A method for rapidly extracting diamide pesticides from fresh milk

Abstract

The present invention provides a method for rapidly extracting diamide pesticides from fresh milk, comprising the following specific steps: S1: placing the fresh milk raw material in a centrifuge tube, and centrifuging to obtain a first liquid phase and a first solid phase; S2: adding acetonitrile to the first solid phase and performing ultrasonic dispersion, vibrating the first solid phase, and centrifuging to obtain a second liquid phase and a second solid phase; S3: adding acetonitrile to the second solid phase and performing ultrasonic dispersion, vibrating the second solid phase, and centrifuging to obtain a third liquid phase and a third solid phase; S4: adding acetonitrile to the first liquid phase, mixing, and centrifuging to obtain a fourth liquid phase and a fourth solid phase; S5: mixing the second liquid phase, the third liquid phase, and the fourth liquid phase, and centrifuging to obtain a fifth liquid phase; S6: concentrating the fifth liquid phase. The present invention does not use the traditional solid phase extraction method for extraction, and does not add various enzymes for decomposition, so the operation is simple and the detection cost is low.

Description

Technical Field

[0001] The present invention relates to the technical field of pesticide extraction, and in particular to a method for quickly extracting diamide pesticides from fresh milk. Background Art

[0002] Diamide insecticides have good control effects on lepidopteran pests such as the diamondback moth, beet armyworm, striped stem borer, and rice leaf roller, and are therefore widely used in agriculture and animal husbandry.

[0003] When dairy cows eat grass containing diamide pesticides, pesticide residues are produced in dairy products. Therefore, testing for diamide pesticide residues in fresh milk is of great significance to food safety.

[0004] During testing, the key focus is extracting diamide pesticides from fresh milk. Currently, the QuEChERS method, a pre-treatment purification technique, is widely used for the detection of diamide pesticide residues in fresh milk. However, it also suffers from cumbersome handling, high organic reagent consumption, and high costs.

[0005] Therefore, there is an urgent need to develop a rapid extraction method for diamide pesticides in fresh milk with low cost, simple operation process, low consumption of organic reagents and high comprehensive recovery rate. Summary of the Invention

[0006] The purpose of the present invention is to solve the deficiencies in the prior art and provide a method for quickly extracting diamide pesticides from fresh milk.

[0007] The object of the present invention is achieved through the following technical solution: a method for quickly extracting diamide pesticides from fresh milk, comprising the following specific steps:

[0008] S1: placing the fresh milk raw material in a centrifuge tube, and centrifuging to obtain a first liquid phase and a first solid phase;

[0009] S2: adding acetonitrile to the first solid phase and performing ultrasonic dispersion, shaking the first solid phase, and centrifuging to obtain a second liquid phase and a second solid phase;

[0010] S3: adding acetonitrile to the second solid phase and performing ultrasonic dispersion, shaking the second solid phase, and centrifuging to obtain a third liquid phase and a third solid phase;

[0011] S4: adding acetonitrile to the first liquid phase, mixing, and then centrifuging to obtain a fourth liquid phase and a fourth solid phase;

[0012] S5: mixing the second liquid phase, the third liquid phase and the fourth liquid phase and separating them by centrifugation to obtain a fifth liquid phase;

[0013] S6: Concentrating the fifth liquid phase.

[0014] Preferably, in step S1, the fresh milk raw material is centrifuged at a temperature of 4°C, with a rotation speed of 12000 r / min and a centrifugal separation time of 20-30 min.

[0015] Preferably, in step S2, the mass ratio of the added acetonitrile to the fresh milk raw material is between 6:1 and 4:1; the ultrasonic dispersion time is 1 min; the oscillation time is 10-15 min; and the centrifugal separation is carried out at a speed of 12000 r / min at a temperature of 4°C for 20-30 min.

[0016] Preferably, in step S3, the mass ratio of the added acetonitrile to the fresh milk raw material is between 6:1 and 4:1; the ultrasonic dispersion time is 1 min, and the oscillation time is 10-15 min; and the centrifugal separation is carried out at a speed of 12000 r / min at a temperature of 4°C for 5-10 min.

