Eco-friendly fabrication of a magnetic dual-template molecularly imprinted polymer for the selective enrichment of organophosphorus pesticides for fruits and vegetables

Preparation of a β-cyclodextrin grafted magnetic biochar for efficient extraction of four antiepileptic drugs in plasma samples

Simultaneous monitoring of plasma concentration levels of multiple antiepileptic drugs (AEDs) is essential for dose adjustment in comprehensive epilepsy treatment, necessitating a sensitive technique for accurate extraction and determination of AEDs. Herein, a magnetic solid-phase extraction (MSPE) technique on the basis of modified biochar (BC) is investigated to extract four AEDs from plasma, in conjunction with high performance liquid chromatography. BC derived from Zizyphus jujuba seed shells was activated by phosphoric acid (PBC) and magnetized via coprecipitation to produce MPBC. The MPBCCD obtained after modification with β-cyclodextrin (CD) was characterized and evaluated for adsorption. It exhibited fast adsorption kinetics based on second-order kinetics and satisfactory adsorption capacity for AEDs. Then it was employed as the MSPE adsorbent and the influencing parameters were optimized. The enrichment factor was 18.75. The validation analysis revealed a favorable linearity that ranged from 0.04 to 20 μg·mL-1 along with a low limit of detection of 6.85 to 10.19 ng·mL-1. The recovery of the AEDs ranged from 78.7 to 109.2 %, with relative standard deviations below 6.7 %. Using quantum chemistry theory calculations and experimental results analysis, the adsorption mechanism was investigated. It disclosed that the suggested strategy built upon MPBCCD was appropriate for the assessment of AEDs in plasma and expanded the usage of BC as the environmentally favorable matrix for the analysis of biological samples.

Biomass waste-derived magnetic material coated with dual-dummy-template molecularly imprinted polymer for simultaneous extraction of organophosphorus and carbamate pesticides

An eco-friendly biomass waste-derived magnetic material coated with a dual-dummy-template molecularly imprinted polymer was fabricated using aqueous ethanol as a green porogen, lower amounts of toxic compounds as template molecules, and tyrosine and tryptophan as biocompatible binary monomers. The binding characteristics and selectivity of the material toward pesticides were assessed. High adsorption capacities ranging from 150.11 to 509.09 mg g-1 and imprinting factors reaching 2.2 were achieved within just 30 s. The material was applied for extraction of organophosphorus and carbamate pesticides prior to HPLC analysis. Under the optimum conditions, low limits of detection and quantitation were achieved, with ranges of 0.05-1.49 μg/L and 0.18-5.00 μg/L, respectively. The established approach enables efficient analysis of vegetable and fruit samples, yielding satisfactory recoveries ranging between 80 and 110 %. The method showed promise as an analytical method for the sensitive enrichment of pesticide residues in vegetable and fruit samples.

Preparation of surface molecularly imprinted polymers with Fe3O4/ZIF-8 as carrier for detection of Dimethoate in cabbage

In this study, molecularly imprinted polymers (MIPs) were prepared for the specific recognition of organophosphorus pesticides and a rapid, efficient and simple method was established for the detection of dimethoate (DIT) in food samples. Fe3O4 magnetic nanoparticles were synthesized by co-precipitation, and Fe3O4/ZIF-8 complexes were prepared by a modified in-situ polymerization method, and then magnetic molecularly imprinted polymers (MMIPs) were prepared and synthetic route was optimized by applying density functional theory (DFT). The morphological characterization showed that the MMIPs were coarse porous spheres with an average particle size of 50 nm. The synthesized materials are highly selective for the organophosphorus pesticide dimethoate with an adsorption capacity of 461.50 mg·g-1 and are effective resistance to matrix effects. A novel method for the determination of DIT in cabbage was developed using the prepared MMIPs in combination with HPLC. The practical results showed that the method can meet the requirements for the determination of DIT in cabbage with recoveries of 85.6-121.1 % and detection limits of 0.033 μg·kg-1.

