Acidic Pesticides Research Articles

Colorimetric detection of acidic pesticides in water.

A water-stable, porphyrin-based metal-organic framework (MOF) produces a distinct colour change in response to acids' pKa and concentrations. This colour change is associated with the protonation of the N-atoms within the porphyrin ligand present in the MOF structure. As a proof-of-concept, we demonstrate the use of this MOF for detecting traces of different acidic pesticides present in water samples spontaneously.

Transforming agricultural waste into adsorbent: application of Fagopyrum esculentum wheat husks treated with H2SO4 to adsorption of the 2,4-D herbicide

Wheat husks (Fagopyrum esculentum) were modified by treatment with sulfuric acid. The precursor material (FEWS) and the modified material (TFEWS) were characterized by different techniques to identify the structural changes promoted by the chemical treatment. Subsequently, TFEWS was applied as an adsorbent to remove the 2,4-dichlorophenoxyacetic acid (2,4-D) pesticide from aqueous solutions. Adsorption studies considered the pH effects and adsorbent dosage on the sorption capacity. Also, it evaluated the kinetics, equilibrium, and thermodynamic behavior. Also, the TFEWS was used to treat spiked-pesticide river waters to check its applicability in actual situations. It was found that the pH of the solution had a strong influence on the adsorption process, selecting pH 2 for the subsequent experiments. Regarding the adsorbent dosage, the best relationship between the percentage of herbicide removal (45%) and the material’s adsorption capacity (24 mg g-1) occurred at 0.95 g L-1. The Avrami-fractional order (also known as Bangham) kinetic model better represented the experimental data. In contrast, the Liu model showed the best adjustment of the equilibrium isotherms of the system, reaching a Qmax of 161.1 mg g-1 at 298 K. The thermodynamic behavior pointed to be spontaneous, favorable, and exothermic, consistent with a mechanism involving electrostatic interactions. The material application in situations close to the actual ones presented 76.00% and 76.30% removals for the simulated effluent of the “Conceição” and “Jacuí” rivers, respectively.

Application of Trichoderma as an Alternative to the use of Sulfuric Acid Pesticides in the Control of Diplodia Disease on Pomelo Citrus

This study aims to determine the ability of Trichoderma asperellum Tc-Pjn-02 compared to sulfuric acid pesticides in controlling the disease stem rot Diplodia on Pomelo citrus (Citrus maxima) caused by Botryodiplodia theobromae Pat. The research was conducted at Balai Penelitian Tanaman Buah Tropika Kebun Percobaan Kraton-Pasuruan, East Java Province, and the Laboratory of Microbiology and Biotechnology of Universitas Muhammadiyah Sidoarjo in February-April 2020. Trichoderma and sulfuric acid were applied in an aqueous paste formulation each of 10 units of diseased plants with rotten stems which were randomly selected as samples. The data from the observations were tested using the t-test at the real level of 5%. The results showed that Trichoderma sp. had a higher ability in suppressing pathogen attack compared to sulfuric acid which was able to heal rotten wounds on the stalks affected by 41.95% and 26.74%, respectively.

LC-MS/MS characterisation and determination of dansyl chloride derivatised glyphosate, aminomethylphosphonic acid (AMPA), and glufosinate in foods of plant and animal origin

Glyphosate and other polar and acidic pesticides have been particularly studied due to the concerns over widespread and intensive use. The chemical properties of these compounds necessitate use of customised methods, such as derivatisation or ion exchange chromatography. These approaches present a compatibility problem with ESI-MS due to presence of salts and non-volatile compounds. For that reason, a simple procedure has been developed for the extraction, pre-column derivatisation with dansyl chloride (5-(dimethylamino)naphthalene-1-sulfonyl chloride), and mass spectrometric detection of glyphosate, AMPA, and glufosinate after the separation on a C18stationary phase. The dansyl derivatives were characterised with ESI-MS and their separation from derivatisation reagent byproducts was demonstrated with UV absorption detection. Reagent byproducts eluted before the analytes and were separated from the analytes completely, thus the proposed procedure did not contaminate the mass spectrometers. The proposed procedure was evaluated with respect to the matrix effects and extraction efficiency, and was validated with different mass spectrometers for milk, cucumber, honey, porridge formula, bovine kidney and liver matrix. The LOQ was 10 μg kg−1 for AMPA and glufosinate, and 10–25 μg kg−1for glyphosate, depending on matrix. Measurement uncertainties ranged from 4 to 44%. Method performance was compared to the QuPPe (Quick Polar Pesticides) procedure in combination with a diethylamino-based column from Waters™. In the case of Orbitrap™ detection, the proposed procedure had a comparable performance to the QuPPe procedure. Although, improved peak shape, higher absolute peak intensity, and lower standard deviation of the calibration curve slope was observed with the proposed procedure. This could be explained by the superior electrospray stability and lower extent of ion suppression.