[0017] Preferably, the mass ratio of acetonitrile to fresh milk added in step S4 is between 2:1 and 1:1; after mixing, the mixture is centrifuged at a speed of 12000 r / min at a temperature of 4° C. for 5-10 minutes.

[0018] Preferably, when the centrifugal separation is performed in step S5, the centrifugal separation is performed at a speed of 12000 r / min at a temperature of 4° C. for 5-10 minutes.

[0019] Preferably, in step S6, the temperature during concentration is 50-55°C, and the constant volume is 1.00 mL.

[0020] Preferably, in step S6, the fifth liquid phase is concentrated by a nitrogen blowing concentration device. The nitrogen blowing concentration device includes a base, a guide rail is provided on the base, a sliding seat is slidably connected to the guide rail, a water bath device is provided on the sliding seat, and a tube rack for placing the concentration tube is provided on the water bath device; a lifting adjustment rod is provided on the base, a lifting plate is provided on the upper end of the lifting adjustment rod, and a nitrogen blowing tube is connected to the lifting plate; the nitrogen blowing tube can be moved up and down relative to the lifting plate; a positioning boss is provided at the lower end of the sliding seat, and the positioning boss is a cylinder; a first positioning lock and a second positioning lock are provided on the base;

[0021] When the positioning boss on the sliding seat is connected to the first positioning latch, the sliding seat is in the working position, and the concentrator tube placed on the water bath device is located directly below the nitrogen blowing tube;

[0022] When the positioning boss on the sliding seat is connected to the first positioning lock, the sliding seat is located in the ready position.

[0023] Preferably, the first positioning lock and the second positioning lock have the same structure, and both the first positioning lock and the second positioning lock comprise a fixed block, on which two elastic clips are symmetrically provided, and the elastic clips are provided with arc-shaped clamping sections.

[0024] Preferably, the lifting plate is provided with a guide cylinder arranged in a vertical direction, a positioning groove is provided on the inner wall of one side of the guide cylinder, the cross section of the positioning groove is rectangular, and the positioning grooves are arranged equidistantly along the axial direction of the guide cylinder, a slider is connected to the guide cylinder, a transition cavity is provided in the slider, a nitrogen blowing pipe is located at the lower end of the slider, and the upper end of the nitrogen blowing pipe is connected to the transition cavity; a connecting pipe is provided at the upper end of the slider, the lower end of the connecting pipe is connected to the transition cavity, and the connecting pipe is connected to the nitrogen supply device;

[0025] A groove is provided on the side of the slider close to the positioning groove, a fixed shaft is provided in the groove, a lever is rotatably connected to the fixed shaft, a contact portion is provided on the side of one end of the lever close to the positioning groove, and a spring is provided between the end and the slider; a clamping portion that can be inserted into the positioning groove is provided on the side of the other end of the lever close to the positioning groove; a protrusion is provided on the side of the other end of the lever away from the positioning groove; a pressure transmission hole is provided in the slider, one end of the pressure transmission hole is connected to the transition chamber, and the other end of the pressure transmission hole passes through the surface of the slider facing the positioning groove and forms an opening corresponding to the protrusion on the surface of the slider, and an elastic membrane is provided on the opening.

[0026] The beneficial effects of the present invention are:

[0027] 1. The method for extracting diamide pesticides in fresh milk provided by the present invention does not use the traditional solid-phase extraction method for extraction, and does not add various enzymes for decomposition. Only a small dose of acetonitrile is used for extraction. The reagents consumed during the extraction process are relatively small, the reagent cost is low, and the acetonitrile can be recovered after the detection is completed, further reducing the detection cost.

[0028] 2. The present invention does not involve complex extraction processes such as ultrasonic extraction, and the entire detection process is simple to operate.

[0029] 3. The present invention uses acetonitrile as an extraction solvent to extract diamide pesticides from fresh milk. Diamide pesticides can be dissolved in the extraction solvent, while solids such as proteins and lipids cannot be dissolved. The concentrated liquid finally obtained by this method contains less impurities such as protein, fat, and lactose that affect detection and analysis. The final concentrated liquid does not need to be purified further and can be directly subjected to liquid phase quantitative analysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a structural diagram of the nitrogen blowing concentration device.

