Visual array sensor constructed based on oxidation reaction of nanometer porphyrin and oxidizing agent to different grades of West Lake Longjing wells in different producing areas and application of visual array sensor

Abstract

The invention belongs to the technical field of bionic array sensors, and particularly relates to a visual array sensor constructed on the basis of oxidation reaction of nano porphyrin and an oxidizing agent on different grades of West Lake Longjing wells in different producing areas and application of the visual array sensor. The visual array sensor constructed by the invention is composed of a plurality of sensing units, and each sensing unit comprises two sensing solutions of nano porphyrin and an oxidizing agent. The visual array sensor can be used for identifying catechin compounds and detecting samples rich in the catechin compounds, and can also be used for accurately identifying Longjing tea in small-scale production areas such as Lion peak, Yunheng, Tiger running and Meikuan.

Description

Technical Field

[0001] The present invention belongs to the technical field of bionic array sensors, and in particular relates to a visual array sensor constructed based on the oxidation reaction of nanoporphyrin and oxidant on West Lake Longjing tea of ​​different grades from different producing areas and its application. Background Art

[0002] Tea, coffee and cocoa are known as the three major beverages in the world, and they have a history of thousands of years. Longjing tea is a typical representative of them, and is famous for its characteristics of "green color, rich fragrance, mellow taste and beautiful shape". There are many types of Longjing tea, but the quality is uneven. However, due to the similar geographical conditions and interweaving of the various Longjing tea producing areas, the processing methods used are also similar. It is very difficult to judge the quality of Longjing tea from the appearance, aroma, taste and other aspects. In addition, the high-quality Longjing tea on the market is in short supply, and the problem of inferior products gradually emerged. In order to improve these problems, a method for quickly and conveniently identifying the quality of Longjing tea is urgently needed.

[0003] Array sensors simulate the mammalian olfactory system and are composed of multiple sensing units. Each individual sensing unit is highly selective to the analyte to be measured and has different response capabilities to different components. Unlike the "lock and key mode" of traditional chemical sensors, array sensors achieve accurate identification of the overall characteristics of the target through specific responses or cross-responses to the analyte to be measured. In recent years, the two types of optical array sensors that have been widely used are fluorescence array sensors and visualization array sensors. The former often needs to be combined with a fluorescence spectrometer to achieve analysis and detection of the target, while the latter can achieve detection of the target by color extraction and analysis under visible light. At present, optical array sensors have been successfully applied to the analysis and detection of many complex systems, for example, they have shown excellent performance in the detection and identification of heavy metal substances, food types and ingredients.

[0004] Porphyrin is a macromolecule containing four pyrrole rings, which has a wide range of application value, such as fluorescent probes, catalysts, etc. However, traditional porphyrin molecules have problems such as low solubility, poor stability, and high biological toxicity, which limit their application. With the development of nanotechnology, nanoporphyrins fill the gaps in porphyrin applications. Nanoporphyrins have the characteristics of strong photosensitivity and fluorescence, good biocompatibility and stability, and small particle size. Based on these characteristics of nanoporphyrins, nanoporphyrins have begun to be widely used in food analysis, but because the types and contents of Longjing tea ingredients in small-scale production areas are not very different, and there are a large number of trace components with similar structures, it is difficult to achieve accurate authenticity detection using only nanoporphyrins themselves. Summary of the invention

[0005] In order to solve the technical gaps and defects existing in the above research background, the purpose of the present invention is to provide a visualization array sensor constructed based on the oxidation reaction of different grades of West Lake Longjing tea from different production areas by nanoporphyrins and oxidants and its application. The present invention utilizes the high selectivity and recognition performance of nanoporphyrins, combined with the antioxidant properties of Longjing tea, to propose a new array sensor design strategy. Nanoporphyrins of different compositions, different forms, and different charges and oxidants with different oxidative properties are assembled into visualization array sensors to accurately identify Longjing tea from small-scale production areas such as Shifeng, Yunqi, Hupao, and Meijiawu, and quantitatively analyze trace catechin compounds. The visualization array sensor has the advantages of convenient operation and rapid response, and can be widely used for the identification of catechin compounds and the visualization online detection of samples rich in such compounds.

[0006] In order to achieve the above object, the present invention adopts the following technical scheme:

[0007] A visual array sensor for identifying tea leaves, the visual array sensor comprising 18 sensing units, each of which comprises a mixed solution of nanoporphyrin and an oxidant, wherein nanoporphyrin 1, nanoporphyrin 2 and nanoporphyrin 3 are respectively arranged and combined with oxidant 1, oxidant 2, oxidant 3, oxidant 4, oxidant 5 and oxidant 6 to form 18 different sensing units. For example, nanoporphyrin 1 is respectively mixed with oxidant 1, oxidant 2, oxidant 3, oxidant 4, oxidant 5 and oxidant 6 to form sensing units N1-N6, nanoporphyrin 2 is respectively mixed with oxidant 1, oxidant 2, oxidant 3, oxidant 4, oxidant 5 and oxidant 6 to form sensing units M1-M6, and nanoporphyrin 3 is respectively mixed with oxidant 1, oxidant 2, oxidant 3, oxidant 4, oxidant 5 and oxidant 6 to form sensing units F1-F6.