Optimization and validation of a method for the determination of acidic pesticides in cabbage and spinach by modifying QuEChERS procedure and liquid chromatography–tandem mass spectrometry

A quick, easy, cheap, effective, rugged, and safe (QuEChERS) method was developed and combined with liquid chromatography–tandem mass spectrometry to analyze 12 acidic pesticides in cabbage and spinach. The extraction solvents, phase partition salts and sorbents effect was studied to optimize the method followed by dilution before sample injection. The extraction involved 5% formic acid in acetonitrile, and the liquid-liquid partition was salt-induced. Carbopack Z, a high surface area graphitized carbon black, was a new sorbent used in the clean-up. The results show that Carbopack Z effectively removes interferences with little loss of acidic pesticides. All tested pesticide recoveries were satisfactory when Carbopack Z was combined with C18 in the clean-up at optimized condition. After clean-up, the extract was subjected to 10-fold dilution to sufficiently reduce the matrix effect (<20%). The limit of quantification (LOQ) was 1–5 ng/g, and the mean recovery was between 95 and 110% with a relative standard deviation <20% (between 2% and 10%) for the spiking of three concentrations: 5, 50, and 500 ng/g. The extract was less pigmented in the modified QuEChERS method than its original version. Thus, the modified method is a useful alternative for investigating the acidic pesticide residues in cabbage and spinach.

Multiresidue method for determining multiclass acidic pesticides in agricultural foods by liquid chromatography-tandem mass spectrometry.

A reliable multiresidue method was developed for determining multiclass acidic pesticides in cereal grains, legumes, vegetables, and fruits. The target pesticides comprise 75 compounds, including phenoxy acid, sulfonylurea, imidazoline, and triazolopyrimidine herbicides, with acidic dissociation constant (pKa) values of 1.9-5.9. The method includes extraction with acidified acetonitrile, salting out, cleanup with octadecyl silica and primary secondary amine cartridges, and subsequent liquid chromatography-tandem mass spectrometry. The analytical performance of the developed method was validated for nine foods (i.e., brown rice, soybeans, peanuts, spinach, cabbage, eggplant, potatoes, apples, and oranges) at a concentration of 0.01 mg kg-1. Because matrix effects were negligible for most pesticide and food combinations, solvent-based calibration curves were used for quantification purposes. Most of the target compounds exhibited satisfactory analytical performance with trueness values of 70-100% and relative standard deviations below 14%. The high selectivity of the developed method was evidenced by the absence of interfering peaks near those of the target analytes. With the exception of 1-naphthaleneacetic acid, for which linearity was observed at 2.5-100 ng mL-1, linear calibration curves were constructed for the target compounds in the 1-100 ng mL-1 range, with coefficients of determination exceeding 0.995. The limits of detection were 3 μg kg-1 or below in the examined matrices. The results demonstrate that the developed method is suitable for monitoring acidic pesticides in a variety of foods.

