Detection device for determining nitrate content in food

Abstract

The utility model discloses a detection device for measuring the content of nitrate in food, which comprises a front module for reducing nitrate in a solvent to be detected into nitrite and mixing the nitrite with a color developing agent, and a detection module for detecting the content of the nitrite, the technical problems that an existing detection device uses toxic heavy metal cadmium powder to reduce nitrate and a traditional spectrophotometric method to detect the nitrate, large risks are brought to the detection process, operation is complex, cost is high, and carrying is not easy are solved. The detection device realizes real-time non-toxic quantitative detection of the nitrate content in food by taking zinc powder as a reducing agent and combining a colorimetric method; the zinc powder is effectively fixed by using the hydrogel, and a relatively large surface specific area is ensured, so that the reduction of nitrate is realized under a non-toxic condition, and the test steps are simplified; the micro-fluidic chip is used for detection, so that the integration degree is high, and the reagent dosage is greatly reduced; the intelligent mobile phone is used for image analysis, compared with a traditional spectrophotometric method, higher operability and portability are achieved, the overall size of the detection device is greatly reduced, operation is easy, and the application range is wide.

Description

Technical Field

[0001] The utility model relates to the technical field of food safety, in particular to a detection device for determining the nitrate content in food. Background Art

[0002] Due to the abuse of artificial fertilizers and food additives, nitrate has become a nitrogen-containing compound widely present in food. Nitrate itself is non-toxic, but when it enters the human body, it will be reduced to nitrite. Excessive intake of nitrite will increase the risk of methemoglobinemia and cancer in the human body. Therefore, the development of accurate and rapid detection devices for nitrate is of great practical significance to safeguard people's livelihood.

[0003] At present, the main methods for determining nitrate include ultraviolet photometry, chromotropic acid photometry, cadmium column reduction-diazo coupling colorimetric method, etc. Among them, ultraviolet photometry requires a large spectrophotometer, chromotropic acid photometry requires a large amount of concentrated sulfuric acid, and the reagent itself is very easy to change color, which is not suitable for rapid on-site determination. The national standard GB5009.33-2016 stipulates the determination method of nitrite and nitrate in food. The determination method of nitrate is to first reduce nitrate to nitrite through a cadmium column, and then react nitrite with p-aminobenzenesulfonic acid and couple with naphthylethylenediamine hydrochloride to produce a color reaction to determine the absorbance value. The cadmium column reduction-diazo coupling colorimetric method in the national standard method is not only cumbersome and time-consuming, but also requires the sample to be brought into the laboratory for analysis, which has poor timeliness. The cadmium column will age with the increase in the number of uses, and the cadmium column reduction efficiency will decrease. In addition, real-life food samples generally contain nitrate and nitrite, and nitrite will also produce some absorbance values. The presence of nitrite greatly interferes with nitrate, and the test results of nitrate need to be corrected. Existing rapid detection methods have large errors and cannot eliminate the interference of nitrite when detecting nitrate.

[0004] Therefore, the Chinese utility model patent with an authorization announcement date of 2020.05.05 and an authorization announcement number of CN 210465266 U discloses a device for detecting nitrate in edible sugar, including a stoppered colorimetric tube for containing a sugar solution to be tested, a first reagent package and a second reagent package for containing reagents for detecting nitrate, a vortexer and a detector for mixing the sugar solution to be tested in the stoppered colorimetric tube with the reagent, the detector including a control unit, a detection unit electrically connected to the control unit, a display unit and an initialization unit, the detection unit being used to detect the absorbance value after the sugar solution to be tested and the reagent are mixed, and the absorbance value is transmitted to the control unit, the initialization unit is used to set and store a nitrate standard curve, and after receiving the absorbance value, the control unit compares it with the nitrate standard curve and outputs the detection result to the display unit.

[0005] The above detection device can realize the rapid detection of nitrate in sugar at the production site and correct the test results of nitrate to eliminate the interference of nitrite. However, the use of toxic heavy metal cadmium powder to reduce nitrate brings great risks to the detection process. It also uses traditional spectrophotometry for detection, which is complicated to operate, costly and not easy to carry. Utility Model Content

[0006] In view of the deficiencies in the above-mentioned background technology, the utility model proposes a detection device for determining the nitrate content in food, which solves the technical problems that the existing detection devices use toxic heavy metal cadmium powder to reduce nitrate and traditional spectrophotometry to detect, which brings great risks to the detection process, is complicated to operate, and is costly and difficult to carry.

