A method for capturing, identifying and assessing the contribution of environmentally persistent organic radicals

Abstract

The application provides a method for capturing, identifying and evaluating environmental persistent organic free radicals. The method for identifying provided by the application adopts a CATT capturing agent, and the structure is shown as formula (1). The CATT capturing agent has good free radical dissociation groups, can capture environmental persistent organic free radicals (EPFRs) in a to-be-detected substance, can release a stable TEMPO nitrogen-oxygen free radical in a 1:1 ratio while capturing the EPFRs, the TEMPO nitrogen-oxygen free radical can be clearly captured by electron paramagnetic resonance (EPR), there is no side reaction, and the free radical capturing adduct generated can be clearly identified by mass spectrometry (MS), that is, EPR and MS information are obtained simultaneously through the CATT capturing agent. Subsequently, ferulic acid with high solubility and few side reactions is screened as an inhibitor, the transfer of free radicals can be realized to inhibit the reaction, and then the contribution evaluation of the target EPFRs is completed.

Description

Technical Field

[0001] This invention relates to the field of environmental analysis technology, and in particular to a method for capturing, identifying, and assessing the contribution of persistent organic free radicals in the environment. Background Technology

[0002] Persistent environmental free radicals (EPFRs) are a class of environmentally hazardous substances with long half-lives, stability, and persistence, proposed in contrast to traditional short-lived, highly reactive free radicals. EPFRs exhibit three distinct characteristics: reactivity, persistence, and mobility. Reactivity refers to their ability to transform into reactive secondary free radicals under certain conditions, enabling them to react with the surrounding environment. Persistence means that compared to highly reactive transient free radicals, EPFRs can exist in the environment for a longer period, up to tens of days, exhibiting paramagnetic stability and posing numerous potential environmental hazards. They can induce oxidative stress in biological systems, causing cell and organismal damage, and consequently leading to cancer. Mobility refers to their ability to migrate with the medium, being widely distributed in soil, water, and the atmosphere; for example, the most common example is PM2.5. 2.5 EPFRs on particles can migrate in the atmosphere along with the particles.

[0003] Currently, common EPFRs are considered to include oxygen-centered semiquinone radicals and phenoxy radicals, and carbon-centered phenoxy and cyclopentadienyl radicals. Besides being highly hazardous emerging environmental pollutants, EPFRs are also common intermediates in various chemical reactions, such as the degradation of pollutants in advanced oxidation processes, lignin depolymerization, and various organic chemical synthesis reactions. Therefore, accurate identification and contribution assessment of EPFRs are of great significance for environmental pollution control and for promoting in-depth research into the mechanisms of various chemical reactions.

[0004] Currently, there are three main methods for identifying the presence of EPFRs: electron paramagnetic resonance (EPR), mass spectrometry (MS), and laser flash photolysis (LFP). EPR, as the most direct method for characterizing the presence of unpaired electrons, is widely used in identifying EPFRs. However, it also suffers from drawbacks such as the inability to obtain structural information of the captured radical, poor sensitivity, and short lifetime (from seconds to hours). More importantly, due to side reactions, EPR results often contain false positives. MS mainly relies on the cross-coupling between persistent radicals and target radicals. MS identification can provide specific target structural information for EPFRs, but it still suffers from low reactivity and poor capture efficiency. LFP technology has limited application scenarios, only applicable to homogeneous systems. In heterogeneous systems, it is difficult to capture the reaction zero point and suffers from severe scattering. The assessment of the contribution of EPFRs currently relies mainly on inhibitors. For example, the antioxidant 2,6-di-tert-butyl-p-cresol (BHT) is often used as an inhibitor of phenoxy radical intermediates in advanced oxidation systems. However, it generally suffers from problems such as insufficient solubility and interference with the reaction process through other side reactions. Therefore, the field of environmental analysis urgently needs new methods for identifying the existence of EPFRs and assessing their contribution. Summary of the Invention

[0005] In view of this, the present invention provides a method for capturing, identifying, and assessing the contribution of environmentally persistent organic free radicals (EPFRs). The identification method provided by the present invention uses a CATT capture agent, which simultaneously provides crucial evidence in EPR and MS while capturing EPFRs. The method is rapid, easy to operate, and provides accurate identification. Furthermore, in terms of contribution assessment, a certain reaction inhibitor is used to achieve the transfer of EPFRs, thereby completing the contribution assessment of EPFRs.

[0006] This invention provides a method for capturing environmentally persistent organic free radicals, wherein the capturing agent used is a CATT capturing agent, having the structure shown in formula (1):

[0007]

[0008] This invention also provides a method for identifying environmentally persistent organic free radicals, wherein the scavenging agent used is a CATT scavenging agent, having the structure shown in formula (1):

[0009]

[0010] Preferably, the identification method includes:

[0011] S1. Mix the analyte, the trapping agent, and the oxidizing agent to obtain a mixed solution;

[0012] S2. Adjust the pH of the mixed solution, then add a catalyst to start the reaction. During the reaction, take samples from the system for UPLC-MS determination and EPR testing to obtain relevant information on persistent organic free radicals in the pollutants.

[0013] Preferably, in step S1, the oxidant is a PMS oxidant.