Preparation of MIL-100 via a novel water-based heatless synthesis technique for the effective remediation of phenoxyacetic acid-based pesticide

An iron-based metal-organic framework (MOF), MIL-100(Fe) has been synthesized by a novel water-based heatless recipe. The physical-chemical qualities of MIL-100(Fe) were examined by X-ray diffraction, Field Emission Scanning Electron Microscopy, Nitrogen adsorption-desorption isotherm, Thermogravimetric Analysis and Fourier Transform Infrared Spectroscopy. With a high specific surface area of 1,893 m2/g, the crystalline MIL-100(Fe) exhibited an extraordinary performance for the adsorptive removal of 2,4-dichlorophenoxyacetic acid (2,4-D) pesticide from the aqueous solution under laboratory and on-site conditions. The adsorption equilibria have been simulated by the nonlinear Langmuir, Freundlich, Sips, Dubinin–Radushkevich, and Redlich–Peterson isotherm models, with a monolayer adsorption capacity for 2,4-D of 858 mg/g. The adsorption kinetics was rapid, with exceeding 50% of the adsorbate loading has been completed within the first 5 min of contact time, and best described by the pseudo-second order kinetic equation. Further analyses with the Bangham, Vermeulen, and intraparticle diffusion models concluded that intraparticle pore diffusion is the controlling mechanism, but it is not the sole rate-limiting step. MIL-100(Fe) retained the adsorptive performance in the 2,4-D loaded tap water and lakewater samples. The profound effects with solution pH and ionic strength on the adsorptive uptake suggested that the prevailing interaction was the electrostatic attraction between the deprotonated 2,4-D and positive-charged MIL-100(Fe). The adsorption process was spontaneous with favorable enthalpy and entropy changes as the thermodynamic driving force. Water stability test illustrated negligible iron leaching from the Fe-MOF. MIL-100(Fe) adsorbent could be reused for at least 5 times, with minor deterioration in the adsorptive uptake via simple solvent stripping. The high adsorptive potential and well-developed porosity, supported by the sustainable preparation methodology, rendered MIL-100(Fe) a promising adsorbent for the effective decontamination of water pollutants.

Facile preparation of hydroxyl bearing covalent organic frameworks for analysis of phenoxy carboxylic acid pesticide residue in plant-derived food

The development of sensitive method for analysis ofpesticide residue is of great significance to ensure food safety and promote globalization of food trade. An original method was proposed for analysis of phenoxy carboxylic acids (PCAs) pesticide in plant-derived food. To concentrate trace PCAs, the TAPT-DHTA-COF was fabricated by a facile room-temperature method and utilized as the solid phase extraction cartridge packing. The TAPT-DHTA-COF exhibited excellent adsorption capacity and recyclability towards PCAs. Theoretical simulation indicated that the adsorption of PCAs onto the TAPT-DHTA-COF was driven by hydrogen bond, halogen bond and π-π interaction. Using liquid chromatography tandem mass spectrometry for detection, good linearity ranged from 0.10 to 40 ng·g−1 and low limits of detection varied from 0.007 to 0.030 ng·g−1 were achieved for PCAs in rice, apple and greengrocery. The recoveries of PCAs from the spiked samples ranged from 81.2% to 107%. The reliability was verified by the accurate determination of certified reference materials.

Target verification of allyl isothiocyanate on the core subunits of cytochrome c oxidase in Sitophilus zeamais by RNAi

Allyl isothiocyanate (AITC) is a volatile organic compound with a potent insecticidal activity to the stored-grain pest Sitophilus zeamais Motschulsky, which severely damages grain storage and container transport worldwide. Our previous study showed that mitochondrial complex IV was the primary target of AITC in adult Sitophilus zeamais. To further verify the targets of AITC, we employed RNA interference (RNAi) by using double-stranded RNA (dsRNA) to knockdown three core subunits of cytochrome c oxidase (COX)-I, -II and -III in 18-day-old larvae prior to their exposure to AITC to detect susceptibility changes. The susceptibility of dsRNACOX-I and -II injection treatments to AITC significantly increased at 72 h while the mortality reached up to 85.56% and 67.78%, respectively, and dsRNACOX-I and dsRNACOX-II injection showed the same subcellular structural characteristics showing vacuolization and vague mitochondrial cristae and decrease of COX activity during AITC fumigation treatment, suggesting the potential of COX-I and COX-II as the targets of AITC. High mortality reached up to 75.55%, 71.88% and 82.22%, respectively, and the phenotype of larvae turning from milky white to dark brown in the thorax and death eventually was confirmed after dsRNACOX-I, -II and -III injection. COX-I and -II were elucidated as the potential targets of AITC and dsRNACOX-I, -II and -III have the potential to be developed into nucleic acid pesticides for their robust lethal effects and are worth pursuing for improving AITC fumigation activity in Sitophilus zeamais control. © 2020 Society of Chemical Industry.

