A method for detecting pesticide residues in agricultural products

Abstract

The invention discloses a method for detecting pesticide residues in agricultural products, comprising the following steps: S1, pre-treating the agricultural products to be detected; S2, placing the pre-treated agricultural products in an extraction device, and collecting the extracting liquid by sequentially performing segmented extrusion, temperature control and solvent spraying; for vegetables with loose cell structures, using pulverization as a pre-treatment step not only helps to destroy the cell structure of the vegetables, so that the pesticide residues therein are more easily exposed, but also helps to reduce the amount of air released in the subsequent extraction process, and improve the penetration efficiency of the solvent; and in the extraction step, by combining segmented extrusion, temperature control and solvent spraying to extract the extracting liquid, the pesticide residue extracting liquid in the agricultural products can be extracted more comprehensively, and then the absorbance change of the detection sample liquid at a specific wavelength is measured by using a spectrophotometer, which can accurately reflect the activity and inhibition of AChE, thereby improving the accuracy of its detection.

Description

Technical Field

[0001] The invention relates to the field of optical technology, in particular to the field of technology of analyzing materials using optical means, and specifically to a method for detecting pesticide residues in agricultural products. Background Art

[0002] Pesticide residues refer to the general term for pesticide parent bodies, pesticide residue hazardous derivatives, metabolites, degradation products and impurities that remain in the environment, organisms and food after pesticide use. The main causes of excessive pesticide residues in vegetables are organophosphorus pesticides and carbamate pesticides that are banned in vegetable production in some countries, such as methyl parathion, omethoate, phorate, parathion, methyl parathion, etc. Eating food containing a large amount of highly toxic and extremely toxic pesticide residues can cause acute poisoning accidents in humans and animals. Although long-term consumption of agricultural and sideline products with excessive pesticide residues will not lead to acute poisoning, it may cause chronic poisoning in humans and animals, leading to the occurrence of diseases, inducing cancer, and even affecting the next generation.

[0003] In the field of agricultural product safety and quality control, the detection of pesticide residues is a crucial link. Especially for vegetables with loose cell structures, such as lettuce and cabbage, their unique cell structure makes the detection process of pesticide residues more complicated. These vegetables easily absorb and accumulate pesticides during growth. At the same time, due to their large intercellular spaces and loose tissues, pesticide residues are more likely to hide in these structures.

[0004] Traditional pesticide residue detection methods often have problems such as low extraction efficiency, poor solvent permeability, and susceptibility to air interference. Especially during the extraction process, since vegetables such as lettuce and cabbage contain a lot of air, the release of air during squeezing will seriously affect the penetration and dissolution effect of the solvent, making it difficult to effectively extract pesticide residues, thereby reducing the accuracy of the detection, which further affects the results of subsequent spectrophotometer measurements using light in the visible light region. Summary of the invention

[0005] The invention overcomes the shortcomings of the prior art and provides a method for detecting pesticide residues in agricultural products.

[0006] To achieve the above object, the technical solution adopted by the present invention is: a method for detecting pesticide residues in agricultural products, comprising the following steps:

[0007] S1. Pre-treating the agricultural products to be tested;

[0008] S2, placing the pretreated agricultural products in an extraction device, and collecting the extract by sequentially performing segmented extrusion, temperature control and solvent spraying;

[0009] S3, mixing the extract with a specific inhibitor of cholinesterase to obtain a test sample solution;

[0010] S4. Send the test sample solution to a spectrophotometer for testing, calculate the inhibition rate of AChE, and determine the pesticide residues in agricultural products by analyzing the inhibition rate.

[0011] In a preferred embodiment of the present invention, in step S1, the agricultural product is a vegetable with a loose cell structure, and the pretreatment is specifically to crush the agricultural product to be tested; in step S2, the solvent is one of acetonitrile, methanol, ethanol or acetone.

[0012] The present invention provides an extraction device for a method for detecting pesticide residues in agricultural products, comprising: a pressure-taking cylinder, a collecting cylinder threadedly connected to the bottom of the pressure-taking cylinder, and a first filter screen detachably connected to the bottom of the pressure-taking cylinder; a spacer is fixed on the inner side of the pressure-taking cylinder, and an extrusion assembly is arranged at the bottom of the spacer; the extrusion assembly comprises: a threaded rod arranged on the inner side of the pressure-taking cylinder, a bracket fixed on the inner side of the pressure-taking cylinder and located at the top of the first filter screen, and a pressure plate threadedly connected to the side of the threaded rod; a limiting member for limiting the sliding of the pressure plate is arranged on the side of the pressure plate, and a heating member for heating the agricultural products when extracting is arranged at the bottom of the bracket;