[0008] Among them, nanoporphyrin 1, nanoporphyrin 2 and nanoporphyrin 3 are each independently selected from any one of 5,10,15,20-tetrakis(4-aminophenyl) nanoporphyrin synthesized with hexadecyltributylphosphonium bromide as a surfactant, 5,10,15,20-tetrakis(4-bromophenyl)manganese nanoporphyrin synthesized with sodium dodecyl sulfate as a surfactant, and 5,10,15,20-tetrakis(4-bromophenyl)manganese nanoporphyrin synthesized with hexadecyltributylphosphonium bromide as a surfactant, and the three nanoporphyrins are different.

[0009] Among them, oxidant 1, oxidant 2, oxidant 3, oxidant 4, oxidant 5, and oxidant 6 are each independently selected from any one of KMnO4, H2O2, N-bromosuccinimide, tetramethylpiperidine, methyltrioxorhenium, and pyridine N-oxide, and the six oxidants are different.

[0010] Furthermore, the step of synthesizing 5,10,15,20-tetrakis(4-aminophenyl) nanoporphyrin includes: mixing an N,N-dimethylformamide solution of 5,10,15,20-tetrakis(4-aminophenyl) porphyrin and an aqueous solution of hexadecyltributylphosphonium bromide, adjusting the pH value to 8±0.1, reacting in a water bath at 40±3°C for 15-30 minutes, and obtaining a 5,10,15,20-tetrakis(4-aminophenyl) nanoporphyrin stock solution.

[0011] Preferably, the concentration of the N,N-dimethylformamide solution of 5,10,15,20-tetrakis(4-aminophenyl)porphyrin is 30-35 mmol / L, the concentration of the aqueous solution of hexadecyltributylphosphonium bromide is 5 mmol / L, and the volume ratio of the N,N-dimethylformamide solution of 5,10,15,20-tetrakis(4-aminophenyl)porphyrin to the aqueous solution of hexadecyltributylphosphonium bromide is 1:40.

[0012] Furthermore, the step of synthesizing 5,10,15,20-tetrakis(4-bromophenyl)manganese nanoporphyrin using sodium dodecyl sulfate or hexadecyltributylphosphonium bromide as a surfactant includes: mixing an N,N-dimethylformamide solution of 5,10,15,20-tetrakis(4-bromophenyl)manganese porphyrin and an aqueous solution of sodium dodecyl sulfate or hexadecyltributylphosphonium bromide, adjusting the pH value to 8±0.1, and reacting in a water bath at 40±3°C for 15-30 minutes to obtain a 5,10,15,20-tetrakis(4-bromophenyl)manganese nanoporphyrin stock solution.

[0013] Preferably, the concentration of the N,N-dimethylformamide solution of 5,10,15,20-tetrakis(4-bromophenyl)manganoporphyrin is 30-35 mmol / L, the concentration of the aqueous solution of sodium dodecyl sulfate or hexadecyltributylphosphonium bromide is 5 mmol / L, and the volume ratio of the N,N-dimethylformamide solution of 5,10,15,20-tetrakis(4-bromophenyl)manganoporphyrin to the aqueous solution of sodium dodecyl sulfate or hexadecyltributylphosphonium bromide is 1:40.

[0014] Furthermore, the concentration of the three nanoporphyrin stock solutions was 7.5×10 -4 -8.5×10 -4 mol / L.

[0015] Furthermore, the concentration of the oxidant KMnO4 is 10 -3 mol / L, the concentration of oxidant H2O2 is 10 -2 mol / L, the concentration of the oxidant N-bromosuccinimide is 10 -1 mol / L, the concentration of the oxidant tetramethylpiperidine was 10 -1 mol / L, the concentration of oxidant methyltrioxorhenium is 10 -2mol / L, the concentration of oxidant pyridine N-oxide is 10 -2 mol / L.

[0016] The application of the above-mentioned visualization array sensor in identifying tea leaves.

[0017] Preferably, the above-mentioned visualization array sensor is used to identify different grades of West Lake Longjing tea from different production areas.

[0018] More preferably, the above-mentioned visualization array sensor is used to identify adulteration of West Lake Longjing tea of ​​different grades from different production areas.

[0019] The above-mentioned visualization array sensor is used in the quantitative analysis of trace catechin compounds in food.

[0020] The application of the visualization array sensor in identifying tea includes the following steps: the tea soup of the tea sample to be tested or other test solution is mixed evenly with the 18 nanoporphyrin-oxidant sensor units in the visualization array sensor, and the reaction is allowed to stand, and the color response of the sensor array to the antioxidant properties of different teas has a color difference, and the fingerprints of the test sample detection system and the blank detection system are collected under visible light and ultraviolet light respectively to obtain the R, G, and B difference between the two, and the R, G, and B difference is directly or amplified by a certain multiple (for example, 1-10 times) and then screened to draw a color difference diagram, and OPLS-DA, PLSR, OCPLS and other chemometric methods are used for discriminant analysis to achieve visual identification of the tea sample to be tested or other foods to be tested.