Photocatalytic removal of 2,4-Dichlorophenoxyacetic acid from aqueous solution using tungsten oxide doped zinc oxide nanoparticles immobilised on glass beads

ABSTRACT Groundwater is the only source of high quality water for human consumption in most parts of the world; however, it can be easily contaminated by domestic, industrial, and agricultural wastes such as fertilisers and pesticides. The main objective of the present research was to study the photocatalytic removal of 2,4-Dichlorophenoxyacetic acid pesticide (2,4-D) from aqueous media. This was a laboratory scale study in which the zinc oxide nanoparticles were doped with 0.5, 1, and 2 molar percent of tungsten oxide. The nanoparticles synthesised were characterised using powder XRD, SEM, FTIR, and UV-Vis Spectroscopy analyses. During the photodegradation of 2,4-D, the operational parameters studied were pH, nanoparticles dosage, initial pesticide concentration, light intensity, contact time, and the mineralisation trend of organic matter. It was found that the doped nanoparticles had a smaller band gap energy, which confirms the effect of doping. The percentage of the dopant can affect the pesticide removal efficiency. The optimal pH value obtained was 7. In addition, the process efficiency, increased from 27% to 78% with increasing UV light intensity from 172 to 505 W/m2 respectively. Moreover, it was found that, with increasing light intensity, contact time and nanoparticle concentration all caused the pesticide removal efficiency to be increased too. In addition, the increase of the pesticide concentration would cause a reduction in the process removal efficiency. This study indicated that the photocatalytic process using tungsten doped zinc oxide nanoparticles can remove the 2,4-D pesticide by around 80% from the aquatic environment.

Citrus Leafminer Management: Jasmonic Acid versus Efficient Pesticides

The citrus leafminer (Phyllocnistis citrella Stainton) is a significant pest for Citrus spp. worldwide. Hence, the effectiveness of jasmonic acid (JA) was compared to three pesticides, abamectin, thiamethoxam, and acetamiprid, against P. citrella infesting mandarin (Citrus reticulata L.) and lime (C. aurantifolia L.) seedlings. Mortality rate was significantly different due to JA and other pesticides treatments. Moreover, on the 3rd day after treatment, JA demonstrated the highest reduction percentage of leafminer (77.08 and 33.33%) on mandarin and lime, respectively. By the 10th day after treatment, JA and abamectin displayed 100% reduction in both plant species. Furthermore, the foliar application of JA enhanced the most vegetative characteristics in the treated seedlings, including growth rate (shoot length/root length), fresh and dry weights of shoot and root as well as the number of leaves/seedling. Moreover, soluble protein content was increased significantly under JA treatment in the two Citrus spp. Jasmonic acid showed a good biological activity, which gives a practical reason to recommend it to be integrated in pest management programs as an alternative product for controlling P. citrella.

Fabrication of Co/Pr co-doped Ti/PbO2 anode for efficiently electrocatalytic degradation of β-naphthoxyacetic acid

The existence of β-naphthoxyacetic acid (BNOA) pesticide in water system has aroused serious environmental problem because of its potential toxicity for humans and organisms. Therefore, exploiting an efficient method without secondary pollution is extremely urgent. Herein, a promising Ti/PbO2–Co-Pr composite electrode has been successfully fabricated through simple one-step electrodeposition for efficiently electrocatalytic degradation of BNOA. Compared with Ti/PbO2, Ti/PbO2–Co and Ti/PbO2-Pr electrodes, Ti/PbO2–Co-Pr electrode with smaller pyramidal particles possesses higher oxygen evolution potential, excellent electrochemical stability and outstanding electrocatalytic activity. The optimal degradation condition is assessed by major parameters including temperature, initial pH, current density and Na2SO4 concentration. The degradation efficiency and chemical oxygen demand removal efficiency of BNOA reach up to 94.6% and 84.6%, respectively, under optimal condition (temperature 35 °C, initial pH 5, current density 12 mA cm−2, Na2SO4 concentration 8.0 g L−1 and electrolysis time 3 h). Furthermore, Ti/PbO2–Co-Pr electrode presents economic energy consumption and superior repeatability. Finally, the possible degradation mechanism of BNOA is put forward according to the main intermediate products identified by liquid chromatography-mass spectrometer. The present research paves a new path to degrade BNOA pesticide wastewater with Ti/PbO2–Co-Pr electrode.

