Visual carbaryl detection method

Abstract

The invention discloses a visual carbaryl detection method, and belongs to the technical field of pesticide detection. The visual carbaryl detection method comprises the following steps: spraying or coating the surface of a to-be-detected sample with a 1, 2, 4, 5-tetracyanobenzene solution, so that the 1, 2, 4, 5-tetracyanobenzene is combined with carbaryl on the surface of the to-be-detected sample, and visual carbaryl detection is realized by analyzing a fluorescence signal on the surface of the to-be-detected sample. According to the present invention, the adopted receptor probe 1, 2, 4, 5-tetracyanobenzene and carbaryl show the high-selectivity intermolecular charge transfer effect; after carbaryl reacts with 1, 2, 4, 5-tetracyanobenzene, a fluorescence signal of the carbaryl has a remarkable distinguishing effect with common carbamate pesticides, a carbaryl alkaline degradation product and a parent nucleus structure. The method can solve the problems that an existing carbaryl detection method is complex, equipment dependence is high, and potential interference exists in the detection process, and efficient and rapid carbaryl detection can be achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of pesticide detection, and particularly relates to a visual carbaryl detection method. Background Art

[0002] Pesticides play an irreplaceable role in preventing crop damage and increasing grain and vegetable yields. Among the numerous insecticide classes, carbamates are widely used due to their strong selectivity, high efficiency, and low toxicity. However, excessive use of these pesticides can lead to unused carbamate residues, which, by inhibiting human acetylcholinesterase activity, can cause neurological disorders and even death. Therefore, carbamate residues pose significant environmental and health risks, necessitating the development of analytical methods and technologies for their detection.

[0003] Currently, commonly used analytical methods for carbamate pesticide residues include spectroscopy, chromatography, electrochemistry, mass spectrometry, and chromatography-mass spectrometry. Based on this, highly sensitive and accurate analysis of carbamate pesticide residues has been achieved. However, most existing methods require complex and expensive large-scale instrumentation or specialized operators to complete the corresponding data processing and detection tasks, resulting in low detection efficiency and hindering the real-time analysis of pesticide residues. In contrast, the development of simpler analytical methods that do not rely on large-scale instrumentation, especially those that can perform direct in situ visualization of pesticide residues, has outstanding advantages and broad application prospects. However, relevant research is still relatively lacking.

[0004] Carbaryl, a representative carbamate insecticide, is widely used in agriculture, and a range of detection methods have been developed. Due to the presence of a naphthalene ring in its structure, the molecule's inherent short-wavelength blue light emission serves as the basis for fluorescence spectroscopy analysis. However, direct visualization of this emission on crop samples is extremely challenging. Some existing carbaryl detection methods utilize the strong blue fluorescence of its alkaline decomposition product, 1-naphthol, for quantitative analysis. Therefore, this degradation product, like other carbamate pesticides, can act as an interference in direct visualization analysis of carbaryl.

[0005] Therefore, the difficulty in developing a visual analysis method for carbaryl lies in the need for the new method to possess both good selectivity and a characteristic signal to eliminate interference from structural analogs and ensure analytical accuracy. Therefore, developing an efficient, rapid, and visual carbaryl detection method to meet practical application needs is particularly important. Summary of the Invention

[0006] The problem to be solved by the present invention is to provide a visual carbaryl detection method to solve the problems of the existing carbaryl detection method being complex, highly dependent on equipment and having potential interference in the detection process.

[0007] The technical solution adopted to solve the technical problem is to provide a visual carbaryl detection method, which includes the following steps: A 1,2,4,5-tetracyanobenzene solution is sprayed or coated on the surface of the sample to be tested, so that 1,2,4,5-tetracyanobenzene combines with carbaryl on the surface of the sample to be tested. Visual carbaryl detection is achieved by analyzing the fluorescence signal on the surface of the sample to be tested.