Molecularly imprinted polymer-coated paper for the selective extraction of organophosphorus pesticides from fruits, vegetables, and cereal grains

Biodegradable molecularly imprinted polymer-coated paper (MIP@paper) was effectively produced by polymerization using azinphos-methyl as a template molecule, terephthalic acid as a functional monomer, ethylene glycol dimethacrylate as a cross-linker, and aqueous ethanol as a green porogenic solvent. The material was subsequently composited onto cellulose paper, which served as the natural substrate, by dip coating with the aid of chitosan and citric acid natural adhesive. The properties, such as static and dynamic adsorption, selectivity, and reusability, were assessed. At rapid adsorption equilibrium (10 min), the MIP@paper had a high adsorption capacity in the range of 2.5-3.7 mg g-1 and good recognition with imprinting factors up to 2.1. In addition, the proposed MIP@paper was utilized efficiently as a sorbent for dispersive solid phase extraction (d-SPE) of eight organophosphorus pesticides (OPPs) prior to high-performance liquid chromatography (HPLC) analysis. The d-SPE-HPLC method displayed low detection limits of 1.2-4.5 μg kg-1 and significant enrichment factors (up to 320-fold). The proposed method was effectively applied for the determination of OPP residues in agricultural products, including fruits, vegetables, and cereal grains, with satisfactory spiked recoveries (80.1-119.1 %). Thus, the MIP@paper material provided a selective and environmentally favorable method for extracting and determining organophosphorus pesticides.

Eco-friendly thermosensitive magnetic-molecularly-imprinted polymer adsorbent in dispersive solid-phase microextraction for gas chromatographic determination of organophosphorus pesticides in fruit samples

A thermosensitive magnetic-molecularly-imprinted polymer (TMMIP) was successfully prepared in an aqueous medium. The TMMIP was applied as an effective adsorbent in dispersive solid-phase microextraction for the selective enrichment of five organophosphorus pesticides (OPPs; diazinon, fenitrothion, fenthion, parathion-ethyl, and ethion) before analysis by gas chromatography. The polymerization was performed using mixed-valence iron hydroxide nanoparticles as the magnetic support, N-isopropyl acrylamide as the thermosensitive monomer, ethion as the template, and methacrylic acid as the functional monomer. The adsorption and desorption mechanisms of OPPs depend on their interactions with the adsorbents and solution temperature. Our methodology provides good linearity (0.50-2000 µgL-1), with a correlation determination of R2 > 0.9980, low limit of detection (0.25-0.50 µgL-1), low limit of quantitation (0.50-1.50 μg L-1), and high precision (%RSD < 7%). The developed method demonstrates excellent applicability for accurately and efficiently determining OPP residuals in fruit and vegetable samples with good recoveries (93-117%).

Trace detection of methcathinone in sewage using targeted extraction based on magnetic molecularly imprinted polymers coupled with liquid chromatography-tandem mass spectrometry

Methcathinone, a new psychoactive substance (NPS), poses a serious threat to public health. Therefore, there is an urgent need to develop a reliable, selective, sensitive and simple analytical technique for monitoring trace amounts of this target NPS in complex matrices. For this purpose, magnetic molecularly imprinted polymers (MMIPs) based on MIPs combined with nano-sized magnetic Fe3O4 were developed for the specific enrichment of methcathinone in wastewater. The binding properties and selectivity of MMIPs toward methcathinone were evaluated and compared with non-imprinted polymer (MNIPs). For sensitive and selective extraction and determination of the target methcathinone, magnetic solid-phase extraction (MSPE) based on MMIPs was combined with liquid chromatography-tandem mass spectrometry (LC-MS/MS). Under optimized conditions, the proposed method was successfully used for the detection of methcathinone in wastewater, which provided a low limit of detection of 0.3 ng L-1 and a limit of quantification of 1.0 ng L-1 with relative standard deviations of less than 6.89% for intra- and inter-day analyses. Good linearity in the range of 1-2000 ng L-1 with a coefficient of determination (R2) greater than 0.98 was observed. Moreover, a certified reference material of water sample was successfully analyzed with satisfactory results and the recoveries of spike experiments ranged from 96.35-116.7%.