Stir bar sorptive extraction combined with deep eutectic solvent-based dispersive liquid–liquid microextraction: application in simultaneous derivatisation and extraction of acidic pesticides

ABSTRACTIn the present study, a stir bar sorptive extraction (SBSE) method coupled with deep eutectic solvent (DES)-based dispersive liquid–liquid microextraction (DLLME) has been developed for the simultaneous derivatisation and extraction of some acidic pesticides before their analysis by gas chromatography-mass spectrometry (GC-MS). In this method, initially, the analytes are adsorbed on a coated stir bar from an aqueous solution. Then, the stir bar is removed and a water-miscible DES is used to elute the analytes. Afterwards, butyl chloroformate (BCF) and a water-immiscible DES are added to the obtained elute as a derivatisation agent and an extraction solvent, respectively. In this work, the use of common toxic organic solvents is omitted, and for the first time, DESs are used as elution (for desorption of the analytes from stir bar), disperser and extraction solvents. Under the optimum conditions, the introduced method indicated high enhancement factor (EnF) (1743–3654), enrichment factor (EF) (1232–1532), and extraction recovery (ER) (74–92%), low limit of detection (LOD) (14–29 ng L–1) and limit of quantification (LOQ) (47–98 ng L–1), good linearity (r2 ≥ 0.9969) and satisfactory repeatabilities. Finally, the proposed method was applied in the analysis of the analytes in various fruit juice samples.

Estimating sorption of monovalent acidic herbicides at different pH levels using a single sorption coefficient.

Monovalent acidic pesticide sorption can be determined for any soil pH if the dissociation constant of the compound is known, and sorption coefficients are available for at least two different pH values, measured in a wide enough range to enable estimating both neutral and anionic form coefficients. Sorption estimates have also been made from a single sorption coefficient available, assuming a non-compound specific value of the anionic form sorption coefficient or considering a generic ratio between sorption coefficients of the two forms. A compound-specific procedure for adjustment of parameters of the equation for estimating sorption of monovalent acidic herbicides at different pH levels, from a single sorption coefficient, is proposed and evaluated. The quality of fits was good for sorption of all three herbicides studied, especially for 2,4-D and flumetsulam at pH above 5, even for diverse soils and experimental procedures and conditions. The best fits resulted in the following ratios of theoretical maximum organic-carbon sorption coefficients for neutral and anionic forms (Kocn':Koca'): 440:1 for 2,4-D; 132:1 for flumetsulam; and 55:1 for sulfentrazone. The ratios of theoretical maximum sorption coefficients for neutral and anionic forms (Kocn':Koca') are compound-specific, thus this procedure should also be applied to pH-sorption datasets for other acidic pesticides to provide the respective ratio between the theoretical maximum sorption coefficients, instead of using generic assigned values. More calibration research is recommended and validation of this approach is required to demonstrate applicability of the method. © 2020 Society of Chemical Industry.

Dispersive liquid–liquid microextraction method for the extraction of acidic pesticides in edible oils; application of short-chain organic acids as co–disperser and protonation agent

ABSTRACT In the present study, a sample pretreatment based on the combination of vortex assisted liquid–liquid extraction and dispersive liquid–liquid microextraction has been proposed for the isolation and preconcentration of three acidic herbicides including fenoxaprop, fluazifop, and haloxyfop from edible oil samples. For this purpose, firstly, the analytes were extracted into sodium hydroxide solution (by deprotonating the analytes) which was used as a dispersive solvent in the following microextraction procedure. The obtained aqueous phase was mixed with acetic acid as a pH adjustment agent and co–disperser solvent. After the addition of dichloromethane (extraction solvent) to the above solution, it was quickly dispersed into deionised water. The validation parameters indicated that the limits of detection and quantification of the proposed method were in the ranges of 0.3–1.8 and 1.0–6.0 ng mL–1, respectively. Relative standard deviations of the method were obtained in the range of 4.8–6.2% and 5.2–9.1% for intra – (n = 6) and inter–day (n = 5) precisions, respectively. High extraction recoveries and enrichment factors ranged from 74 to 91%, and 185 to 227 were the other advantages of the method. These merits showed that the proposed method is efficient and sensitive for the determination of the studied analytes in the edible oil samples.

