Method for improving Raman spectrum signal in carbendazim and acetamiprid detection

Abstract

The invention discloses a method for improving Raman spectrum signals in carbendazim and acetamiprid detection, and belongs to the technical field of pesticide residue detection. The specific method comprises the following steps: when the concentration of carbendazim and acetamiprid is detected by adopting a surface enhanced Raman spectrum technology, uniformly mixing a sample to be detected with colloidal silver nanoparticles, then adding an MgSO4 solution, and finally detecting a Raman spectrum signal. By adding the MgSO4 solution, the surface enhanced Raman spectrum signal of sample molecules is further enhanced, the method can realize simultaneous detection of the carbendazim and the acetamiprid, the detection limit of the carbendazim reaches 0.01 mu g / mL, the detection limit of the acetamiprid reaches 0.01 mu g / mL, the sensitivity is relatively high, and the method is suitable for large-scale popularization and application. And an effective detection means is provided for rapid detection of multiple scenes.

Description

Technical Field

[0001] The present invention relates to a method for improving the Raman spectrum signal in the detection of carbendazim and acetamiprid, belonging to the technical field of pesticide residue detection Background Art

[0002] Carbendazim and acetamiprid are fungicides and insecticides widely used in agricultural production. The combination of the two can simultaneously control fungi and pests, thereby improving the control effect. However, the mixed use of pesticides may increase the amount of pesticide residues on plants, posing a serious threat to food safety and the ecological environment. In addition, carbendazim and acetamiprid degrade slowly in the soil and may accumulate through the food chain. Long-term low-dose exposure to humans may lead to chronic poisoning and even potential carcinogenic risks. Therefore, it is urgent to establish a stable, reliable and efficient analytical method to achieve highly sensitive detection of carbendazim and acetamiprid, thereby providing technical support for the risk prevention and control of pesticide residues in food.

[0003] At present, the traditional methods for detecting the two types of pesticides include high performance liquid chromatography (HPLC), gas chromatography-mass spectrometry (GC-MS), liquid chromatography-mass spectrometry (LC-MS), spectroscopy, etc. However, these methods have problems such as expensive equipment, complex operation, inability to detect on-site, and low sensitivity; surface enhanced Raman spectroscopy (SERS) is an ultra-sensitive analytical technology based on the surface plasmon resonance effect of nanomaterials. Its core principle is: when the target molecule is adsorbed on the surface of rough precious metal nanostructures (such as gold and silver nanoparticles), the local electromagnetic field is significantly enhanced, and at the same time, the chemical enhancement effect (charge transfer) further amplifies the Raman signal, thereby achieving trace or even single-molecule level detection; microfluidics is a technology that precisely manipulates fluids in micron-scale channels. By integrating sample pretreatment, reaction, separation and detection modules, the miniaturization, automation and high-throughput of the analysis process are achieved; in the face of the hidden risks of mixed pesticide residues and the bottleneck of detection technology, the combination of SERS and microfluidics technology can give full play to the complementarity of the two in sensitivity, throughput and automation, providing convenience for the detection of carbendazim and acetamiprid. When using SERS combined with microfluidics technology to detect carbendazim and acetamiprid, the improvement of Raman spectral signals is very important. Therefore, the present invention proposes a method for improving Raman spectral signals in the detection of carbendazim and acetamiprid. Summary of the Invention

[0004] In order to solve the problems existing in the prior art, the present invention provides a method for improving the Raman spectral signal in the detection of carbendazim and acetamiprid. The method mainly comprises: when using surface-enhanced Raman spectroscopy technology to detect the concentration of carbendazim and acetamiprid, the test solution is evenly mixed with colloidal silver nanoparticles to obtain a mixed solution, and then MgSO4 solution is added to the mixed solution to detect the Raman spectral signal.

[0005] Specifically, the purpose of the present invention is achieved through the following solutions:

[0006] (1) The solution to be tested and the colloidal silver nanoparticles are mixed uniformly to obtain a mixed solution.

[0007] (2) The mixed solution and the MgSO4 solution were injected into the microfluidic chip at the same time, and the Raman spectrum intensity of carbendazim and the Raman spectrum intensity of acetamiprid were obtained by Raman spectrometer.

