Tea polyphenol detection method and tea polyphenol detection device based on infrared evanescent wave absorption spectrum

Abstract

The invention belongs to the field of optical sensing technology and food component analysis, and discloses a tea polyphenol detection method and a tea polyphenol detection device based on an infrared evanescent wave absorption spectrum. Comprising the following steps that a conical infrared optical fiber sensor is provided, the conical infrared optical fiber sensor is obtained by drawing an optical fiber with the diameter of 150-1000 microns to obtain a conical infrared optical fiber, and then the end faces of the two ends of the conical infrared optical fiber sensor are polished till the end faces of the optical fiber are free of scratches, so that the two end faces of the optical fiber are flat, smooth and bright and form mirror faces; the conical infrared optical fiber sensor is packaged in the sample pool, the upper end of the sample pool is open, and a to-be-detected sample solution is injected and fully coats the optical fiber; an 850-4000 cm <-1 > infrared light source is provided, focused infrared light enters the optical fiber and is fully coupled with the optical fiber, an infrared evanescent wave absorption spectrum is collected, and qualitative and quantitative analysis is carried out on the tea polyphenol content based on the tea polyphenol characteristic peak intensity. The method for detecting the tea polyphenol has the characteristics of rapidness, high sensitivity and low detection limit.

Description

Technical Field This invention belongs to the field of optical sensing technology and food component analysis, specifically relating to a method and device for detecting tea polyphenols based on infrared evanescent absorption spectroscopy, which is used to detect the content of tea polyphenols in food rapidly, non-destructively, and with high sensitivity. Background Technology Tea polyphenols are the main active components in tea, possessing diverse biological activities and widely used in the food, health product, and pharmaceutical fields. Currently, the quantitative analysis of tea polyphenols mainly relies on methods such as gas chromatography, high-performance liquid chromatography (HPLC), spectrophotometry, colorimetry, and three-dimensional fluorescence spectroscopy. However, these methods often require complex sample pretreatment procedures (e.g., derivatization or solid-phase extraction), have long analysis times for each sample, and depend on expensive instruments. Furthermore, some methods (e.g., colorimetry) are susceptible to interference from reducing substances (such as sugars and ascorbic acid), and the stability of chromogenic agents further limits their applicability. These limitations significantly hinder in-depth research into the biological activities and mechanisms of action of tea polyphenols.

[0001] Infrared spectroscopy is a widely used analytical method for investigating molecular vibrations and chemical bond characteristics. It identifies the structure of tea polyphenols through functional group fingerprinting (e.g., the OH stretching vibration of phenols and the C=C vibration of aromatic compounds), enabling rapid quantitative assessment and providing the possibility for real-time monitoring in tea production. However, traditional infrared techniques face challenges in direct liquid phase analysis due to interference from strong water absorption.

[0002] The next-generation fiber-optic-based spectroscopic analysis technology, fiber evanescent wave spectroscopy (FEWS), differs from traditional fiber optic sensing technologies that utilize light transmission characteristics (such as reflection, transmission, and interference) to detect changes in the surrounding environment. FEWS relies on the interaction between the evanescent waves of optical fibers and the surrounding medium, detecting and analyzing samples by monitoring changes in characteristic peaks. Developing a FEWS-based method for detecting tea polyphenols would effectively avoid the water interference problem encountered in traditional infrared spectroscopy. However, current reports on tea polyphenol detection technologies suffer from high costs, complex detection procedures, susceptibility to interference, insufficient accuracy, long detection times, low efficiency, and low sensitivity. Methods such as high-performance liquid chromatography (HPLC) and gas chromatography require complex sample pretreatment (e.g., derivatization, solid-phase extraction), have long detection times, and rely on expensive large-scale instruments. Some conventional methods, such as colorimetry, are easily interfered with by other reducing substances in the sample (e.g., sugars, ascorbic acid), and the stability of the chromogenic reagents can also affect the accuracy of the detection results. Therefore, developing a rapid, accurate, and sensitive method for detecting tea polyphenols is of great significance. Summary of the Invention

[0003] The technical problem to be solved by this invention is to address the aforementioned shortcomings in the existing technology by providing a method for detecting tea polyphenols based on infrared evanescent absorption spectroscopy and a device for detecting tea polyphenols based on a cone-shaped infrared fiber optic sensor. This method is characterized by its speed, high sensitivity, and low detection limit for tea polyphenol detection.