[0013] The side surfaces of the threaded rod are rotatably connected to the inner sides of the pressing cylinder, the spacer and the bracket respectively; a spray assembly for spraying solvent is arranged on the pressing plate, and a power assembly is arranged on the top of the spacer; the power assembly comprises: a cable tray arranged on the top of the spacer, a rotating groove provided at the bottom of the cable tray, and a cable tray groove provided on the side of the cable tray; a clockwork spring is arranged on the inner side of the rotating groove, a pull rope is wound around the inner side of the cable tray groove, a pull ring is fixed to one end of the pull rope located outside the pressing cylinder, and marking rings for controlling the pulling amount of the pull rope are evenly fixed in sections on the pull rope.

[0014] In a preferred embodiment of the present invention, the inner side of the cable drum is fixed to the side surface of the threaded rod located at the top of the spacer, the bottom of one end of the clockwork spring is fixed to the top of the spacer, and the side surface of the other end is fixed to the inner side of the rotating groove; the end of the pull rope located inside the pressure-taking cylinder is fixed to the inner side of the cable groove.

[0015] In a preferred embodiment of the present invention, the spray assembly comprises: a connector fixed to the side of the pressure-taking cylinder, a circular groove provided on the inner side of the pressure plate, and a bellows fixed between one end of the connector and the top of the pressure plate; a plurality of first through grooves and a plurality of second through grooves are sequentially provided at the bottom of the pressure plate, and the cross-sectional width of the first through groove is successively smaller than the cross-sectional width of the second through groove and the circular groove;

[0016] The first through groove and the second through groove are both inclined, and the inclination direction is toward the middle of the pressure plate, and the interior of the connecting head is sequentially connected with the interiors of the bellows, the annular groove, a plurality of the second through grooves and a plurality of the first through grooves.

[0017] In a preferred embodiment of the present invention, the limiting member includes: a plurality of limiting grooves provided on the inner side of the pressing cylinder, and a plurality of limiting blocks fixed on the side of the pressure plate; the side surfaces of the plurality of limiting blocks are engaged with the inner sides of the plurality of limiting grooves.

[0018] In a preferred embodiment of the present invention, the heating element comprises: a plurality of electric heating rods installed at the bottom of the bracket; the electric heating rods have a waterproof function.

[0019] In a preferred embodiment of the present invention, a plurality of slide grooves are provided at the bottom of the pressing cylinder, a plurality of arc-shaped grooves are provided at the tops of the plurality of slide grooves, a plurality of clamping blocks are fixed to the side surfaces of the first filter screen, the side surfaces of the clamping blocks are slidably connected to the inner sides of the arc-shaped grooves, and the width of the clamping blocks is the same as the width of the slide grooves.

[0020] In a preferred embodiment of the present invention, a second filter is fixed to the inner side of the collecting tube near the top, a liquid outlet head is fixed to the side of the collecting tube near the bottom, a valve is provided on the liquid outlet head, and the interior of the liquid outlet head is connected with the interior of the collecting tube.

[0021] In a preferred embodiment of the present invention, an observation window for conveniently observing the internal conditions of the squeezing cylinder is provided on the side of the squeezing cylinder.

[0022] The present invention solves the defects existing in the background technology and has the following beneficial effects:

[0023] (1) The present invention provides a method for detecting pesticide residues in agricultural products. For vegetables with loose cell structures, pulverization is used as a pretreatment step, which not only helps to destroy the cell structure of the vegetables, making the pesticide residues therein more easily exposed, but also helps to reduce the amount of air released during the subsequent extraction process and improve the penetration efficiency of the solvent. In the extraction step, the extraction of the extract is carried out by combining segmented extrusion, temperature control and spraying of the solvent to extract the extract, so that the pesticide residue extract sample in the agricultural products can be extracted more comprehensively. Then, the absorbance change of the detection sample at a specific wavelength is measured by a spectrophotometer, which can accurately reflect the activity and inhibition of AChE, thereby improving the accuracy of its detection.

[0024] (2) The extraction device provided in the present invention can continuously extrude the agricultural products through the cooperation of the power component and the extrusion component when obtaining the pesticide residue extraction sample liquid of the agricultural products, thereby destroying the cell structure of the agricultural products and releasing the internal liquid for extraction. At the same time, through the cooperation of the spraying component, the solvent can be sprayed to cover the surface of the agricultural products, thereby promoting the contact and dissolution of the solvent and the agricultural products. Since the agricultural products with loose cell structures will release a large amount of air during the extrusion process, affecting the penetration and dissolution effect of the solvent, the cooperation of the heating element and the segmented extrusion can reduce the interference with the penetration and dissolution of the solvent, thereby improving the efficiency of the pesticide residue extraction. The extraction device has a compact structure design, is easy to carry and transport, is easy to operate, is suitable for a variety of scenarios, and meets the fast and convenient requirements in agricultural product testing.