[0021] The blank detection system is relative to the detection system (added with tea soup), that is, the detection system is added with water of the same volume as the tea soup.

[0022] The application steps of the visual array sensor in the quantitative analysis of trace catechin compounds in food are the same as those for identifying tea leaves, and only the tea soup needs to be replaced by food or raw materials or diluent or extract obtained by simple pretreatment.

[0023] The order of adding the tea soup and the sensor unit is: nanoporphyrin, oxidant, tea soup.

[0024] Preferably, the concentration of nanoporphyrin added to the detection system is 1.5×10 -4 -1.7×10 -4 mol / L.

[0025] Preferably, the concentration of the oxidant added to the detection system is: the concentration of KMnO4 is 10 -3 mol / L, the concentration of H2O2 is 10 -2 mol / L, the concentration of N-bromosuccinimide is 10 -1mol / L, the concentration of tetramethylpiperidine is 10 -1 mol / L, the concentration of methyltrioxorhenium is 10 -2 mol / L, the concentration of pyridine N-oxide is 10 -2 mol / L.

[0026] Preferably, the volume ratio of nanoporphyrin, oxidant and tea soup is 1:1:1.

[0027] Preferably, the static reaction time is 1-5 min.

[0028] Among them, the tea to be tested is West Lake Longjing tea of ​​different grades from different producing areas, including at least one of Yunqi special grade, Yunqi first grade, Yunqi second grade, Hupao special grade, Hupao first grade, Hupao second grade, Meijiawu special grade, Meijiawu first grade, Meijiawu second grade, Shifeng special grade, and Shifeng first grade.

[0029] Preferably, 0.05 g of tea leaves are soaked in 10 ml of deionized water at 60° C. for 30 min, then taken out and cooled to room temperature to obtain the corresponding tea soup.

[0030] Among them, the collection of fingerprint spectra is carried out in a dark room to minimize the impact of ambient light on the acquisition of fingerprint spectra.

[0031] Compared with the existing technology, the beneficial effects of the present invention are:

[0032] The present invention provides a visualization array sensor based on the color difference of the color response of the nanoporphyrin-oxidant sensor array to the antioxidant properties of different teas. The visualization array sensor can realize instant color development reaction at room temperature (subsequently extract R, G, B color difference by collecting fingerprint spectrum and drawing to highlight the color difference), and has the advantages of high accuracy and fast speed. It provides a method for on-site identification and analysis of West Lake Longjing tea, and also provides a way of thinking for authenticity analysis of other foods. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 Schematic diagram of the mechanism of the visualization array sensor of the present invention for detecting West Lake Longjing tea.

[0034] Figure 2 This is a schematic diagram of the subdivision color difference of 11 types of West Lake Longjing tea of ​​different grades from different producing areas detected by the visualization array sensor of the present invention.

[0035] Figure 3 This is the evaluation of 11 types of West Lake Longjing tea using OPLS-DA.

[0036] Figure 4 This is a color difference diagram of the concentration gradient of catechin compounds detected by the visualized array sensor of the present invention, in which A is catechin and B is epicatechin.

[0037] Figure 5 This is the linear discriminant diagram of PLSR for catechin compounds, where A is catechin and B is epicatechin.

[0038] Figure 6 This is a color difference diagram of the mixtures of catechin / epicatechin with different ratios detected by the visualization array sensor of the present invention.

[0039] Figure 7 Figure 1 is the linear discriminant diagram of PLSR for mixtures of catechin / epicatechin with different ratios. Figures A and B are the discrimination results of catechin and epicatechin with a volume ratio of 1:1-1:0.01, and Figures C and D are the discrimination results of catechin and epicatechin with a volume ratio of 1:9-9:1.

[0040] Figure 8 This is a schematic diagram of the color difference of adulterated samples of Shifeng Special Grade / Meijiawu Second Grade and Shifeng Special Grade / Wuniuzao with different volume ratios detected by the visualization array sensor of the present invention, in which A and C are adulterated samples of Shifeng Special Grade / Meijiawu Second Grade, and B and D are adulterated samples of Shifeng Special Grade / Wuniuzao.

[0041] Fig. 9 This is the OCPLS evaluation of the adulterated samples of Shifeng Special Grade / Meijiawu Second Grade. In the figure, A is the training sample result; B is the predicted sample result; C is the enlarged view of the regular point area in the predicted sample result.

[0042] Fig.10 This is the OCPLS evaluation of the adulterated samples of Shifeng Special Grade / Wuniuzao. In the figure, A is the training sample result; B is the predicted sample result; C is the enlarged view of the regular point area in the predicted sample result.

[0043] Fig.11 These are the stability and anti-interference chromatic aberration diagrams of the visualization array sensor of the present invention, where A, C, and E are stability chromatic aberration diagrams, and B, D, and F are anti-interference chromatic aberration diagrams.