[0014] Preferably, in step S2:

[0015] The catalyst is a carbon-based Co single-atom catalyst;

[0016] The pH value is adjusted to a value of 5.0 to 9.0.

[0017] Preferably, the trapping agent is prepared by the following method:

[0018] A) 2-Bromomethacrylate reacts with TEMPO to give 2-(TEMPO meth)acrylate as shown in formula (1-a);

[0019]

[0020] B) Mix the methyl 2-(TEMPO meth)acrylate of formula (1-a) with NaOH solution, and then mix with HCl solution to obtain a mixed solution; purify the mixed solution to obtain 2-(TEMPO meth)acrylate of formula (1-b);

[0021]

[0022] C) The 2-(TEMPO meth)acrylic acid shown in formula (1-b) reacts with cyclohexylamine to obtain the CATT scavenger shown in formula (1);

[0023]

[0024] Preferably, in step A), the reaction temperature is 40–80°C and the time is 36–72 h.

[0025] Preferably, in step B), the concentration of the NaOH solution is 0.5–2.0 M, and the concentration of the HCl solution is 1.0–4.0 M.

[0026] In step A), the ratio of methyl 2-bromomethacrylate to NaOH solution in step B) is 1.0 mmol: (20-100) mL;

[0027] In step A), the ratio of methyl 2-bromomethacrylate to HCl solution in step B) is 1.0 mmol: (10–50) mL;

[0028] In step C), the reaction is carried out in the presence of O-(benzotriazol-1-yl)-N,N,N',N'-tetramethylurea hexafluorophosphate and N,N-diisopropylethylamine.

[0029] This invention also provides a method for assessing the contribution of environmentally persistent organic free radicals, comprising:

[0030] K1. To identify the presence of persistent organic free radicals in the analyte;

[0031] The identification method is the identification method for environmentally persistent organic free radicals as described in any one of claims 1 to 8;

[0032] K2. Mix the analyte and the oxidant to obtain a mixed solution;

[0033] K3. After adjusting the pH of the mixed solution, a catalyst and an inhibitor are added to start the reaction. During the reaction, the sample solution in the system is mixed with Na2S2O3 solution for quenching. Then, the concentration of the analyte is detected by CPLC to assess the contribution of persistent organic free radicals in the environment.

[0034] Preferably, the inhibitor is ferulic acid.

[0035] The identification method provided by this invention uses the CATT scavenger shown in formula (1), which has good free radical dissociation groups and can capture environmentally persistent organic free radicals (EPFRs) in the analyte. While capturing EPFRs, it can release a stable TEMPO nitroxide free radical in a 1:1 ratio. This TEMPO nitroxide free radical can be clearly captured by electron paramagnetic resonance (EPR) without side reactions. Moreover, the resulting free radical capture adduct can be clearly identified by mass spectrometry (MS). That is, EPR and MS information are obtained simultaneously through the CATT scavenger, which can identify the presence, type and structural information of EPFRs. Then, ferulic acid with high solubility and few side reactions is screened as an inhibitor, which can realize the transfer of free radicals and thus inhibit the reaction, thereby completing the contribution assessment of the target EPFRs. Since the CATT scavenger provides key evidence of EPR and MS at the same time, it is more reliable than the traditional single identification method. With the addition of ferulic acid as an inhibitor, the detection and evaluation of EPFRs can be completed from the perspectives of presence and contribution, which has broad application prospects in the fields of environmental catalysis and environmental toxicology. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0037] Figure 1 This is a schematic diagram illustrating the principle of using CATT scavengers to identify persistent organic free radicals in the environment according to the present invention.

[0038] Figure 2 This is a schematic diagram illustrating the principle of environmental persistent organic free radical inhibition reaction in a Fenton-like system.

[0039] Figure 3 The image shows the characterization of the CATT trapping agent obtained in Example 1; wherein, Figure 3 (a)-(b) are ultra-high phase liquid chromatography-mass spectra (UPLC-MS). Figure 3 (c) is the Fourier transform infrared spectrum (FT-IR). Figure 3 (d) is the nuclear magnetic resonance (NMR) spectrum;

[0040] Figure 4 The graph shows the test results of CATT capturing phenoxy radicals in Fenton-like reactions; where, Figure 4 (a) is the UPLC-MS spectrum of the captured phenoxy radical adduct. Figure 4 (b) EPR signal diagram of TEMPO released simultaneously when phenoxy radicals are captured;

[0041] Figure 5 The graph shows the test results of using FA as an inhibitor in a Fenton-like system to evaluate the contribution of the reaction intermediate phenoxy radical.

[0042] Figure 6 This is a graph showing the effect of FA on oxidant consumption when FA is used as an inhibitor in a Fenton-like system. Detailed Implementation

[0043] Regarding the CATT capture agent, it has the structure shown in formula (1):

[0044]

[0045] The aforementioned CATT trap is a trap capable of capturing environmentally persistent free radicals (EPFRs). It is a novel cyclohexyl-based trap of allyl-2,2,6,6-tetramethylpiperidin-1-yl)oxyl(TEMPO)-based. This invention names it CATT (Allyl-(2,2,6,6-tetramethylpiperidin-1-yl)oxyl(TEMPO)-based traps containing cyclohexyl). This trap enables precise capture and rapid identification of EPFRs.