[0004] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: The first aspect of this invention provides a method for detecting tea polyphenols based on infrared evanescent absorption spectroscopy, comprising the following steps: A tapered infrared fiber sensor is provided. The tapered infrared fiber sensor is obtained by drawing an optical fiber with a diameter of 150-1000 μm to obtain a tapered infrared fiber, and then polishing the end faces of the fiber until there are no scratches on the fiber end faces, so that the end faces of the fiber are flat and smooth to present a mirror surface. The tapered infrared fiber includes a first tapered region, the first tapered region includes a transition region and a first waist region, and a part of the first waist region is stretched again to form a second tapered region. The second tapered region includes a second transition region and a second waist region. The second waist region is bent into a ring to form a micro-ring structure. A conical infrared fiber optic sensor is encapsulated in a sample cell with an opening at the top. The sample liquid to be detected is injected into the sample cell to fully cover the fiber optic cable. Provides 850-4000 cm -1 An infrared light source is used to focus the infrared light into an optical fiber, where it is fully coupled to collect the infrared evanescent absorption spectrum. The content of tea polyphenols is then qualitatively and quantitatively analyzed based on the intensity of the characteristic peaks. According to the above scheme, the radius of the microring structure is preferably 0.2-3.0 mm.

[0005] Preferably, the tapered infrared optical fiber has two tapered regions, with the total length of the first and second waist regions being 3-20 mm, the diameter of the first waist region being 150-300 μm, and the diameter of the second waist region being 20-100 μm.

[0006] Preferably, the tapered infrared optical fiber is an infrared glass optical fiber with a diameter of 350-800 μm and a transmission range of 850-4000 cm. -1 Mid-infrared light.

[0007] Preferably, the infrared glass fiber is made of chalcogenide glass fiber, including but not limited to chalcogenide glass fibers such as Ge-As-Se-Te, As-Se, and Ge-As-Se.

[0008] According to the above scheme, based on the C–O stretching vibration peak (1150 cm⁻¹) -1 Qualitative and quantitative analysis was conducted.

[0009] According to the above scheme, the quantitative analysis is as follows: the solution to be tested is dropped into the sample cell, and samples are collected from 1131-1170 cm. -1 The infrared evanescent absorption spectrum of the range was used to perform quantitative analysis of tea polyphenols in the sample according to the standard detection curve of tea polyphenols.

[0010] According to the above scheme, the method for obtaining the standard detection curve of tea polyphenols is as follows: prepare at least 5 groups of tea polyphenol standard solutions with different concentrations, collect absorption spectra, and establish the relationship curve between the concentration of the tea polyphenol standard solution and the area of ​​its characteristic absorption peak according to Lambert-Beer's law, which is the tea polyphenol standard curve.

[0011] According to the above scheme, the sample to be tested is tea or its products, and the sample liquid to be tested is a methanol extract of the sample to be tested.

[0012] According to the above scheme, pure methanol solution is used as solvent to collect infrared spectra, then the optical fiber is cleaned, the sample solution to be detected is added, the spectral signal is processed by difference subtraction, and then quantitative analysis is performed based on characteristic absorption peaks.

[0013] A second aspect of the present invention provides a tea polyphenol detection device based on an infrared evanescent wave sensor, comprising: An infrared spectrometer that provides an infrared light source; An optical system used to guide infrared beams into optical fibers and to focus and couple the beams; A conical infrared fiber optic sensor is embedded in a sample cell, with an opening at the top for injecting sample detection liquid. A collimating lens used to collimate the infrared light output from an optical fiber; A detector used to detect the output infrared light.