[0025] (3) The power assembly of the present invention, in cooperation with the pull ring, the pull rope, the cable tray, the cable tray slot, the rotating slot and the clockwork spring, can provide power for the forward rotation and automatic reverse rotation of the threaded rod, further making the pressure plate complete the up and down extrusion action with better controllability and continuity, ensuring automatic reset after each extrusion, while making the power transmission smoother and the energy conversion efficiency significantly improved. Compared with traditional manual or single-direction mechanical extrusion, it can be more efficient and labor-saving. At the same time, with the cooperation of the marking ring, it provides the user with an intuitive basis for controlling the downward pressure and frequency, which can effectively control the speed and force of the cable tray rotation, and control the downward pressure and frequency of the pressure plate, thereby improving the effect of precise extrusion.

[0026] (4) In the present invention, by setting the spraying assembly, with the cooperation of the connector, the bellows, the annular groove, the plurality of second through grooves, the plurality of first through grooves and the pressure plate, the input solvent can be discharged through the bottom of the pressure plate at a relatively high flow rate. At the same time, since the first through groove and the second through groove are both inclined and the inclined direction is toward the inner wall of the pressing cylinder, the rapidly flowing solvent will be sprayed onto the inner wall of the pressing cylinder and can be blocked by the inner wall to form splashing, which helps to make the solvent evenly cover the agricultural products, improve the uniformity of solvent penetration and dissolution, and further improve the efficiency of pesticide residue extraction. At the same time, when the conveying medium is water, the upper and lower scraping of the pressure plate and the splashing of the water flow can effectively clean the inner wall of the pressing cylinder, avoiding the contamination of the residue on the next use, thereby ensuring the accuracy of subsequent detection and the service life of the device.

[0027] (5) In the present invention, by setting a heating element, with the cooperation of a plurality of electric heating rods, heat conduction can be performed on the agricultural products located on the top of the first filter, thereby providing suitable temperature conditions for the extraction process. For agricultural products with a loose cell structure, the solubility of air in the solvent can be reduced to promote its escape, thereby improving the permeability of the solvent and further enhancing the extraction effect of pesticide residues. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art are briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative work.

[0029] Figure 1 It is a flow chart of a method for detecting pesticide residues in agricultural products according to a preferred embodiment of the present invention;

[0030] Figure 2 is a three-dimensional structural diagram of an extraction device according to a preferred embodiment of the present invention;

[0031] Figure 3 It is the overall half-section structure of the extraction device of the preferred embodiment of the present invention and its partial enlarged view;

[0032] Figure 4 is a plan view of the pull rope structure of the extraction device of the preferred embodiment of the present invention;

[0033] Figure 5 It is a half-section structural diagram of a pressure extraction cylinder and a pressure plate of an extraction device according to a preferred embodiment of the present invention;

[0034] Figure 6 It is a structure of the connection between the block and the arc groove of the extraction device of the preferred embodiment of the present invention and a partial enlarged view thereof;

[0035] In the figure: 1. pressing cylinder; 2. collecting cylinder; 3. first filter screen; 4. spacer; 5. threaded rod; 51. bracket; 52. pressure plate; 6. cable tray; 61. rotating groove; 62. cable tray; 63. spring; 64. pull rope; 65. pull ring; 66. marking ring; 7. connector; 71. circular groove; 72. bellows; 73. first through groove; 74. second through groove; 8. limit groove; 81. limit block; 9. electric heating rod; 10. slide groove; 11. arc groove; 12. block; 13. second filter screen; 14. liquid outlet; 15. observation window. DETAILED DESCRIPTION

[0036] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein. Therefore, the protection scope of the present invention is not limited to the specific embodiments disclosed below.

[0038] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the scope of protection of the present application. In addition, the terms "first", "second", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the invention, unless otherwise specified, "multiple" means two or more.

[0039] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood by specific circumstances.