[0044] Fig.12 The transmission electron microscope image (AI) and infrared spectrum image (JL) of the nanoporphyrin before and after combining with the oxidant in Example 1. DETAILED DESCRIPTION

[0045] The following examples are provided to facilitate a better understanding of the present invention, but are not intended to limit the present invention. The following uses catechin compounds and Longjing tea of ​​different grades from different origins as examples, and further describes the technical solution of the present invention in detail in conjunction with the accompanying drawings.

[0046] Example 1: A method for establishing a visual array sensor based on the oxidation reaction of nanoporphyrin and oxidant on West Lake Longjing tea of ​​different grades from different production areas

[0047] Step 1: Synthesis of Nanoporphyrin

[0048] Synthesis of 5,10,15,20-tetrakis(4-aminophenyl) nanoporphyrin (hereinafter referred to as "nanoporphyrin 1"): 0.1015 g (0.2 mmol) of hexadecyl tributyl phosphonium bromide was weighed and dissolved in 40 ml of deionized water, and the pH value was adjusted to 8. After that, the water bath was heated to 40 °C, 0.022 g of 5,10,15,20-tetrakis(4-aminophenyl) porphyrin was dissolved in 1 mL of DMF, and then dripped into the above aqueous solution dropwise, and slowly stirred for 30 min to obtain a final concentration of 8×10 -4 mol / L 5,10,15,20-tetrakis(4-aminophenyl) nanoporphyrin stock solution is dark brown and is stored in a refrigerator at 4°C.

[0049] Synthesis of 5,10,15,20-tetrakis(4-bromophenyl)manganese nanoporphyrin 12 (hereinafter referred to as "nanoporphyrin 2"): 0.05767 g (0.2 mmol) of sodium dodecyl sulfate was weighed and dissolved in 40 ml of deionized water, and the pH value was adjusted to 8. After that, the water bath was heated to 40 °C, 0.03 g of 5,10,15,20-tetrakis(4-bromophenyl)manganese porphyrin was dissolved in 1 mL of DMF, and then dripped into the above aqueous solution drop by drop, and slowly stirred for 30 min to obtain a final concentration of 8×10 -4 mol / L 5,10,15,20-tetrakis(4-bromophenyl)manganese nanoporphyrin 12 stock solution is dark green and is stored in a refrigerator at 4°C.

[0050] Synthesis of 5,10,15,20-tetrakis(4-bromophenyl)manganese nanoporphyrin 16 (hereinafter referred to as "nanoporphyrin 3"): 0.1015 g (0.2 mmol) of hexadecyl tributyl phosphonium bromide was weighed and dissolved in 40 ml of deionized water, and the pH value was adjusted to 8. After that, the water bath was heated to 40 °C, 0.03 g of 5,10,15,20-tetrakis(4-bromophenyl)manganese porphyrin was dissolved in 1 mL of DMF, and then dripped into the above aqueous solution dropwise, and slowly stirred for 30 min to obtain a final concentration of 8×10 -4 mol / L 5,10,15,20-tetrakis(4-bromophenyl)manganese nanoporphyrin 16 stock solution is dark green and is stored in a refrigerator at 4°C.

[0051] Transmission electron microscopy images of nanoporphyrin 1 (NP1), nanoporphyrin 2 (NP2), and nanoporphyrin 3 (NP3) are shown in Fig.12 In Figures A, D, and G, it can be seen that the surface morphologies of the three nanoporphyrins are different. -3 mol / L KMnO4 solution or 5×10 -1mol / L tetramethylpiperidine solution), the etching morphology of the same nanoporphyrin surface is different with the different oxidizing ability of the oxidant, see Fig.12 After adding oxidants with different oxidizing properties to the nanoporphyrin, the infrared spectrum of the nanoporphyrin also changed significantly, as shown in Fig.12 In the figure, J (NP1), K (NP2), and L (NP3), the black line refers to nanoporphyrin, the red line refers to the addition of KMnO4, and the blue line refers to the addition of tetramethylpiperidine, which verifies the different optical response characteristics of the sensing units in the array sensor. At the same time, it reflects the diversity and rationality of the design of each sensing unit of the array sensor of the present invention.

[0052] Step 2: Create a Visual Array Sensor

[0053] The visualized array sensor consists of 18 sensing units, each of which includes two sensing solutions, namely nanoporphyrin and oxidant. The oxidants KMnO4, H2O2, N-bromosuccinimide, tetramethylpiperidine, methyltrioxorhenium, and pyridine N-oxide are numbered 1-6, respectively. The six oxidants KMnO4, H2O2, N-bromosuccinimide, tetramethylpiperidine, methyltrioxorhenium, and pyridine N-oxide are mixed with 5, 10, 15, 20-tetrakis(4-aminophenyl) nanoporphyrin ("nanoporphyrin 1") to form sensing units N1-N6, and the six oxidants KMnO4, H2O2, N-bromosuccinimide, tetramethylpiperidine, methyltrioxorhenium, and pyridine N-oxide are respectively mixed with 5, 10, 15, 20-tetrakis(4-aminophenyl) nanoporphyrin ("nanoporphyrin 1") to form sensing units N1-N6. The oxidants KMnO4, H2O2, N-bromosuccinimide, tetramethylpiperidine, methyltrioxorhenium, and pyridine N-oxide are respectively mixed with 5,10,15,20-tetrakis(4-bromophenyl)manganese nanoporphyrin 12 ("nanoporphyrin 2") to form sensing units M1-M6, and the six oxidants KMnO4, H2O2, N-bromosuccinimide, tetramethylpiperidine, methyltrioxorhenium, and pyridine N-oxide are respectively mixed with 5,10,15,20-tetrakis(4-bromophenyl)manganese nanoporphyrin 16 ("nanoporphyrin 3") to form sensing units F1-F6.