A biobased magnetic dual-dummy-template molecularly imprinted polymer using a deep eutectic solvent as a coporogen for highly selective enrichment of organophosphates

An eco-friendly magnetic dual-dummy-template molecularly imprinted polymer (MDDMIP) was prepared by a "one-pot" green synthesis using mixed-valence iron hydroxide as the magnetic material, a deep eutectic solvent as the coporogen, and caffeic acid and glutamic acid as binary monomers. The adsorption properties toward organophosphorus pesticides (OPPs) were investigated. High adsorption capacities (269.65-304.93 mg g^-1), quick adsorption times (20 s), and high imprinting factors (2.28-3.83) were obtained. The proposed MDDMIP was utilized for magnetic solid phase extraction (MSPE) of OPPs prior to quantification by high performance liquid chromatography (HPLC). The developed method exhibited outstanding linearity (0.05-500 μg L^-1), low detection limits (0.003-0.015 μg L^-1), and excellent enrichment factors (940-1310 folds). The MSPE-HPLC method was successfully applied for the detection of OPPs in vegetable, fruit, and grain samples with acceptable recoveries (80-119%). This method is a good potential method for the analysis of pesticide residues in complex matrices.

Strategy of Choosing Templates in Molecular Imprinting to Expand the Recognition Width for Family-Selectivity

The class-selective molecular-imprinted polymers (MIPs) have shown the recognition ability to multiple targeted molecules through using one or multiple templates. However, choosing the right templates, the core problem, still lacks a systemic guide and decision-making. In this work, we propose a strategy of selecting templates through expanding the recognition width for the improvement of class-selectivity. First, three families of genotoxic impurity (GTI) were selected as model objects, and the spatial size and binding energy of each GTI-monomer complexes were obtained and compared by computational simulation. The two indexes of energy width (W_E) and size width (W_L) were introduced to compare the similarity and differences on the two recognition factors, binding strength and spatial size, among these GTIs in each family. Through shortening the width to increase similarity on binding energy and size, the dual templates in the aromatic amines (AI) family and sulfonic acid esters (SI) family were successfully selected. Correspondingly, the prepared dual-template MIPs in the two GTI families can simultaneously recognize all the GTIs comparing with that of single template MIP, respectively. Meanwhile, through comparing the adsorption capacity of the selected template and its analogues in one GTI family, the recognition efficiency of the dual-template MIPs was higher than that of the single-template MIP. This indicates that though using the selected right templates, the higher class-selectivity and the larger recognition width can be realized. Thus, this work can solve the problem of blind template selection, and provide the useful theoretical guidance for designing family-selective molecular imprinting.

Trace-Level Determination of Triazole Fungicides Using Effervescence-Assisted Liquid-Liquid Microextraction Based on Ternary Deep Eutectic Solvent Prior to High-Performance Liquid Chromatography

A simple and sensitive preconcentration method, namely, effervescence-assisted liquid-liquid microextraction based on the ternary deep eutectic solvent method, was developed for enrichment of triazole fungicide residues prior to their determination by high-performance liquid chromatography coupled with UV detection. In this method, a ternary deep eutectic solvent (as extractant) was prepared by combination of octanoic acid, decanoic acid, and dodecanoic acid. The solution was well dispersed with sodium bicarbonate (as effervescence powder) without using auxiliary devices. In order to obtain relatively high extraction efficiency, analytical parameters were investigated and optimized. Under optimum conditions, the proposed method showed good linearity within the range of 1-1000 μg L^-1 with a coefficient for determination (R²) greater than 0.997. The low limits of detection (LODs) were in the range of 0.3-1.0 μg L^-1. The precisions were assessed from the relative standard deviations (RSDs) of retention time and peak area obtained from intra- (n = 3) and inter-day (n = 5 × 5) experiments, which were greater than 1.21 and 4.79%, respectively. Moreover, the proposed method provided high enrichment factors ranging from 112 to 142 folds. A matrix-match calibration method was used for analysis of real samples. Finally, the developed method was successfully applied for determination of the triazole fungicide in environmental water (near agricultural area), honey, and bean samples, and it represents a promising alternative method for analysis of triazoles. The recoveries of the studied triazoles were obtained in the range of 82-106% with an RSD less than 4.89.

