 531.6 eV, and the O1s peak shifts to a slightly higher binding energy. This is because the peak at this point is mainly contributed by newly generated S=O bonds, while still containing a small amount of C=O bond contributions. Since sulfur has a higher electronegativity than carbon, the binding energy shifts slightly upward.

[0062] Reference Figure 3 f, the S2p spectrum shows that the peak range of SRGO is between 164 eV and 171 eV, indicating the chemical state of sulfur. The S2p peak can be divided into S2p... 3 / 2 and S2p 1 / 2 Two spin orbital peaks, located at 167.4 eV and 168.58 eV respectively, represent the characteristic signal of sulfur existing in the form of sulfonate groups. The spin orbital spacing is 1.18 eV, with an intensity ratio of 2:1. Finally, the N1s fraction of the deconvolutioned N1s at 399.72 (-N=) and 401.47 (-N-) indicates that hydrazine containing 4-HBS induced the formation of hydrazine bonds during the reduction process. In contrast, no obvious N1s and S2p peaks were observed on GO. In summary, during the reduction process, the hydrazine moiety in the 4-HBS portion acted as a reducing agent, successfully reducing GO to rGO and grafting sulfonate groups onto the RGO sheet, producing SRGO.

[0063] Comparative Example 1

[0064] The GO / CC electrode was prepared using the same method as in Example 1, with the following differences:

[0065] The composite material contains only graphene oxide (GO) and does not contain SRGO, CNT-COOH and β-CD. Specifically, 10 mg of GO powder is weighed and added to 2.5 mL of pure water, and ultrasonically dispersed for 30 min to obtain a GO dispersion.

[0066] The carbon cloth treatment and electrode modification steps are the same as in Example 1. The carbon cloth is cut into 1×1 cm², and after alternating ultrasonic cleaning with ethanol / deionized water and activation with 50W plasma for 80s, 50μL of the above GO dispersion is dropped onto it and dried in an oven at 60℃ for 12h to obtain the GO CC electrode.

[0067] Comparative Example 2

[0068] The SRGO CC electrode was prepared using the same method as in Example 1, with the following difference:

[0069] The composite material contains only SRGO and no CNT-COOH or β-CD. Specifically, 10 mg of SRGO powder is weighed and added to 2.5 mL of pure water, and ultrasonically dispersed for 30 min to obtain an SRGO dispersion.

[0070] The carbon cloth treatment and electrode modification steps are the same as in Example 1. The carbon cloth is cut into 1×1 cm², and after alternating ultrasonic cleaning with ethanol / deionized water and activation with 50W plasma for 80s, 50μL of the above SRGO dispersion is drop-coated and dried in an oven at 60℃ for 12h to obtain the SRGO CC electrode.

[0071] Comparative Example 3

[0072] The SRGO / CNT-COOH CC electrode was prepared using the same method as in Example 1, with the difference being:

[0073] The composite material contains SRGO and CNT-COOH, but does not contain β-CD. Specifically, 10 mg of SRGO powder and 5 mg of CNT-COOH are weighed, added to 2.5 mL of pure water, and ultrasonically dispersed for 30 min to obtain an SRGO / CNT-COOH dispersion.

[0074] The carbon cloth treatment and electrode modification steps are the same as in Example 1. The carbon cloth is cut into 1×1 cm², and after alternating ultrasonic cleaning with ethanol / deionized water and activation with 50W plasma for 80s, 50μL of the above SRGO dispersion is dropped onto it and dried in an oven at 60℃ for 12h to obtain the SRGO / CNT-COOH CC electrode.

[0075] Comparative Example 4

[0076] The same carbon cloth treatment method as in Example 1 was used, but without any composite material modification. The specific steps are as follows:

[0077] Cut the carbon cloth into standard size of 1×1 cm², and use ethanol and deionized water to ultrasonically clean it more than 3 times (10 minutes each time) until there are no more floating impurities on the surface of pure water.

[0078] After drying, the cleaned carbon cloth is placed in a plasma cleaner (50W, 80s) to enhance the surface hydrophilicity, and then placed in an oven for 1 hour.