[0014] The optical path system includes a plane mirror, an off-axis parabolic mirror, and a ZnSe lens. The plane mirror and the off-axis parabolic mirror are placed opposite each other. Infrared light is reflected by the plane mirror and the off-axis parabolic mirror and then enters the ZnSe lens for beam focusing. The focused infrared light enters the optical fiber and is fully coupled with the optical fiber.

[0015] In some embodiments, the collimating lens is a ZnSe lens.

[0016] In some embodiments, the detector used to detect the output infrared light is an MCT liquid nitrogen-cooled detector.

[0017] In some embodiments, a conical infrared fiber optic sensor is mounted on a stage. The stage position is adjustable to achieve the maximum spectral signal value.

[0018] The beneficial effects of this invention are: This invention successfully realizes the detection of tea polyphenols based on infrared evanescent absorption spectroscopy, and significantly improves sensitivity and detection limit (the sensor has a sensitivity of 0.062 au / (mg·mL-1) for tea polyphenols in the 1131-1170 cm-1 band and a detection limit of 0.25 mg / mL).

[0019] This invention's detection method requires no complex pretreatment, offers rapid detection, and significantly reduces detection time and cost. It utilizes the infrared fingerprint spectral characteristics of tea polyphenol molecules for identification and quantification, exhibiting high specificity and effectively avoiding interference and instability issues associated with chemical reagents. The tapered optical fiber encapsulated in the sample cell is reusable, convenient to use, requires small sample volumes, and has a short detection time.

[0020] This invention innovatively employs a "cone-within-a-cone" structure combined with a curved micro-ring design. By optimizing the structural parameters through COMSOL simulation, the intensity of the evanescent field and the interaction between light and matter are significantly enhanced. This increases the penetration depth of the evanescent wave in the optical fiber and the number of reflections of light in the optical fiber. The infrared evanescent wave sensor designed in this way, together with the optical path system, collimating lens, and detector, constructs a tea polyphenol detection device based on the infrared evanescent wave sensor. This device can be used for tea polyphenol detection, achieving highly sensitive detection of tea polyphenols based on the infrared evanescent wave absorption spectrum. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the sensing principle of the conical infrared fiber optic sensor of the present invention; Figure 2 This invention relates to a tea polyphenol detection device based on a conical infrared fiber optic sensor. Figure 3 Schematic diagrams of conical Ge-As-Se-Te chalcogenide glass fiber sensors with different structures; Figure 4 Infrared evanescent absorption spectra of ethanol solutions were tested for different fiber optic sensors. Figure 5 Test the sensitivity curves of ethanol solution sensing for different fiber optic sensors; Figure 6 To detect the infrared evanescent absorption spectra of seven types of tea. Detailed Implementation

[0022] Current tea polyphenol detection technologies suffer from high costs, complex detection procedures, susceptibility to interference, insufficient accuracy, long detection times, low efficiency, and low sensitivity. The applicant, through extensive research, has developed a rapid, accurate, and highly sensitive tea polyphenol detection method and a tea polyphenol detection device based on a cone-shaped infrared fiber optic sensor. The following will describe in detail the tea polyphenol detection method and device based on infrared evanescent wave absorption spectroscopy proposed in this invention. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of the invention.

[0023] A method for detecting tea polyphenols based on infrared evanescent absorption spectroscopy is provided, comprising the following steps: A tapered infrared fiber sensor is provided. The tapered infrared fiber sensor is obtained by drawing an optical fiber with a diameter of 150-1000 μm to obtain a tapered infrared fiber, and then polishing the end faces of the fiber until there are no scratches on the fiber end faces, so that the end faces of the fiber are flat and smooth to present a mirror surface. The tapered infrared fiber includes a first tapered region, the first tapered region includes a transition region and a first waist region, and a part of the first waist region is stretched again to form a second tapered region. The second tapered region includes a second transition region and a second waist region. The second waist region is bent into a ring to form a micro-ring structure. A conical infrared fiber optic sensor is encapsulated in a sample cell with an opening at the top. The sample liquid to be detected is injected into the sample cell to fully cover the fiber optic cable. Provides 850-4000 cm -1 An infrared light source is used to focus the infrared light into an optical fiber, where it is fully coupled to collect the infrared evanescent absorption spectrum. The content of tea polyphenols is then qualitatively and quantitatively analyzed based on the intensity of the characteristic peaks. Preferably, the bending radius of the microring structure is 0.2-3.0 mm.