[0054] Figure 1 Schematic diagram of the mechanism of the visualization array sensor of the present invention for detecting West Lake Longjing tea.

[0055] Step 3: The method of visual array sensor identifying different grades of West Lake Longjing tea from different production areas includes the following steps:

[0056] (1) Preparation of sensing solution and tea sample to be tested

[0057] 1) Nanoporphyrin: The three nanoporphyrins prepared in the first step are dark in color, so the three nanoporphyrin stock solutions were diluted 5 times with deionized water to a concentration of 1.6×10 -4 mol / L, let stand and store.

[0058] 2) Prepare six oxidants: KMnO4, H2O2, N-bromosuccinimide, tetramethylpiperidine, methyltrioxorhenium, pyridine N-oxide, the concentration of oxidant KMnO4 is 10 -3 mol / L, the concentration of oxidant H2O2 is 10 -2 mol / L, the concentration of the oxidant N-bromosuccinimide is 10 -1 mol / L, the concentration of the oxidant tetramethylpiperidine was 10 -1 mol / L, the concentration of oxidant methyltrioxorhenium is 10 -2 mol / L, the concentration of oxidant pyridine N-oxide is 10 -2 mol / L.

[0059] 3) Preparation of tea samples to be tested: The West Lake Longjing tea identified in this embodiment includes Yunqi special grade, Yunqi first grade, Yunqi second grade, Hupao special grade, Hupao first grade, Hupao second grade, Meijiawu special grade, Meijiawu first grade, Meijiawu second grade, Shifeng special grade, and Shifeng first grade. The tea leaves are pre-treated to obtain corresponding tea soup. The pre-treatment steps are: take 0.05g of tea leaves and soak them in 10ml of deionized water at 60°C for 30min, then take them out and cool them to room temperature (25°C) to obtain the corresponding tea soup.

[0060] (2) Visual array sensor identifies different grades of West Lake Longjing tea from different production areas

[0061] First, prepare three 96-well plates. In the first 96-well plate, 72 wells are arranged in 6×12 (rows×columns). 1.6×10 -4 mol / L 5,10,15,20-tetrakis(4-aminophenyl) nanoporphyrin ("nanoporphyrin 1"), 1.6×10 -4 mol / L 5,10,15,20-tetrakis(4-bromophenyl)manganese nanoporphyrin 12 ("nanoporphyrin 2"), 1.6×10 -4 mol / L 5,10,15,20-tetrakis(4-bromophenyl)manganese nanoporphyrin 16 ("nanoporphyrin 3"), the amount of nanoporphyrin added to each well was 100 μL;

[0062] Three 96-well plates, after adding nanoporphyrins, add one oxidant in each row from top to bottom. The order of addition from top to bottom is: KMnO4, H2O2, N-bromosuccinimide, tetramethylpiperidine, methyltrioxorhenium, pyridine N-oxide, a total of six rows, and the amount of oxidant added to each well is 100 μL;

[0063] In three 96-well plates, deionized water was added to the first column of the wells after adding the oxidant as a blank control group, and 100 μL of deionized water was added to each well; tea soup of West Lake Longjing tea of ​​different production areas and grades was added to the right side of the same row in sequence. The order from left to right is: Yunqi Special Grade, Yunqi Grade One, Yunqi Grade Two, Hupao Special Grade, Hupao Grade One, Hupao Grade Two, Meijiawu Special Grade, Meijiawu Grade One, Meijiawu Grade Two, Shifeng Special Grade, Shifeng Grade One, for a total of six rows, and 100 μL of tea soup was added to each well.

[0064] It should be noted that, in order to control the effect of the addition time on the reaction, all the same samples were added using an eppendorf multichannel pipette.