[0008] (3) The Raman spectrum intensity of carbendazim obtained in step (2) is substituted into the carbendazim standard curve to obtain the carbendazim concentration in the solution to be tested; the Raman spectrum intensity of acetamiprid obtained in step (2) is substituted into the acetamiprid standard curve to obtain the acetamiprid concentration in the solution to be tested.

[0009] Preferably, in step (1), the volume ratio of the solution to be detected to the colloidal silver nanoparticles is 1:1.

[0010] Preferably, in step (2), the volume ratio of the mixed solution I to the MgSO4 solution is 1:1, and the concentration of MgSO4 in the MgSO4 solution is 0.4 to 0.8 mol / L.

[0011] Preferably, the preparation method of the colloidal silver nanoparticles is as follows: heating a silver nitrate solution to boiling, then adding a trisodium citrate solution, stirring and heating thoroughly, and filtering the solution after it stops changing color and cools down to obtain the colloidal silver nanoparticles.

[0012] Preferably, the volume ratio of the silver nitrate solution to the trisodium citrate solution is 45:1, wherein the concentration of the silver nitrate solution is 0.001 mol / L, and the mass concentration of trisodium citrate in the trisodium citrate solution is 1%.

[0013] Preferably, the method for preparing the carbendazim standard curve and the acetamiprid standard curve in step (3) is as follows: a standard mixed solution of carbendazim and acetamiprid with gradient concentrations is prepared using an organic solvent, a standard curve of carbendazim gradient concentration and Raman spectral intensity is established, and a carbendazim standard curve is obtained; a standard curve of acetamiprid gradient concentration and Raman spectral intensity is established to obtain a acetamiprid standard curve.

[0014] Preferably, the preparation method of the colloidal silver nanoparticles is as follows: heating a silver nitrate solution to boiling, then adding a trisodium citrate solution, stirring and heating thoroughly, and filtering the solution after cooling to obtain the colloidal silver nanoparticles.

[0015] Preferably, the microfluidic chip consists of a "Y" inlet, an "S"-shaped mixing channel, a detection area and an outlet; the "Y" inlet is connected to the "S"-shaped mixing channel, the "S"-shaped mixing channel is connected to the detection area, and the circular detection area is connected to the outlet.

[0016] Preferably, the microfluidic chip is prepared by soft lithography using polydimethylsiloxane and glass, wherein the upper layer is composed of polydimethylsiloxane and microfluidic channels, and the lower layer is a glass support layer, and the two are bonded together by plasma bonding.

[0017] Technical effects of the present invention:

[0018] (1) When the present invention uses surface-enhanced Raman spectroscopy to detect the concentrations of carbendazim and acetamiprid, MgSO4 solution is added. The MgSO4 solution regulates the aggregation state of silver nanoparticles, thereby enhancing the local electromagnetic field enhancement effect and the adsorption behavior of the molecules to be tested. More "hot spots" are generated by the adsorption of the molecules to be tested, thereby enhancing the absorption of the molecules at 1110 cm -1 1008cm -1 Surface enhanced Raman spectroscopy signal at .

[0019] (2) The method established in the present invention can realize the simultaneous detection of carbendazim and acetamiprid. The detection limit of carbendazim reaches 0.01 μg / mL, and the detection limit of acetamiprid reaches 0.01 μg / mL. The sensitivity is high, providing an effective detection means for rapid detection in various scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of the microfluidic chip structure of the present invention.

[0021] Figure 2 Schematic diagram of the detection of carbendazim and acetamiprid based on the SERS microfluidic chip of the present invention.

[0022] Figure 3 This is the SEM image of the AgNPs solution of the present invention.

[0023] Figure 4 This is a two-dimensional model simulation diagram of the liquid mixing velocity in the microfluidic chip structure described in the present invention.

[0024] Figure 5 This is a comparison chart of the SERS enhancement effects of different solutions of the present invention on mixed solution II.

[0025] Figure 6 This is a comparison chart of the SERS enhancement effects of different concentrations of magnesium sulfate on mixed solution II described in the present invention.