[0046] The preparation method of CATT capture agent includes the following steps:

[0047] A) 2-Bromomethacrylate reacts with TEMPO to give 2-(TEMPO meth)acrylate as shown in formula (1-a);

[0048]

[0049] B) Mix the methyl 2-(TEMPO meth)acrylate of formula (1-a) with NaOH solution, and then mix with HCl solution to obtain a mixed solution; purify the mixed solution to obtain 2-(TEMPO meth)acrylate of formula (1-b);

[0050]

[0051] C) The 2-(TEMPO meth)acrylic acid shown in formula (1-b) reacts with cyclohexylamine to obtain the CATT scavenger shown in formula (1);

[0052]

[0053] Regarding step A) :

[0054] A) Methyl 2-bromomethacrylate reacts with TEMPO to give methyl 2-(TEMPO meth)acrylate as shown in formula (1-a).

[0055] The reaction route for this step is as follows:

[0056]

[0057] In this invention, the sources of methyl 2-bromomethacrylate and TEMPO (tetramethylpiperidine oxide) are not particularly limited, and commercially available products are acceptable. Preferably, the molar ratio of methyl 2-bromomethacrylate to TEMPO is 1.0:1.2.

[0058] In this invention, the reaction temperature is preferably 40–80°C, specifically 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, or 80°C. The reaction time is preferably 36–72 hours, specifically 36 hours, 40 hours, 44 hours, 48 ​​hours, 52 hours, 56 hours, 60 hours, 64 hours, 68 hours, or 72 hours.

[0059] In this invention, the reaction is preferably carried out under a protective atmosphere. This invention does not have any particular limitation on the type of gas providing the protective atmosphere; any conventional protective gas in the art, such as nitrogen or argon, is acceptable.

[0060] In this invention, the reaction is preferably carried out under stirring conditions.

[0061] In this invention, the reaction is preferably carried out in the presence of NaI and Na2SO3. In this invention, the molar ratio of methyl 2-bromomethacrylate to NaI is preferably 1.0:2.0. In this invention, the molar ratio of methyl 2-bromomethacrylate to Na2SO3 is preferably 1.0:3.0.

[0062] In this invention, the reaction is preferably carried out in an organic solvent medium. The organic solvent is preferably at least one of acetonitrile. The preferred molar ratio of methyl 2-bromomethacrylate to the organic solvent is 1.0 mol:(50-200) mL.

[0063] In this invention, step A) preferably includes: dissolving methyl 2-bromomethacrylate, TEMPO, NaI and Na2SO3 in an organic solvent, stirring and reacting under a protective atmosphere to obtain methyl 2-(TEMPO meth)acrylate as shown in formula (1-a).

[0064] In this invention, after the above reaction, a reaction solution containing methyl 2-(TEMPO meth)acrylate as shown in formula (1-a) is obtained. Preferably, the reaction solution is further post-treated as follows: solvent removal, extraction, drying, filtration, and purification. The solvent removal is preferably performed by rotary evaporation under vacuum. The extraction operation preferably includes adding water first, followed by extraction with ethyl acetate. The number of extractions is preferably 2 to 4 times; the amount of extractant used in each extraction is preferably 20 to 200 mL. After extraction, drying and filtration are performed, preferably using MgSO4 and / or Na2SO4. Then, the solvent is preferably removed again to obtain an orange-yellow oily solid. Finally, purification and separation are performed, preferably using rapid silica gel column chromatography, to obtain methyl 2-(TEMPO meth)acrylate as shown in formula (1-a).

[0065] Regarding step B) :

[0066] B) Mix the methyl 2-(TEMPO meth)acrylate of formula (1-a) with NaOH solution, and then mix with HCl solution to obtain a mixed solution; purify the mixed solution to obtain 2-(TEMPO meth)acrylate of formula (1-b).

[0067] The reaction route for this step is as follows:

[0068]

[0069] In this invention, the NaOH solution is an aqueous solution of NaOH. The concentration of the NaOH solution is preferably 0.5–2.0 M, specifically 0.5 M, 1.0 M, 1.5 M, or 2.0 M. In this invention, the preferred ratio of methyl 2-bromomethacrylate in step A) to the NaOH solution in step B) is 1.0 mmol:(20–100) mL, specifically 1.0 mmol:20 mL, 1.0 mmol:30 mL, 1.0 mmol:40 mL, 1.0 mmol:50 mL, 1.0 mmol:60 mL, 1.0 mmol:70 mL, 1.0 mmol:80 mL, 1.0 mmol:90 mL, or 1.0 mmol:100 mL.

[0070] In this invention, the HCl solution is an aqueous HCl solution. The concentration of the HCl solution is preferably 1.0–4.0 M, specifically 1.0 M, 1.5 M, 2.0 M, 2.5 M, 3.0 M, 3.5 M, or 4.0 M. In this invention, the preferred ratio of methyl 2-bromomethacrylate in step A) to the HCl solution in step B) is 1.0 mmol:(10–50) mL, specifically 1.0 mmol:10 mL, 1.0 mmol:20 mL, 1.0 mmol:30 mL, 1.0 mmol:40 mL, or 1.0 mmol:50 mL.

