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Physical Chemistry Chemical Physics :... May 2023Guest molecules containing chromophore groups encapsulated by β-cyclodextrin (β-CD) generate circular dichroism (CD) signals, which enables a preliminary prediction of...
Guest molecules containing chromophore groups encapsulated by β-cyclodextrin (β-CD) generate circular dichroism (CD) signals, which enables a preliminary prediction of their binding modes. However, the accurate determination of the representative binding conformation (RC) remains a challenging task due to the complex conformational space of these host-guest systems. Here, we combine a molecular dynamics/quantum mechanics/continuum solvent model (MD/QM/CSM) with induced circular dichroism (ICD) data (N. L. Pacioni, A. B. Pierini and A. V. Veglia., 2013, , 319-324.) to explore the binding mechanism of β-CD with four -methylcarbamate molecules: promecarb (PC), bendiocarb (BC), carbaryl (CY) and carbofuran (CF). In aqueous solution, their stability decreases as: PC > BC > CY > CF. Comparing the ECD spectra computed from TD-DFT with the ICD data can help eliminate many common binding configurations and identify the RC. The host-guest binding affinities (BAs) estimated using a ONIOM2(B971:PM6)/SMD model reproduce the measured binding trend, reveal the competition between the non-covalent interaction and solvent effect and explain the large difference in their binding modes. We also examine the fluctuations in the computed BA using similar structures.
Topics: beta-Cyclodextrins; Molecular Dynamics Simulation; Solvents
PubMed: 37184134
DOI: 10.1039/d3cp01252b -
ACS Omega Apr 2022Magnetic sorbents based on iron-aluminum-mixed metal hydroxides composited with metal-organic frameworks (MOFs) were designed and synthesized using different benzoate...
Magnetic Solid-Phase Extraction of Carbamate Pesticides Using Magnetic Metal-Organic Frameworks Derived from Benzoate Ligands, Followed by Digital Image Colorimetric Screening and High-Performance Liquid Chromatography Analysis.
Magnetic sorbents based on iron-aluminum-mixed metal hydroxides composited with metal-organic frameworks (MOFs) were designed and synthesized using different benzoate ligands, including terephthalic acid, 2-aminoterephthalic acid, 2,5-dihydroxyterephthalic acid, 1,3,5-benzenetricarboxylic acid, and 1,2,4,5-benzenetetracarboxylic acid. The magnetic MOF derived from terephthalic acid ligand exhibited an excellent extraction efficiency, with adsorption capacities in the range of 2193-4196 mg kg, and was applied for magnetic solid-phase extraction (MSPE) of carbamate pesticides, that is, bendiocarb, carbosulfan, carbofuran, carbaryl, propoxur, isoprocarb, and promecarb. Simple digital image colorimetry based on the diazotization reaction and high-performance liquid chromatography (HPLC) were utilized for fast screening and quantification purposes, respectively. A good analytical performance for a simple screening approach using portable equipment was obtained with detection limits in the range of 1.0-18.0 μg L. Under the optimized MSPE-HPLC conditions, the entire developed procedure provided a wide linear range between 0.015 and 1000 μg L, low limits of detection, and limits of quantitation ranging from 0.005 to 0.090 and 0.015-0.300 μg L, respectively. Enrichment factors up to 184 were achieved. The intra- and interday relative standard deviations were below 6.7 and 9.4%, respectively. The proposed MSPE-digital image colorimetry and MSPE-HPLC methods were successfully applied for screening and determining carbamate pesticides in fruits and vegetables. The recoveries were obtained in a satisfactory range of 71.5-122.8%. This discovery has led to the development of integration methods using newly synthesized sorbent materials for the enrichment of carbamate pesticides prior to their analysis in complicated samples. The developed MSPE coupled with digital image colorimetry was efficient for fast carbamate contamination screening, while MSPE-HPLC offered a sensitive analytical methodology for quantifying contaminated samples.
PubMed: 35449973
DOI: 10.1021/acsomega.2c00596 -
Electrophoresis Mar 2015The applicability of an ionic liquid-based cationic surfactant 1-dodecyl-3-methyl-imidazolium tetrafluoroborate (C12 MImBF4 ) as pseudostationary phase in MEKC has been...