Development of a stir bar sorptive extraction method coupled to solidification of floating droplets dispersive liquid-liquid microextraction based on deep eutectic solvents for the extraction of acidic pesticides from tomato samples.

A stir bar sorptive extraction method coupled with deep eutectic solvent based solidification of floating organic droplets-dispersive liquid-liquid microextraction has been used for the simultaneous derivatization and extraction of some acidic pesticides in tomato samples. In this method, initially the analytes are adsorbed on a coated stir bar from tomato juice filled in a narrow tube. After extraction, the stir bar is removed and a water-miscible deep eutectic solvent is used to elute the analytes. Afterward, a derivatization agent and a water-immiscible deep eutectic solvent (as an extraction solvent) with melting point near to room temperature are added to the obtained eluant at µL-levels and the obtained mixture is rapidly injected into deionized water. Under the optimum conditions, the introduced method indicated high enhancement (1543-3353) and enrichment (2530-2999) factors, low limits of detection (7-14ng/L) and quantification (23-47ng/L), good linearity (r2 ≥ 0.9982), and satisfactory repeatabilities (relative standard deviation ≤12% for intra- and inter-day precisions at a concentration of 100ng/L of each analyte). Finally, the proposed method was applied in analysis of the analytes in tomato samples.

Association of urinary metabolites of organophosphate and pyrethroid insecticides, and phenoxy herbicides with endometriosis

Endometriosis is a hormone-responsive gynecologic disease, signifying its connotations across a woman’s life span. Previous studies suggested that endocrine disrupting chemicals were risk factors for endometriosis. Nevertheless, little is known on exposure to organophosphate, pyrethroid and phenoxy acid pesticides on endometriosis diagnosis. In this study, we determined the concentrations of 11 pesticides, metabolites of organophosphate and pyrethroid insecticides, and phenoxy herbicides, in urine collected from 619 reproductive-age women in Utah and California, using liquid chromatography-tandem mass spectrometry. The association of urinary concentrations of pesticides with an increase in the odds of endometriosis diagnosis was examined in 594 women who underwent laparoscopy/laparotomy (operative cohort: n = 471) or pelvic magnetic resonance imaging (population cohort: n = 123), during 2007–2009. 2-Isopropyl-4-methyl-6-hydroxypyrimidine (IMPY), malathion dicarboxylic acid (MDA), para-nitrophenol (PNP), 3,5,6-trichloro-2-pyridinol (TCPY), 3-phenoxybenzoic acid (3-PBA), and 2,4-dichlorophenoxyacetic acid (2,4-D) were detected in ≥95% of the urine samples analyzed. Urinary concentrations of IMPY, MDA, PNP, 3-PBA and 2,4-D tended to be higher in younger, non-Hispanic black, nulliparous and less affluent women. IMPY was the most dominant compound in urine followed by PNP and TCPY. When women in the 4th quartile of IMPY and the 2nd quartile of TCPY concentrations (μg/g creatinine) were compared with women in the 1st quartile, the odds ratios (ORs) for diagnosis of endometriosis increased significantly in unadjusted models (IMPY OR = 1.89, 95% confidence interval (Cl) = 1.12–3.20; TCPY OR = 1.65, 95% Cl = 1.02–2.69) for the operative (n = 471) and entire data set (n = 594), respectively. Our results suggest that exposure to elevated concentrations of diazinon (the parent compound of IMPY) and chlorpyrifos and chlorpyrifos-methyl (parent compounds of TCPY) may be associated with endometriosis.