[0007] The technical solution of this application is:

[0008] A detection device for determining the nitrate content in food, comprising a front module for reducing nitrate in a solvent to be tested into nitrite and mixing nitrite with a color developer, and a detection module for detecting nitrite content, wherein the front module comprises a first microfluidic chip and a second microfluidic chip, wherein the first microfluidic chip and the second microfluidic chip are both provided with a color development area for mixing nitrite with a color developer, and a reduction area connected to an inlet of the color development area, wherein the reduction area of ​​the first microfluidic chip is provided with pre-set zinc powder for reducing nitrate in the solvent to be tested into nitrite, and the color development pool of the color development area is aligned up and down with the detection module.

[0009] The first microfluidic chip and the second microfluidic chip provided by the technical solution are collectively referred to as microfluidic chips. Microfluidic channels are highly integrated on the microfluidic chip. The solvent to be tested is added to the microfluidic chip. The microfluidic channel is divided into a reduction zone and a color development zone in sequence according to the flow order of the solvent to be tested. The solvent to be tested on the first microfluidic chip passes through the zinc powder set in the reduction zone, and the nitrate in the solvent to be tested is reduced to nitrite. The nitrite and the color developer are mixed and reacted and then enter the color development pool. The color of the mixed solvent in the color development pool is in a certain proportional relationship with the nitrite content. The detection module detects the nitrite content through the color of the color development pool. The solvent to be tested on the second microfluidic chip passes through the reduction zone and the color development zone. The detection module directly detects the nitrite content in the solvent to be tested through the color of the color development pool. The difference between the two test results is the nitrate content in the solvent to be tested.

[0010] Preferably, the detection module includes a camera for taking pictures and an intelligent terminal for image analysis. The intelligent terminal is connected to the top of a fixed bracket, and slots matching the first microfluidic chip and the second microfluidic chip are provided at the bottom of the fixed bracket. The intelligent terminal is snap-fitted on the top of the fixed bracket, and the vertical plates on both sides of the fixed bracket fix the intelligent terminal. The first microfluidic chip and the second microfluidic chip are installed on the fixed bracket through the slots. The color development pools on the microfluidic chips are aligned with the cameras of the intelligent terminal, and image analysis is performed using the image analysis software in the intelligent terminal.

[0011] Preferably, a hydrogel for fixing pre-set zinc powder is provided in the reduction zone. The reduction zone uses the hydrogel to fix zinc particles as a reducing agent. The hydrogel is a methacrylated hydrogel, i.e., Gelma. The hydrogel has a porous structure, and the solvent to be tested can pass through smoothly.

[0012] Preferably, the reduction zone is a circular groove with a diameter of 15 - 50 microns, and the ratio of the radius to the height of the circular groove is 5:1. The inlet of the reduction zone is connected to an inlet part for introducing the reagent or deionized water to be tested, and the outlet of the reduction zone is connected to the color development zone.

[0013] Preferably, the color development zone includes a mixing part and a color development pool connected in sequence. The inlet of the mixing part is connected to the outlet of the reduction zone, and the outlet of the color development pool is connected to a waste liquid collection bottle. The mixing part is used to mix the reagent to be tested with the color developer, and the waste liquid collection bottle is used to collect and discharge the waste liquid in the microfluidic chip.

[0014] Preferably, the mixing part is provided with a microfluidic channel, and a plurality of periodically arranged regular triangular prism microstructures are provided in the microfluidic channel. The color development pool is a circular cavity. The regular triangular prism microstructures can increase the contact time between the solvent to be tested and the color developer, ensuring full mixing of the solvent to be tested and the color developer. The circular color development pool corresponds to the shape of the camera of the detection device.

[0015] Preferably, a first inlet for introducing the solvent to be tested or deionized water is provided at the inlet of the reduction zone, and a second inlet for introducing the color developer is provided between the inlet of the mixing part and the outlet of the reduction zone. Deionized water can be used to clean the microfluidic channel. The second inlet is located between the reduction zone and the mixing part of the color development zone, enabling the color developer to react with all the nitrites in the solvent to be tested after reduction.

[0016] Preferably, an inlet branch is provided between the inlet of the reduction zone and the first inlet. The inlet branch includes a plurality of microfluidic channels. One end of each microfluidic channel is connected to the first inlet, and the other end is connected to the inlet of the reduction zone. The plurality of microfluidic channels in the inlet branch can ensure that the solvent to be tested reacts with the reducing agent over a larger area, thereby improving the reduction rate.

