Method for oxidation pretreatment of phoxim in organophosphorus pesticide based on photo-initiation free radical oxidation system

Abstract

The invention discloses an oxidation pretreatment method for phoxim in an organophosphorus pesticide based on a photo-initiation free radical oxidation system, and the method comprises the following steps: mixing the organophosphorus pesticide with a photoinitiator, and carrying out oxidation pretreatment under illumination; the organophosphorus pesticide contains phoxim; the photoinitiator is any one or more than two of curcumin, alpha-terthienyl, a photoinitiator 819, a photoinitiator 2959 and tetraphenylporphyrin. The problems that in the prior art, an excessively added oxidizing agent cannot be completely reduced, the cost is high, and the detection result is inaccurate are solved. After illumination is stopped, free radicals in a reaction system can be dissipated in an extremely short time to form a neutralized state, and an additional reducing agent does not need to be added. The method disclosed by the invention has a very good effect on phoxim and also has important significance on guaranteeing food safety.

Description

Technical Field

[0001] This invention relates to a method for pre-oxidation treatment of organophosphorus pesticides, specifically a method for pre-oxidation treatment of phoxim in organophosphorus pesticides based on a photo-initiated free radical oxidation system. Background Technology

[0002] Organophosphorus pesticides (OPs) account for about 80% of the total pesticide use in China. Except for a few OPs used as herbicides, fungicides and plant growth regulators, most OPs are widely used as agricultural pesticides due to their high efficiency and broad activity range. High residues of these types of OPs pesticides pose a threat to human health.

[0003] Studies have shown that opioid poisoning is caused by the inhibition of acetylcholinesterase activity, leading to a large accumulation of acetylcholine at synaptic terminals, resulting in severe neurological damage, acute poisoning, and even death. Based on this mechanism, a rapid enzyme inhibition method for detecting opioid residues was developed. However, different types of opioids have varying inhibitory effects on acetylcholinesterase. While rapid enzyme inhibition methods are highly sensitive for P=O bond opioids, some P=S bond opioids (such as dimethoate, chlorpyrifos, and phoxim) with lower inhibitory effects on cholinesterase cannot be accurately quantified, leading to false negative results and potentially posing significant safety risks to human health.

[0004] Previous studies on organophosphorus pesticides (OPs) have shown that some P=S bond-type OOPs with weak cholinesterase inhibitory activity may still exhibit strong toxicity in vivo. Research has demonstrated that this toxicity is due to the oxidative metabolism of hepatic P450 enzymes, which convert them into P=O bond-type OOPs with strong cholinesterase inhibitory activity, thereby improving the sensitivity of enzyme inhibition methods for OOP detection. To address this issue, researchers have developed various oxidation pretreatment methods to pre-oxidize P=S bond organophosphorus pesticide residues in food samples to P=O bonds, avoiding false negatives and enabling trace detection of various P=S bond organophosphorus pesticides (including N-bromosuccinimide, trifluoroacetic anhydride, and bromine water). However, in the pretreatment process of organophosphorus pesticide oxidation, the inevitable excess of oxidant, coupled with the inability to guarantee that the added reducing agent will completely react with the oxidant, may lead to false positives or false negatives due to oxidant or reducing agent residues. (On the one hand, excess oxidant, after oxidizing the P=S bond, may damage other chemical structures of the organophosphorus pesticide molecule, making it unrecognizable by acetylcholinesterase, resulting in false negatives; on the other hand, the presence of excess oxidant necessitates the addition of an equal excess of reducing agent to the system to avoid the influence of excess oxidant on acetylcholinesterase activity, thus preventing false positives.) Furthermore, the dosage of reducing agent is difficult to control, complicating experimental procedures and increasing experimental costs and time, which to some extent limits the development of rapid, efficient, and low-cost detection methods for P=S type organophosphorus pesticides. Summary of the Invention

[0005] The purpose of this invention is to provide a method for the pretreatment of phoxim, an organophosphorus pesticide, based on a photo-initiated free radical oxidation system. This method solves the problems of existing technologies where excessive oxidant cannot be completely reduced, resulting in high costs and inaccurate detection results. It eliminates the need for additional reducing agents and has a very good effect on phoxim, which is of great significance for ensuring food safety.