[0031] Figure 2 This is a side view of the nitrogen blowing concentration device.

[0032] Figure 3 Schematic diagram of the structure of the first locking component.

[0033] Figure 4 This is a front view of the nitrogen blowing concentration device.

[0034] Figure 5 for Figure 4 Enlarged view of part A in the middle.

[0035] Figure 6 for Figure 5 Enlarged view of part B in the middle.

[0036] In the figure: 1. base, 2. guide rail, 3. sliding seat, 4. water bath device, 5. tube rack, 6. concentrating tube, 7. first positioning lock, 7-1. fixing block, 7-2. elastic clip, 8. lifting adjustment rod, 8-1. sleeve, 8-2. telescopic rod, 8-3. locking screw, 9. lifting plate, 10. guide cylinder, 11. connecting tube, 12. connecting head, 13. nitrogen blowing tube, 14. second positioning lock, 15. slider, 16. transition chamber, 17. positioning boss, 18. pressure transmission hole, 19. groove, 20. fixed shaft, 21. lever, 22. contact part, 23. clamping part, 24. spring, 25. positioning groove, 26. elastic membrane, 27. protrusion. DETAILED DESCRIPTION

[0037] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention are within the scope of protection of the present invention.

[0038] A method for rapidly extracting diamide pesticides from fresh milk comprises the following specific steps:

[0039] S1: Place fresh milk in a centrifuge tube and centrifuge to obtain a first liquid phase and a first solid phase. In this step, the sample size of the fresh milk is 5-10 grams. The fresh milk can be fresh goat milk or fresh cow milk, and must be mixed before sampling.

[0040] The fresh milk raw material is centrifuged at a temperature of 4°C, a rotation speed of 12000 r / min, and a centrifugal separation time of 20-30 min.

[0041] S2: adding acetonitrile to the first solid phase and performing ultrasonic dispersion, shaking the first solid phase, and centrifuging to obtain a second liquid phase and a second solid phase;

[0042] In this step, the mass ratio of the added acetonitrile to the fresh milk raw material is between 6:1 and 4:1; the ultrasonic dispersion time is 1 minute; the oscillation time is 10-15 minutes; and the centrifugal separation is carried out at a speed of 12000 r / min at a temperature of 4°C for 5-10 minutes.

[0043] S3: Add acetonitrile to the second solid phase and perform ultrasonic dispersion, oscillate and centrifuge the second solid phase to obtain a third liquid phase and a third solid phase.

[0044] In this step, the mass ratio of the added acetonitrile to the fresh milk raw material is between 6:1 and 4:1; the ultrasonic dispersion time is 1 minute; the oscillation time is 10-15 minutes; and the centrifugal separation is carried out at a speed of 12000 r / min at a temperature of 4°C for 5-10 minutes.

[0045] S4: Add acetonitrile to the first liquid phase, mix well, and then centrifuge to obtain a fourth liquid phase and a fourth solid phase.

[0046] In this step, the acetonitrile and the first liquid phase can be mixed by a vortex mixer. The mass ratio of acetonitrile to fresh milk added in this step is between 2:1 and 1:1. After mixing, the mixture is centrifuged at 12,000 rpm for 5-10 minutes at a temperature of 4°C.

[0047] S5: The second liquid phase, the third liquid phase and the fourth liquid phase are mixed and centrifuged to obtain a fifth liquid phase.

[0048] During the centrifugal separation in this step, the centrifugal separation is performed at a temperature of 4° C. and a rotation speed of 12,000 r / min for 5-10 minutes.

[0049] S6: Concentrating the fifth liquid phase.

[0050] In this step, the temperature during concentration is 50-55°C; the constant volume is 1.00 mL, i.e., the liquid is concentrated to 1.00 mL. The concentrated liquid obtained after concentration is filtered through an organic filter membrane and then subjected to liquid phase quantitative analysis to determine the content of the diamide pesticide in the concentrated liquid.