[0040] like Figure 1 As shown, a method for detecting pesticide residues in agricultural products comprises the following steps:

[0041] S1. Pre-treating the agricultural products to be tested;

[0042] S2, placing the pretreated agricultural products in an extraction device, and collecting the extract by sequentially performing segmented extrusion, temperature control and solvent spraying;

[0043] S3, mixing the extract with a specific inhibitor of cholinesterase to obtain a test sample solution;

[0044] S4. Send the test sample solution to a spectrophotometer for testing, calculate the inhibition rate of AChE, and determine the pesticide residues in agricultural products by analyzing the inhibition rate.

[0045] In step S1, the agricultural product is a vegetable with a loose cell structure, and the pretreatment is specifically to crush the agricultural product to be tested; in step S2, the solvent is one of acetonitrile, methanol, ethanol or acetone.

[0046] It should be noted that agricultural products with a loose cell structure (such as lettuce, cabbage, etc.) have thin cell walls and large cell gaps, which allow them to accommodate more air. After being squeezed, the applied external force will cause the volume of the agricultural products to be compressed, increase the internal pressure, destroy the cell structure, and cause the internal air to be released. The released air will form certain bubbles in the solvent sprayed on the agricultural products, hindering the contact between the solvent and the agricultural product tissue, reducing the penetration and dissolution efficiency of the solvent, and will interfere with the contact time and area of ​​the solvent with the pesticide residues to a certain extent, thereby reducing the extraction efficiency.

[0047] Specifically, by using pulverization as a pretreatment step, it not only helps to destroy the cell structure of vegetables, making it easier to expose the pesticide residues therein, but also helps to reduce the amount of air released during the subsequent extraction process and improve the penetration efficiency of the solvent. At the same time, polar, organic solvents are able to dissolve a variety of organic matter, so as to better penetrate and dissolve the pesticide residue juice in agricultural products when squeezed.

[0048] In step S2, by extracting the extracting solution by combining segmented extrusion, temperature control and spraying solvent in the extraction step, the pesticide residue extracting sample solution in the agricultural product can be extracted more comprehensively.

[0049] In step S3, acetylcholinesterase (AChE) can catalyze the hydrolysis of acetylcholine to produce choline and acetic acid. When the extract contains organophosphorus or carbamate pesticides, these pesticides will inhibit the activity of AChE, resulting in the inability to hydrolyze acetylcholine.

[0050] In step S4, the absorbance change of the test sample solution at a specific wavelength (412nm) is measured using a spectrophotometer, which can accurately reflect the activity and inhibition of AChE. According to a pre-set standard or threshold, it is determined whether the sample contains organophosphorus or carbamate pesticides. If the inhibition rate exceeds a certain level (such as 50%), it is considered that the sample contains such pesticides.

[0051] like Figure 2 and Figure 3As shown, an agricultural product pesticide residue extraction device for pesticide residue detection comprises: a pressing cylinder 1, a collecting cylinder 2 threadedly connected to the bottom of the pressing cylinder 1, and a first filter screen 3 detachably connected to the bottom of the pressing cylinder 1; a spacer 4 is fixed to the inner side of the pressing cylinder 1, and an extrusion assembly is arranged at the bottom of the spacer 4; the extrusion assembly comprises: a threaded rod 5 arranged on the inner side of the pressing cylinder 1, a bracket 51 fixed to the inner side of the pressing cylinder 1 and located at the top of the first filter screen 3, and a pressure plate 52 threadedly connected to the side of the threaded rod 5; a limiter for limiting the sliding of the pressure plate 52 is arranged on the side of the pressure plate 52, and a heating element for heating the agricultural product during extraction is arranged at the bottom of the bracket 51; the side of the threaded rod 5 is rotatably connected to the inner side of the pressing cylinder 1, the spacer 4 and the bracket 51 respectively, the top of the spacer 4 is provided with a power assembly for providing forward rotation and automatic reverse rotation for the threaded rod 5, and the pressure plate 52 is provided with a spray assembly for spraying a solvent.

[0052] It should be noted that the shapes of the pressure cylinder 1 and the collecting cylinder 2 are both hollow cylinders, the bottom of the pressure cylinder 1 is open, and the top of the collecting cylinder 2 is a buckle; the shape of the bracket 51 is a circular ring in the middle, and the outer side is dispersed in a plurality of strips; the diameters of the first filter screen 3 and the pressure plate 52 are the same as the inner diameter of the pressure cylinder 1; the collecting cylinder 2, the first filter screen 3, the threaded rod 5, the bracket 51 and the pressure plate 52 are all arranged coaxially with the pressure cylinder 1.