[0026] Figure 7 This is the standard SERS spectrum of the mixed solution A described in the present invention.

[0027] Figure 8 This is the standard SERS spectrum of the mixed solution B described in the present invention.

[0028] Figure 9 These are SERS spectra of mixed standard solutions of different concentrations described in the present invention.

[0029] Figure 10 The mixed solution II of the present invention is at 1110cm -1 The linear relationship between the characteristic peak intensity at 400 nm and the concentration of acetamiprid.

[0030] Figure 11 The mixed solution II of the present invention is at 1008cm -1 The linear relationship between the characteristic peak intensity and the concentration of carbendazim.

[0031] Figure 12 This is a comparison chart of the SERS results obtained before and after the experiment using the microfluidic chip described in the present invention. DETAILED DESCRIPTION

[0032] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments, but the protection scope of the present invention is not limited to the contents described above.

[0033] Example 1

[0034] The preparation steps of colloidal silver nanoparticles are as follows:

[0035] (1) Accurately weigh 100 mg of trisodium citrate powder using an electronic balance and place it in a 10 ml test tube. Add ultrapure water to the test tube and mix thoroughly to obtain a 1 wt% trisodium citrate solution.

[0036] (2) 20 mL of 0.01 mol / L silver nitrate solution was added to 180 mL of ultrapure water and diluted 10 times to 0.001 mol / L. The diluted solution was stirred and heated to boiling, and then 4 mL of the trisodium citrate solution prepared in step (1) was added. Stirring and heating were continued. It was observed that the color of the solution gradually changed from colorless to bright yellow, and finally to yellow-green and did not change. After cooling, it was filtered using a filter membrane with a pore size of 0.1 μm. Colloidal silver nanoparticles (AgNPs solution) were successfully prepared. Finally, the obtained colloidal silver nanoparticles were placed in a brown sample bottle and placed in a 4°C refrigerator to avoid light.

[0037] The surface morphology of the prepared AgNPs was characterized. Figure 3 As shown, Figure 3 It shows that the silver nanoparticles are irregular spherical, most of the particles are aggregated, and a few nanoparticles are distributed individually. The particle size range of the silver nanoparticles is between 40-54nm.

[0038] Example 2

[0039] A method for improving the surface-enhanced Raman spectroscopy signal for detecting carbendazim and acetamiprid, the main steps of which are as follows:

[0040] (1) Use a pipette to take 1 mL of 100 μg / mL carbendazim and acetamiprid standard solutions into two 10 mL test tubes, then add 9 mL of ultrapure water and shake well to obtain 10 μg / mL carbendazim and acetamiprid standard solutions, and obtain their respective standard spectra.

[0041] (2) 10 μg / mL carbendazim and acetamiprid standard solutions were mixed with the AgNPs solution at a volume ratio of 1:1 to obtain mixed solution A and mixed solution B.

[0042] (3) Mixed solution A and mixed solution B were injected with MgSO4 solution (the concentration of MgSO4 in the MgSO4 solution was 1 mol / L) from inlet 1 and inlet 2 of the microfluidic chip at a flow rate of 0.002 m / s using a syringe pump. The volume ratio of mixed solution A and mixed solution B to the MgSO4 solution was 1:1. After the two solutions were fully mixed in the "S"-shaped mixing channel and flowed to the circular detection area, Raman spectra were detected using a Raman spectrometer. The acquisition parameters were set as follows: laser wavelength 785 nm, integration time 10 s, excitation power 30 mW, cumulative integration times 3 times, and spectrum acquisition range 400-1600 cm -1 The schematic diagram of the microfluidic chip used is shown in Figure 1 shown.

[0043] The SERS spectra of mixed solution A and mixed solution B are shown in Figure 2. Figure 7 and 8 As shown, from Figure 7 It can be seen that the Raman characteristic peaks of carbendazim are mainly located at 629, 1008, 1035, 1228, 1274, 1464 and 1522 cm -1 From Figure 8 It can be seen that the Raman characteristic peaks of acetamiprid are mainly located at 631, 825, 855, 1035, 1110 and 1496 cm -1 At 1000 nm, carbendazim and acetamiprid have different SERS characteristic peaks in aqueous solution, which makes it possible to detect them simultaneously. Based on the considerations of intensity and similarity, the more suitable characteristic peaks of each were selected as the quantitative analysis peaks (acetamiprid: 1110 cm -1 ; Carbendazim: 1008cm -1 ).