The applicability of an ionic liquid-based cationic surfactant 1-dodecyl-3-methyl-imidazolium tetrafluoroborate (C12 MImBF4 ) as pseudostationary phase in MEKC has been evaluated for the analysis of 11 carbamate pesticides (promecarb, carbofuran, metolcarb, fenobucarb, aldicarb, propoxur, asulam, benomyl, carbendazim, ethiofencarb, isoprocarb) in juice samples. Under optimum conditions (separation buffer, 35 mM NaHCO3 and 20 mM C12 MImBF4 , pH 9.0; capillary temperature 25°C; voltage -22 kV) the analysis was carried out in less than 12 min, using hydrodynamic injection (50 mbar for 7.5 s) and detection at 200 nm. For the extraction of these CRBs from juice samples, a dispersive liquid-liquid microextraction (DLLME) procedure has been proposed, by optimization of variables affecting the efficiency of the extraction. Following this treatment, sample throughput was approximately 12 samples per hour, obtaining a preconcentration factor of 20. Matrix-matched calibration curves were established using tomato juice as representative matrix (from 5 to 250 μg/L for CBZ, BY, PX, CF, FEN, ETH, ISP, and 25-250 μg/L for ASL, ALD, PRC, MTL), obtaining quantification limits ranging from 1 to 18 μg/L and recoveries from 70 to 96%, with RSDs lower than 9%.
Topics: Beverages; Borates; Carbamates; Chromatography, Micellar Electrokinetic Capillary; Imidazoles; Ionic Liquids; Linear Models; Solanum lycopersicum; Models, Chemical; Reproducibility of Results; Sensitivity and Specificity; Surface-Active Agents
PubMed: 25546365
DOI: 10.1002/elps.201400311 -
Talanta Nov 2013A new extraction method, based on Dispersive Nano-Solid material-Ultrasound Assisted Micro-Extraction (DNSUAME), was used for the preconcentration of the bendiocarb and...
Dispersive nano solid material-ultrasound assisted microextraction as a novel method for extraction and determination of bendiocarb and promecarb: response surface methodology.
A new extraction method, based on Dispersive Nano-Solid material-Ultrasound Assisted Micro-Extraction (DNSUAME), was used for the preconcentration of the bendiocarb and promecarb pesticides in the water samples prior to high performance liquid chromatography (HPLC). The properties of NiZnS nanomaterial loaded on activated carbon (NiZnS-AC) are characterized by FT-IR, TEM, and BET. This novel nanomaterial showed great adsorptive ability towards the bendiocarb and promecarb pesticides. The effective variables such as the amount of adsorbent (mg: NiZnS-AC), the pH and ionic strength of sample solution, the vortex and ultrasonic time (min), the ultrasonic temperature (°C), and desorption volume (mL) are investigated by screening 2(7-4) experiments of Plackett-Burman (PB) design. The important variables optimized by using a central composite design (CCD) were combined by a desirability function (DF). At optimum conditions, the method has linear response over 0.0033-10 µg mL(-1) with detection limit between 0.0010 and 0.0015 µg mL(-1) with relative standard deviations (RSDs) less than 5.5% (n=3). The method has been successfully applied for the determination of the bendiocarb and promecarb pesticides in the water samples.
Topics: Carbamates; Carbon; Chromatography, High Pressure Liquid; Factor Analysis, Statistical; Fresh Water; Humans; Hydrogen-Ion Concentration; Insecticides; Limit of Detection; Nanostructures; Nickel; Phenylcarbamates; Solid Phase Microextraction; Sonication; Sulfides; Water Pollutants, Chemical; Zinc Compounds
PubMed: 24148456
DOI: 10.1016/j.talanta.2013.07.013 -
Acta Chimica Slovenica Dec 2012The feasibilities of two strategies for the simultaneous analysis of five carbamate insecticides (i.e. propoxur, carbofuran, carbaryl, isoprocarb, and promecarb) by high...
The feasibilities of two strategies for the simultaneous analysis of five carbamate insecticides (i.e. propoxur, carbofuran, carbaryl, isoprocarb, and promecarb) by high performance liquid chromatography (HPLC) have been investigated. The first method is the preconcentration strategy based on micelle-mediated extraction (MME) using sodium dodecyl sulfate. The second strategy uses chemical derivatization with 2,4-dimethoxyaniline (DMA) reagent before subjecting to HPLC. The parameters affecting the analysis were optimized. For MME, the optimum conditions were 4.0% (w/v) SDS in the presence of 5.0 mol L-1 HCl. Meanwhile, the DMA derivatization condition was 1.5 mmol L-1 DMA, 7 mmol L-1 NaNO2, and 50 mmol L-1 HCl, and 250 mmol L-1 NaOH for the hydrolysis of carbamates before their derivatization. The target carbamates and their derivatives were monitored at wavelengths of 270 and 380 nm for the MME and DMA derivatization methods, respectively. The capability of each developed method was compared in terms of separation time and limits of detection (LODs). The results show that the five studied insecticides were successfully separated within 8 min (DMA) and 27 min (MME), respectively. LODs of the insecticides obtained from DMA (0.01-0.04 mg L-1) were lower than those obtained from MME (0.1-0.7 mg L-1). The proposed DMA method is versaltile and superior to MME for the analysis of carbamate insecticides in tap water samples.