[0071] In this invention, methyl 2-(TEMPO meth)acrylate as shown in formula (1-a) is first mixed with NaOH solution. The mixing method is preferably stirring. There are no special restrictions on the mixing temperature; it can be carried out at room temperature, such as 25±10℃. The mixing time is preferably 12–36 hours.

[0072] In this invention, after the above treatment, HCl solution is added for mixing. The mixing method is preferably stirring. There are no special restrictions on the mixing temperature; it can be carried out at room temperature, such as 25±10℃. The mixing time is preferably 0.5–2 hours. After the above mixing, a mixed solution is obtained.

[0073] In this invention, after obtaining the mixed solution, it is naturally cooled to room temperature. Subsequently, the following post-processing is preferably performed: extraction, drying and filtration, solvent removal by evaporation, and purification. Ethyl acetate is preferably used as the extraction solvent. The number of extractions is preferably 2 to 4 times; the amount of extraction solvent used in each extraction is preferably 20 to 200 mL. After extraction, drying and filtration are performed, preferably using MgSO4 and / or Na2SO4. Solvent removal is preferably performed by rotary evaporation; after evaporation of the solvent, a golden-yellow oily solid is obtained. Finally, it is purified and separated, preferably using rapid silica gel column chromatography, to obtain 2-(TEMPO meth)acrylic acid as shown in formula (1-b).

[0074] Regarding step C) :

[0075] C) The reaction of 2-(TEMPO meth)acrylic acid, as shown in formula (1-b), with cyclohexylamine yields the CATT scavenger shown in formula (1).

[0076] The reaction route for this step is as follows:

[0077]

[0078] In this invention, the source of the cyclohexylamine is not particularly limited, and it can be a commercially available product. In this invention, the molar ratio of 2-(TEMPO meth)acrylic acid (as shown in formula (1-b)) to cyclohexylamine is preferably 1.0:1.0.

[0079] In this invention, the reaction is preferably carried out in the presence of O-(benzotriazol-1-yl)-N,N,N',N'-tetramethylurea hexafluorophosphate (HBTU) and N,N-diisopropylethylamine (DIPEA). In this invention, the molar ratio of 2-(TEMPO meth)acrylic acid (as shown in formula (1-b)) to O-(benzotriazol-1-yl)-N,N,N',N'-tetramethylurea hexafluorophosphate is preferably 1.0:1.1. The molar ratio of 2-(TEMPO meth)acrylic acid (as shown in formula (1-b)) to N,N-diisopropylethylamine is preferably 1.0:2.1.

[0080] In this invention, the temperature conditions of the reaction are not particularly limited and can be carried out at room temperature, which can be 25±10℃. The reaction time is preferably 12 to 24 hours. The reaction is preferably carried out under stirring conditions.

[0081] In this invention, after the above reaction, the following post-processing is preferably performed: washing with salt solution, extraction and drying, solvent evaporation, and purification separation. The salt solution is preferably a saturated NaHCO3 aqueous solution; based on the amount of 2-(TEMPO meth)acrylic acid shown in formula (1-b), the amount of the saturated NaHCO3 aqueous solution is preferably 10 L / mol. Ethyl acetate is preferably used as the extraction solvent. The number of extractions is preferably 2 to 4; the amount of extraction solvent used in each extraction is preferably 20 to 200 mL. The organic extract layer is washed again with brine, then dried and filtered, preferably specifically dried and filtered with MgSO4 and / or Na2SO4. Then, preferably, the solvent is evaporated again to obtain the crude product. Finally, it is purified and separated, preferably by rapid silica gel column chromatography, to obtain the CATT capture agent shown in formula (1).

[0082] The present invention also provides a method for capturing environmentally persistent organic free radicals, wherein the capturing agent used is the CATT capturing agent described in the above technical solution.

[0083] The present invention also provides a method for identifying environmentally persistent organic free radicals, wherein the scavenging agent used is the CATT scavenging agent described in the above technical solution.

[0084] This invention also provides a method for identifying persistent environmental organic radicals in a Fenton-like system, wherein the scavenging agent used is the CATT scavenging agent described in the above-mentioned technical solution. That is, the CATT scavenging agent provided by this invention has been successfully used in a Fenton-like system to identify persistent environmental organic radicals. In this invention, the Fenton-like system includes: an analyte, an oxidant, and a catalyst. The oxidant is preferably PMS (peroxymonosulfate). The analyte can be a pollutant, more specifically 2,6-dimethylphenol (2,6-M-PhOH), including but not limited to the above-mentioned types, and can also detect and identify persistent environmental organic radicals in other substances. The catalyst is preferably a carbon-based Co single-atom catalyst. The molar amount of oxidant is only twice that of the pollutant, which cannot achieve the mineralization and removal of the pollutant. Instead, the highly selective oxidation pathway mediated by a single atom will generate phenoxy radicals from the pollutant through a proton-coupled electron transfer (PCET) pathway, which are then transferred to the catalyst surface during polymerization, with phenoxy radicals acting as the key active species. The CATT scavenger provided by this invention can be used in Fenton-like systems, in which phenoxy radicals were successfully captured. The adduct was detected by UPLC-MS, and the generated stable and persistent organic radicals were detected by EPR.