[0006] To achieve the above objectives, the present invention provides a method for the pretreatment of phorate in organophosphorus pesticides based on a photo-initiated free radical oxidation system, the method comprising:

[0007] Organophosphorus pesticides are mixed with photoinitiators and subjected to oxidative pretreatment under light irradiation; the organophosphorus pesticides include phoxim; the photoinitiators are any one or more of curcumin, α-terthiophene, photoinitiator 819, photoinitiator 2959 and tetraphenylporphyrin.

[0008] Preferably, the oxidation pretreatment time is ≥5 min.

[0009] Preferably, the volume ratio of the organophosphorus pesticide to the photoinitiator is 11:5.

[0010] More preferably, the final concentration of the α-terthiophene is 20 μmol / L to 160 μmol / L; the final concentration of the photoinitiator 819 is 60 μmol / L to 175 μmol / L; the final concentration of the photoinitiator 2959 is 4 mmol / L to 24 mmol / L; and the final concentration of the tetraphenylporphyrin is 80 μmol / L to 240 μmol / L.

[0011] More preferably, when the photoinitiator is photoinitiator 819, the final concentration of photoinitiator 819 is 100 μmol / L.

[0012] More preferably, when the photoinitiator is photoinitiator 2959, the final concentration of photoinitiator 2959 is 8 mmol / L.

[0013] More preferably, when the photoinitiator is tetraphenylporphyrin, the final concentration of the tetraphenylporphyrin is 180 μmol / L.

[0014] More preferably, when the photoinitiator is α-terthiophene, the final concentration of the α-terthiophene is 120 μmol / L.

[0015] More preferably, after mixing, the final concentration of the organophosphorus pesticide is 1.2 × 10⁻⁶. -6 mol / L.

[0016] More preferably, the oxidation pretreatment time is 5 minutes.

[0017] This invention provides a method for the pretreatment of phorate in organophosphorus pesticides based on a photo-initiated free radical oxidation system. This method solves the problems of existing technologies, such as the inability to completely reduce excessive oxidant, high cost, and inaccurate detection results. It has the following advantages:

[0018] 1. Compared with existing technologies, the photoinitiator oxidation pretreatment of this invention can save operating costs and steps, and effectively avoid the problem of "false positive" or "false negative" test results caused by residual oxidant. At the same time, the oxidation conditions of this oxidation system are mild, and oxidation can be controlled in real time by light irradiation.

[0019] 2. Due to the extremely short lifetime of free radicals, the free radicals in the reaction system dissipate and neutralize within a very short time after the light exposure stops, eliminating the need for additional reducing agents. Therefore, this novel rapid detection method for P=S bond type organophosphorus pesticide molecules based on a photo-initiated free radical oxidation system is particularly effective against phoxim and is of great significance for ensuring food safety. Attached Figure Description

[0020] Figure 1 This diagram illustrates the effect of various photoinitiators of the present invention on the enhancement of the inhibition rate of acetylcholinesterase after pretreatment with phoxim at different concentration gradients and specific wavelengths of light for 5 minutes.

[0021] Figure 2 The diagram shows how the photoinitiator itself can be excluded from inhibiting acetylcholinesterase in this invention.

[0022] Figure 3 This diagram illustrates the effect of various photoinitiators of the present invention on the enhancement of the inhibition rate of acetylcholinesterase after pretreatment with phoxim at optimal oxidation concentrations and under specific wavelength light for different durations.

[0023] Figure 4 The graph shows the effect of treating phoxim with a combination of photoinitiators with the same excitation wavelength as in this invention on improving the inhibition rate of acetylcholinesterase.