[0053] Specifically, in the detection of pesticide residues, when it is necessary to obtain the agricultural residue extract of agricultural products through the extraction device, since the first filter screen 3 is detachably connected to the bottom of the pressing cylinder 1, before the first filter screen 3 is installed at the bottom of the pressing cylinder 1, the crushed agricultural products are placed on the top of the first filter screen 3, and the first filter screen 3 together with the agricultural products to be extracted are installed to the bottom of the pressing cylinder 1. With the cooperation of the power assembly on the top of the spacer 4, the threaded rod 5 can be driven to rotate forward inside the pressing cylinder 1, and the pressure plate 52 threadedly connected to the side of the threaded rod 5 is driven to move linearly downward along the length direction of the threaded rod 5. At the same time, the limiting piece on the side of the pressure plate 52 can slide the pressure plate 52 to limit the posture, so that the pressure plate 52 can squeeze the agricultural products at the bottom of the inner side of the pressing cylinder 1. During the extrusion process, the solvent can be sprayed during the extrusion process through the cooperation of the spraying component, so that the solvent covers the surface of the agricultural products, promoting the contact and dissolution of the solvent and the agricultural products. Since the agricultural products have a loose cell structure, a large amount of air will be released during the extrusion process, affecting the penetration and dissolution effect of the solvent. Through the cooperation of the heating element, the temperature during the extraction process can be increased, the solubility of air in the solvent can be reduced to promote its escape, thereby improving the permeability of the solvent, and after extrusion, the power component can automatically reverse the rotation of the threaded rod 5, and further make the pressure plate 52 move linearly upward along the length direction of the threaded rod 5. Such repeated movement can realize continuous extrusion of the agricultural products, destroy the cell structure of the agricultural products, and release the internal liquid for extraction.

[0054] In some embodiments, an observation window 15 is provided on the side of the squeezing cylinder 1 for conveniently observing the internal conditions of the squeezing cylinder 1 ; the setting of the observation window 15 facilitates the user to observe the internal conditions of the squeezing cylinder 1 through the observation window 15 , thereby improving visibility.

[0055] like Figure 3 and Figure 4 As shown, in some embodiments, the power assembly includes: a cable tray 6 arranged on the top of the spacer 4, a rotating groove 61 opened at the bottom of the cable tray 6, and a cable tray groove 62 opened on the side of the cable tray 6; a clockwork spring 63 is arranged on the inner side of the rotating groove 61, a pull rope 64 is wound on the inner side of the cable tray groove 62, a pull ring 65 is fixed at one end of the pull rope 64 located outside the pressing cylinder 1, and marking rings 66 for controlling the pulling amount of the pull rope 64 are evenly fixed on the pull rope 64 in sections.

[0056] It should be noted that the inner side of the cable drum 6 is fixed to the side of the threaded rod 5 located at the top of the spacer 4, the bottom of one end of the clockwork spring 63 is fixed to the top of the spacer 4, and the side of the other end is fixed to the inner side of the rotating groove 61; one end of the pull rope 64 located inside the pressure-taking cylinder 1 is fixed to the inner side of the cable drum 62; the cross-sectional shape of the cable drum 6 is "m"-shaped, and is coaxially arranged with the threaded rod 5.

[0057] Specifically, when providing power to the threaded rod 5 to press the agricultural products, the inner side of the cable drum 6 can be subjected to the restoring force of the clockwork spring 63, and the pull rope 64 can be kept wound in the cable groove 62 on the side of the cable drum 6. The user holds the pull ring 65 with one finger, pulls the pull ring 65 to pull the pull rope 64 to extend to the outside of the pressing cylinder 1. When the pull rope 64 located inside the cable groove 62 is gradually extended, it can drive the cable drum 6 and the threaded rod 5 to rotate forwardly. At the same time, the clockwork spring 63 will store and maintain a reverse rotation under the rotation of the cable drum 6. The force for the reset rotation, when gradually canceling the pulling force on the pull rope 64, the reverse reset rotation force of the clockwork spring 63 can automatically make the cable tray 6 rotate in the reverse direction, which is the power for the forward rotation and automatic reverse rotation of the threaded rod 5, and further makes the pressure plate 52 complete the up and down extrusion action with better controllability and continuity, ensuring automatic reset after each extrusion. At the same time, the power transmission is smoother, and the energy conversion efficiency is significantly improved. Compared with traditional manual or single-direction mechanical extrusion, it can be more efficient and labor-saving.