[0085] In this invention, the method for identifying environmentally persistent organic free radicals preferably includes:

[0086] S1. Mix the analyte, the trapping agent, and the oxidizing agent to obtain a mixed solution;

[0087] S2. Adjust the pH of the mixed solution, then add a catalyst to start the reaction. During the reaction, take samples from the system for UPLC-MS determination and EPR testing to obtain relevant information on persistent organic free radicals in the pollutants.

[0088] Regarding step S1 :

[0089] In this invention, the analyte is preferably a contaminant, more specifically, 2,6-dimethylphenol (2,6-M-PhOH). The capturing agent is the CATT capturing agent described in the above technical solution. The oxidant is preferably PMS (peroxymonosulfate). The molar ratio of the capturing agent to the analyte is preferably (0.5–4):1, specifically 0.5:1, 1.0:1, 1.5:1, 2.0:1, 2.5:1, 3.0:1, 3.5:1, or 4.0:1. The molar ratio of the oxidant to the analyte is preferably (1–4):1, specifically 1:1, 2:1, 3:1, or 4:1, more preferably 2:1. There are no particular restrictions on the method of mixing the analyte, capturing agent, and oxidant; the materials can be mixed evenly according to conventional mixing methods in the art to obtain a mixed solution.

[0090] Regarding step S2 :

[0091] In this invention, the pH adjuster is preferably an H2SO4 solution and / or a NaOH solution. The concentration of the adjuster is preferably 0.1–1 mM, more preferably 0.5 mM. In this invention, the pH is preferably adjusted to a value of 5.0–9.0, more preferably 7.0.

[0092] In this invention, after adjusting the pH value, a catalyst is added to initiate the reaction. The catalyst is preferably a carbon-based Co single-atom catalyst, i.e., a catalyst with Co single atoms supported on a carbon-based support. This invention does not have any particular restrictions on the source of the carbon-based Co single-atom catalyst; it can be prepared according to conventional methods in the art. In the embodiments of this invention, the carbon-based Co single-atom catalyst was prepared according to the method disclosed in Chen, F. et al. Molecular Engineering toward Pyrrolic N-Rich M-N4 (M=Cr,Mn,Fe,Co,Cu) Single-Atom Sites for Enhanced Heterogeneous Fenton-Like Reaction. Adv. Funct. Mater. 31, 2007877 (2021).

[0093] In this invention, the preferred ratio of catalyst to analyte is (0.01-0.04) g: 10 mmol.

[0094] In this invention, the preferred temperature condition for the reaction is 25±10℃.

[0095] In this invention, during the reaction process, samples are taken from the system for UPLC-MS and EPR measurements. Specifically, samples are taken at different reaction times, and then subjected to UPLC-MS and EPR measurements. Preferably, the first sampling is performed after 20–60 minutes of reaction, and more preferably after 30 minutes. The sampling involves taking a suspension from the system, filtering it through a filter membrane (preferably a 0.22 μm membrane), and then performing UPLC-MS (ultra-high performance liquid chromatography-mass spectrometry) analysis on the filtrate. UPLC-MS analysis detects free radical adducts. A second sampling is performed after 12–48 hours of reaction, more preferably after 24 hours. Similarly, this sampling also involves taking a suspension from the system, filtering it through a filter membrane (preferably a 0.22 μm membrane), and then performing EPR (electron paramagnetic resonance) analysis on the filtrate. EPR analysis detects a TEMPO signal peak, indicating that the CATT scavenger accumulates a large amount of TEMPO while capturing free radicals.

[0096] In this invention, the environmentally persistent organic free radicals (EPFRs) include at least one of semiquinone free radicals, phenoxy free radicals, and cyclopentadiene free radicals. Taking phenoxy free radicals as an example, the principle of using CATT scavenging agents to identify environmentally persistent organic free radicals is as follows: Figure 1As shown. In this invention, the environmentally persistent organic free radicals (EPFRs) are novel pollutants with environmental toxicity. They are widely present in the natural environment, distributed in the atmosphere, soil, and water, and can migrate freely between the three phases. At the same time, EPFRs are also common intermediates in the degradation of pollutants in advanced oxidation processes, lignin depolymerization, and various organic chemical synthesis reactions.

[0097] In the identification method provided by this invention, the CATT scavenger has good free radical dissociation groups, which can capture environmentally persistent organic free radicals (EPFRs) in the analyte. While capturing EPFRs, it can release a stable TEMPO nitroxide free radical in a 1:1 ratio. This TEMPO nitroxide free radical can be clearly captured by electron paramagnetic resonance (EPR) without any side reactions. Moreover, the resulting free radical capture adduct can be clearly identified by mass spectrometry (MS). That is, EPR and MS information are obtained simultaneously through the CATT scavenger, which can identify the presence, type and structural information of EPFRs. This method is more reliable than traditional single identification methods.

[0098] This invention also provides a method for assessing the contribution of environmentally persistent organic free radicals, comprising:

[0099] K1. To identify the presence of persistent organic free radicals in the analyte;

[0100] The identification method is the method for identifying environmentally persistent organic free radicals described in the above technical solution;

[0101] K2. Mix the analyte and the oxidant to obtain a mixed solution;

[0102] K3. After adjusting the pH of the mixed solution, a catalyst and an inhibitor are added to start the reaction. During the reaction, the sample solution in the system is mixed with Na2S2O3 solution for quenching. Then, the concentration of the analyte is detected by CPLC to assess the contribution of persistent organic free radicals in the environment.