[0065] When the last sample is added, mix it evenly at room temperature and react for 5 minutes, then place the 96-well plate under a shadowless bottom lamp and an ultraviolet lamp (each sensor unit has two images, the number V represents the image under visible light, and the number K represents the image under 354nm ultraviolet light, for example, MV1-MV6 refers to the image of sensor units M1-M6 under visible light, and MK1-MK6 refers to the image of sensor units M1-M6 under ultraviolet light), and take pictures with a SLR camera in a dark room, that is, record the fingerprint of the blank control group and each kind of tea soup, and repeat the parallel experiment 3 times for each sample. It can be known that the array sensor has a differential response to different teas only by the method of naked eye judgment. In order to make the difference display more obvious, the R, G, B values ​​of the photographed pictures are extracted by Photoshop to obtain the R, G, B values ​​between the reaction wells of different grades of West Lake Longjing tea from different production areas and the control group, and obtain the corresponding R, G, B difference. The R, G, B difference is enlarged 10 times and drawn into a color difference diagram. The drawn color difference map is screened to obtain several sensor units with obvious color differences, such as Figure 2 As shown, the discriminant analysis was then performed using partial least squares discriminant analysis (OPLS-DA), as shown in Figure 3 As shown, the serial numbers 1-11 in the figure correspond to the tea soup of Yunqi special grade, Yunqi first grade, Yunqi second grade, Hupao special grade, Hupao first grade, Hupao second grade, Meijiawu special grade, Meijiawu first grade, Meijiawu second grade, Shifeng special grade, Shifeng first grade Longjing tea. The figure shows that the visual array sensor can accurately distinguish Longjing tea from small-scale production areas, expand the application scope of the nanoporphyrin composite system in tea identification, and lay the foundation for subsequent applications.

[0066] Example 2: Visual array sensor identification of two catechin compounds (catechin and epicatechin) in tea leaves

[0067] The visualized array sensor constructed by the present invention can also realize the recognition of two catechin compounds (catechin and epicatechin) in tea leaves.

[0068] Green tea extract contains several polyphenolic components with antioxidant properties, but the main active ingredient is the flavanol monomer, i.e. catechin, which accounts for 25-35% of the dry weight of green tea. The antioxidant capacity of tea leaves is closely related to its content. In order to distinguish these two isomers, array sensors were constructed according to their different antioxidant capacities.

[0069] (1) Identification of single catechin compounds

[0070] The visual array sensor and the method for identifying different grades of West Lake Longjing tea from different producing areas established in Example 1 are also applicable to identifying two catechin compounds in tea. It is only necessary to replace the different tea soups with nine different concentrations of catechin compounds (catechin or epicatechin) of the same volume, and the other conditions are the same. The nine different concentrations are 1×10 -3 ,7×10 -4 , 5×10 -4 , 3×10 -4 , 1×10 -4 , 5×10 -5 , 1×10 -5 , 1×10 -6 , 1×10 -7 mol / L.

[0071] Similarly, record the fingerprints of the blank control group and each concentration of the compound, and repeat the experiment three times for each sample. Only by visual judgment can it be known that the array sensor has different responses to different compounds. In order to make the difference more obvious, the R, G, B values ​​of the captured pictures are extracted through Photoshop to obtain the R, G, B values ​​between the reaction wells of each concentration and the control group, and obtain the corresponding R, G, B differences. Magnify the R, G, B differences by 10 times and draw a color difference map. Screen the drawn color difference map to obtain several sensor units with obvious color differences, such as Figure 4 As shown in the figure, A is catechin and B is epicatechin. The results in the figure show that the visual array sensor has good selectivity for catechin and epicatechin, even if the concentration of both is as low as 1×10 -7 mol / L, and can also specifically identify. Then, partial least squares regression (PLSR) is used for linear discriminant analysis. After the introduction of the PLSR model, a series of concentrations of 1×10 -7 -1×10 -3 mol / L of catechin or epicatechin can be accurately quantified. Figure 5 As shown, A is catechin and B is epicatechin. The results show that the visual array sensor has good detection performance for trace amounts and structurally similar components.

[0072] (2) Identification of mixed catechin compounds

[0073] The visual array sensor and the method for identifying different grades of West Lake Longjing tea from different producing areas established in Example 1 are also applicable to identifying two catechin compounds in tea leaves. It is only necessary to replace the different tea soups with eleven 1×10 -4 mol / L catechins and 1×10 -4 The eleven different volume ratios of catechin to epicatechin are 1:1 (under this volume ratio, the amount of the mixed solution added is 200 μL, and the amount of the mixed solution added is 100 μL if no special instructions are given for other volume ratios), 1:0.1, 1:0.01, 1:9, 2:8, 3:7, 4:6, 5:5, 6:4, 7:3, 8:2, and 9:1.

[0074] Similarly, record the fingerprints of the blank control group and each mixture ratio, and repeat the experiment three times for each sample. It can be known that the array sensor has differential responses to different compounds only by visual judgment. In order to make the difference more obvious, the R, G, B values ​​of the captured pictures are extracted through Photoshop to obtain the R, G, B values ​​between the reaction wells of each ratio and the control group, and obtain the corresponding R, G, B differences. Magnify the R, G, B differences by 10 times and draw a color difference diagram. Screen the drawn color difference diagram to obtain several sensor units with obvious color differences, such as Figure 6 As shown. Then, partial least squares regression (PLSR) is used for linear discriminant analysis, as shown Figure 7 As shown, A and B in the figure are the discrimination results of catechin and epicatechin with a volume ratio of 1:1, 1:0.1, and 1:0.01, and C and D in the figure are the discrimination results of catechin and epicatechin with a volume ratio of 1:9, 2:8, 3:7, 4:6, 5:5, 6:4, 7:3, 8:2, and 9:1. Since the ratio of catechin to epicatechin in different Longjing teas is different, it is necessary to detect and analyze the mixture of catechin and epicatechin with different ratios, and the results also show that the visual array sensor has obtained good quantitative analysis results for the recognition of the two isomers.