[0008] The beneficial effects of the above-mentioned technical solution are as follows: The present method for visualizing carbaryl detection is based on an intermolecular charge transfer (ICT) fluorescence sensing mechanism. This method is based on the specific electron donor-acceptor interaction between carbaryl as a donor and the 1,2,4,5-tetracyanobenzene (TCNB) acceptor. The amino (-NH-) nitrogen atom in the carbaryl molecular structure carries a lone pair of electrons, making it a typical electron-rich group that can act as an electron donor. When in proximity with a suitable acceptor, it tends to partially or completely transfer electrons from its highest occupied molecular orbital (HOMO) to the lowest unoccupied molecular orbital (LUMO) of the acceptor. TCNB is a planar, highly symmetrical molecule. The four cyano groups (-C≡N) in its structure are extremely strong electron-withdrawing groups, giving the entire TCNB molecule an extremely low LUMO energy level and a very high electron affinity, making it a very strong electron acceptor. Furthermore, due to the electron-withdrawing inductive effect of the cyano groups and the conjugation effect, the TCNB backbone is also electron-deficient. During the binding process, strong electrostatic attraction and orbital interactions between carbaryl and TCNB lead to intermolecular charge transfer. The resulting charge-transfer complex has an electronic structure distinct from both the donor and acceptor alone, with significant changes in the energies of its ground and excited states. The red shifts in its absorption and emission spectra caused by the ICT mechanism serve as effective identification signals, enabling visual and efficient detection of carbaryl.

[0009] Preferably, the sample to be tested is a crop leaf or fruit.

[0010] Preferably, the 1,2,4,5-tetracyanobenzene solution is prepared using a mixed solution of dichloromethane and acetonitrile, ethanol, methanol or acetone.

[0011] More preferably, the volume ratio of dichloromethane to acetonitrile in the mixed solution of dichloromethane and acetonitrile is (8-9):(1-2).

[0012] More preferably, the 1,2,4,5-tetracyanobenzene solution is prepared in acetone.

[0013] More preferably, the concentration of the 1,2,4,5-tetracyanobenzene solution is 1-50 mg / mL.

[0014] More preferably, the concentration of the 1,2,4,5-tetracyanobenzene solution is 1 mg / mL.

[0015] More preferably, the mass ratio of carbaryl on the surface of the sample to be tested to 1,2,4,5-tetracyanobenzene in the 1,2,4,5-tetracyanobenzene solution is (1-10):(1-50).

[0016] More preferably, the mass ratio of carbaryl on the surface of the sample to be tested to 1,2,4,5-tetracyanobenzene in the 1,2,4,5-tetracyanobenzene solution is 1:1.

[0017] More preferably, the detection concentration of carbaryl is 0.1-1.6 mg / mL.

[0018] Preferably, analyzing the fluorescence signal on the surface of the sample to be tested includes: using ultraviolet light to irradiate the surface of the sample to be tested to generate characteristic yellow-green fluorescence to detect carbaryl, or performing numerical analysis of carbaryl on the surface of the sample to be tested by analyzing the RGB values ​​of the fluorescence imaging image.

[0019] The present invention has the following beneficial effects: The present invention leverages the space charge effect of intermolecular charge transfer to bring about significant differences in absorption and fluorescence signals. Targeting the carbamate pesticide carbaryl, an effective charge transfer receptor, 1,2,4,5-tetracyanobenzene, was screened and obtained. After carbaryl and 1,2,4,5-tetracyanobenzene form an intermolecular charge transfer complex, a characteristic yellow-green fluorescence signal is generated. This signal is significantly distinguishable from 1-naphthol, a carbaryl alkaline degradation product, and other typical carbamate pesticides, such as isoprocarb, propamocarb, and pirimicarb. Furthermore, the intensity of the fluorescence signal gradually increases with increasing carbaryl concentration (0.1-1.6 mg / mL), enabling visual analysis of carbaryl on the surface of crop leaves. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The results of the intermolecular charge transfer receptor screening are shown in FIG. 1 ; (a) is a molecular structure diagram of carbaryl and polycyanobenzene receptors; (b) is a fluorescence imaging diagram of the interaction between carbaryl and polycyanobenzene receptor molecules; (c) is a fluorescence spectrum diagram of the interaction between carbaryl and polycyanobenzene receptor molecules; Figure 2 Figure 1 shows the results of selecting the donor-acceptor ratio of carbaryl to TCNB. (a) shows the fluorescence imaging of the interaction between carbaryl and TCNB at different ratios; (b) shows the fluorescence spectrum at a ratio where no obvious charge transfer occurs; and (c) shows the fluorescence spectrum at a ratio where obvious charge transfer occurs. Figure 3 IR spectra of carbaryl, TCNB and carbaryl-TCNB complex; Figure 4 Figure 1 shows the selectivity analysis results of TCNB for carbaryl; (a) shows the molecular structure of potential interferents; (b) shows the fluorescence imaging of the interaction between five potential interferents and TCNB; (c) shows the fluorescence spectra of the interaction between five potential interferents and TCNB; Figure 5 The RGB numerical analysis results of fluorescence imaging of carbaryl-TCNB complexes with different concentrations; Figure 6 The following are visualization analysis diagrams of two concentrations of carbaryl on citrus leaves; (a) is the analysis diagram of carbaryl with a mass concentration of 1.6 mg / mL; (b) is the analysis diagram of carbaryl with a mass concentration of 0.4 mg / mL; Figure 7 The following are visualization analysis results of two concentrations of carbaryl on blueberry leaves; (a) is the analysis diagram of carbaryl with a mass concentration of 1.6 mg / mL; (b) is the analysis diagram of carbaryl with a mass concentration of 0.4 mg / mL; Figure 8 The following are visualization analysis results of two concentrations of carbaryl on apple leaves; (a) is the analysis diagram of carbaryl with a mass concentration of 1.6 mg / mL; (b) is the analysis diagram of carbaryl with a mass concentration of 0.4 mg / mL; Figure 9 The RGB numerical analysis results of the removal effect of 0.4 mg / mL carbaryl on apple leaves after washing treatment; among them, (a) is the fixed-point diagram of leaf data collection; (b) is the RGB numerical analysis result diagram without washing treatment; (c) is the RGB numerical analysis result diagram after one washing treatment; (d) is the RGB numerical analysis result diagram after two washing treatments. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. That is, the embodiments described are only part of the embodiments of the present invention, rather than all of the embodiments.