[0024] Preferably, the tapered infrared optical fiber has two tapered regions, with the total length of the first and second waist regions being 3-20 mm, the diameter of the first waist region being 150-300 μm, and the diameter of the second waist region being 20-100 μm.

[0025] Preferably, the tapered infrared optical fiber is an infrared glass optical fiber with a diameter of 350-800 μm and a transmission range of 850-4000 cm. -1 Mid-infrared light.

[0026] Specifically, the infrared glass fiber is made of chalcogenide glass fiber, including but not limited to chalcogenide glass fibers such as Ge-As-Se-Te, As-Se, and Ge-As-Se. In some embodiments, it is specifically Ge-As-Se-Te chalcogenide glass.

[0027] In some embodiments, the sample cell can be fabricated using 3D printing technology; the material of the sample cell includes, but is not limited to, plastic materials such as polylactic acid (PLA), acrylonitrile-butadiene-styrene copolymer (ABS), and photosensitive resin.

[0028] This invention also provides a tea polyphenol detection device based on a cone-shaped infrared fiber optic sensor, comprising: An infrared spectrometer that provides an infrared light source; An optical system used to guide infrared beams into optical fibers and to focus and couple the beams; A conical infrared fiber optic sensor is embedded in a sample cell, with an opening at the top for injecting sample detection liquid. A collimating lens used to collimate the infrared light output from an optical fiber; A detector used to detect the output infrared light.

[0029] The optical path system includes a plane mirror, an off-axis parabolic mirror, and a ZnSe lens. The plane mirror and the off-axis parabolic mirror are placed opposite each other. Infrared light is reflected by the plane mirror and the off-axis parabolic mirror and then enters the ZnSe lens for beam focusing. The focused infrared light enters the optical fiber and is fully coupled with the optical fiber.

[0030] In some embodiments, the collimating lens is a ZnSe lens.

[0031] In some embodiments, the detector used to detect the output infrared light is an MCT liquid nitrogen-cooled detector.

[0032] In some embodiments, a conical infrared fiber optic sensor is mounted on a stage. The stage position is adjustable to achieve the maximum spectral signal value.

[0033] This system employs an infrared light source capable of emitting a broad spectrum of infrared light, covering the characteristic absorption bands of various chemical bonds in the sample. After being coupled into a tapered optical fiber, the infrared light propagates from an optically denser medium to an optically less dense medium. If the angle of incidence exceeds the critical angle, total internal reflection occurs. At the interface of the optically less dense medium, a wave propagates along the surface, its amplitude decaying exponentially with increasing depth; this is called an evanescent wave. When this evanescent field interacts with molecules in the solution, it excites the characteristic vibrational modes of their functional groups. By analyzing the energy distribution of group vibrations corresponding to the propagation characteristics of the evanescent wave, the structural features of the molecules can be determined.

[0034] The drawn tapered optical fiber is encapsulated in a sample cell, which is then placed in the optical path. The stage position is adjusted to maximize the signal value obtained by the spectrometer sensor. During contact, the evanescent wave penetrates the sample liquid layer. Specific chemical bonds in the sample selectively absorb infrared light energy matching their vibrational frequencies, resulting in attenuation of the light intensity at the corresponding wavelength. The detector receives the emitted light signal after the sample interaction. By comparing the light intensity difference with and without the sample, the infrared evanescent wave absorption spectrum can be obtained, thus reflecting the molecular structure information of the sample.

[0035] By conducting multiple tests with an infrared spectrometer, a series of infrared evanescent absorption spectra of the analyte are obtained. Quantitative analysis of the target substance can be performed based on the characteristic peaks. Alternatively, an unknown concentration of the analyte can be added to a sample cell to collect infrared evanescent absorption spectra. Based on the established relationship curve between the concentration of the standard solution and the area of ​​its characteristic absorption peak, quantitative analysis of the target analyte in the sample solution can be performed.