[0017] Preferably, a filtering device is connected to the inlet of the first inlet. When the sample solution to be measured is an actual food sample, a filtering device needs to be installed in front of the first inlet. The filtering device can be a filter made of a membrane with a certain pore size, such as a cellulose acetate membrane and a nylon membrane made of a polymer. The filtering device can further remove the unprocessed macromolecular residues in the food sample and decolorize the food sample.

[0018] Preferably, the reduction zone and the color development zone are connected through a horizontal microfluidic channel and a vertical microfluidic channel. The width of the horizontal microfluidic channel is equal to the width of the vertical microfluidic channel, and the depth of the horizontal microfluidic channel is equal to the depth of the vertical microfluidic channel. The ratio of the width to the depth is 2:1. Both the horizontal microfluidic channel and the vertical microfluidic channel can enable the solvent to be measured to pass through quickly.

[0019] Compared with the prior art, the technical solution disclosed by the present utility model has the following beneficial effects:

[0020] 1. By using zinc powder as a reducing agent and combining with a colorimetric method, real-time non-toxic quantitative detection of nitrate content in food can be achieved; the hydrogel can effectively fix the zinc powder and ensure a large specific surface area, which can realize the reduction of nitrate under the premise of non-toxicity and simplify the subsequent detection steps; using a microfluidic chip for detection has a high degree of integration and requires a small amount of reagents;

[0021] 2. Using a smartphone for image analysis has stronger operability and portability compared with traditional spectrophotometric detection. The volume of the detection device is greatly reduced, the operation is simple, and it can be applied to the determination of nitrate content in various food samples, which has important research value. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present utility model, the drawings required for the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present utility model. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0023] Figure 1 is a schematic diagram of the overall structure of the detection device of the present utility model;

[0024] Figure 2 is a schematic diagram of the structure of the first microfluidic chip;

[0025] Figure 3 is a schematic diagram of the structure of the second microfluidic chip;

[0026] Figure 4 is a schematic diagram of the structure of the fixing bracket of the detection device;

[0027] Figure 5 It is a detailed view of the reduction area in the embodiment of the present utility model;

[0028] Figure 6 It is a relationship diagram between the concentration of nitrate standard solution and RGB involved in the embodiment of the present utility model.

[0029] Explanation of the reference numerals in the drawings:

[0030] 1 Detection module, 101 Intelligent terminal, 102 Fixed bracket, 103 Slot, 2 Microfluidic chip, 201 First microfluidic chip, 202 Second microfluidic chip, 3 Inlet part, 301 First inlet, 302 Inlet branch, 303 Second inlet, 304 Filter device, 4 Reduction area, 5 Color development area, 501 Mixing part, 502 Color development pool, 6 Waste liquid collection bottle. Specific implementation mode

[0031] Next, the technical solutions in the embodiments of the present utility model will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present utility model. Obviously, the described embodiments are only a part of the embodiments of the present utility model, rather than all of the embodiments. Based on the core concept of the present utility model and the following embodiments, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present utility model.

[0032] Embodiment 1, a detection device for measuring the nitrate content in food, as Figures 1 to 4 shown, includes a detection module 1, a first microfluidic chip 201 and a second microfluidic chip 202. The first microfluidic chip 201 and the second microfluidic chip 202 are collectively referred to as the microfluidic chip 2. The detection module 1 includes an intelligent terminal 101, a fixed bracket 102, and a slot 103. An inlet part 3, a reduction area 4, a color development area 5, and a waste liquid collection bottle 6 are provided on the microfluidic chip 2. The inlet part 3 includes a first inlet 301, an inlet branch 302, and a second inlet 303. The color development area 5 includes a mixing part 501 and a color development pool 502.

[0033] Specifically, as Figure 1 shown, the microfluidic chip 2 is inserted into the fixed bracket 102 through the slot 103. The intelligent terminal 101 is clamped on the top of the fixed bracket 102. The vertical plates on both sides of the fixed bracket 102 fix the intelligent terminal 101. The intelligent terminal 101 can be a smart phone. The camera of the intelligent terminal 101 is aligned with the color development pool 502 on the microfluidic chip 2. The camera and image analysis software of the intelligent terminal 101 can take pictures of the color development area 502 and perform RGB analysis on the images.