[0022] Therefore, the detailed description of the embodiments of the present invention provided below is not intended to limit the scope of the claimed invention, but rather represents only selected embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative work are within the scope of protection of the present invention.

[0023] The following examples further describe the features and properties of the present invention. Carbaryl, propamocarb, isoprocarb, pirimicarb, 1-naphthol, 1,3-dicyanobenzene (1,3-DCB), 1,3,5-tricyanobenzene (TCB), TCNB, and 7,7,8,8-tetracyanoquinodimethane (TCNQ) in the examples were sourced from Shanghai Aladdin Biochemical Technology Co., Ltd.; naphthalene was sourced from Chengdu Kelon Chemical Reagent Factory; and dichloromethane, acetone, and sodium chloride were sourced from Chongqing Chuandong Chemical Group Chemical Reagent Factory. Propamocarb, isoprocarb, and pirimicarb were analytical standards, while all other reagents were of analytical grade and used directly in the following examples without further treatment.

[0024] Example 1 Screening of Intermolecular Charge Transfer Receptors Based on the structural characteristics of carbaryl, it was preliminarily determined that its electron-rich naphthalene ring is suitable as an intermolecular charge transfer (ICT) donor. This allowed the screening of polycyanobenzene receptor molecules for effective receptors capable of forming ICT pairs with carbaryl. The polycyanobenzene receptor molecules were specifically 1,3-DCB, TCB, TCNB, and TCNQ. The specific screening steps were as follows: (1) Carbaryl was mixed with 1,3-DCB, TCB, TCNB, and TCNQ at a mass ratio of 1:1 to obtain a premix; (2) 2 mg of the premix was used as the raw material, and 10 mL of a mixed solution of dichloromethane and acetonitrile in a volume ratio of 9:1 was added to each of the two solutions, and the mixture was allowed to stand for solvent evaporation to obtain the complex; (3) Fluorescence imaging of single carbaryl, the above four polycyanobenzene receptor molecules and the corresponding four complexes was performed under 10W ultraviolet light and the fluorescence color was observed. At the same time, the corresponding fluorescence spectrum was detected (fluorescence spectrometer: Hitachi, F7100).

[0025] The molecular structure of polycyanobenzene receptors and the test results are as follows Figure 1 shown.

[0026] from Figure 1 As can be seen from the figure, the naphthalene ring in the carbaryl structure can serve as an electron-rich center, so the ICT receptor commonly used in polycyanobenzenes was screened as a potential charge transfer receptor ( Figure 1 a); Fluorescence imaging photos ( Figure 1b) shows that the reaction of carbaryl with TCNB can produce bright green fluorescence emission that is significantly different from other polycyanobenzene acceptor groups; the reaction of other polycyanobenzenes with carbaryl does not produce obvious changes in fluorescence emission, and still shows blue fluorescence emission similar to that of carbaryl; at the same time, bright field imaging photos show that the reaction of carbaryl with TCNB produces a significant absorption red shift, which is different from the brown color of the carbaryl and TCNQ group, which comes from the dilution of the TCNQ color, which indirectly confirms that TCNB and carbaryl have a significant interaction.