[0044] (4) Use a pipette to take 1 mL of 100 μg / mL carbendazim and 1 mL of 100 μg / mL acetamiprid standard into a 10 mL test tube, then add 8 mL of ultrapure water and shake well to obtain a mixed solution I (the concentrations of carbendazim and acetamiprid in the mixed solution I are 10 μg / mL, respectively). Then, use ultrapure water to dilute the mixed solution I into three actual test samples with different gradient concentrations (1, 0.1, and 0.01 μg / mL).

[0045] (5) Mixed solution I with different concentrations (1, 0.1, and 0.01 μg / mL) was mixed with the AgNPs solution at a volume ratio of 1:1 to obtain mixed solution II.

[0046] (6) Mixed solution II and MgSO4 solution (MgSO4 concentration in MgSO4 solution is 0.4 mol / L) of different concentrations were injected from inlet 1 and inlet 2 of the microfluidic chip at a flow rate of 0.002 m / s using a syringe pump. The volume ratio of mixed solution II to MgSO4 solution was 1:1. After the two solutions were fully mixed in the "S"-shaped mixing channel and flowed to the circular detection area, Raman spectra were detected using a Raman spectrometer. The acquisition parameters were set as follows: laser wavelength 785 nm, integration time 10 s, excitation power 30 mW, cumulative integration times 3 times, and spectrum acquisition range 400-1600 cm -1 The schematic diagram of the microfluidic chip used is shown in Figure 1 shown.

[0047] The SERS spectra of mixed solution II with different concentrations are shown in Figure 2. Figure 9 As shown in the figure, it can be seen that with the decrease of the concentration of carbendazim and acetamiprid in the mixed solution, the intensity of the Raman characteristic peak gradually weakened. It was observed that when the concentration was reduced to 0.01μɡ / mL, most of the characteristic peaks disappeared.

[0048] The SERS enhancement effect of MgSO4 solution on mixed solution II is as follows: Figure 5 and Figure 6 As shown in the figure, it can be seen that MgSO4 has the most obvious SERS enhancement effect, which is because Mg 2+ and SO4 2-It can destroy the double-layer structure on the surface of silver nanoparticles, thereby weakening the electrostatic repulsion and making the particles easier to approach and aggregate. Therefore, MgSO4 achieves dual optimization of AgNPs aggregation state and molecular adsorption dynamics by regulating the double-layer structure and electrostatic interaction, providing ideal electrolyte conditions for high-sensitivity SERS detection. When the magnesium sulfate concentration is 0.4 mol / L, the double-layer compression effect induced by magnesium sulfate is significant, and the electrostatic shielding effect between particles is weakened. At this time, the aggregation induced by magnesium sulfate produces a stable "hot spot", and the local electromagnetic field is significantly enhanced, thereby simultaneously improving the mixed solution II at 1110 cm -1 1008cm -1 The SERS signal intensity.

[0049] The Raman spectrum intensity corresponding to the mixed solution with gradient concentration was used to establish a standard curve. Figure 10 Acetamiprid is shown at 1110 cm -1 The relationship between the Raman spectrum intensity and concentration at , the Raman spectrum intensity of acetamiprid and the concentration in the range of 0.01 ~ 10μg / mL showed a good linear correlation, the standard curve of acetamiprid was: y = 9764.5x + 70701, and the correlation coefficient was R 2 =0.9956, Figure 11 It shows that carbendazim is at 1008cm -1 The relationship between the Raman spectrum intensity and concentration at the 0.01-10 μg / mL range of carbendazim Raman spectrum intensity and concentration showed a good linear correlation. The carbendazim standard curve was: y = 17109.7x + 76790.6, and the correlation coefficient was R 2 =0.9981, the detection limits of acetamiprid and carbendazim in the mixed solution were both 0.01 μg / mL. Taking a 10 μg / mL mixed solution as an example, the SERS spectra before and after using the microfluidic chip were compared. The results are as follows: Figure 12 As shown, it can be observed that the signal intensity is significantly increased after using the microfluidic chip, indicating that the use of the microfluidic chip can further improve the detection sensitivity of the mixed solution.