[0036] The aforementioned tea polyphenol detection device based on a cone-shaped infrared fiber optic sensor can be used for both qualitative and quantitative analysis. The qualitative identification involves comparing the acquired evanescent absorption spectrum with a standard infrared spectral database. Different compounds possess unique "fingerprint" absorption peaks; by identifying the characteristic peak positions, the functional groups and even specific substances present in the sample can be determined.

[0037] Quantitative detection: According to the Lambert-Beer absorption law, the absorbance of a sample to infrared light of a specific wavelength is directly proportional to its concentration. By establishing a standard curve of characteristic absorption peak intensity versus concentration, the accurate concentration of the target component can be determined.

[0038] The following describes in detail the method for detecting tea polyphenols based on infrared evanescent wave absorption spectroscopy of the present invention. Figure 1 This is a schematic diagram illustrating the sensing principle of the conical infrared fiber optic sensor of the present invention.

[0039] 1. Fabrication of fiber optic sensors: Chalcogenide glass is processed into optical fiber preforms, which are then drawn into optical fibers with diameters of 150-1000 μm using a drawing tower. A 5 cm unclad chalcogenide glass optical fiber is used, and a cone-within-a-cone structure is fabricated using a hot-drawing process, comprising a primary cone region and a secondary cone region formed by redrawing a portion of the first waist region within the primary cone region. The secondary conical region is further bent to form a micro-ring structure; the end faces of both ends of the conical fiber are polished with a polishing machine until the fiber end faces are free of scratches and have a mirror finish, thus obtaining the conical infrared fiber optic sensor, i.e., sensor D. Figure 3 As shown.

[0040] Finally, the optical fiber was encapsulated in a polylactic acid (PLA) sample cell with an opening at the top.

[0041] 2. Construct a tea polyphenol detection device based on a cone-shaped infrared fiber optic sensor, such as... Figure 2 As shown, an infrared spectrometer is used as the infrared light source. The spectrometer is turned on, and the infrared light source is adjusted to external optical path mode. The conical infrared fiber optic sensor is placed in the test optical path. The beam is focused using a plane mirror, an off-axis parabolic mirror, and a ZnSe lens, ensuring the focused infrared light fully couples with the fiber optic cable. The ZnSe lens is then used for collimation, and the infrared evanescent absorption spectrum is collected. The infrared evanescent absorption spectrum of the conical infrared fiber optic sensor is used as the background signal. In actual operation, the positions of the conical infrared fiber optic sensor and the MCT liquid nitrogen-cooled detector can be adjusted to achieve the optimal signal.

[0042] Prepare at least 5 sets of tea polyphenol standard solutions with different concentrations, collect the infrared evanescent absorption spectra of each standard solution, and calculate and establish the tea polyphenol standard curve based on the concentration of the tea polyphenol standard solution and the area of ​​its characteristic absorption peak according to the Lambert-Beer law. The slope of the curve is the fiber optic sensitivity. 3. Methods for detecting tea polyphenols: According to the national standard method (GB / T 8313-2018 "Determination of tea polyphenols and catechins in tea"), tea polyphenols were extracted from tea samples and a standard solution was prepared. Weigh uniformly ground high-purity tea polyphenol reagent (98%) and five commercially available tea lozenge samples using an analytical balance. Place them separately in 10 mL centrifuge tubes, and add 5 mL of preheated anhydrous methanol (70°C) for extraction. Vortex mix for 1 min, then immediately transfer to a 70°C water bath for 10 min, stirring every 5 min. After extraction, cool to room temperature, centrifuge at 3500 rpm for 10 min, and extract the supernatant. Extract the residue again with 5 mL of anhydrous methanol solution, repeating the above operation. Combine the extracts and dilute to 10 mL, shake thoroughly, and filter through a 0.5 μm membrane. o Save as C.

[0043] The processing method for commercially available tea is the same as above. Take tea of ​​the same weight (including green tea, black tea, white tea, dark tea, jasmine tea, and Longjing tea), grind them into powder, extract with anhydrous ethanol, and repeat the above operation.