Urea-based magnetic porous organic frameworks as novel adsorbent for the enrichment of phenylurea herbicides in foods

A novel urea-based magnetic porous organic frameworks Fe₃O₄@UPOFs (ETTA-PPDI) was synthesized by a simple polymerization reaction under mild conditions. The adsorbent displayed desirable adsorption performance for phenylurea herbicides (PUHs) with optimized adsorption time of only 4 min. The adsorption capacities of the adsorbent for PUHs ranged from 47.30 to 111.93 mg g^-1. A magnetic solid-phase extraction based on Fe₃O₄@UPOFs combined with high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) was established for the efficient determination of six PUHs in food samples (wheat, edible oil and cucumber), with determination coefficient (R²) ≥ 0.9972. The LODs of the method were in the range of 0.003-0.07 μg kg^-1 and recoveries ranged from 82.00 to 112.53%. The relative standard deviations were lower than 6.7%. The newly prepared adsorbent displayed great application prospects for the efficient enrichment of trace phenylurea herbicides in complex food matrices.

Efficient analyses of triazole fungicides in water, honey and soy milk samples by popping candy-generated CO2 and sugaring-out-assisted supramolecular solvent-based microextraction prior to HPLC determinations

An enrichment method, namely popping candy-generated CO₂ and sugaring-out-assisted supramolecular solvent-based microextraction (PGS-SUPRA), was investigated for the determination of triazole fungicide residues in water, honey and soy milk samples. The extraction process was carried out by adding popping candies into a centrifuge tube. Consequently, rapid dispersion and mass transfer of extractants can be achieved without using dispersants and auxiliary devices, and therefore, the extraction efficiency increased. The extraction parameters affecting the efficiency of the developed method were investigated. The presented method was then analysed by high-performance liquid chromatography. Under the selected condition, the wide linearity of triazole fungicides after preconcentration by the proposed microextraction method ranged from 30 to 1000 μg L^-1 for triadimefon and from 90 to 1000 μg L^-1 for myclobutanil, tebuconazole and hexaconazole, with a coefficient for determination (R ²) greater than 0.992. The limits of detection (LODs) and limits of quantitation (LOQs) were in the range of 10-30 μg L^-1 and 30-90 μg L^-1, respectively. The precisions were assessed from the relative standard deviations (RSDs) of the retention time and peak area obtained from intra- (n = 3) and inter-day (n = 3 × 5) experiments, and were greater than 1.66% and 13.52%, respectively. Moreover, the proposed method provided high enhancement factors (EnFs) ranging from 14 to 51 folds. This technique has been prosperously applied for the extraction of fungicide residues in water, honey and soy milk samples with a recovery within the range of 60-114%. Overall, the developed method was found to be advantageous as compared with other sample preparation methods.

Sodium-Alginate-Functionalized Silver Nanoparticles for Colorimetric Detection of Dimethoate

Sodium alginate (SA) was used to functionalize the surfaces of silver nanoparticles (AgNPs) to form SA-AgNPs for sensing dimethoate with a rapid and sensitive visual readout. UV-Vis spectrophotometry, Fourier transform infrared spectroscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and zeta potential measurements were used to characterize SA-AgNPs that were synthesized under the ideal conditions. SA-AgNPs were spherical with an average size of 14.6 nm. The stability of SA-AgNPs was investigated with changes in pH, salinity, and storage time. This colorimetric assay of dimethoate relied on the change in the absorption ratio (A₄₇₅/A₄₀₀) of SA-AgNPs, resulting in their aggregation caused by dimethoate, leading to a visual change for SA-AgNPs from yellow to pale yellow. As a result, the absorption ratio (A₄₇₅/A₄₀₀) of SA-AgNPs showed good linearity in the range of 0.05 to 2.0 ppm (R² = 0.9986) with a limit of detection (LOD) of 30 ppb. Adding other pesticides did not significantly change the absorption ratio of SA-AgNPs, indicating its high selectivity as a colorimetric assay. The sensor was successfully used to detect dimethoate in actual water samples.