[0027] Furthermore, the fluorescence spectrum characterization results showed that the complex of TCNB and carbaryl had a maximum emission peak around 520 nm, which was consistent with the green emission of fluorescence imaging ( Figure 1 c) The emission from other polycyanobenzene acceptor-carbaryl complexes all remained near 420 nm, without a significant red-shift in the emission spectrum. This indicates that the ICT complex formed by TCNB and carbaryl exhibits a significantly red-shifted and bright green fluorescence emission, providing the optical signal foundation for visualization analysis.

[0028] Example 2 Selection of Carbaryl-TCNB Donor-Acceptor Ratio Considering that in actual application, the concentration of carbaryl may appear in a wide range, in order to explore the application value of TCNB for visual analysis of carbaryl, the carbaryl-TCNB ratio range that can bring about significant fluorescence signal changes was investigated; a series of carbaryl-TCNB ratios of 100:1, 50:1, 10:1, 5:1, 3:1, 2:1, 1.5:1, 1:1, 1:1.5, 1:2, 1:3, 1:5, 1:10, 1:50, and 1:100 were set, and a series of ICT complexes were prepared by the solvent evaporation method described in Example 1. Fluorescence imaging and fluorescence spectroscopy were performed on them. The results are shown as follows: Figure 2 shown.

[0029] Figure 2 The results showed that in the two groups with a low TCNB ratio of 100:1 and 50:1, the ICT effect was insufficient due to insufficient TCNB, and the blue fluorescence emission of TCNB was dominant. Figure 2 a~b); The group with too high a TCNB ratio (carbaryl:TCNB ratio of 1:100) had weak fluorescence emission and was not valuable for analytical applications; this phenomenon was caused by the low content of carbaryl, which plays an important role in the luminescence of the complex, resulting in low fluorescence emission intensity. In addition, the fluorescence emission of the two groups with high TCNB ratios (carbaryl:TCNB ratios of 1:10 and 1:50) further shifted red to yellow ( Figure 2a~c); Although it is somewhat different from the green fluorescence emission, it can also be significantly distinguished from the blue emission of carbaryl, and therefore can also be used for the visualization analysis of carbaryl.

[0030] That is, the ratio of carbaryl to TCNB ranging from 10:1 to 1:50 can produce effective ICT effects and bring significant fluorescence signals. Therefore, the method of the present invention has good application potential for the visualization analysis of carbaryl.

[0031] Example 3 Analysis of Carbaryl-TCNB Interaction In order to confirm that carbaryl and TCNB had an ICT reaction, dry potassium bromide was used as a diluent for tableting. Infrared spectroscopy (Fourier transform infrared spectrometer: Shimadzu, IRTracer-100) was performed on carbaryl, TCNB, and carbaryl-TCNB complex. The results are as follows: Figure 3 shown.

[0032] from Figure 3 As can be seen from the figure, compared with the cyano group in TCNB at 2243 cm -1 The characteristic peak at 2245 cm-1 red-shifts to 2245 cm-1 after reacting with carbaryl. -1 The reason for this shift is that the electron cloud density increases after the charge transfer reaction between TCNB and carbaryl, which confirms that carbaryl and TCNB have undergone ICT reaction. In addition, compared with the infrared spectrum of carbaryl itself, carbaryl has a higher peak at 1720 cm after the reaction with TCNB. -1 The carbonyl characteristic peak at 3315 cm -1 The vibration intensity of the secondary amide characteristic peak at the position is significantly reduced, and the changes in these characteristic signals also reflect the occurrence of ICT effect.

[0033] Example 4 Detection of the Selectivity and Analytical Performance of TCNB for Carbaryl 1 Selectivity analysis To investigate the specificity of the fluorescence signal of the ICT complex formed by TCNB and carbaryl, isoprocarb, which lacks a distinct conjugated structure, propamocarb, which contains a benzene ring structure, and pirimicarb, which contains an nitrogen heterocycle, were selected as potential interferents of carbamate insecticides for investigation. A series of ICT complexes were prepared by the solvent evaporation method described in Example 1. Simultaneously, 1-naphthol, a carbaryl degradation product, and naphthalene, a parent core structure, were investigated as potential interferents. ICT complexes were prepared from 1-naphthol and naphthalene by a grinding method. The specific steps were as follows: 1-naphthol and naphthalene were mixed uniformly with TCNB, ground with a grinding rod, and the grinding effect was assessed under 10 W ultraviolet light until bright fluorescence was generated to obtain the ICT complex.