[0051] In this step, the fifth liquid phase is concentrated by a nitrogen blowing concentration device, such as Figures 1 to 6As shown, the nitrogen blowing and concentrating device includes a base 1, a guide rail 2 is provided on the base 1, a sliding seat 3 is slidably connected to the guide rail 2, a water bath device 4 is provided on the sliding seat 3, and a pipe rack 5 for placing the concentration tube 6 is provided on the water bath device 4; a lifting adjustment rod 8 is provided on the base 1, and a lifting plate 9 is provided on the upper end of the lifting adjustment rod 8, and a nitrogen blowing pipe 13 is connected to the lifting plate 9; the nitrogen blowing pipe 13 can be moved up and down relative to the lifting plate 9; a positioning boss 17 is provided at the lower end of the sliding seat 3, and the positioning boss 17 is a cylinder; a first positioning lock 7 and a second positioning lock 14 are provided on the base 1; when the positioning boss 17 on the sliding seat 3 is connected to the first positioning lock 7, the sliding seat 3 is in the working position, and the concentration tube 6 placed on the water bath device 4 is located directly below the nitrogen blowing pipe 13; when the positioning boss 17 on the sliding seat 3 is connected to the first positioning lock 7, the sliding seat 3 is in the preparation position.

[0052] When concentrating the fifth liquid phase, the fifth liquid phase is first placed in the concentrating tube 6, the sliding seat 3 is slid to the preparation position, the concentrating tube 6 containing the fifth liquid phase is placed on the tube rack 5 on the water bath device 4, and then the sliding seat 3 is slid to the working position, the water bath device 4 is turned on, and the water bath heating temperature is set (in this embodiment, the water bath heating temperature is set to 50-55°C); the height of the lifting plate 9 is adjusted by the lifting adjustment rod 8, and the height position of the nitrogen blowing tube 13 is finely adjusted so that the height between the lower end of the nitrogen blowing tube 13 and the liquid level in the concentrating tube 6 is 6-10 mm; the nitrogen blowing tube 13 is connected to a nitrogen supply device, and nitrogen of a certain pressure is supplied to the nitrogen blowing tube 13 by the nitrogen supply device. The nitrogen is blown out from the lower end of the nitrogen blowing tube 13 and blown toward the liquid surface. The nitrogen purges the liquid surface and accelerates the growth of the liquid surface, thereby shortening the concentration time.

[0053] The base 1 is equipped with two lift adjustment rods 8, with a lift plate 9 positioned between the upper ends of the two lift adjustment rods 8. The lift adjustment rods 8 comprise a sleeve 8-1 and a telescopic rod 8-2. The sleeve 8-1 is fixed to the base 1, and the telescopic rod 8-2 slides in engagement with the sleeve 8-1. A locking screw 8-3 is attached to the sleeve 8-1, securing the telescopic rod 8-2. To adjust the height of the lift plate 9, first loosen the locking screw 8-3, move the lift plate 9 to the desired height, and then tighten the locking screw 8-3.

[0054] The first positioning lock 7 and the second positioning lock 14 have the same structure. Both the first positioning lock 7 and the second positioning lock 14 include a fixed block 7-1, on which two elastic clips 7-2 are symmetrically arranged. The elastic clips 7-2 are provided with arc-shaped clamping sections. The first positioning lock 7 is used to stably keep the sliding seat 3 in the working position, and the second positioning lock is used to stably keep the sliding seat 3 in the standby position. When the positioning boss 17 is connected to the first positioning lock, the two elastic clips 7-2 on the first positioning lock clamp the positioning boss 17. Similarly, when the positioning boss 17 is connected to the second positioning lock, the two elastic clips 7-2 on the second positioning lock clamp the positioning boss 17.

[0055] Furthermore, the lifting plate 9 is provided with a guide cylinder 10 arranged in a vertical direction, and a positioning groove 25 is provided on the inner wall of one side of the guide cylinder 10. The cross-section of the positioning groove 25 is rectangular, and the positioning grooves 25 are arranged equidistantly along the axial direction of the guide cylinder 10. A slider 15 is connected to the guide cylinder 10, and a transition chamber 16 is provided in the slider 15. The nitrogen blowing pipe 13 is located at the lower end of the slider 15, and the upper end of the nitrogen blowing pipe 13 is connected to the transition chamber 16; the upper end of the slider 15 is provided with a connecting pipe 11, and the lower end of the connecting pipe 11 is connected to the transition chamber 16, and the connecting pipe 11 is connected to the nitrogen supply device. Among them, the upper end of the connecting pipe 11 is provided with a connector 12, and the connector 12 is connected to the nitrogen supply device through an air guide pipe. Nitrogen of a certain pressure is input into the connecting pipe 11 through the nitrogen supply device.