[0058] In another embodiment, when it is necessary to improve the accuracy of the pressure plate 52 in obtaining the downward pressure, the distance that the pull rope 64 is extended can be designed to enable the pressure plate 52 to move downward along the threaded rod 5, and the marking ring 66 is fixed in sections on the pull rope 64 at the distance designed for the precise downward pressure. When the pull rope 64 is pulled out toward the outside of the pressure-taking cylinder 1, after the marking ring 66 of the first section on the pull rope 64 is pulled to the outside of the pressure-taking cylinder 1, the pulling force is gradually canceled, so that the pull rope 64 is reset and wound into the cable groove 62, and the pull rope 64 is pulled again until the marking ring of the next section after the first section is reached. After 66 is pulled to the outside of the pressing cylinder 1, the pulling force is gradually cancelled, thereby providing the user with an intuitive basis for controlling the downward pressure and frequency, which can effectively control the speed and force of the rotation of the wire bundle disk 6, and control the downward pressure and frequency of the pressure plate 52, thereby improving the effect of precise extrusion, and further enable the pressure plate 52 to gradually increase the pressure when extracting agricultural products. In the extraction of agricultural products with loose cell structures, the air in the cells has enough time to escape, thereby reducing the impact of reducing the extraction efficiency due to interference with solvent penetration and dissolution.

[0059] like Figure 3 and Figure 5 As shown, in some embodiments, the spray assembly includes: a connector 7 fixed to the side of the pressure cylinder 1, an annular groove 71 provided on the inner side of the pressure plate 52, and a bellows 72 fixed between one end of the connector 7 and the top of the pressure plate 52; a plurality of first through grooves 73 and a plurality of second through grooves 74 are sequentially provided at the bottom of the pressure plate 52, and the cross-sectional width of the first through groove 73 is smaller than the cross-sectional width of the second through groove 74 and the annular groove 71 in turn.

[0060] It should be noted that the first through groove 73 and the second through groove 74 are both inclined, and the inclination direction is toward the inner wall of the pressing cylinder 1, and the interior of the connecting head 7 is sequentially connected with the interior of the bellows 72, the annular groove 71, the plurality of second through grooves 74 and the plurality of first through grooves 73; the number of the plurality of first through grooves 73 and the plurality of second through grooves 74 is the same, and they are all evenly distributed in a circular array inside the pressure plate 52.

[0061] Specifically, after the connector 7 is externally connected to the solvent delivery pipeline, during the process of the pressing plate 52 repeatedly pressing down the agricultural products, the bellows 72 is stretched or squeezed to extend or contract, and the connection between the connector 7 and the annular groove 71 is maintained. The solvent enters from the connector 7 and can be sequentially input into the bellows 72 and the annular groove 71, and sequentially passes through the plurality of second through grooves 74 and the plurality of first through grooves 73 connected to the annular groove 71. Since the cross-sectional width of the first through groove 73 is smaller than the cross-sectional width of the second through groove 74 and the annular groove 71, when the solvent is After the annular groove 71 enters the second through groove 74 and the first through groove 73 in turn, the internal cross-sectional area is reduced in turn, and the solvent can obtain a larger flow rate and be discharged through the bottom of the pressure plate 52. At the same time, since the first through groove 73 and the second through groove 74 are both inclined, and the inclination direction is toward the inner wall of the pressing cylinder 1, the rapidly flowing solvent will be sprayed onto the inner wall of the pressing cylinder 1, and can be blocked by the inner wall to form splashing, which helps to make the solvent evenly cover the agricultural products, improve the uniformity of solvent penetration and dissolution, and further improve the efficiency of pesticide residue extraction.

[0062] It should be noted that according to the continuity equation in fluid mechanics, when a liquid passes through a contracting or expanding pipe, the flow rate will change with the change of the cross-sectional area of ​​the pipe. When the pipe contracts, the flow rate of the liquid will increase because the flow rate of the liquid must be equal at any two points in the pipe. Bernoulli's equation describes the relationship between flow rate, pressure and fluid potential energy in an ideal fluid. When gas flows from a larger pipe into a part with a suddenly reduced diameter, the flow rate will increase, and the pressure of the fluid will increase at the same time. This pressure difference can drive the liquid to flow out faster.

[0063] In another embodiment, after the extraction of pesticide residues is completed using the extraction device, the conveying medium of the external conveying pipeline of the connector 7 is replaced with water, and the collecting cylinder 2 and the first filter screen 3 are disassembled and removed from the bottom of the pressing cylinder 1. While driving the pressure plate 52 to move linearly up and down, water enters from the connector 7, flows out quickly from the bottom of the chassis, and splashes onto the inner wall of the pressing cylinder 1. The upper and lower scraping of the pressure plate 52 and the splashing of the water flow can effectively clean the inner wall of the pressing cylinder 1, avoiding the contamination of the residue on the next use, and ensuring the accuracy of subsequent detection and the service life of the device.