[0024] Figure 5 This is a fitting graph of the IC50 curves of α-trithiophene before and after oxidation of phorate in this invention. Detailed Implementation

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] The specific sources of the reagents involved in the following embodiments of the present invention are as follows:

[0027] Curcumin, terthiophene, photoinitiator 2959, photoinitiator 819 and tetraphenylporphyrin were all purchased from the Tansoole platform https: / / www.tansoole.com / , in 250mg form.

[0028] The organophosphorus pesticide phoxim was purchased from the Tansoole platform (https: / / www.tansoole.com / ), specification: 100mg pure form.

[0029] Curcumin is an oxidative free radical generated under 450nm wavelength light irradiation, terthiophene is an oxidative free radical generated under 365nm wavelength light irradiation, photoinitiator 2959 is an oxidative free radical generated under 365nm wavelength light irradiation, photoinitiator 819 is an oxidative free radical generated under 365nm wavelength light irradiation, and tetraphenylporphyrin is an oxidative free radical generated under 450nm wavelength light irradiation. The specific light wavelengths for the above photoinitiators are all from the literature "Research Progress of Non-Thermal Photodynamic Sterilization Technology in Food Safety"; doi:10.16429 / i.1009-7848.2018.07.039.

[0030] This invention constructs a novel, rapid, simple, and efficient method for detecting organophosphorus pesticides based on a photoinitiated free radical reaction system. This method is highly effective against phoxim, and the type and concentration of the photoinitiator and the duration of illumination are investigated in detail below:

[0031] 1. To investigate whether different types of photoinitiators can have the expected oxidative pretreatment effect on phoxim.

[0032] The effect of oxidation pretreatment with the corresponding photoinitiator at different concentrations for 5 min was evaluated. The specific operation was as follows: at a concentration of 4 × 10⁻⁶... -6495 μL of each of the following photoinitiators were added to 225 L of P=S type organophosphorus pesticide phoxim: photoinitiator 2959, tetraphenylporphyrin, photoinitiator 819, curcumin, or α-terthiophene. The mixture was then subjected to oxidation pretreatment for 5 min under light irradiation (curcumin at 450 nm, terthiophene at 365 nm, photoinitiator 2959 at 365 nm, photoinitiator 819 at 365 nm, and tetraphenylporphyrin at 450 nm). The final concentrations of photoinitiator 819 were 0, 30 μmol / L, 60 μmol / L, 80 μmol / L, 100 μmol / L, 125 μmol / L, 150 μmol / L, and 175 μmol / L, respectively; the final concentrations of α-terthiophene were 0, 10 μmol / L, 20 μmol / L, 40 μmol / L, 80 μmol / L, 120 μmol / L, 160 μmol / L, and 200 μmol / L, respectively; and the final concentration of photoinitiator 2959 was... The final concentrations of tetraphenylporphyrin were 0, 1 mmol / L, 2 mmol / L, 4 mmol / L, 8 mmol / L, 16 mmol / L, and 24 mmol / L, respectively; the final concentrations of curcumin were 0, 80 μmol / L, 120 μmol / L, 160 μmol / L, 180 μmol / L, 200 μmol / L, and 240 μmol / L, respectively; and the final concentrations of curcumin were 20, 40, 80, 120, 160, 240, and 280 μmol / L, respectively. Each experiment was performed in triplicate.

[0033] like Figure 1 As shown in the figure, the inhibition rate of acetylcholinesterase is improved after irradiation with a specific wavelength of light for 5 min by various photoinitiators of the present invention at different concentration gradients. In the figure, A is photoinitiator 819; B is α-trithiophene; C is photoinitiator 2959; D is tetraphenylporphyrin; and E is curcumin.