[0075] Example 3: Visual array sensor identifies whether Longjing tea is adulterated

[0076] The visual array sensor constructed by the present invention can not only identify and detect catechin compounds, but also detect whether Longjing tea is adulterated.

[0077] The present application selects Shifeng special tea, Wuniu morning tea and Meijiawu second-grade tea as samples for identifying tea adulteration. First, the tea is pre-treated according to the method in Example 1 to obtain the corresponding tea soup. Then, Shifeng special tea and Meijiawu second-grade tea soup are mixed in a volume ratio of 1:1, 1:0.1, 1:0.01, 1:0.001, 9:1, 8:2, 7:3, 6:4, 5:5 to obtain mixed tea soups with different volume ratios; Shifeng special tea and Wuniu morning tea soup are mixed in a volume ratio of 1:1, 1:0.1, 1:0.01, 1:0.001, 9:1, 8:2, 7:3, 6:4, 5:5 to obtain mixed tea soups with different volume ratios.

[0078] The visualization array sensor established in Example 1 and the method thereof for identifying different grades of West Lake Longjing tea from different production areas are also applicable to identifying whether Longjing tea is adulterated. It is only necessary to replace the different tea soups with the same volume of nine mixed tea soups with different volume ratios (Shifeng Special Grade / Meijiawu Second Grade or Shifeng Special Grade / Wuniuzao), and the other conditions are the same. The volume ratio of Shifeng Special Grade / Meijiawu Second Grade or Shifeng Special Grade / Wuniuzao in the nine mixed tea soups with different volume ratios is 1:1 (under this volume ratio, the amount of mixed tea soup added is 200 μL, and the amount of mixed tea soup added is 100 μL for other volume ratios not specifically stated), 1:0.1, 1:0.01, 1:0.001, 9:1, 8:2, 7:3, 6:4, 5:5.

[0079] Similarly, record the fingerprints of the blank control group and each ratio of adulterated tea, and repeat the experiment three times for each sample. It can be known that the array sensor has different responses to different teas only through the method of visual judgment. In order to make the difference more obvious, the R, G, B values ​​of the captured pictures are extracted through Photoshop to obtain the R, G, B values ​​between the reaction wells of each ratio and the control group, and obtain the corresponding R, G, B differences. Magnify the R, G, B differences by 10 times and draw a color difference map. Screen the drawn color difference map to obtain several sensor units with obvious color differences, such as Figure 8 As shown in the figure, A and C are Shifeng Special Grade / Meijiawu Second Grade, and B and D are Shifeng Special Grade / Wuniuzao. Then, one-class partial least squares (OCPLS) was used for discriminant analysis. Fig. 9 The OCPLS evaluation of adulterated samples of Shifeng Special Grade / Meijiawu Second Grade, in which A is the training sample result, B is the predicted sample result, and C is the enlarged view of the regular point area in the predicted sample result; Fig.10The OCPLS evaluation of adulterated samples of Shifeng Special Grade / Wuniuzao, in which A is the training sample result, B is the predicted sample result, and C is the enlarged view of the regular point area in the predicted sample result. The results show that both adulteration cases such as Shifeng Special Grade / Wuniuzao and inferior adulteration cases such as Shifeng Special Grade / Meijiawu Second Grade can be accurately identified.

[0080] Example 4: Stability and anti-interference of the visual array sensor

[0081] (1) Stability

[0082] In order to determine that the visualization array sensor constructed by the present invention has good stability, the different tea soups in the visualization array sensor and the method for identifying different grades of West Lake Longjing tea from different producing areas established in Example 1 are replaced with pH buffer solutions of different pH values ​​of the same volume, and the other conditions are the same. The pH value range of the pH buffer solution is 4-11.

[0083] Similarly, record the fingerprints of the blank control group and each solution, and extract the R, G, B values ​​of the captured images through Photoshop to obtain the R, G, B values ​​between the reaction wells where each solution is located and the control group, and obtain the corresponding R, G, B difference. Magnify the R, G, B difference by 10 times and draw a color difference map. Screen the drawn color difference map to obtain several sensor units with obvious color differences, such as Fig.11 As shown in A, C, and E. The results show that the visual array sensor has good stability and is little affected by changes in environmental pH.

[0084] (2) Anti-interference

[0085] In order to determine whether the visualization array sensor constructed by the present invention has anti-interference ability, the different tea soups in the visualization array sensor and the method for identifying different grades of West Lake Longjing tea from different producing areas established in Example 1 were replaced with 1×10 -4 mol / L inorganic metal salt solution or amino acid solution, and the other conditions are the same. The inorganic metal salt solution is MgSO4, Na2SO4, KCl, CaCl2, Fe(NO3)2 solution, and the amino acid solution is glycine (Gly), glutamic acid (Glu), alanine (Ala) solution.