[0034] Fluorescence imaging and fluorescence spectrum measurement were performed on the ICT complex formed by TCNB and various potential interfering substances mentioned above. The structure and analysis results of potential interfering substances are shown in the figure below. Figure 4 shown.

[0035] from Figure 4 As can be seen in the figure, three typical carbamate insecticides, when mixed with TCNB, exhibited fluorescence signals significantly different from those of the carbaryl-TCNB complex. Among them, only pirimicarb exhibited a moderately intense orange fluorescence signal, attributed to the strong electron-rich nature of the nitrogen heterocycle. 1-Naphthol exhibited a low-intensity orange fluorescence signal. Naphthalene reacted with TCNB to produce cyan fluorescence, which was also significantly different from the fluorescence signal of the carbaryl-TCNB complex. This demonstrates that TCNB has the ability to specifically discriminate carbaryl.

[0036] 2 Analysis of the relationship between the fluorescence signal of the carbaryl-TCNB complex and the amount of carbaryl As can be seen from the results of Example 2 above, the complex primarily emits green or yellow fluorescence. Therefore, statistical analysis of the responses was primarily performed on the R value (red value) and the G value (green value). The relationship between the fluorescence signal of the carbaryl-TCNB complex and the amount of carbaryl was analyzed by analyzing the RGB values ​​of the fluorescence imaging photographs. This analysis was primarily performed using a mobile phone app for RGB value statistical analysis. The specific steps are as follows: (1) 0.1, 0.2, 0.4, 0.8, 1.6, 3.2, and 6.4 mg / mL carbaryl acetone solutions were mixed with 1 mg / mL TCNB acetone solution in a 1:1 ratio, and then a certain amount of sodium chloride was used as a diluent. After evaporation, fluorescence imaging of the three sets of parallel samples was performed; (2) Using Huawei mobile phone APP (color picker Pro) to perform RGB value statistical analysis, where RGB values ​​correspond to the intensity values ​​of red, green and blue respectively. The analysis results are as follows Figure 5 shown.

[0037] from Figure 5 It can be seen that the G value reaches saturation (close to 255) when the carbaryl concentration reaches 0.8 mg / mL, while the R value reaches saturation (close to 255) at 3.2 mg / mL. Therefore, the combined (R+G) / 2 (simulated superimposed color yellow) reaches saturation at 1.6 mg / mL.

[0038] That is, the detection limit of this method for carbaryl is 0.1 mg / mL, and an obvious fluorescence signal is present at this mass concentration; therefore, within the range of low concentrations to the dose used in crops, the fluorescence signal of carbaryl-TCNB shows an increasing trend with the amount of carbaryl, and has good potential for application in visual analysis.

[0039] Example 5 Visual Analysis of Carbaryl Residues in Crop Leaves 1 Visualization analysis of carbaryl residues in crop leaves In order to confirm whether the above-mentioned visual carbaryl detection method can be used for the visual analysis of carbaryl residues on crop leaves, citrus leaves, blueberry leaves, and apple leaves were selected as research models. Carbaryl at two concentrations of 1.6 and 0.4 mg / mL was applied to the above three leaves, respectively. After drying, it was developed with 1 mg / mL TCNB. Blank leaves without carbaryl and leaves with only carbaryl applied but not TCNB were used as control groups. In order to investigate the visual analysis of the effect of washing on the removal of carbaryl on leaves, each concentration of carbaryl was washed twice with water, and each time with water sprayed with a spray bottle for 5 s. Fluorescence imaging was performed on all the different states of the leaves in the above groups, and the results are shown as follows. Figures 6-8 shown.

[0040] from Figures 6-8 The results show that compared with the blank leaves, the leaves treated with carbaryl showed no obvious fluorescence signals at both concentrations, which can be attributed to the weak fluorescence signal of carbaryl itself. After TCNB development, carbaryl at both concentrations of 1.6 and 0.4 mg / mL can emit clear yellow-green fluorescence, of which 1.6 mg / mL carbaryl showed a significantly higher fluorescence signal intensity. The experimental results of the effect of water washing on the residual amount of carbaryl on the leaf surface showed that the water washing process showed a high removal ability for carbaryl residues at both concentrations. However, this removal effect was more obvious in citrus leaves than in blueberry leaves and apple leaves. It is speculated that this is closely related to the structure of citrus leaves, such as the cuticle. In-depth research and mechanism analysis of this phenomenon are of great value for the rational use of pesticides and reducing the harm of pesticide residues.