[0034] like Figure 2 As shown in the diagram, this invention excludes the inhibitory effect of the photoinitiator itself on acetylcholinesterase, where A is photoinitiator 819; B is α-terthiophene; photoinitiator 2959; D is tetraphenylporphyrin; and E is curcumin.

[0035] Depend on Figures 1-2It can be seen that curcumin has a moderate effect. Photoinitiator 819 showed a significant trend in increasing the inhibition rate, and at a final concentration of 100 μmol / L, phoxim showed the greatest increase in the inhibition rate of acetylcholinesterase after 5 minutes of light exposure, while the negative control showed no significant effect at this concentration. α-Trithiophene showed a significant trend in increasing the inhibition rate, and at a final concentration of 120 μmol / L, phoxim showed the greatest increase in the inhibition rate of acetylcholinesterase after 5 minutes of light exposure, while the negative control showed no significant effect at this concentration. Photoinitiator 2959 showed a relatively significant trend in increasing the inhibition rate, and at a final concentration of 8 mmol / L, phoxim showed the greatest increase in the inhibition rate of acetylcholinesterase after 5 minutes of light exposure, while the negative control showed no significant effect at this concentration. Tetraphenylporphyrin (450 nm) showed a very obvious trend of increasing the inhibition rate. At a final concentration of 180 μmol / L, phoxim showed the greatest increase in the inhibition rate of acetylcholinesterase after 5 min of light irradiation. Meanwhile, the negative control showed no significant effect at this concentration.

[0036] 2. Evaluate the effect of photoinitiator on oxidation pretreatment at different times.

[0037] To evaluate the effect of oxidation pretreatment of the corresponding photoinitiator at different times, the specific operation steps are as follows: at a concentration of 4×10 -6 Oxidative pretreatment was carried out by adding 495 μL of tetraphenylporphyrin, photoinitiator 819, or α-terthiophene to 225 μL of P=S type organophosphorus pesticide phoxim at a concentration of mol / L. The treatment was carried out under light irradiation (curcumin was irradiated at a wavelength of 450 nm, terthiophene at a wavelength of 365 nm, photoinitiator 2959 at a wavelength of 365 nm, photoinitiator 819 at a wavelength of 365 nm, and tetraphenylporphyrin at a wavelength of 450 nm). The final concentration of photoinitiator 819 was 100 μmol / L, and the illumination time was 0, 5 min, 10 min, 20 min, 30 min, and 40 min, respectively; the final concentration of α-terthiophene was 120 μmol / L, and the illumination time was 0, 5 min, 10 min, 20 min, 30 min, and 40 min, respectively; the final concentration of tetraphenylporphyrin was 180 μmol / L, and the illumination time was 0, 1 min, 2 min, 3 min, 4 min, and 5 min, respectively; each experiment was performed in triplicate.

[0038] like Figure 3 The figure shows the effect of various photoinitiators of the present invention on the enhancement of the inhibition rate of acetylcholinesterase after pretreatment with phoxim at optimal oxidation concentrations and under specific wavelength light for different times. A is α-terthiophene; B is photoinitiator 819; and C is tetraphenylporphyrin. Figure 3It can be seen that photoinitiator 819 showed the highest inhibition rate increase after 20 minutes of illumination, but considering the research on rapid detection methods, an illumination time of 10 minutes was most ideal. α-Trithiophene showed a significant and gradual increase in inhibition rate across an illumination time gradient of 5 to 40 minutes; therefore, considering the research on rapid detection methods, an illumination time of 5 minutes was most ideal. Tetraphenylporphyrin (450 nm) showed little change in inhibition rate increase from 1 to 5 minutes.

[0039] 3. Evaluate the effect of combined photoinitiator and oxidative pretreatment.