[0056] A groove 19 is provided on the side of the slider 15 near the positioning groove 25. A fixed shaft 20 is provided in the groove 19. A lever 21 is rotatably connected to the fixed shaft 20, and the middle portion of the lever 21 is rotatably connected to the fixed shaft 20. A contact portion 22 is provided on one end of the lever 21 near the positioning groove 25, and a spring 24 is provided between this end and the slider 15. A clamping portion 23 that can be snapped into the positioning groove 25 is provided on the other end of the lever 21 near the positioning groove 25. A protrusion 27 is provided on the other end of the lever 21 away from the positioning groove 25. A pressure transmission hole 18 is provided in the slider 15. One end of the pressure transmission hole 18 is connected to the transition chamber 16. The other end of the pressure transmission hole 18 passes through the surface of the slider 15 facing the positioning groove 25 and forms an opening on the surface of the slider 15 corresponding to the protrusion 27. An elastic membrane 26 is provided on the opening.

[0057] In this embodiment, the elastic membrane 26 is made of rubber.

[0058] When the nitrogen supply device does not supply nitrogen to the connecting pipe 11, the contact portion 22 at one end of the lever 21 contacts the side wall of the guide cylinder 10 provided with a positioning groove 25 under the action of the spring 24, wherein the width of the contact portion 22 is greater than the width of the positioning groove 25, so that the contact portion 22 cannot be completely embedded in the positioning groove 25. The spring 24 forms a certain contact pressure between the contact portion 22 and the side wall; the surface of the contact portion 22 facing the positioning groove 25 is an arc surface; in this state, the slider 15 can slide in the guide cylinder 10, thereby fine-tuning the height of the nitrogen blowing pipe 13.

[0059] When the nitrogen blowing pipe 13 blows nitrogen outward, the nitrogen supply device introduces nitrogen with a certain pressure into the connecting pipe 11. The nitrogen passes through the transition chamber 16 and is blown out of the nitrogen blowing pipe 13. At the same time, the nitrogen pressure is transmitted to the elastic membrane 26 through the pressure transmission hole 18, causing the elastic membrane 26 to bulge outward. After the elastic membrane 26 bulges, it pushes the protrusion 27 at one end of the lever 21, so that the clamping portion 23 is engaged with the positioning groove 25. In this way, the height of the nitrogen blowing pipe 13 can be kept stable during the blowing process, thereby preventing the height of the nitrogen blowing pipe 13 from changing and affecting the concentration rate of the liquid.

[0060] When the nitrogen supply device stops supplying nitrogen, the nitrogen pressure acting on the elastic membrane 26 disappears, and the lever 21 rotates to its initial state under the action of the spring 24. The clamping portion 23 on the lever 21 disengages from the positioning groove 25, and the slider 15 can move in the guide cylinder 10, thereby resuming the height adjustment of the nitrogen blowing pipe 13.

[0061] The present invention is used to determine diamide pesticides in fresh milk, and the diamide pesticides include but are not limited to flubendiamide, fluazifop, bromocyanamide, etc.

[0062] Two specific operation examples of the present invention are provided below:

[0063] Operation Example 1:

[0064] S1: Weigh 5.0 g of mixed fresh goat milk into a centrifuge tube, and centrifuge at 12,000 rpm for 20 min at 4°C to obtain a first liquid phase and a first solid phase;

[0065] S2: 20 mL of acetonitrile was transferred to the centrifuge tube containing the first solid phase. After ultrasonic dispersion for 1 min to desorb the solids attached to the bottom of the centrifuge tube, the tube was shaken at 1000 rpm for 10 min, and then centrifuged at 12000 rpm for 5 min at 4°C to obtain the second liquid phase and the second solid phase, respectively.