[0034] Specifically, as Figure 2 and Figure 3As shown, microfluidic channels are provided on both the first microfluidic chip 201 and the second microfluidic chip 202. The microfluidic channels are sequentially divided into a reduction zone 4, a color development zone 5, and a waste liquid collection bottle 6 according to the flow sequence of the solvent to be tested. A first inlet 301 and an inlet branch 302 are sequentially provided at the inlet of the reduction zone 4. A second inlet 303 is provided between the outlet of the reduction zone 4 and the inlet of the color development zone 5. The first inlet 301, the inlet branch 302, and the second inlet 303 are collectively referred to as the inlet part 3.

[0035] During the test, the solvent to be tested is added to the first inlet 301 on the first microfluidic chip 201. The solvent to be tested on the first microfluidic chip 201 passes through the inlet branch 302 and reacts with the zinc powder provided in the reduction zone 4. The nitrate in the solvent to be tested is reduced to nitrite. A color developer is added to the second inlet 303. The nitrite reacts with the color developer under acidic conditions to form a pink azo dye. After the nitrite and the color developer are mixed and reacted in the mixing part 501, they enter the color development pool 502. The color of the mixed solvent in the color development pool 502 has a certain proportional relationship with the content of nitrite. The detection module 1 detects the content of nitrite through the color of the color development pool 502. According to the analysis of the image captured by the camera, the corresponding relationship between the RGB parameters and the nitrite concentration can be obtained, and the real-time processing and effective storage of data information can be realized.

[0036] Similarly, the solvent to be tested is added to the first inlet 301 on the second microfluidic chip 202. The solvent to be tested sequentially passes through the inlet branch 302 and the reduction zone 4. A color developer is added to the second inlet 303. The nitrite reacts with the color developer under acidic conditions to form a pink azo dye. After the nitrite and the color developer are mixed and reacted in the mixing part 501, they enter the color development pool 502. The color of the mixed solvent in the color development pool 502 has a certain proportional relationship with the content of nitrite. The detection module 1 directly detects the content of nitrite in the solvent to be tested through the color of the color development pool 502. According to the analysis of the image captured by the camera, the corresponding relationship between the RGB parameters and the nitrite concentration can be obtained, and the real-time processing and effective storage of data information can be realized. The difference between the test results of the first microfluidic chip 201 and the second microfluidic chip 202 is the content of nitrate in the solvent to be tested.

[0037] Preferably, as Figure 1As shown in the figure, to avoid the influence of external environmental light, shooting distance and other factors on image analysis, the fixed bracket 102 of the detection module 1 is an airtight box. The microfluidic chip 2 is made of the organic material polydimethylsiloxane, abbreviated as PDMS. The manufacturing process is as follows: First, a mask plate is made according to the pattern drawn by the design software, and then the pattern is developed on the silicon wafer through ultraviolet lithography technology. In this embodiment, the depths of the color development pool 502, the inlet part 3, and the mixing part 501 are different, and different photoresists are required for secondary overetching to finally obtain the PDMS template. Then, the uncured PDMS is poured on the PDMS mold and baked at a temperature of 75 °C for 1 hour to solidify. Then, the surfaces of the PDMS chip and the glass slide are treated with plasma to enhance the adhesion of the PDMS polymer surface. After bonding, a hydrophilic microfluidic chip 2 can be obtained, which is inexpensive and easy to replace, avoiding the pollution caused by long-term use.

[0038] In this embodiment, the first inlet 301 is used to introduce the sample solution to be tested, deionized water, and the Gelma mixed solution containing zinc powder, and the second inlet 303 is used to introduce the color developer. The widths of the first inlet 301 and the second inlet 303 are both 200 microns, and the depths are both 100 microns. In this embodiment, the sample solution to be tested is introduced through the first inlet 301, and the sample solution to be tested is a nitrite standard solution or a food sample prepared in the laboratory. When the sample solution to be tested is an actual food sample, a filtering device 304 needs to be installed in front of the first inlet 301. The filtering device 304 is a filter made of a membrane with a certain pore size. The membrane can be made of a polymer, such as cellulose acetate membrane and nylon membrane. The filtering device 304 can further remove the large molecular residues that are not completely treated in the food sample and decolorize the food sample. In addition, the first inlet 301 is also used to introduce deionized water to clean the microfluidic channel.