[0050] Example 3

[0051] A method for improving the surface-enhanced Raman spectroscopy signal for detecting carbendazim and acetamiprid, the main steps of which are as follows:

[0052] (1) Use a pipette to take 1 mL of 100 μg / mL carbendazim and 1 mL of 100 μg / mL acetamiprid standard into a 10 mL test tube, then add 8 mL of ultrapure water and shake well to obtain mixed solution I (the concentrations of carbendazim and acetamiprid in mixed solution I are 10 μg / mL, respectively). Then use ultrapure water to dilute the mixed solution I into three different gradient concentrations (1, 0.1 and 0.01 μg / mL) of the actual test samples.

[0053] (2) The actual test samples with different concentrations (1, 0.1, and 0.01 μg / mL) were added to the prepared AgNPs solution at a volume ratio of 1:1 to obtain mixed solution II.

[0054] (3) Mixed solution II and MgSO4 solution (the concentration of MgSO4 in the MgSO4 solution is 0.6 mol / L) of different concentrations were injected from the inlet of the microfluidic chip using a syringe pump at a flow rate of 0.002 m / s. The volume ratio of mixed solution II to MgSO4 was 1:1. After the two solutions were fully mixed in the "S"-shaped mixing channel and flowed to the circular detection area, Raman spectrometer was used for Raman spectrum detection. The acquisition parameters were set as follows: laser wavelength 785 nm, integration time 10 s, excitation power 30 mW, cumulative integration times 3 times, and spectrum acquisition range 400-1600 cm -1 .

[0055] When the concentration of MgSO4 solution is 0.6mol / L, the mixed solution II at 1110cm -1 1008cm -1 The SERS enhancement effect is as follows Figure 6 shown.

[0056] Example 4

[0057] A method for improving the surface-enhanced Raman spectroscopy signal for detecting carbendazim and acetamiprid, the main steps of which are as follows:

[0058] (1) Use a pipette to take 1 mL of 100 μg / mL carbendazim and 1 mL of 100 μg / mL acetamiprid standard into a 10 mL test tube, then add 8 mL of ultrapure water and shake well to obtain mixed solution I (the concentrations of carbendazim and acetamiprid in mixed solution I are 10 μg / mL, respectively). Then use ultrapure water to dilute the mixed solution I into three different gradient concentrations (1, 0.1 and 0.01 μg / mL) of the actual test samples.

[0059] (2) The actual test samples with different concentrations (1, 0.1, and 0.01 μg / mL) were added to the prepared AgNPs solution at a volume ratio of 1:1 to obtain mixed solution II.

[0060] (3) Mixed solution II and MgSO4 solution (the concentration of MgSO4 in the MgSO4 solution is 0.8 mol / L) of different concentrations were injected from the inlet of the microfluidic chip using a syringe pump at a flow rate of 0.002 m / s. The volume ratio of mixed solution II to MgSO4 was 1:1. After the two solutions were fully mixed in the "S"-shaped mixing channel and flowed to the circular detection area, Raman spectrometer was used for Raman spectrum detection. The acquisition parameters were set as follows: laser wavelength 785 nm, integration time 10 s, excitation power 30 mW, cumulative integration times 3 times, and spectrum acquisition range 400-1600 cm -1 .

[0061] When the concentration of MgSO4 solution is 0.8mol / L, the mixed solution II at 1110cm -1 1008cm -1 The SERS enhancement effect is as follows Figure 6 shown.

[0062] Comparative Example 1

[0063] For comparison, the difference between this comparative example and Example 2 is that NaCl solution is used instead of MgSO4 solution, and the remaining steps are the same as Example 2.

[0064] SERS enhancement effect such as Figure 5 As shown in the figure, it can be seen that NaCl solution has no enhancement effect on SERS. This is because NaCl solution is neutral and has no enhancement effect on SERS of the mixed solution.