[0103] In step K1 of this invention, EPFRs in the test sample are first identified. Specifically, the method for identifying EPFRs described in the above technical solution is used to identify them. This method can identify the presence or absence of EPFRs, the types and structures of EPFRs, and other information. Then, appropriate inhibitors are selected for subsequent contribution evaluation.

[0104] This invention can identify and assess the presence and contribution of persistent organic radicals in a Fenton-like system. The Fenton-like system, as described above, includes: an analyte, an oxidant, and a catalyst. Specifically, it can be implemented through steps K2-K3. The analyte can be a pollutant, more specifically 2,6-dimethylphenol (2,6-M-PhOH), including but not limited to the above-mentioned types, and can also detect and identify persistent organic radicals in other substances. The oxidant is preferably PMS (peroxymonosulfate). The molar ratio of the oxidant to the analyte is preferably (1-4):1, more preferably 2:1. The pH adjuster used in step K3 is preferably H2SO4 solution and / or NaOH solution. The concentration of the adjuster is preferably 0.1-1 mM, more preferably 0.5 mM. In this invention, the pH adjustment is preferably to a pH of 5.0-9.0, more preferably 7.0.

[0105] After adjusting the pH value, a catalyst and an inhibitor are added to initiate the reaction. The catalyst is preferably a carbon-based Co single-atom catalyst, i.e., a catalyst with Co single atoms supported on a carbon-based support. This invention does not have any particular restrictions on the source of the carbon-based Co single-atom catalyst; it can be prepared according to conventional methods in the art. In this invention, the amount of the catalyst in the reaction system is preferably 0.5–2 g / L, more preferably 1.0 g / L. The inhibitor is preferably ferulic acid (FA); this invention screened a series of antioxidants of EPFRs as inhibitors, preferably using ferulic acid as an inhibitor due to its high solubility, few side reactions, and ability to achieve phenoxy radical transfer, thereby inhibiting chemical reactions using EPFRs as intermediates and enabling the assessment of the significant contribution of EPFRs. The molar ratio of the inhibitor to the analyte is preferably (5–40):1, more preferably 20:1. The preferred temperature condition for the reaction is 25 ± 10 °C.

[0106] In this invention, during the reaction process, a sample solution from the system is taken and mixed with a Na2S2O3 solution to quench the reaction. The Na2S2O3 solution is an aqueous solution of Na2S2O3. The concentration of the Na2S2O3 solution is preferably 50–500 mM, more preferably 200 mM. The volume ratio of the sample solution to the Na2S2O3 solution is preferably 1:(0.1–0.5), more preferably 1:0.2. After the quenching process, filtration is preferred; more preferably, membrane filtration is used; the membrane is preferably a 0.22 μm membrane. After filtration, the concentration of the analyte in the filtrate is detected using CPLC (ultra-high performance liquid chromatography) to assess the contribution of the inhibitor to the consumption of the oxidant.

[0107] The key contribution of inhibitors lies in their direct consumption of oxidants, thereby reducing the reaction rate. By detecting the consumption of the oxidant PMS in the FA-inhibited reaction, the crucial contribution of the reaction intermediate phenoxy radical can be assessed. Taking phenoxy radicals and the inhibitor FA as an example, FA facilitates the transfer of phenoxy radicals, keeping 2,6-M-PhOH in its original state in solution, preventing further polymerization on the material surface, thus inhibiting the reaction. Its inhibition mechanism is as follows: Figure 2 As shown.

[0108] In the identification method provided by this invention, the CATT scavenger possesses a good free radical dissociation group, which can capture environmentally persistent organic free radicals (EPFRs) in the analyte. Simultaneously, it releases a stable TEMPO nitroxide radical in a 1:1 ratio. This TEMPO nitroxide radical can be clearly captured by electron paramagnetic resonance (EPR) without side reactions, and the resulting free radical capture adduct can be clearly identified by mass spectrometry (MS). In other words, EPR and MS information are obtained simultaneously through the CATT scavenger, allowing for the identification of the presence, type, and structure of EPFRs. Subsequently, ferulic acid, with high solubility and few side reactions, is selected as an inhibitor, enabling free radical transfer and thus inhibiting the reaction, thereby completing the contribution assessment of the target EPFRs. Since the CATT scavenger provides crucial evidence from both EPR and MS, it is more reliable than traditional single identification methods. Combined with ferulic acid as an inhibitor, it can complete the detection and evaluation of EPFRs from both the presence and contribution perspectives, showing broad application prospects in environmental catalysis, environmental toxicology, and other fields.

[0109] The CATT scavenger provided by this invention has been successfully applied in a Fenton-like system. Specifically, the CATT scavenger successfully captured phenoxy radicals in this system, and the adduct was detected by UPLC-MS. Simultaneously, the generated stable persistent organic radical was detected by EPR. Furthermore, FA, as an inhibitor, completely suppressed the reaction, confirming the crucial contribution of the phenoxy radical intermediate. This invention provides, for the first time in the environmental field, crucial evidence for the presence and contribution of persistent organic radicals, achieving the first identification of phenoxy radicals in this field. Therefore, considering accuracy, completeness, and other factors, this invention has enormous application potential in the environmental field.