[0040] Considering the impact of the combined use of photoinitiators on the experiment, the specific operating procedures are as follows: at a concentration of 4×10 -6 Oxidative pretreatment was carried out by adding 495 μL of each of the following to 225 μL of 2 mol / L P=S type organophosphorus pesticide phoxim: α-terthiophene, photoinitiator 819, curcumin, tetraphenylporphyrin, a combination of α-terthiophene and photoinitiator 819, half concentrations of each combination of α-terthiophene and photoinitiator 819, a combination of curcumin and tetraphenylporphyrin, and a combination of curcumin and tetraphenylporphyrin. The mixtures were then subjected to light irradiation (curcumin at 450 nm, terthiophene at 365 nm, photoinitiator 2959 at 365 nm, photoinitiator 819 at 365 nm, and tetraphenylporphyrin at 450 nm). The concentrations of photoinitiator 819 and photoinitiator 819 were as follows: 100 μmol / L for 10 min; 120 μmol / L for 5 min; and 180 μmol / L for 5 min. In the combined use of α-terthiophene and photoinitiator 819, the concentrations of α-terthiophene and photoinitiator 819 were 120 μmol / L and 100 μmol / L, respectively. In the combined use of photoinitiator 819, the concentrations of α-terthiophene were 60 μmol / L and photoinitiator 819 were 50 μmol / L in half concentrations; in the combined use of curcumin and tetraphenylporphyrin, the concentrations of tetraphenylporphyrin and curcumin were 180 μmol / L and 80 μmol / L; in the combined use of curcumin and tetraphenylporphyrin, the concentrations of tetraphenylporphyrin and curcumin were 90 μmol / L and 40 μmol / L in half concentrations; each experiment was performed in triplicate.

[0041] like Figure 4 The diagram shows the effect of combined treatment of phoxim with photoinitiators of the same excitation wavelength, resulting in an increased inhibition rate of acetylcholinesterase. In diagram A, α-trithiophene and photoinitiator 819 are used alone or in combination; in diagram B, curcumin and tetraphenylporphyrin are used alone or in combination. Figure 4It can be seen that when photoinitiators with the same excitation wavelength are used in combination to treat phoxim, the inhibition rate of acetylcholinesterase is improved to a certain extent compared with the effect of pretreatment with photoinitiators alone, but the improvement in inhibition rate is relatively insignificant for α-terthiophene.

[0042] The above analysis shows that α-terthiophene at a final concentration of 120 μmol / L has the best effect on the pretreatment of phorate oxidation under 5 min of light irradiation. Therefore, the detection limit before and after oxidation was analyzed by measuring the IC50 curve.

[0043] like Figure 5 The figure shows the IC50 curve fitting diagrams of α-trithiophene before and after oxidation of phorate, where A is the curve fitting diagram without pre-oxidation treatment; B is the curve fitting diagram after pre-oxidation treatment. Figure 5 It can be seen that the detection limit of phoxim without pre-oxidation treatment is 1.51E-05 mol / L. The detection limit of phoxim after pre-oxidation treatment with α-terthiophene is 9.01E-09 mol / L. Among the detection limits corresponding to 50% inhibition rate, the detection limit after oxidation is 1675 times higher than that before oxidation.

[0044] 4. Recycling of actual fruit and vegetable samples with added spikes

[0045] Equal masses (10g) of cabbage, scallion, carrot, bean sprout, lettuce, onion, and potato samples were spiked with 0.2μg and 0.02mg of phoxim, respectively. The spiked samples were then immersed in α-terthiophene at a final concentration of 120μmol / L and a volume of 495μL. The samples were subjected to pre-oxidation treatment under light (curcumin at 450nm, terthiophene at 365nm, photoinitiator 2959 at 365nm, photoinitiator 819 at 365nm, and tetraphenylporphyrin at 450nm) for 5 min. The spiked recoveries were determined by IC50 curve analysis.

[0046] Table 1. Recovery rates of phoxim at 0.2 μg and 0.02 mg spiked levels in different vegetable samples.

[0047]

[0048] As can be seen from Table 1, the method of Example 1 can be used for the determination of phoxim in actual fruits and vegetables.