[0065] Comparative Example 2

[0066] For comparison, the difference between this comparative example and Example 2 is that Na2CO3 solution is used instead of MgSO4 solution, and the remaining steps are the same as Example 2.

[0067] SERS enhancement effect such as Figure 5 As shown in the figure, it can be seen that the enhancement effect of Na2CO3 solution on SERS is weak. This is because Na2CO3 solution is alkaline, which causes the sample molecules to be unstable in an alkaline environment. The surface of silver nanoparticles usually has a negative charge and maintains a dispersed state through electrostatic repulsion.

[0068] Comparative Example 3

[0069] For comparison, the difference between this comparative example and Example 2 is that the concentration of MgSO4 in the MgSO4 solution is 0.2 mol / L, and the remaining steps are the same as those in Example 2.

[0070] SERS enhancement effect such as Figure 6As shown in the figure, it can be seen that when the magnesium sulfate concentration is 0.2 mol / L, the particles are mainly monodispersed and the enhancement effect is not obvious. This is because the ionic strength of the solution only changes slightly, the electrostatic repulsion between the particles is partially weakened, but no obvious aggregation is formed, and the "hot spots" are sparse.

[0071] Comparative Example 4

[0072] For comparison, the difference between this comparative example and Example 2 is that the concentration of MgSO4 in the MgSO4 solution is 1 mol / L, and the remaining steps are the same as those in Example 2.

[0073] SERS enhancement effect such as Figure 6 As shown in the figure, it can be seen that when the concentration of magnesium sulfate is 1 mol / L, the aggregation state between particles is excessive and the reinforcement effect is poor.

[0074] In summary, the present invention effectively enhances the strong Raman spectral signal by adding MgSO4 solution, which is more conducive to the detection of low-concentration pesticides.

Claims

1. A method for improving the Raman spectral signal in the detection of carbendazim and acetamiprid, characterized in that: The specific method is as follows: when using surface enhanced Raman spectroscopy to detect the concentrations of carbendazim and acetamiprid, the test solution is evenly mixed with colloidal silver nanoparticles to obtain a mixed solution, and then MgSO4 solution is added to the mixed solution to detect the Raman spectral signal.

2. The method for improving the Raman spectral signal in the detection of carbendazim and acetamiprid according to claim 1, characterized in that: The concentration of MgSO4 in the MgSO4 solution is 0.4-0.8 mol / L, and the volume ratio of the mixed solution to the MgSO4 solution is 1:

1.

3. The method for improving the Raman spectral signal in the detection of carbendazim and acetamiprid according to claim 1, characterized in that: The specific method is as follows: (1) uniformly mixing the solution to be tested and the colloidal silver nanoparticles to obtain a mixed solution; (2) The mixed solution and the MgSO4 solution were simultaneously injected into the microfluidic chip, and the Raman spectrum intensity of carbendazim and the Raman spectrum intensity of acetamiprid were obtained by Raman spectrometer detection; (3) The Raman spectrum intensity of carbendazim obtained in step (2) is substituted into the carbendazim standard curve to obtain the carbendazim concentration in the solution to be tested; the Raman spectrum intensity of acetamiprid obtained in step (2) is substituted into the acetamiprid standard curve to obtain the acetamiprid concentration in the solution to be tested.

4. The method for improving the Raman spectral signal in the detection of carbendazim and acetamiprid according to claim 2, characterized in that: In step (1), the volume ratio of the solution to be detected to the colloidal silver nanoparticles is 1:

1.

5. The method for improving the Raman spectral signal in the detection of carbendazim and acetamiprid according to claim 2, characterized in that: The preparation method of the colloidal silver nanoparticles is as follows: heating a silver nitrate solution to boiling, then adding a trisodium citrate solution, stirring and heating thoroughly, and filtering the solution after it cools until it no longer changes color to obtain colloidal silver nanoparticles.

6. The method for improving the Raman spectral signal in the detection of carbendazim and acetamiprid according to claim 5, characterized in that: The volume ratio of the silver nitrate solution to the trisodium citrate solution is 45:1, wherein the concentration of the silver nitrate solution is 0.001 mol / L, and the mass concentration of the trisodium citrate in the trisodium citrate solution is 1%.

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