[0044] The infrared evanescent absorption spectrum of the scanning cone infrared fiber optic sensor was used as the background signal. The sample solution was injected into the sensor's sample cell, and data were collected from 1131 to 1170 cm⁻¹. -1 Infrared evanescent absorption spectrum within the range; Based on the C–O stretching vibration peak (1150 cm⁻¹) -1 Qualitative and quantitative analysis was conducted. A standard curve was plotted based on the Lambert-Beer law, and the concentration of tea polyphenols was calculated using the standard curve method, with a sensitivity of 0.062 au / (mg·mL). -1 The detection limit is 0.25 mg / mL.

[0045] Fiber optic evanescent wave sensing is based on the interaction between the evanescent wave of an optical fiber and the surrounding medium, detecting and analyzing samples by monitoring changes in characteristic peaks. The fiber optic structure directly affects the feasibility of detection, the signal-to-noise ratio, and the detection sensitivity. Sensors A, B, C, and D are four types of fiber optic sensor structures, such as... Figure 3 As shown.

[0046] The results of using four fiber optic sensors (A, B, C, and D) for ethanol detection are shown in Table 1.

[0047] Table 1 shows the parameters and detection results of the established conical infrared fiber optic sensor; Table 1

[0048] Table 1 shows that different sensor structures directly affect the detection results. Sensor D significantly improves sensitivity (by 3.26 times) and lowers the detection limit compared to sensor A.

[0049] like Figure 4-5 As shown, sensors A, B, C, and D tested five volume concentrations (1%, 3%, 5%, 7%, and 9%) of ethanol-water solutions. As the diameter of the fiber waist decreased, the fiber sensitivity gradually increased. The bent structure improved the fiber sensitivity and lowered the detection limit. Furthermore, the cone-within-a-cone design exhibits lower noise compared to the traditional single-cone bend, resulting in a higher signal-to-noise ratio and higher sensitivity.

[0050] When sensor D was placed for 7 days, ethanol detection was performed. The sensitivity change of the sensor was less than 0.076 au / vol% over 7 days, indicating that the fiber optic sensor of the present invention has good stability.

[0051] Table 2 shows a comparison between the detected values ​​and the nominal values ​​of tea polyphenol tablets.

[0052] Table 2

[0053] Table 3 compares the results of tea polyphenol detection with those of HPLC detection.

[0054] Table 3

[0055] The above results show that the tea polyphenol detection method of the present invention has good accuracy and also demonstrates that the detection method of the present invention has excellent detection sensitivity.

[0056] In summary, the above research demonstrates that this invention, through its innovative "cone-within-a-cone" structure combined with a curved microring design and optimized structural parameters via COMSOL simulation, significantly enhances the intensity of the evanescent field and the interaction between light and matter, thus achieving the detection of tea polyphenols. Compared with existing technologies, it has the following advantages: Strong anti-interference and high sensitivity: It uses infrared evanescent waves to collect molecular signals, effectively suppressing water molecule interference and achieving high sensitivity; Quick and easy: No complicated pretreatment is required, enabling rapid detection of tea polyphenols in tea and its products; It has a stable structure and good detection stability.

[0057] It should be understood that those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A method for detecting tea polyphenols based on infrared evanescent absorption spectroscopy, characterized in that, Includes the following steps: A tapered infrared fiber sensor is provided. The tapered infrared fiber sensor is obtained by drawing an optical fiber with a diameter of 150-1000 μm to obtain a tapered infrared fiber, and then polishing the end faces of the fiber until there are no scratches on the fiber end faces, so that the end faces of the fiber are flat and smooth to present a mirror surface. The tapered infrared fiber includes a first tapered region, the first tapered region includes a transition region and a first waist region, and a part of the first waist region is stretched again to form a second tapered region. The second tapered region includes a second transition region and a second waist region. The second waist region is bent into a ring to form a micro-ring structure. A conical infrared fiber optic sensor is encapsulated in a sample cell with an opening at the top. The sample liquid to be detected is injected into the sample cell to fully cover the fiber optic cable. Provides 850-4000 cm -1 An infrared light source is used to focus infrared light, which is then fully coupled into an optical fiber to collect data in the 1131-1170 cm range. -1 The infrared evanescent absorption spectrum of the range was used to perform qualitative and quantitative analysis of tea polyphenol content based on the intensity of characteristic peaks.