PubMed: 24061368
DOI: No ID Found -
Spectrochimica Acta. Part A, Molecular... Feb 2013Detailed insights regarding the inclusion process between β-cyclodextrin and the N-methylcarbamates insecticides like Bendiocarb, Carbaryl, Carbofuran and Promecarb,...
Detailed insights regarding the inclusion process between β-cyclodextrin and the N-methylcarbamates insecticides like Bendiocarb, Carbaryl, Carbofuran and Promecarb, are proposed in bases of experimental and computational methods. The results from Fourier transform infrared spectroscopy, differential scanning calorimetry, induced circular dichroism and molecular dynamics indicate that only in the case of Promecarb the interaction with the macrocycle is produced by the alkyl rest of the molecule. In all other cases the aromatic moiety is the part of the insecticide that is partially included in the cavity of β-cyclodextrin.
Topics: Calorimetry, Differential Scanning; Carbamates; Circular Dichroism; Insecticides; Molecular Dynamics Simulation; Spectroscopy, Fourier Transform Infrared; Thermodynamics; beta-Cyclodextrins
PubMed: 23261629
DOI: 10.1016/j.saa.2012.11.004 -
Journal of Chromatographic Science Jul 2012The influence of salt additive on cloud point extraction (CPE) of isoprocarb and promecarb insecticides is described. Types of salt (Na(2)CO(3), CaCl(2), MgSO(4),...
The influence of salt additive on cloud point extraction (CPE) of isoprocarb and promecarb insecticides is described. Types of salt (Na(2)CO(3), CaCl(2), MgSO(4), Na(2)SO(4), NaHCO(3) and NaCl) and concentrations were studied. The extracted target compounds were analyzed using reversed phase high-performance liquid chromatography. Among the salts studied, Na(2)CO(3) was found to be the most effective salt for salting out of both insecticides, resulting in high extraction efficiency (>95%) and high enrichment factor of up to 18 compared to extraction without preconcentration. The optimum CPE conditions were 1.5% (w/v) Triton X-114, 3.0% (w/v) Na(2)CO(3), and 20-min equilibration at 45°C. Under the selected conditions, the linear range of 0.05 to 3.0 mg/L was found for both analytes. The limits of detection for isoprocarb and promecarb were 10 and 20 µg/L, respectively. High intra-day (n = 9) and inter-day (n = 3 × 4 days) precisions with relative standard deviations <1% and <8% were obtained for retention time and peak area, respectively. The proposed method was successfully applied for the residue analysis of target compounds in beverages (i.e., fruit juice, vegetable juice and wine samples), which provided high recoveries (>80%, on average) for spiked samples at three levels (0.05, 0.10 and 0.50 mg/L).
PubMed: 22532589
DOI: 10.1093/chromsci/bms043 -
Journal of Economic Entomology Feb 2012Both chemical and biological methods are essential for control of insects, for example, lepidopterans, on rice. Thus, it is important to know the effect of chemicals on...