[0079] Without dripping any dispersion, the treated carbon cloth is directly used as the working electrode, i.e., the blank carbon cloth (CC) electrode.

[0080] Performance testing

[0081] This invention uses an electrochemical workstation (CHI660E, Shanghai Chenhua Instrument Co., Ltd., China) to test the electrodes. All experiments were conducted in a three-electrode system, using the SRGO / CNT-COOH / β-CD CC electrode prepared in Example 1 as the working electrode, a platinum electrode as the auxiliary electrode, and an Ag / AgCl electrode as the reference electrode. The electrodes were tested in an environment containing 5.0 mM [Fe(CN)6]³⁻ / 4 The electrochemical activity of the prepared SRGO / CNT-COOH / β-CD electrode was evaluated by cyclic voltammetry (CV) in a 0.1 M KCl solution. A three-electrode system was used: the working electrode was the preparative electrode, the auxiliary electrode was a platinum electrode, and the reference electrode was an Ag / AgCl electrode. The test potential range was set to -0.2 V to +0.6 V, the equilibration time was 2 s, and the scan rate was 50 mV / s.

[0082] Based on Example 1 and Comparative Examples 1-4, blank electrode, GO / CC, SRGO CC, SRGO / CNT-COOH CC, and SRGO / CNT-COOH / β-CD CC electrodes were used as working electrodes, respectively, with a platinum electrode as the auxiliary electrode and Ag / AgCl as the reference electrode. (Refer to...) Figure 4a. In CV current response tests conducted in potassium ferricyanide solution, the unmodified blank carbon cloth electrode exhibited significantly lower redox peak currents, and the inter-peak potential difference (ΔEp) was approximately 1.5 times that of the other four electrodes, indicating poor charge transfer capability on its electrode surface. Compared to the GO CC electrode, the SRGO CC electrode showed significantly higher redox currents. This is because, even though GO itself possesses abundant functional groups and long-term stability, the electronic insulation properties of the GO surface delay its electrochemical performance and reduce its conductivity. This phenomenon also indicates that the SRGO electrode obtained by sulfonation reduction of GO has excellent conductivity and electron transfer rate. This may be attributed to the restoration of the conductive structure of graphene during the reduction process, while the introduced sulfonic acid groups significantly improve the hydrophilicity and ion transport efficiency of the material, reduce charge transfer impedance, and increase electrochemical active sites, thereby effectively promoting the redox reaction on the electrode surface. Furthermore, after being composited with carboxylated carbon nanotubes with high specific surface area, the SRGO / CNT-COOH CC and SRGO / CNT-COOH / β-CD CC electrodes also showed slightly better redox currents and peak potentials than the SRGO CC electrode. This is attributed to the enhancing effect of the synergistic interaction between SRGO and CNT-COOH. The main effect of cyclodextrin is to enhance the dispersibility of both and improve their adhesion to the carbon cloth electrode. Therefore, the SRGO / CNT-COOH / β-CD CC electrode did not exhibit a significantly higher redox current than the SRGO / CNT-COOH CC electrode. To further understand the electron transport and recombination characteristics of various electrode surfaces, electrochemical impedance spectroscopy was used to analyze the electrode surfaces. This method provides accurate characteristics of the electrode surface interface without damaging the electrode.

[0083] To further investigate the charge transfer characteristics of the electrode, under the same 5.0 mM [Fe(CN)6]³⁻ / 4 Electrochemical impedance spectroscopy (EIS) was performed in 0.1 MkCl solution. The detection frequency range was 10⁻² ~ 10⁻¹. 6 The AC perturbation voltage amplitude was 5 mV at Hz, and measurements were performed using a three-electrode system. Parameters such as charge transfer resistance (Rct) were obtained through Nyquist curve fitting to characterize the electron transport rate and electrochemical activity at the electrode interface.