[0064] In some embodiments, the limiting member includes: a plurality of limiting grooves 8 provided on the inner side of the pressing cylinder 1 , and a plurality of limiting blocks 81 fixed on the side of the pressure plate 52 ; the side surfaces of the plurality of limiting blocks 81 are engaged with the inner sides of the plurality of limiting grooves 8 .

[0065] It should be noted that the number of the plurality of limiting grooves 8 and the number of the plurality of limiting blocks 81 are the same, and the cross-sectional shapes of both are rectangular.

[0066] Specifically, when the pressure plate 52 is rotated by the threaded rod 5, the several limit blocks 81 on the side of the pressure plate 52 are clamped in the inner sides of the several limit grooves 8, so that the pressure plate 52 can move linearly on the side of the threaded rod 5, and the limit blocks 81 can slide on the inner sides of the limit grooves 8, which can play a path limiting effect on the movement of the pressure plate 52.

[0067] In some embodiments, the heating element includes: a plurality of electric heating rods 9 installed at the bottom of the bracket 51; the electric heating rods 9 have a waterproof function.

[0068] Specifically, during the extraction process, a number of electric heating rods 9 are started to conduct heat to the agricultural products located on the top of the first filter 3, which can provide suitable temperature conditions for the extraction process. For agricultural products with a loose cell structure, the solubility of air in the solvent can be reduced to promote its escape, thereby improving the permeability of the solvent and further enhancing the extraction effect of pesticide residues.

[0069] like Figure 3 and Figure 6 As shown, in some embodiments, a plurality of slide grooves 10 are opened at the bottom of the pressing cylinder 1, a plurality of arc grooves 11 are opened at the top of the plurality of slide grooves 10, a plurality of blocks 12 are fixed to the side of the first filter screen 3, the side of the block 12 is slidably connected to the inner side of the arc groove 11, and the width of the block 12 is the same as the width of the slide groove 10.

[0070] It should be noted that the cross-sectional shape of the connecting slide groove 10 and the arc-shaped groove 11 is an inverted "L" shape, and the number of the slide grooves 10, the arc-shaped grooves 11 and the blocks 12 is the same.

[0071] Specifically, when it is necessary to install the first filter screen 3 to the bottom of the pressing cylinder 1, first align the first filter screen 3 coaxially with the bottom of the pressing cylinder 1, and align the plurality of blocks 12 on the side of the first filter screen 3 with the bottom of the plurality of slide grooves 10, slide the plurality of blocks 12 into the inner sides of the plurality of slide grooves 10, and when the plurality of blocks 12 slide up to the tops of the plurality of slide grooves 10, rotate the first filter screen 3 to drive the plurality of blocks 12 on the side to slide toward the inner sides of the arc grooves 11, so that the first filter screen 3 can be clamped at the bottom of the pressing cylinder 1 with the cooperation of the blocks 12 and the arc grooves 11. During the extrusion extraction process, the first filter screen 3 can filter the fibers and impurities of the agricultural products, and allow the extract to pass into the collecting cylinder 2, which helps to improve the quality of the extract.

[0072] like Figure 3 As shown, in some embodiments, a second filter screen 13 is fixed to the inner side of the collecting cylinder 2 near the top, and a liquid outlet head 14 is fixed to the side of the collecting cylinder 2 near the bottom. A valve is provided on the liquid outlet head 14, and the interior of the liquid outlet head 14 is connected to the interior of the collecting cylinder 2.

[0073] Specifically, after the extraction is completed, the extract in the collecting cylinder 2 can be discharged by opening the valve on the liquid outlet head 14. After the extract from the bottom of the pressing cylinder 1 is preliminarily filtered through the first filter screen 3 and enters the top of the collecting cylinder 2, the second filter screen 13 located on the inner side of the collecting cylinder 2 near the top can further refine the filtration of the extract to ensure that the fibers or impurities squeezed through the first filter screen 3 are separated from the extract, thereby ensuring the purity of the extract and providing a reliable sample for subsequent testing.

[0074] The above is based on the ideal embodiment of the present invention. Through the above description, it is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is limited by the attached claims rather than the above description, and it is intended to include all changes within the meaning and scope of the equivalent elements of the claims. Any figure mark in the claims should not be regarded as limiting the claims involved.