[0039] In this embodiment, the first inlet 301 is connected to the reduction area 4 through a plurality of inlet branches 302. The width of each inlet branch 302 is 50 microns, and the height is 100 microns to ensure that the test sample can react with the reducing agent over a larger area, thereby improving the reduction rate. The length of the microfluidic channel in the color development area 5 is 1000 microns, the width is 500 microns, and the height is 100 microns. To ensure the full mixing of the sample solution and the color developer, a plurality of periodically arranged regular triangular prism microstructures are provided in the mixing part 501 of the color development area 5. The bottom side length of the regular triangular prism is 30 microns, the distance between the regular triangular prisms in each column is 100 microns, and the angle with the horizontal direction is 60°. At this time, the mixing effect is better. The color development pool 501 in the color development area 5 is a circular cavity, the radius of the circle is 500 microns, and the height is 100 microns.

[0040] Specifically, as Figure 5As shown in the figure, the reduction zone 4 needs to be pre - loaded with zinc powder using a hydrogel. The operation process is as follows: Mix 1.0 g of zinc powder with 2 ml of hydrogel and stir at a speed of 50 rmp for 30 min. Then inject the mixed liquid from the first inlet 301 into the reduction zone 4, and then irradiate it under an ultraviolet lamp for 1000 ms for photocuring, and rinse it with deionized water. The hydrogel is GelMA hydrogel, the diameter of the zinc powder is in the range of 15 - 50 microns, the mass percentage of GelMA hydrogel in the hydrogel solution is 10%, the reduction zone 4 is a circular groove, the radius of the circle is 500 microns, and the depth of the groove is 100 microns.

[0041] Preferably, the chromogenic agent is Griess reagent, which is introduced through the second inlet 303. The Griess reagent is a mixture of a 10 g / L sulfanilamide solution and a 1 g / L N - (1 - naphthyl)ethylenediamine dihydrochloride solution in a ratio of 1:1. The specific preparation method is as follows: Slowly add 50 mL of hydrochloric acid to 300 ml of water under stirring to obtain a hydrochloric acid solution. Then weigh 5 g of sulfanilamide and dissolve it in 350 mL of the hydrochloric acid solution to obtain a 10 g / L sulfanilamide solution. Then weigh 0.5 g of N - (1 - naphthyl)ethylenediamine dihydrochloride and dissolve it in 500 mL of ultrapure water to obtain a 1 g / L N - (1 - naphthyl)ethylenediamine dihydrochloride solution. Then mix the above sulfanilamide solution and N - (1 - naphthyl)ethylenediamine dihydrochloride solution in a ratio of 1:1 to obtain the Griess reagent. The Griess reagent needs to be stored in a brown bottle. After the solution becomes turbid, it needs to be re - prepared.

[0042] Based on the above structure, when using the detection device of the present utility model for detection, the microfluidic chip 2 realizes the high integration of the detection device, and greatly reduces the amount of the solvent to be measured required for detection. Using the hydrogel pre - loaded with zinc powder to reduce nitrate, it is safe and non - toxic. Combining with intelligent image analysis, the corresponding relationship between the RGB parameters and the nitrite concentration is obtained, which has the advantages of good selectivity, high sensitivity, accuracy, stability and reliability, etc. At the same time, it combines intelligent image analysis, greatly reduces the size of the instrument, and can realize the real - time processing and effective storage of data information, making real - time on - site detection possible.

[0043] Specifically, in this embodiment, taking the measurement of the concentration of nitrate standard solution as an example, the operation method of the detection device is described as follows:

[0044] 1. Use a micro - injection pump to slowly push deionized water into the first inlet 301 to clean the microfluidic channel.

[0045] 2. After the cleaning is completed, the sample solution to be measured is pumped into the first microfluidic chip 201 and the second microfluidic chip 302 from the first inlet 301 at a flow rate of 200 μL / min. At the same time, the color developer is pumped into the second inlet 303 at a flow rate of 50 μL / min for 1 min, so that the solution to be detected on the first microfluidic chip 201 is reduced and then fully mixed and reacted with the indicator.

[0046] 3. Insert the microfluidic chip 2 into the slot 103 of the fixed bracket 102, and use the intelligent terminal 101 installed with image analysis software to take pictures of the color development pool 502 and perform RGB analysis of the images.

[0047] In this embodiment, the sample solutions to be measured are nitrate standard working solutions with prepared concentrations of 0 μM, 1 μM, 2 μM, 3 μM, 4 μM, 6 μM, 8 μM, 10 μM, 20 μM, and 30 μM respectively. Then, the test processes of the above steps 1 to 3 are respectively performed, so as to record the color development product images of the nitrate standard solutions with different concentrations after passing through the detection device respectively, and perform RGB analysis. The specific analysis process is as follows: taking the concentration as a variable and using the combination formulas of RGB such as R, G, B, G / (R + G + B), R / G, R + G - B, R / B, G / B, 1 - B / R, etc. as parameters for analysis, and selecting the intensity formula with a larger coefficient of determination. After multiple experiments and formula optimization, the RGB intensity determination formula is obtained as I = 1 - B / R.