2. The method for detecting tea polyphenols according to claim 1, characterized in that: The tapered infrared optical fiber has two tapered regions. The total length of the first and second waist regions is 3-20 mm. The diameter of the first waist region is 150-300 μm, and the diameter of the second waist region is 20-100 μm.

3. The method for detecting tea polyphenols according to claim 1, characterized in that: The radius of the microring structure is 0.2-3.0 mm.

4. The method for detecting tea polyphenols according to claim 1, characterized in that: The tapered infrared optical fiber is an infrared glass optical fiber with a diameter of 350-800 μm and a transmission range of 850-4000 cm. -1 Mid-infrared light.

5. The method for detecting tea polyphenols according to claim 1, characterized in that: The infrared glass fiber is made of chalcogenide glass fiber, including but not limited to Ge-As-Se-Te, As-Se, and Ge-As-Se chalcogenide glass fibers.

6. The method for detecting tea polyphenols according to claim 1, characterized in that: Qualitative and quantitative analysis was performed based on the C–O stretching vibration peak. The quantitative analysis involved adding the test solution to the sample cell and collecting samples from the 1131-1170 cm⁻¹ peak. -1 The infrared evanescent absorption spectrum of the range was used to perform quantitative analysis of tea polyphenols in the sample according to the standard detection curve of tea polyphenols.

7. The method for detecting tea polyphenols according to claim 1, characterized in that: Method for obtaining the standard detection curve of tea polyphenols: Prepare at least 5 groups of tea polyphenol standard solutions with different concentrations, collect absorption spectra, and establish the relationship curve between the concentration of the tea polyphenol standard solution and the area of ​​its characteristic absorption peak according to Lambert-Beer's law, i.e., the tea polyphenol standard curve.

8. The method for detecting tea polyphenols according to claim 1, characterized in that: The sample to be tested is tea or its products, and the sample liquid to be tested is a methanol extract of the sample to be tested; Infrared spectra were collected using pure methanol solution as solvent. Then, the optical fiber was cleaned, the sample solution to be tested was added, the sample spectrum was collected and processed by spectral subtraction, and then quantitative analysis was performed based on characteristic absorption peaks.

9. A tea polyphenol detection device based on an infrared evanescent wave sensor, characterized in that: include An infrared spectrometer that provides an infrared light source; An optical system used to guide infrared beams into optical fibers and to focus and couple the beams; A tapered infrared fiber optic sensor is embedded in a sample cell with an opening at the top for injecting sample detection liquid. The tapered infrared fiber optic sensor is made by drawing a 150-1000 μm diameter fiber to obtain a tapered infrared fiber, and then polishing both ends until there are no scratches on the fiber ends, making the two ends of the fiber flat and smooth to present a mirror surface. The tapered infrared fiber includes a first tapered region, which includes a transition region and a first waist region. Part of the first waist region is stretched again to form a second tapered region, which includes a second transition region and a second waist region. The second waist region is bent into a ring to form a micro-ring structure. A collimating lens used to collimate the infrared light output from an optical fiber; A detector used to detect the output infrared light; The optical path system includes a plane mirror, an off-axis parabolic mirror, and a ZnSe lens. The plane mirror and the off-axis parabolic mirror are placed opposite each other. Infrared light is reflected by the plane mirror and the off-axis parabolic mirror and then enters the ZnSe lens for beam focusing. The focused infrared light enters the optical fiber and is fully coupled with the optical fiber.

10. The tea polyphenol detection device according to claim 9, characterized in that: The collimating lens is a ZnSe lens; the detector used to detect the output infrared light is an MCT liquid nitrogen-cooled detector.

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