[0084] Based on Example 1 and Comparative Examples 1-4, blank electrode, GO / CC, SRGO CC, SRGO / CNT-COOH CC, and SRGO / CNT-COOH / β-CD CC electrodes were used as working electrodes, respectively, with a platinum electrode as the auxiliary electrode and Ag / AgCl as the reference electrode. (Refer to...) Figure 4Figure b shows the Nyquist plot obtained after EIS measurement. Each semicircle in the curve can be modeled using components to analyze interface characteristics, internal resistance, and charge transfer kinetics. Generally, the semicircular portion in the high-frequency region corresponds to electron transport confinement processes, while the linear portion in the low-frequency region corresponds to diffusion confinement processes. Observing the obtained Nyquist plot, the electrode characteristics are found to exhibit a small arc, a semicircle, and a linear tail. Therefore, when performing circuit fitting using Zview software, a circuit fitting is performed using two series-connected resistor-capacitor components and a Warburg diffusion element. Here, Rs represents the solution resistance, mainly related to electrolyte concentration and ionic conductivity; R1 and CPE1 together describe the interfacial film impedance and non-ideal capacitive behavior introduced by the electrode surface modification layer; Rct and CPE2 reflect the electron transfer process and double-layer behavior at the electrode-electrolyte interface, which are key parameters for evaluating electrode reaction kinetics; W is the Warburg impedance, representing the contribution of diffusion confinement in the mid-to-low frequency region. The fitted electrode parameters show that the solution resistances obtained for different electrodes are not significantly different. Rct, a key factor in evaluating charge transfer impedance, varies considerably across different electrodes. The blank electrode exhibits an extremely high resistance of 550.7 Ω, indicating a slow interfacial charge transfer rate and poor electrode reaction kinetics. With the gradual introduction of composite materials, the resistance of the GO-modified electrode decreased significantly (72.47 Ω). The SRGOCC, SRGO / CNT-COOH CC, and SRGO / CNT-COOH / β-CD CC electrodes showed even lower Rct resistances, with the SRGO / CNT-COOH / β-CD CC electrode reaching 5.706 Ω. These results are consistent with the conclusions of the aforementioned CV tests, further confirming that SRGO provides a good conductive channel, and the synergistic effect of carboxylated carbon nanotubes with SRGO enhances the charge transfer capability of the electrode.

[0085] Based on Example 1, using an SRGO / CNT-COOH / β-CD CC electrode as the working electrode, and a platinum electrode as the auxiliary electrode, and Ag / AgCl as the reference electrode, at 5.0 mM [Fe(CN)6]³⁻ / 4 ⁻ Cyclic voltammetry was performed on the system in 0.1 M KCl solution at different scan rates (10–100 mV / s) to analyze the variation of the oxidation peak current with the scan rate. The results show that, referring to… Figure 4 c and Figure 4 d. The oxidation peak current exhibits a good linear relationship with the square root of the scan rate, and its regression equation is: I (µA) = 30678.3972 ν¹ / 2 (V / s)¹ / 2 – 617.1076, R² = 0.999. According to the classic Randles–Ševčík equation, under diffusion-controlled processes, the peak current should be linearly correlated with the square root of the scan rate. The correlation coefficient for this system is as high as 0.999, proving that the electrode reaction process is mainly diffusion-controlled. Simultaneously, the larger fitting slope indicates that the modified electrode has a larger electrochemically active surface area. Calculations based on the formula show that the effective active area of ​​the electrode is 8.27 cm², significantly higher than the 1.55 cm² of the blank electrode. This higher active area provides abundant electrochemical reaction sites and accelerates electron transfer, thus contributing to the efficient redox process of capsaicin.

[0086] First, capsaicin was dissolved in anhydrous ethanol to prepare a 50 mM stock solution, which was then diluted to 100 μM with an electrolyte solution containing 0.01 mol·L⁻¹ HCl and 0.1 mol·L⁻¹ KCl. Cyclic voltammetry (CV) was performed on the prepared electrode to investigate its electrochemical response to capsaicin. The test potential window was -0.6 V to +0.8 V, and the scan rate was 50 mV / s. The obtained current response can be used to evaluate the electrode's recognition and catalytic ability for capsaicin molecules.