[0049] Based on the analysis of all the data above, it can be concluded that the α-terthiophene oxidation pretreatment can be used as a rapid method for detecting phorate in food. At the same time, this novel organophosphorus oxidation pretreatment method can also be extended to use other two-dimensional materials to generate oxygen free radicals through photocatalysis as a pretreatment method.

[0050] Based on the above research, this invention provides a method for the pre-treatment of phoxim in organophosphorus pesticides based on a photo-initiated free radical oxidation system. Specific embodiments are as follows:

[0051] 4×10 -6 225 μL of the P=S type organophosphorus pesticide phoxim was mixed with 495 μL of curcumin, 495 μL of α-terthiophene, 495 μL of photoinitiator 819, 495 μL of photoinitiator 2959, or 495 μL of tetraphenylporphyrin, respectively (resulting in an oxidation treatment system of 720 μL). The final concentration of the organophosphorus pesticide in the 720 μL system, after conversion, was 1.2 × 10⁻⁶. -6 The final concentrations of curcumin (80 mol / L), α-terthiophene (120 μmol / L), photoinitiator 819 (100 μmol / L), photoinitiator 2959 (8 mmol / L), and tetraphenylporphyrin (180 μmol / L) were subjected to oxidation pretreatment for 5 min under light irradiation (curcumin at 450 nm, terthiophene at 365 nm, photoinitiator 2959 at 365 nm, photoinitiator 819 at 365 nm, and tetraphenylporphyrin at 450 nm).

[0052] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A method for the pretreatment of phorate in organophosphorus pesticides based on a photo-initiated free radical oxidation system, characterized in that, The method includes: Organophosphorus pesticides were mixed with photoinitiators and subjected to oxidation pretreatment under light. The organophosphorus pesticide includes phoxim; The photoinitiator is any one or more of curcumin, α-terthiophene, photoinitiator 819, photoinitiator 2959, and tetraphenylporphyrin.

2. The method according to claim 1, characterized in that, The oxidation pretreatment time is ≥5 min. When the photoinitiator is curcumin, it is carried out under light with a wavelength of 450 nm; when the photoinitiator is terthiophene, it is carried out under light with a wavelength of 365 nm; when the photoinitiator is photoinitiator 2959, it is carried out under light with a wavelength of 365 nm; when the photoinitiator is photoinitiator 819, it is carried out under light with a wavelength of 365 nm; when the photoinitiator is tetraphenylporphyrin, it is carried out under light with a wavelength of 450 nm.

3. The method according to claim 1, characterized in that, The volume ratio of the organophosphorus pesticide to the photoinitiator is 11:

5.

4. The method according to claim 3, characterized in that, The final concentration of the α-terthiophene is 20 μmol / L to 160 μmol / L; the final concentration of the photoinitiator 819 is 60 μmol / L to 175 μmol / L; the final concentration of the photoinitiator 2959 is 4 mmol / L to 24 mmol / L; and the final concentration of the tetraphenylporphyrin is 80 μmol / L to 240 μmol / L.

5. The method according to claim 4, characterized in that, When the photoinitiator is photoinitiator 819, the final concentration of photoinitiator 819 is 100 μmol / L.

6. The method according to claim 4, characterized in that, When the photoinitiator is photoinitiator 2959, the final concentration of photoinitiator 2959 is 8 mmol / L.

7. The method according to claim 4, characterized in that, When the photoinitiator is tetraphenylporphyrin, the final concentration of the tetraphenylporphyrin is 180 μmol / L.

8. The method according to claim 4, characterized in that, When the photoinitiator is α-terthiophene, the final concentration of α-terthiophene is 120 μmol / L.

9. The method according to claim 8, characterized in that, After mixing, the final concentration of the organophosphorus pesticide is 1.2 × 10⁻⁶. -6 mol / L.

10. The method according to claim 9, characterized in that, The oxidation pretreatment time is 5 minutes.

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