[0048] Using the R, G, B values in Table 1 and the RGB intensity formula ΔI = I - I0, where I0 is the intensity when the nitrite concentration is 0, as Figure 6 shown, there is a good linear relationship between the RGB intensity and the concentration of the solution to be detected. The actual concentration of any sample after being detected by this device can be deduced by using the linear relationship. Compared with the traditional detection devices, the nitrate detection device provided in this embodiment has a significant reduction in size and a high degree of intelligence, and can realize the detection of non-toxic nitrate content.

[0049] Table 1 Experimental results of the embodiment

[0050]

[0051] The details not described in this utility model are all conventional technical means well known to those skilled in the art.

[0052] The above content shows and describes the basic principles, main features and the beneficial effects of this utility model. The above description is only a preferred embodiment of this utility model and is not intended to limit this utility model. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of this utility model shall be included in the protection scope of this utility model.

Claims

1. A detection device for determining the nitrate content in food, comprising a pre-module for reducing nitrate in a solvent to be detected to nitrite and mixing nitrite with a color developer, and a detection module (1) for detecting the nitrite content, characterized in that: The front module comprises a first microfluidic chip (201) and a second microfluidic chip (202). The first microfluidic chip (201) and the second microfluidic chip (202) are both provided with a color development area (5) for mixing nitrite with a color developer and a reduction area (4) connected to an inlet of the color development area (5). The reduction area (4) of the first microfluidic chip (201) is provided with pre-set zinc powder for reducing nitrate in a solvent to be tested into nitrite. The color development pool (502) of the color development area (5) is aligned with the detection module (1) in upper and lower directions.

2. The detection device for determining the nitrate content in food according to claim 1, characterized in that: The detection module (1) comprises a camera for taking pictures and an intelligent terminal (101) for image analysis. The intelligent terminal (101) is connected to the top of a fixed bracket (102). The bottom of the fixed bracket (102) is provided with a slot (103) that matches the first microfluidic chip (201) and the second microfluidic chip (202).

3. The detection device for determining the nitrate content in food according to claim 1, characterized in that: The reduction zone (4) is provided with a hydrogel for fixing the pre-set zinc powder.

4. The detection device for determining the nitrate content in food according to claim 1, characterized in that: The reduction zone (4) is a circular groove with a diameter of 15-50 microns, and the ratio of the radius of the circular groove to the height of the circular groove is 5:

1.

5. The detection device for determining the nitrate content in food according to claim 1, characterized in that: The color development zone (5) comprises a mixing section (501) and a color development pool (502) which are connected in sequence, the inlet of the mixing section (501) is connected to the outlet of the reduction zone (4), and the outlet of the color development pool (502) is connected to a waste liquid collection bottle (6).

6. The detection device for determining the nitrate content in food according to claim 5, characterized in that: The mixing portion (501) is provided with a microfluidic channel, and a plurality of periodically arranged regular triangular prism microstructures are provided in the microfluidic channel. The color development pool (502) is a circular cavity.

7. The detection device for determining the nitrate content in food according to claim 5, characterized in that: The inlet of the reduction zone (4) is provided with a first inlet (301) for introducing a solvent to be tested or deionized water, and a second inlet (303) for introducing a developer is provided between the inlet of the mixing section (501) and the outlet of the reduction zone (4).

8. The detection device for determining the nitrate content in food according to claim 7, characterized in that: An inlet branch (302) is provided between the inlet of the reduction zone (4) and the first inlet (301), and the inlet branch (302) comprises a plurality of microfluidic channels, one end of each microfluidic channel is connected to the first inlet (301), and the other end is connected to the inlet of the reduction zone (4).

9. The detection device for determining the nitrate content in food according to claim 7 or 8, characterized in that: The inlet of the first inlet (301) is connected to a filtering device (304).

10. The detection device for determining the nitrate content in food according to claim 1, characterized in that: The reduction zone (4) and the color development zone (5) are connected via a transverse microfluidic channel and a longitudinal microfluidic channel, the width of the transverse microfluidic channel is equal to the width of the longitudinal microfluidic channel, the depth of the transverse microfluidic channel is equal to the depth of the longitudinal microfluidic channel, and the ratio of the width to the depth is 2:1.

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