[0086] Similarly, record the fingerprints of the blank control group and each solution, and extract the R, G, B values ​​of the captured images through Photoshop to obtain the R, G, B values ​​between the reaction wells where each solution is located and the control group, and obtain the corresponding R, G, B difference. Magnify the R, G, B difference by 10 times and draw a color difference map. Screen the drawn color difference map to obtain several sensor units with obvious color differences, such as Fig.11 As shown in B, D, and F. The results show that the visual array sensor has good anti-interference ability and is not interfered by common metal ions and amino acids.

Claims

1. A visual array sensor for identifying tea leaves, characterized in that: The visualization array sensor includes 18 sensing units, each of which includes a mixed solution of nanoporphyrin and oxidant, and nanoporphyrin 1, nanoporphyrin 2 and nanoporphyrin 3 are respectively arranged and mixed with oxidant 1, oxidant 2, oxidant 3, oxidant 4, oxidant 5 and oxidant 6 to form 18 different sensing units; Among them, nanoporphyrins 1-3 are 5,10,15,20-tetrakis(4-aminophenyl) nanoporphyrin synthesized with hexadecyltributylphosphonium bromide as a surfactant, 5,10,15,20-tetrakis(4-bromophenyl)manganese nanoporphyrin synthesized with sodium dodecyl sulfate as a surfactant, and 5,10,15,20-tetrakis(4-bromophenyl)manganese nanoporphyrin synthesized with hexadecyltributylphosphonium bromide as a surfactant; Among them, oxidants 1-6 are KMnO4, H2O2, N-bromosuccinimide, tetramethylpiperidine, methyltrioxorhenium, and pyridine N-oxide, respectively.

2. The visualization array sensor according to claim 1, characterized in that: The steps of synthesizing the nanoporphyrin include: mixing an N,N-dimethylformamide solution of 5,10,15,20-tetrakis(4-aminophenyl)porphyrin or 5,10,15,20-tetrakis(4-bromophenyl)manganese porphyrin with an aqueous solution of a corresponding surfactant, adjusting the pH value to 8±0.1, reacting in a water bath at 40±3°C for 15-30 minutes, and obtaining a nanoporphyrin stock solution.

3. The visualization array sensor according to claim 2, characterized in that: The concentration of the N,N-dimethylformamide solution of 5,10,15,20-tetrakis(4-aminophenyl)porphyrin or 5,10,15,20-tetrakis(4-bromophenyl)manganeseporphyrin is 30-35 mmol / L, the concentration of the aqueous solution of sodium dodecyl sulfate or hexadecyltributylphosphonium bromide is 5 mmol / L, and the volume ratio of the former solution to the latter solution is 1:

40.

4. Use of the visualization array sensor according to any one of claims 1 to 3 in identifying tea leaves.

5. Use of the visualization array sensor according to any one of claims 1 to 3 in identifying different grades of West Lake Longjing tea from different producing areas.

6. Use of the visualization array sensor according to any one of claims 1 to 3 in identifying adulteration of West Lake Longjing tea of ​​different grades from different producing areas.

7. Use of the visualization array sensor according to any one of claims 1 to 3 in quantitative analysis of trace catechin compounds in food.

8. The use according to any one of claims 4 to 7, characterized in that: The method comprises the following steps: evenly mixing tea soup of a tea sample to be tested or other solution to be tested with 18 nanoporphyrin-oxidant sensor units in a visualization array sensor respectively, allowing the mixture to react, utilizing the color difference of the color response of the sensor array due to the antioxidant properties of different teas, collecting fingerprints of a detection system of the sample to be tested and a blank detection system under visible light and ultraviolet light respectively and obtaining R, G, and B differences between the two, drawing a color difference diagram by directly or after screening the R, G, and B differences after amplifying them by a certain multiple, and performing discrimination analysis with the aid of a chemometric method, thereby realizing visualization identification of the tea sample to be tested or other food to be tested.

9. The use according to claim 8, characterized in that: The order of adding samples when mixing tea soup with the sensor unit is: nanoporphyrin, oxidant, tea soup; Preferably, the concentration of nanoporphyrin added to the detection system is 1.5×10 -4 -1.7×10 -4 mol / L; Preferably, the concentration of the oxidant added to the detection system is: the concentration of KMnO4 is 10 -3 mol / L, the concentration of H2O2 is 10 - 2 mol / L, the concentration of N-bromosuccinimide is 10 -1 mol / L, the concentration of tetramethylpiperidine is 10 -1 mol / L, the concentration of methyltrioxorhenium is 10 -2 mol / L, the concentration of pyridine N-oxide is 10 -2 mol / L; Preferably, the volume ratio of nanoporphyrin, oxidant and tea soup is 1:1:1; Preferably, the static reaction time is 1-5 min.

10. The use according to claim 8, characterized in that: The tea to be tested includes at least one of Yunqi special grade, Yunqi first grade, Yunqi second grade, Hupao special grade, Hupao first grade, Hupao second grade, Meijiawu special grade, Meijiawu first grade, Meijiawu second grade, Shifeng special grade, and Shifeng first grade; Preferably, 0.05 g of tea leaves are soaked in 10 ml of deionized water at 60±5° C. for 30±5 min, then taken out and cooled to room temperature to obtain the corresponding tea soup.

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