[0110] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims of the present invention.

[0111] Example 1: Synthesis of CATT scavenging agent

[0112] A) Dissolve 10 mmol of methyl 2-bromomethacrylate, 12 mmol of TEMPO, 20 mmol of NaI, and 30 mmol of Na2SO3 in 100 mL of acetonitrile. Purge under N2 atmosphere and react with gentle stirring at 65 °C for 48 h. Then, evaporate the acetonitrile to dryness under vacuum by rotary evaporation; subsequently, add 100 mL of water and extract with ethyl acetate (extract 3 times, 100 mL each time); filter after drying with MgSO4, evaporate the solvent again to obtain an orange-yellow oily solid, which is further purified by rapid silica gel column chromatography to obtain methyl 2-(TEMPO meth)acrylate as shown in formula (1-a).

[0113] B) Take 6.20 mmol of methyl 2-(TEMPO meth)acrylate (formula (1-a)) obtained in step A) and add it to 40 mL of NaOH aqueous solution (concentration 1.0 M). Stir at room temperature for 24 h, then add 20 mL of HCl solution (concentration 2.0 M) and continue stirring for 48 h to obtain a mixed solution. Cool the mixed solution naturally to room temperature and extract it with ethyl acetate (extract 3 times, 40 mL each time); dry and filter with MgSO4, then evaporate the solvent to obtain a golden yellow oily solid. Further purify it using rapid silica gel column chromatography to obtain a white crystalline product, namely 2-(TEMPO meth)acrylate (formula (1-b)).

[0114] C) Take 2.00 mmol of 2-(TEMPO meth)acrylic acid (as shown in formula (1-b) obtained in step B), 2.20 mmol of HBTU, 4.00 mmol of DIPEA, and 2.00 mmol of cyclohexane, and stir the mixture at room temperature for 18 h. Then, wash with saturated NaHCO3 aqueous solution (10 L / mol), and extract the product with ethyl acetate (extract 3 times, 10 mL / mol each time); wash the organic extract layer again with brine (i.e., saturated NaHCO3 aqueous solution), dry with MgSO4 and filter, and then evaporate the solvent to obtain the crude product, which is further purified by rapid silica gel column chromatography to obtain the CATT capture agent shown in formula (1).

[0115] Characterization:

[0116] The product was characterized in various ways, and the results are as follows: Figure 3 As shown, Figure 3 The image shows the characterization of the CATT trapping agent obtained in Example 1, wherein... Figure 3 (a)-(b) are ultra-high phase liquid chromatography-mass spectra (UPLC-MS). Figure 3 (c) is the Fourier transform infrared spectrum (FT-IR). Figure 3(d) shows the nuclear magnetic resonance (NMR) spectrum. The UPLC-MS method used was as follows: the mobile phase was acetonitrile:5 mM ammonia, with a solvent ratio of 40:60 (V / v). ACN ∶V NH3·H2O The flow rate was 0.4 mL / min, the detection wavelength of CATT was 211 nm, and mass spectrometry analysis was performed using an ESI source in positive ionization mode. The mass calibration range was between 50 and 1000 Da, and the resolution was always maintained above 24000.

[0117] Depend on Figure 3 The characterization results show that at RT = 1.38 min (M+H) in the UPLC-MS results... + The signal of / Z=323.2687 clearly indicates the synthesis of pure CATT. The results of FT-IR and NMR show that the functional groups of the actually synthesized CATT are consistent with the theoretical structure, indicating the successful synthesis of CATT.

[0118] Example 2: Identification and contribution assessment of phenoxy radicals in Fenton-like systems

[0119] 1. Identifying the presence of phenoxy radicals in Fenton-like systems

[0120] S1. Mix 2,6-M-PhOH, CATT and oxidant PMS to obtain a mixed solution.

[0121] S2. Adjust the pH of the mixed solution to 7.0 with H2SO4 solution (concentration 0.5mM), add carbon-based Co single-atom catalyst to start the reaction, and after reacting for 30 min, take 1 mL of suspension and filter it through a 0.22 μm filter membrane. Perform UPLC-MS on the filtrate. After reacting for 24 h, take another 1 mL of suspension and filter it through a 0.22 μm filter membrane. Perform EPR test on the filtrate.

[0122] In the reaction system, the amount of 2,6-M-PhOH is 0.5 mmol, the amount of CATT is 0.5 mmol, the amount of PMS is 1.0 mmol, the amount of carbon-based Co single-atom catalyst is 1.0 g / L, the pH is 7.0, and the total volume is 20 mL.

[0123] Test results are as follows Figure 4 As shown, Figure 4 The graph shows the test results of CATT capturing phenoxy radicals in Fenton-like reactions, where... Figure 4 (a) UPLC-MS spectrum of the captured phenoxy radical adduct (UPLC-MS test method is the same as above). Figure 4(b) EPR signal of TEMPO released simultaneously upon capture of the phenoxy radical. The results indicate that the phenoxy radical adduct signal in the reaction system was identified by UPLC-MS as (M+H). + / Z = 288.1930. The EPR showed a typical triplet signal peak of TEMPO, indicating that a large amount of TEMPO was accumulated while capturing phenoxy radicals, demonstrating the excellent performance of this scavenger in capturing phenoxy radicals.