Evaluation of selected buffers for simultaneous determination of ionic and acidic pesticides including glyphosate using anion exchange chromatography with mass spectrometric detection

Ion chromatography coupled with mass spectrometry is an established technique for determination of ionic analytes, however, sophisticated buffer removal equipment is required to eliminate inorganic compounds from the eluate before introduction into the ion source of mass spectrometer. A standard high-performance liquid chromatography coupled with tandem mass spectrometry setup using an ion exchange column (Metrosep® A Supp 5) is proposed as an alternative approach. For that reason, some buffers including non-volatile carboxylic acid based solutions have been evaluated for simultaneous trace determination of ionic and acidic pesticides including glyphosate in the same extract without a need for sophisticated buffer removal equipment. Two differently designed ionisation sources were compared qualitatively for the application of non-volatile buffers. The study revealed that the choice of buffers had a strong influence on matrix effects in case of spiked extract injections. Finally, pesticides with very different physicochemical properties (logP<0, logP≥0) and structures (containing carboxylate, phosphonate, azolide, azanide, phenolate, bromate, and chlorate moieties) were quantified in spiked beer and oat extracts with acceptable recoveries (80-110%) using tandem mass spectrometry detection with AB SCIEX QTRAP 5500 instrument after separation using edetate buffer.

Molecular basis for the resistance of American sloughgrass to aryloxyphenoxypropionic acid pesticides and its environmental relevance: A combined experimental and computational study

Organic pesticides are one of the main environmental pollutants, and how to reduce their environmental risks is an important issue. In this contribution, we disclose the molecular basis for the resistance of American sloughgrass to aryloxyphenoxypropionic acid pesticides using site-directed mutagenesis and molecular modeling and then construct an effective screening model. The results indicated that the target-site mutation (Trp-1999-Leu) in acetyl-coenzyme A carboxylase (ACCase) can affect the effectiveness of the pesticides (clodinafop, fenoxaprop, cyhalofop, and metamifop), and the plant resistance to fenoxaprop, clodinafop, cyhalofop, and metamifop was found to be 564, 19.5, 10, and 0.19 times, respectively. The established computational models (i.e. wild-type/mutant ACCase models) could be used for rational screening and evaluation of the resistance to pesticides. The resistance induced by target gene mutation can markedly reduce the bioreactivity of the ACCase-clodinafop/fenoxaprop adducts, and the magnitudes are 10 and 102, respectively. Such event will seriously aggravate environmental pollution. However, the biological issue has no distinct effect on cyhalofop (RI＝10), and meanwhile it may markedly increase the bioefficacy of metamifop (RI＝0.19). We could selectively adopt the two chemicals so as to decrease the residual pesticides in the environment. Significantly, research findings from the computational screening models were found to be negatively correlated with the resistance level derived from the bioassay testing, suggesting that the screening models can be used to guide the usage of pesticides. Obviously, this story may shed novel insight on the reduction of environmental risks of pesticides and other organic pollutants.

Amino-modified covalent organic framework as solid phase extraction absorbent for determination of carboxylic acid pesticides in environmental water samples

The amino-modified covalent organic framework (NH2@COF) was synthesized via the thiol-ene click reaction of vinyl covalent organic framework (COF) with 4-aminobenzenethiol. The introduction of amino groups can interact with the anionic headgroup of carboxylic acid pesticides. Moreover, ample hydrophilic surface area can boost absorption in the water media. The NH2@COF was fully characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. Compared with vinyl COF and four commercial absorbents, the NH2@COF shows higher extraction efficiency for carboxylic acid pesticides. The solid phase extraction (SPE) conditions, involving flow rate, ionic strength, sample pH, desorption solvent, and desorption solvent volume, were optimized in details. Under the optimized conditions, the NH2@COF was successfully applied for the enrichment and determination of six carboxylic acid pesticides in environmental water samples combined with high performance liquid chromatography. The method features wide linearity (0.2–100 ng mL−1, r > 0.999), low limits of quantification (0.04–0.20 ng mL−1), and excellent precision (RSDs ≤ 8.7%). The recoveries range from 89.6% to 102.4% with RSDs ≤ 7.1%. Therefore, the NH2@COF-SPE method is an efficient pretreatment procedure and can be utilized for the selective extraction of carboxylic acid pesticides from environmental water samples.