Both chemical and biological methods are essential for control of insects, for example, lepidopterans, on rice. Thus, it is important to know the effect of chemicals on the biological control agents. In this study, we assessed the toxicity of commonly used insecticides on a biological control agent, Trichogramma japonicum Ahmead (an egg parasitoid of rice lepidopterans) by using a dry film residue method. Results showed that thirty insecticides from seven chemical classes exhibited various degree of toxicity to this parasitoid. Among the seven classes of chemicals tested, organophosphates (chlorpyrifos, fenitrothion, phoxim, profenofos, and triazophos) and carbamates (carbaryl, carbsulfan, isoprocarb, metolcarb, and promecarb) exhibited the highest intrinsic toxicity to T. japponicum, with an LC50 of 0.035 (0.029-0.044) to 0.49 (0.34-0.87) mg active ingredient (a.i.) L(-1), followed by antibiotics (abamectin, emamectin benzoate, and ivermectin), phenylpyrazoles (butane-fipronil, ethiprole, and fipronil), pyrethroids (cyhalthrin, cypermethrin, fenpropathrin, and lambda-cyhaothrin), and neonicotinoids (acetamiprid, imidacloprid, imidaclothiz, nitenpyram, thiacloprid, and thiamethoxam). Moreover, the insect growth regulator insecticides (chlorfluazuron, fufenozide, hexaflumuron and tebufenozide) exhibited the lowest toxicity to the wasps with an LC50 of 3,383 (2406-5499) to 30206 (23107-41008) mg ai. L(-1). Risk quotient analysis showed that phenylpyrazoles, pyrethroids, insect growth regulators, neonicotinoids (with the exception of thiamethoxam), and antibiotics (with the exception of abamectin) are classified as safe agents to the parasitoid, while organophosphates and carbamates are classified as slightly, moderately, or highly toxic agents to the parasitoid. The data presented in this paper provided useful information on the selection of compatible insecticides with T. japonicum.
Topics: Animals; Biological Control Agents; Dose-Response Relationship, Drug; Insecticides; Lethal Dose 50; Moths; Oryza; Risk Assessment; Toxicity Tests; Wasps
PubMed: 22420260
DOI: 10.1603/ec11259 -
Analytica Chimica Acta Aug 2011A rapid and simple method for the extraction and preconcentration of N-methylcarbamates (NMCs) (carbofuran, carbaryl and promecarb) in water samples using dispersive...
Determination of N-methylcarbamate insecticides in water samples using dispersive liquid-liquid microextraction and HPLC with the aid of experimental design and desirability function.
A rapid and simple method for the extraction and preconcentration of N-methylcarbamates (NMCs) (carbofuran, carbaryl and promecarb) in water samples using dispersive liquid-liquid microextraction (DLLME) using chemometrics was developed. Influence variables such as volume of extracting (CHCl(3)) and dispersing solvents (ACN), pH and ionic strength, extraction time and centrifugation time and speed were screened in a 2(7-4) Plackett-Burman design was investigated. The significant variables were optimized by using a central composite design (CCD) combined with desirability function (DF). At optimum conditions values of variables set as 126 μL chloroform, 1.5 mL acetonitrile, 1 min extraction time, 10 min centrifugation at 4000 rpm min(-1), natural pH, 4.7% (w/v) NaCl, the separation was reached in less than 14 min using a C(18) column and an isocratic binary mobile phase (acetonitrile: water (50:50, v/v)) with flow rate of 1.0 mL min(-1). At optimum conditions method has linear response over 0.001-10 μg mL(-1) with detection limit between 0.0001 and 0.0005 μg mL(-1) with relative standard deviations (RSDs) in the range 2.18-5.06% (n=6).
Topics: Carbamates; Carbaryl; Carbofuran; Chromatography, High Pressure Liquid; Hydrogen-Ion Concentration; Insecticides; Osmolar Concentration; Research Design; Solvents; Water Pollutants, Chemical
PubMed: 21704765
DOI: 10.1016/j.aca.2011.04.011 -
Talanta Jun 2011A simple and rapid method for preconcentration of carbamate insecticides, including methomyl, propoxur, carbofuran, carbaryl, isoprocarb, methiocarb and promecarb, has...
A simple and rapid method for preconcentration of carbamate insecticides, including methomyl, propoxur, carbofuran, carbaryl, isoprocarb, methiocarb and promecarb, has been developed. It was based on a liquid-liquid microextraction using a [C(4)MIM][PF(6)] room temperature ionic liquid as an extraction solvent prior to analysis by high performance liquid chromatography with UV detection. Experimental parameters affecting the extraction performance, such as the volumes of sample, extractant and dissolving solvent, and extraction time, were studied. Under the selected conditions, the enrichment factors in the range between 10 and 25 could be achieved with the limit of detection in the range of 2-40 μg L(-1), and with the relative standard deviations of lower than 0.6 and 10.2% for retention time and peak area, respectively. The proposed method offers advantages in reduction of the exposure danger to toxic solvents used in the conventional liquid-liquid extraction, simplicity of the extraction processes, rapidity, and sensitivity enhancement. The method was demonstrated to apply to the analysis of fruit and natural surface water samples.
Topics: Carbamates; Chemical Fractionation; Chromatography, Liquid; Imidazoles; Ionic Liquids; Pesticide Residues; Temperature; Water
PubMed: 21641434
DOI: 10.1016/j.talanta.2011.01.002