[0066] S3: 20 mL of acetonitrile was transferred to the centrifuge tube containing the second solid phase. After ultrasonic dispersion for 1 min to desorb the solids attached to the bottom of the centrifuge tube, the tube was shaken at 1000 rpm for 10 min, and then centrifuged at 12000 rpm at 4°C for 5 min to obtain the third liquid phase and the third solid phase, respectively.

[0067] S4: Add 5 mL of acetonitrile to the first liquid phase obtained in step S1, vortex mix, and then centrifuge at 12,000 rpm for 5 minutes at 4°C to obtain a fourth liquid phase and a fourth solid phase, respectively;

[0068] S5: The second, third, and fourth phases were combined, vortexed, and then centrifuged at 12,000 rpm for 5 min at 4°C to obtain the fifth phase.

[0069] S6: The fifth liquid phase was transferred to a concentrator tube, concentrated to 1.00 mL by nitrogen blowing at 55° C., and the concentrate was filtered through a 0.22 μm organic filter membrane.

[0070] Operation Example 2:

[0071] S1: Weigh 10.0 g of mixed fresh goat milk into a centrifuge tube, and centrifuge at 12,000 rpm for 30 min at 4°C to obtain a first liquid phase and a first solid phase;

[0072] S2: 50 mL of acetonitrile was transferred to the centrifuge tube containing the first solid phase. After ultrasonic dispersion for 1 min to desorb the solids attached to the bottom of the centrifuge tube, the tube was shaken at 1000 rpm for 10 min, and then centrifuged at 12000 rpm for 5 min at 4°C to obtain the second liquid phase and the second solid phase, respectively.

[0073] S3: 50 mL of acetonitrile was transferred to the centrifuge tube containing the second solid phase. After ultrasonic dispersion for 1 min to desorb the solids attached to the bottom of the centrifuge tube, the tube was shaken at 1000 rpm for 10 min, and then centrifuged at 12000 rpm at 4°C for 5 min to obtain the third liquid phase and the third solid phase, respectively.

[0074] S4: Add 10 mL of acetonitrile to the first liquid phase obtained in step S1, vortex mix, and then centrifuge at 12,000 rpm for 5 minutes at 4°C to obtain a fourth liquid phase and a fourth solid phase, respectively;

[0075] S5: The second, third, and fourth phases were combined, vortexed, and then centrifuged at 12,000 rpm for 5 min at 4°C to obtain the fifth phase.

[0076] S6: The fifth liquid phase was transferred to a concentrator tube, concentrated to 1.00 mL by nitrogen blowing at 55° C., and the concentrate was filtered through a 0.22 μm organic filter membrane.

[0077] The present invention is not limited to the above-mentioned optimal implementation mode. Anyone can derive other forms of products under the inspiration of the present invention. However, no matter what changes are made in the shape or structure, any technical solution that is the same or similar to that of the present application falls within the scope of protection of the present invention.

Claims

1. A method for rapidly extracting diamide pesticides from fresh milk, characterized in that: The specific steps include: S1: placing the fresh milk raw material in a centrifuge tube, and centrifuging to obtain a first liquid phase and a first solid phase; S2: adding acetonitrile to the first solid phase and performing ultrasonic dispersion, shaking the first solid phase, and centrifuging to obtain a second liquid phase and a second solid phase; S3: adding acetonitrile to the second solid phase and performing ultrasonic dispersion, shaking the second solid phase, and centrifuging to obtain a third liquid phase and a third solid phase; S4: adding acetonitrile to the first liquid phase, mixing, and then centrifuging to obtain a fourth liquid phase and a fourth solid phase; S5: mixing the second liquid phase, the third liquid phase and the fourth liquid phase and separating them by centrifugation to obtain a fifth liquid phase; S6: Concentrating the fifth liquid phase.

2. The method for rapid extraction of diamide pesticides in fresh milk according to claim 1, characterized in that: In step S2, the fresh milk raw material is centrifuged at a temperature of 4°C, with a rotation speed of 12000 r / min and a centrifugal separation time of 20-30 min.

3. The method for rapid extraction of diamide pesticides in fresh milk according to claim 1, characterized in that: In step S2, the mass ratio of the added acetonitrile to the fresh milk raw material is between 6:1 and 4:1; the ultrasonic dispersion time is 1 minute; the oscillation time is 10-15 minutes; and the centrifugal separation is carried out at a speed of 12000 r / min at a temperature of 4°C for 5-10 minutes.