[0041] 2 Numerical analysis of carbaryl residues in crop leaves Numerical analysis of the residual carbaryl content was performed on the fluorescent imaging photos of the apple leaves treated with 0.4 mg / mL carbaryl in three states: untreated, washed once, and washed twice. RGB scanning of 22 pixels was performed on the same parts corresponding to the three states, and RGB line scan analysis of carbaryl fluorescence imaging on the leaves was completed using Image-Pro Plus 6.0 software. Taking the main vein in the middle of the leaf as a reference, the downward trend of carbaryl content was examined, and the results are as follows: Figure 9 shown.

[0042] Figure 9The results show that the R and G values ​​reach their maximum values ​​in the 6-9 pixel range, the left boundary of the carbaryl residue. This indicates a strong yellow-green fluorescence signal, and the R and G values ​​exhibit a decreasing trend. In addition to this decreasing trend in absolute R and G intensity, the R and G values ​​also exhibit a gradually decreasing signal ratio, using the background signal value of the main vein of the apple leaf in the 17-19 pixel range (maintained around 210) as a reference. Combining these two methods effectively confirms the reliability of the analysis results. These results demonstrate that water washing is effective in removing carbaryl residues. It is foreseeable that thorough washing of fruits and vegetables that may have been sprayed with carbaryl can significantly reduce the amount of carbaryl residue on their surfaces, thereby effectively mitigating its potential health risks.

[0043] In summary, the present invention successfully constructed an effective ICT donor-acceptor pair with carbaryl as the donor and TCNB as the acceptor. Carbaryl and TCNB can produce a bright green fluorescent signal with significant discrimination through ICT. This signal can effectively distinguish other typical carbamate insecticides and 1-naphthol, the alkaline degradation product of carbaryl. Furthermore, this signal increases with increasing carbaryl dosage within the carbaryl dosage range. This fluorescent signal allows for visualization of carbaryl residues on typical fruit tree leaves and intuitive analysis of the pesticide residue removal effect of washing. Furthermore, this characteristic fluorescent signal and mobile phone app color value analysis software enable convenient and in-situ analysis of carbaryl residues in crops.

[0044] The present invention has been described according to the above embodiments. It should be understood that the above embodiments do not limit the present invention in any form. Any technical solutions obtained by equivalent replacement or equivalent transformation fall within the scope of the present invention.

Claims

1. A visual carbaryl detection method, characterized in that: The following steps are involved: A 1,2,4,5-tetracyanobenzene solution is sprayed or coated on the surface of the sample to be tested, so that 1,2,4,5-tetracyanobenzene combines with carbaryl on the surface of the sample to be tested. Visual carbaryl detection is achieved by analyzing the fluorescence signal on the surface of the sample to be tested.

2. The visual carbaryl detection method according to claim 1, wherein: The 1,2,4,5-tetracyanobenzene solution is prepared by using a mixed solution of dichloromethane and acetonitrile, ethanol, methanol or acetone.

3. The visual carbaryl detection method according to claim 2, wherein: The concentration of the 1,2,4,5-tetracyanobenzene solution is 1-50 mg / mL.

4. The visual carbaryl detection method according to claim 3, wherein: The concentration of the 1,2,4,5-tetracyanobenzene solution is 1 mg / mL.

5. The visual carbaryl detection method according to claim 1 or 4, wherein: The mass ratio of carbaryl on the surface of the sample to be tested to 1,2,4,5-tetracyanobenzene in the 1,2,4,5-tetracyanobenzene solution is (1-10):(1-50).

6. The visual carbaryl detection method according to claim 5, wherein: The mass ratio of carbaryl on the surface of the sample to be tested to 1,2,4,5-tetracyanobenzene in the 1,2,4,5-tetracyanobenzene solution is 1:

1.

7. The visual carbaryl detection method according to claim 1, wherein: The analysis of the fluorescence signal on the surface of the sample to be tested includes: using ultraviolet light to irradiate the surface of the sample to be tested to generate characteristic yellow-green fluorescence to detect carbaryl, or performing numerical analysis of carbaryl on the surface of the sample to be tested by analyzing the RGB values ​​of the fluorescence imaging picture.

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