[0124] 2. Evaluate the contribution of phenoxy radicals in Fenton-like systems.

[0125] (2.1) Following step 1 above, 2,6-M-PhOH and the oxidant PMS were mixed to obtain a mixed solution. The pH of the mixed solution was adjusted to 7.0 with H2SO4 solution (concentration 0.5 mM), and a carbon-based Co single-atom catalyst (as described above) and inhibitor FA were added to initiate the reaction. During the reaction, 1 mL of sample solution was added to Na2S2O3 aqueous solution (concentration 200 mM, volume 0.2 mL) for quenching. The solution was filtered through a 0.22 μm filter membrane, and the concentration of 2,6-M-PhOH in the filtrate was detected by CPLC.

[0126] In the reaction system, the amount of 2,6-M-PhOH is 10 mmol, the amount of FA is 10 mmol, the amount of PMS is 1.0 mmol, the amount of carbon-based Co single-atom catalyst is 1.0 g / L, the pH is 7.0, and the total volume is 20 mL.

[0127] The inhibitory mechanism of using FA as an inhibitor in Fenton-like systems is as follows: Figure 2 As shown, FA enables the transfer of phenoxy radicals, keeping 2,6-M-PhOH in its original state in the solution and preventing further polymerization on the material surface.

[0128] Inhibition effect such as Figure 5 As shown, Figure 5 The use of FA as an inhibitor in a Fenton-like system to assess the key contribution of the reaction intermediate phenoxy radical was demonstrated. The reaction was completely inhibited, indicating the important contribution of the phenoxy radical in the reaction process.

[0129] (2.2) The important contribution of inhibitors lies in the direct consumption of oxidants, thereby reducing the reaction rate. Therefore, the consumption of PMS in the FA inhibition reaction was detected. Three systems were tested: PMS + 10 mmol FA, PMS + 10 mmol FA + catalyst, and PMS + 10 mmol FA + catalyst + 2,6-M-PhOH. The amounts of each component in the above three systems were consistent with those in (2.1). The test method is as follows: 0.1 mL of the reaction solution was added to a KI mixed solution (concentration 10 mM, volume 4.9 mL), and the absorbance was measured at 352 nm after reacting for 5 min. The KI mixed solution was prepared as follows: (0.166 g KI + 0.04 g NaHCO3) / 100 mL water.

[0130] Test results are as follows Figure 6 As shown, Figure 6 The study demonstrated the effect of FA on oxidant consumption in a Fenton-like system using FA as an inhibitor. PMS was still effectively activated in the presence of 10 mM FA, indicating that the inhibitor can suppress phenoxy radicals at low concentrations without interfering with the normal reaction.

[0131] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of these embodiments are merely to aid in understanding the method and core ideas of the present invention, including the best mode, and to enable any person skilled in the art to practice the present invention, including manufacturing and using any device or system, and implementing any combined method. It should be noted that those skilled in the art can make various improvements and modifications to the present invention without departing from its principles, and these improvements and modifications also fall within the scope of protection of the claims. The scope of protection of this patent is defined by the claims and may include other embodiments that can be conceived by those skilled in the art. If these other embodiments have structural elements similar to those expressed in the claims, or if they include equivalent structural elements that are not substantially different from those expressed in the claims, then these other embodiments should also be included within the scope of the claims.

Claims

1. A method for identifying environmentally persistent organic free radicals in a Fenton-like system, characterized in that, include: S1. Mix the analyte, the trapping agent, and the oxidizing agent to obtain a mixed solution; S2. Adjust the pH of the mixed solution, then add a catalyst to start the reaction. During the reaction, take a sample from the system for UPLC-MS determination and EPR test to obtain relevant information on persistent organic free radicals in the analyte. The capture agent used is CATT capture agent, which has the structure shown in formula (1): Equation (1); The oxidant is a PMS oxidant; The catalyst is a carbon-based Co single-atom catalyst; The pH value is adjusted to a value of 5.0~9.0; The molar ratio of the trapping agent to the analyte is (0.5~4):1; The molar ratio of the oxidant to the analyte is (1~4):1; The environmentally persistent organic free radical is a phenoxy free radical.

2. A method for assessing the contribution of environmentally persistent organic free radicals, characterized in that, include: K1. To identify the presence of persistent organic free radicals in the analyte; The identification method is the method for identifying environmentally persistent organic free radicals in a Fenton-like system as described in claim 1; K2. Mix the analyte and the oxidant to obtain a mixed solution; wherein the oxidant is a PMS oxidant; K3. After adjusting the pH of the mixed solution, add the catalyst and inhibitor to start the reaction. During the reaction, take a sample solution from the system and... The solution is mixed for quenching, and then the concentration of the analyte is detected by UPLC to assess the contribution of persistent organic radicals in the environment; wherein the catalyst is a carbon-based Co single-atom catalyst; and the inhibitor is ferulic acid.

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