4. The method for rapid extraction of diamide pesticides in fresh milk according to claim 1, characterized in that: In step S3, the mass ratio of the added acetonitrile to the fresh milk raw material is between 6:1 and 4:1; the ultrasonic dispersion time is 1 minute; the oscillation time is 10-15 minutes; and the centrifugal separation is carried out at a speed of 12000 r / min at a temperature of 4°C for 5-10 minutes.

5. The method for rapid extraction of diamide pesticides in fresh milk according to claim 1, characterized in that: The mass ratio of acetonitrile to fresh milk added in step S4 is between 2:1 and 1:1; after mixing, the mixture is centrifuged at a speed of 12000 r / min at a temperature of 4° C. for 5-10 minutes.

6. The method for rapid extraction of diamide pesticides in fresh milk according to claim 1, characterized in that: When centrifuging in step S5, the centrifuge is performed at a speed of 12000 r / min at a temperature of 4° C. for 5-10 minutes.

7. The method for rapid extraction of diamide pesticides in fresh milk according to claim 1, characterized in that: In step S6, the temperature during concentration is 50-55° C., and the constant volume is 1.00 mL.

8. The method for rapid extraction of diamide pesticides in fresh milk according to claim 1, characterized in that: In step S6, the fifth liquid phase is concentrated by a nitrogen blowing concentration device; the nitrogen blowing concentration device includes a base, a guide rail is provided on the base, a sliding seat is slidably connected to the guide rail, a water bath device is provided on the sliding seat, and a tube rack for placing the concentrator tube is provided on the water bath device; a lifting adjustment rod is provided on the base, a lifting plate is provided at the upper end of the lifting adjustment rod, and a nitrogen blowing tube is connected to the lifting plate; the nitrogen blowing tube can be moved up and down relative to the lifting plate; a positioning boss is provided at the lower end of the sliding seat, and the positioning boss is cylindrical; a first positioning lock and a second positioning lock are provided on the base; When the positioning boss on the sliding seat is connected to the first positioning latch, the sliding seat is in the working position, and the concentrator tube placed on the water bath device is located directly below the nitrogen blowing tube; When the positioning boss on the sliding seat is connected to the first positioning lock, the sliding seat is located in the ready position.

9. The method for rapid extraction of diamide pesticides in fresh milk according to claim 8, characterized in that: The first positioning lock and the second positioning lock have the same structure. Both the first positioning lock and the second positioning lock include a fixing block. Two elastic clips are symmetrically provided on the fixing block. The elastic clips are provided with arc-shaped clamping sections.

10. The method for rapid extraction of diamide pesticides in fresh milk according to claim 8, characterized in that: The lifting plate is provided with a guide cylinder arranged in a vertical direction, and a positioning groove is provided on the inner wall of one side of the guide cylinder. The cross section of the positioning groove is rectangular, and the positioning grooves are arranged equidistantly along the axial direction of the guide cylinder. A slider is connected to the guide cylinder, and a transition cavity is provided in the slider. The nitrogen blowing pipe is located at the lower end of the slider, and the upper end of the nitrogen blowing pipe is connected to the transition cavity; a connecting pipe is provided at the upper end of the slider, and the lower end of the connecting pipe is connected to the transition cavity, and the connecting pipe is connected to the nitrogen supply device; A groove is provided on the side of the slider close to the positioning groove, a fixed shaft is provided in the groove, a lever is rotatably connected to the fixed shaft, a contact portion is provided on the side of one end of the lever close to the positioning groove, and a spring is provided between the end and the slider; a clamping portion that can be inserted into the positioning groove is provided on the side of the other end of the lever close to the positioning groove; a protrusion is provided on the side of the other end of the lever away from the positioning groove; a pressure transmission hole is provided in the slider, one end of the pressure transmission hole is connected to the transition chamber, and the other end of the pressure transmission hole passes through the surface of the slider facing the positioning groove and forms an opening corresponding to the protrusion on the surface of the slider, and an elastic membrane is provided on the opening.

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