[0075] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A method for detecting pesticide residues in agricultural products, characterized in that: The following steps are involved: S1. Pre-treating the agricultural products to be tested; S2, placing the pretreated agricultural products in an extraction device, and collecting the extract by sequentially performing segmented extrusion, temperature control and solvent spraying; S3, mixing the extract with a specific inhibitor of cholinesterase to obtain a test sample solution; S4, sending the test sample solution into a spectrophotometer for testing, calculating the inhibition rate of AChE, and determining the pesticide residues in the agricultural products by analyzing the inhibition rate; In the step S1, the agricultural product is a vegetable with a loose cell structure, and the pretreatment is specifically to crush the agricultural product to be tested; in the step S2, the solvent is one of acetonitrile, methanol, ethanol or acetone; In the step S2, the extraction device comprises: a pressure-taking cylinder, a collecting cylinder threadedly connected to the bottom of the pressure-taking cylinder, and a first filter screen detachably connected to the bottom of the pressure-taking cylinder; a spacer is fixed on the inner side of the pressure-taking cylinder, and an extrusion assembly is arranged at the bottom of the spacer; the extrusion assembly comprises: a threaded rod arranged on the inner side of the pressure-taking cylinder, a bracket fixed on the inner side of the pressure-taking cylinder and located at the top of the first filter screen, and a pressure plate threadedly connected to the side of the threaded rod; a limiting member for limiting the sliding of the pressure plate is arranged on the side of the pressure plate, and a heating member for heating the agricultural products when extracting is arranged at the bottom of the bracket; The side surfaces of the threaded rod are rotatably connected to the inner sides of the pressing cylinder, the spacer and the bracket respectively; a spray assembly for spraying solvent is arranged on the pressing plate, and a power assembly is arranged on the top of the spacer; the power assembly comprises: a cable tray arranged on the top of the spacer, a rotating groove provided at the bottom of the cable tray, and a cable tray groove provided on the side of the cable tray; a clockwork spring is arranged on the inner side of the rotating groove, a pull rope is wound around the inner side of the cable tray groove, a pull ring is fixed to one end of the pull rope located outside the pressing cylinder, and marking rings for controlling the pulling amount of the pull rope are evenly fixed in sections on the pull rope.

2. The method for detecting pesticide residues in agricultural products according to claim 1, characterized in that: The inner side of the cable tray is fixed to the side of the threaded rod located at the top of the spacer, the bottom of one end of the clockwork spring is fixed to the top of the spacer, and the side of the other end is fixed to the inner side of the rotating groove; the end of the pull rope located inside the pressure-taking cylinder is fixed to the inner side of the cable tray.

3. The method for detecting pesticide residues in agricultural products according to claim 1, characterized in that: The spray assembly comprises: a connector fixed to the side of the pressure-taking cylinder, a circular groove provided on the inner side of the pressure plate, and a bellows fixed between one end of the connector and the top of the pressure plate; a plurality of first through grooves and a plurality of second through grooves are sequentially provided at the bottom of the pressure plate, and the cross-sectional width of the first through groove is smaller than the cross-sectional width of the second through groove and the circular groove in turn; The first through groove and the second through groove are both inclined, and the inclination direction is toward the middle of the pressure plate, and the interior of the connecting head is sequentially connected with the interiors of the bellows, the annular groove, a plurality of the second through grooves and a plurality of the first through grooves.

4. The method for detecting pesticide residues in agricultural products according to claim 1, characterized in that: The limiting member comprises: a plurality of limiting grooves provided on the inner side of the pressing cylinder, and a plurality of limiting blocks fixed on the side of the pressing plate; the side surfaces of the plurality of limiting blocks are clamped with the inner sides of the plurality of limiting grooves.

5. The method for detecting pesticide residues in agricultural products according to claim 1, characterized in that: The heating element comprises: a plurality of electric heating rods installed at the bottom of the bracket; the electric heating rods have a waterproof function.

6. The method for detecting pesticide residues in agricultural products according to claim 1, characterized in that: A plurality of slide grooves are provided at the bottom of the pressing cylinder, a plurality of arc grooves are provided at the tops of the slide grooves, a plurality of clamping blocks are fixed on the side of the first filter screen, the side of the clamping block is slidably connected to the inner side of the arc groove, and the width of the clamping block is the same as the width of the slide groove.

7. The method for detecting pesticide residues in agricultural products according to claim 1, characterized in that: A second filter is fixed to the inner side of the collecting tube near the top, a liquid outlet head is fixed to the side of the collecting tube near the bottom, a valve is arranged on the liquid outlet head, and the interior of the liquid outlet head is connected with the interior of the collecting tube.

8. The method for detecting pesticide residues in agricultural products according to claim 1, characterized in that: An observation window for conveniently observing the internal condition of the squeezing cylinder is arranged on the side of the squeezing cylinder.

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