[0087] Based on Example 1 and Comparative Examples 1-4, blank electrode, GO / CC, SRGO CC, SRGO / CNT-COOH CC, and SRGO / CNT-COOH / β-CD CC electrodes were used as working electrodes, with a platinum electrode as the auxiliary electrode and Ag / AgCl as the reference electrode. Referring to 5a, the CV response of each electrode is shown. The CV test curves of all electrodes showed obvious oxidation and reduction peaks. The blank carbon cloth electrode showed a weak response current of only 122.563 μA. This is because the blank electrode surface lacks substances that enhance catalytic performance, resulting in a slow charge transfer rate and a small oxidation peak current. The modified GO carbon cloth electrode showed a significant increase in oxidation peak potential, while the SRGO-modified electrode obtained after sulfonation reduction showed a superior electrochemical response. The electrode obtained after adding carboxylated multi-walled carbon nanotubes and cyclodextrin also showed a better synergistic effect, producing a higher oxidation peak current. These results are consistent with those in the potassium ferricyanide test, and the effects are more significant than those in the potassium ferricyanide test solution. This indicates that the prepared electrode is suitable for the detection of capsaicin. During the binding process of SRGO and CNT-COOH, multiple functional groups and chemical bonds interact, and the SRGO / CNT-COOH / β-CD CC electrode exhibits the best electrocatalytic performance for capsaicin.

[0088] Using an SRGO / CNT-COOH / β-CD CC electrode as the working electrode and a platinum electrode as the auxiliary electrode, with Ag / AgCl as the reference electrode, and 0.01 mol·L⁻¹ HCl and 0.1 mol·L⁻¹ KCl solutions as electrolytes, the potential range was set to -0.6 to 0.8 V, and the equilibrium time was 2 s. The CV curves of capsaicin at different scan rates were tested within the range of 10–200 mV / s. Referring to 5b, as the scan rate increased, the oxidation peak shifted to the right, and the reduction peak shifted to the left. Furthermore, the square root of the scan rate showed a good positive correlation with the peak current, indicating that the redox process of capsaicin is diffusion-controlled.

[0089] Capsaicin content detection

[0090] Capsaicin solutions of different concentrations were prepared in electrolyte solutions, namely 0.01 mol·L⁻¹ HCl and 0.1 mol·L⁻¹ KCl.

[0091] The SRGO / CNT-COOH / β-CD carbon cloth electrode prepared in Example 1 was used as the working electrode, the platinum electrode as the counter electrode, and the Ag / AgCl electrode as the reference electrode to form a three-electrode system.

[0092] Cyclic voltammetry (CV) was performed on the electrode in capsaicin solution, and the oxidation peak current value was recorded; (Refer to...) Figure 5 c and Figure 5 d. The peak current value was linearly fitted to the capsaicin concentration. When the detection range was 1–30 μM, the fitting equation was: Ip1(μA) = 20.70x (μM) + 380.68 (R1² = 0.993); when the detection range was 30–340 μM, the fitting equation was: Ip2(μA) = 7.917x (μM) + 740.91 (R2² = 0.997), where I represents the current intensity and x represents the capsaicin concentration.

[0093] The capsaicin content was calculated based on the obtained linear equation, and the limit of detection (LOD) and limit of quantitation (LOQ) were determined by the signal-to-noise ratio (S / N) method, where the LOD was 1.67 μM (S / N = 3) and the LOQ was 5.56 μM (S / N = 10).

[0094] Using the above method, the SRGO / CNT-COOH / β-CD carbon cloth electrode can quantitatively detect capsaicin in a wide concentration range of 1–340 μM, with a low detection limit and good linearity, providing a reliable detection method for the subsequent development of a portable capsaicin electrochemical detection system.

[0095] SRGO / CNT-COOH / β-CD CC sensor anti-interference test

[0096] Capsaicin standard was prepared into a 50 μM electrolyte solution, which was a mixture of 0.01 mol·L⁻¹ HCl and 0.1 mol·L⁻¹ KCl. Common organic and inorganic compounds were then added to the solution at a concentration of 500 μM, which is 10 times the concentration of capsaicin. Interfering substances included, in order, calcium chloride (CaCl₂), potassium chloride (KCl), potassium nitrate (KNO₃), sodium hydroxide (NaOH), sodium chloride (NaCl), glucose, sodium citrate, and sodium nitrite (NaNO₂). In the final experiment, capsaicin was added dropwise to the system again.

[0097] The SRGO / CNT-COOH / β-CD CC electrode prepared in Example 1 was used as the working electrode, the platinum electrode as the counter electrode, and the Ag / AgCl electrode as the reference electrode to form a three-electrode system for testing. Differential pulse voltammetry (DPV) was used, with the following detection conditions: potential range 0 to +0.8 V, pulse amplitude 50 mV, pulse width 0.2 s, pulse period 0.5 s, and equilibration time 2 s. Each sample was tested at least three times, and the average value was taken.

[0098] Reference Figure 5 e. After sequentially adding CaCl2, KCl, KNO3, NaOH, NaCl, glucose, sodium citrate, and NaNO2, the measured DPV peak current showed no significant difference compared to the electrolyte solution containing only 50 μM capsaicin. The peak current only increased significantly upon further addition of capsaicin. This indicates that the SRGO / CNT-COOH / β-CD CC electrode exhibits excellent selectivity for capsaicin detection, unaffected by the aforementioned interfering substances.

[0099] Stability testing of SRGO / CNT-COOH / β-CD CC sensor

[0100] To evaluate the stability and consistency of the prepared electrodes, six sets of SRGO / CNT-COOH / β-CD CC electrodes were inserted into an electrolyte solution containing 100 μM capsaicin. The electrolyte solution was a mixture of 0.01 mol·L⁻¹ HCl and 0.1 mol·L⁻¹ KCl.

[0101] Differential pulse voltammetry (DPV) was used to test each group of electrodes under the following conditions: potential range 0 to +0.8V, pulse amplitude 50 mV, pulse width 0.2s, pulse period 0.5s, and equilibration time 2s. Each group of electrodes was tested at least three times, and the average value was taken.

[0102] Reference Figure 5 f, except for electrode 2, which showed a significant difference from the other electrodes, the detection results of the other electrodes were not significantly different. Statistical analysis of the intra-group detection results of the six electrodes showed that the relative standard deviation (RSD) was less than 4.12%. The difference in electrode 2 may be due to the uneven distribution of the modification material on the electrode surface.

[0103] Therefore, it can be considered that the SRGO / CNT-COOH / β-CD CC electrode prepared in Example 1 has good stability within the group and good consistency between groups, which can ensure the reliability of subsequent electrochemical detection results.

[0104] Reference Figure 6 The diagram shows the workflow of an electrochemical detection system for capsaicin, which is used to implement the above detection method. It mainly includes a three-electrode system, a battery module 1, a power supply module 2, an MCU module 3, an electrochemical detection circuit 4, a signal conditioning circuit 5, and a communication module 6 to achieve rapid detection of capsaicin.

[0105] The three-electrode system includes the working electrode, auxiliary electrode, and reference electrode of Example 1.

[0106] Battery module 1 provides initial power to the system. Battery module 1 is a rechargeable battery that supplies power to the system. It can be powered by an 18650 lithium battery connected via an XH2.54 connector, controlled by a slide switch, and includes a power indicator light.

[0107] Power module 2 is connected to battery module 1 and is used to convert and regulate the electrical energy output from battery module 1 to provide the voltage required by the system. Power module 2 includes a positive voltage generation unit, a negative voltage generation unit, a working voltage generation unit, and a high-precision reference voltage generation unit, used to provide matching voltages to each module of the system. Preferably, power module 2 includes a 5V boost module, a -5V negative voltage module, a 3.3V reference voltage module, and a 2.048V reference voltage module. The 5V boost module is based on the MT3608 chip, which boosts and regulates the lithium battery supply voltage and supplies it to other modules; the -5V negative voltage module uses two TPS60400 chips to supply -5V voltage to the buffers and other devices on the board; the 3.3V voltage regulator module is based on the AMS1117 chip, which provides 3.3V voltage to the MCU; and the 2.048V reference voltage module is based on the ADR440 chip, which provides a high-precision reference voltage to the MCU's 16-bit ADC.

[0108] MCU module 3 is used to generate the electrochemical scan voltage and acquire the processed signal. Based on the STM32F373CCT6, MCU module 3 generates the triangular wave voltage required for the electrochemical scan via a DAC. This voltage is then applied to the three-electrode system through the electrochemical detection circuit 4. The current generated by the reaction is differentially amplified and filtered by the I / V conversion and signal conditioning circuit 5, and then acquired by the 16-bit ADC built into MCU module 3. The MCU transmits the acquired data to the host computer via the communication module 6 in serial-to-USB and Wi-Fi formats, with a sampling frequency of 100Hz.

[0109] The electrochemical detection circuit 4 is connected to both the MCU module 3 and the three-electrode system. It is used to apply the scanning voltage generated by the MCU module 3 to the three-electrode system and acquire the current signal generated by the reaction. The electrochemical detection circuit 4 includes a subtractor circuit and a potentiostat circuit.

[0110] The subtractor circuit uses two BUF634T buffer chips to receive the output voltages VIN1 and VIN2 from the MCU's 12-bit DAC, which serve as the triangular wave scanning voltage VDAC and the bias voltage VBIA, respectively. These two voltages are subtracted by the op-amp OP1 subtractor circuit to achieve a bipolar scanning voltage output. For example, to generate a scanning voltage of -0.4V to 0.6V, VIN1 outputs a triangular wave scanning voltage of 0 to 1V, and VIN2 outputs a constant voltage of 0.4V. The final generated scanning voltage is supplied to the potentiostat module, while the MCU samples the scanning voltage using a 16-bit ADC.

[0111] The potentiostat module first uses a voltage follower circuit composed of operational amplifier OP2 for isolation from the preceding stage. OP3-OP5 constitute the potentiostat circuit. During circuit operation, OP3, 4, and 5 all operate in negative feedback mode, where virtual short and virtual open characteristics are applicable. Let the scanning voltage be... The voltage across the reference electrode RE is Analysis of OP4 has ; Analysis of OP3 has , It is possible to obtain This achieves controllable voltage on the reference electrode. The output of OP3 is connected to the counter electrode through a buffer to provide sufficient current for the reaction. OP5, an 8-channel multiplexer CD4051, and 8 resistors form a variable gain transimpedance amplifier. The MCU's three GPIO ports control the level of address lines A0~A2, enabling any one of the eight channels CH0~CH7 of the CD4051 to conduct. The reaction current flows through the working electrode into the transimpedance amplifier, is converted into a voltage value, and then enters the signal conditioning module for further processing.

[0112] The input of signal conditioning circuit 5 is connected to electrochemical detection circuit 4, and its output is connected to MCU module 3. It is used to convert, amplify, and filter the current signal. It includes a transimpedance conversion module, a differential amplifier module, and a filter module, which work in sequence. The transimpedance conversion module consists of an operational amplifier and a feedback resistor. It converts the microampere-level reaction current output from electrochemical detection circuit 4 into a voltage signal, with the conversion relationship V=I×R. The transimpedance conversion module can use an OPA277 operational amplifier, and the feedback resistor is adjustable from 100K, 200K, to 500K, selected using a CD4051 multiplexer. It can linearly convert the 0.1~10μA microampere-level reaction current output from the electrochemical detection circuit into a 0.01~1V voltage signal with a conversion error ≤0.5%. The differential amplifier module is based on an AD627 instrumentation amplifier. It first adjusts the converted voltage signal through a voltage divider resistor network, then performs a 7x differential amplification to output voltage, ensuring accuracy and not exceeding the ADC input limit. The filtering module performs low-pass filtering using a second-order Sallen-Key low-pass filter. The filter's -3dB frequency is around 10Hz, which can effectively filter out mid- and high-frequency interference. The final output voltage is sampled by the MCU's 16-bit ADC.

[0113] Communication module 6 is connected to MCU module 3 and is used to transmit data acquired by MCU module 3 to a host computer, which can be a computer, smartphone, or dedicated data acquisition terminal. The host computer receives data via serial port protocol or wireless protocol. Communication module 6 supports at least one wired or wireless data transmission method. Preferably, communication module 6 includes wired and wireless transmission. Wired transmission uses a CH340 serial-to-USB chip and connects to the host computer via a TYPE-C interface for data transmission; wireless transmission uses a serial port to communicate with the ESP8266 module and sends data via WiFi.

[0114] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. An electrochemical detection method for capsaicin, characterized in that, Includes the following steps: (1) A three-electrode system is provided, the three-electrode system including a working electrode, an auxiliary electrode and a reference electrode; wherein the working electrode is a carbon cloth electrode with a surface modified with carbon nanocomposite material, the carbon nanocomposite material including graphene derivatives, carbon nanotube derivatives and cyclodextrin; (2) Prepare an electrolyte solution by diluting the standard sample or the sample to be tested containing capsaicin into the electrolyte solution; (3) The solution from step (2) is electrochemically detected using the three-electrode system to obtain the oxidation peak current signal; (4) Based on the correspondence between the oxidation peak current signal and the capsaicin concentration, determine the capsaicin content in the sample to be tested; The graphene derivative is sulfonated reduced graphene oxide, the carbon nanotube derivative is carboxylated multi-walled carbon nanotubes, and the cyclodextrin is β-cyclodextrin.

2. The detection method according to claim 1, characterized in that, The preparation method of the carbon nanocomposite material includes the following steps: The graphene derivative, the carbon nanotube derivative, and the cyclodextrin were dispersed in water at a mass ratio of (1-2):(0.5-1):(1-2), and the dispersion was obtained by ultrasonic treatment.

3. The detection method according to claim 1, characterized in that, The method for preparing the working electrode includes the following steps: After cleaning and surface activation treatment of the carbon cloth, a dispersion of the carbon nanocomposite material is coated onto the surface of the carbon cloth, and after drying, a modification layer is formed.

4. The detection method according to claim 1, characterized in that, The electrolyte solution is an acidic mixed solution comprising 0.005-0.02M hydrochloric acid and 0.05-0.2M soluble chloride, with a pH of 1-3.

5. The detection method according to claim 1, characterized in that, In step (3), cyclic voltammetry is used for detection, with a scanning potential range of -0.8V to +1.0V and a scanning rate of 10-100mV / s.

6. The detection method according to claim 1, characterized in that, The correspondence described in step (4) is a linear equation. The linear correlation coefficient R² ≥ 0.993 in the concentration range of 1~30 μM and the linear correlation coefficient R² ≥ 0.997 in the concentration range of 30~340 μM. The detection limit is 1.67 μM and S / N = 3.

7. An electrochemical detection system for capsaicin, characterized in that, To implement the detection method according to any one of claims 1-6, comprising: A three-electrode system, which includes a working electrode, an auxiliary electrode, and a reference electrode; The battery module is used to provide initial electrical energy to the system; A power module, which is connected to the battery module, is used to convert and regulate the electrical energy output by the battery module in order to provide the voltage required by the system. The MCU module is used to generate electrochemical scan voltages and acquire processed signals. An electrochemical detection circuit, which is connected to the MCU module and the three-electrode system respectively, is used to apply the scanning voltage generated by the MCU module to the three-electrode system and acquire the current signal generated by the reaction; The signal conditioning circuit has its input terminal connected to the electrochemical detection circuit and its output terminal connected to the MCU module, and is used to convert, amplify and filter the current signal; A communication module, which is connected to the MCU module, is used to transmit the data collected by the MCU module to the host computer.

8. The detection system according to claim 7, characterized in that, The power module includes a positive voltage generation unit, a negative voltage generation unit, a working voltage generation unit, and a high-precision reference voltage generation unit, which are used to provide matching voltages for each module of the system; the battery module is a rechargeable battery that provides power to the system.

9. The detection system according to claim 7, characterized in that, The signal conditioning circuit includes a transimpedance conversion module, a differential amplifier module, and a filter module; the transimpedance conversion module is used to convert the microampere-level reactive current into a voltage signal; the differential amplifier module is used to amplify the converted voltage signal; and the filter module is used to filter the amplified voltage signal to remove mid- and high-frequency interference. The communication module supports at least one wired or wireless data transmission method.

Images