Acetylcholinesterase-Cu3(PO4)2 hybrid nanoflowers for electrochemical detection of dichlorvos using square-wave voltammetry

Immobilization of enzymes is one of the key steps in the development of high-performance enzymatic electrochemical biosensors, and various nanostructured materials have been designed and developed to achieve this goal. Herein, hybrid nanoflowers (HNFs) were synthesized using acetylcholinesterase (AChE) as an organic component and copper phosphate (Cu₃(PO₄)₂) as an inorganic component. These AChE-Cu₃(PO₄)₂ HNFs exhibit a three-dimensional hierarchical flower-like structure, which not only has a large specific surface area but also promotes the affinity between AChE and its substrate with better catalytic activity. Not only that, the surface modification of the glassy carbon electrode (GCE) by the joint use of gold nanoparticles (AuNPs) and graphene oxide (GO) extended the electroactive area. Using square-wave voltammetry (SWV), the as-prepared biosensor (i.e., AChE-Cu₃(PO₄)₂ HNF/AuNP/GO/GCE) demonstrated superior sensing performance in the detection of dichlorvos. The detection limit is as low as 0.07 pM, and the linear detection range can range from 0.5 pM to 10 μM. In addition, the biosensor was feasible in real agricultural samples with satisfactory recoveries (98.65% to 103.43%). The reported biosensor provides an alternative tool for the direct measurements of AChE activity and its inhibition. Besides organophosphorus pesticides represented by dichlorvos, this biosensor has the potential to detect other AChE inhibitors, such as carbamate pesticides, drugs for Alzheimer's disease, etc., thus having broader applications in food safety and drug screening.

Modified Peanut Shell as an Eco-Friendly Biosorbent for Effective Extraction of Triazole Fungicide Residues in Surface Water and Honey Samples before Their Determination by High-Performance Liquid Chromatography

An eco-friendly sample preparation method that is based on the use of a modified peanut shell as an efficient biosorbent for the extraction of triazole residues before their analysis by high-performance liquid chromatography was reported. The four triazole fungicides were separated on a Purospher STAR RP-18 endcapped (4.6 × 150 mm, 5 μm) column with a mobile phase of 50% (v/v) acetonitrile at a flow rate of 1.0 mL min^-1 and detection wavelength set at 220 nm. Peanut shells modified by didodecyldimethylammonium bromide were selected as an effective biosorbent material in the microextraction method. Scanning electron microscopy, transmission electron microscopy, and Fourier transform infrared spectroscopy were used to characterize the biosorbent. The effect of dominant parameters on the proposed microextraction method including the amount of sorbent, kind and concentration of surfactant, sodium hydroxide concentration, kind and amount of salt, sample volume, adsorption time, kind and volume desorption solvent, and desorption time was studied. Under the optimum condition, a good analytical performance for the proposed microextraction method was obtained with a wide linear range within the range of 9-1000 μg L^-1, and low limits of detection (0.03 μg L^-1 for all analytes) were obtained. Enrichment factors were achieved within the range of 30-51. The intra and interday precision values were evaluated in terms of percentage relative standard deviations (%RSD) and were less than 0.09 and 5.34% for the retention time and peak area, respectively. The proposed microextraction methods were used for extraction and analysis of triazole fungicides in water and honey samples. The recoveries in a satisfactory range of 70.0-118.8% were obtained.

Simultaneous Preconcentration of Triazole Fungicide Residues Using In-Situ Coacervative Extraction Based on a Double-Solvent Supramolecular System Prior to High Performance Liquid Chromatographic Analysis

An in situ coacervative extraction (IS-CAE) based on a double-solvent supramolecular system coupled to liquid–liquid microextraction is investigated for extraction and enrichment of triazole fungicides. The formation of a double-solvent supramolecular system was generated by in situ formation and used as an extraction solvent for the coacervative extraction method. No disperser solvent was required. This new double-solvent supramolecular system has a higher extraction ability than any of its components alone. The different factors that could affect the extraction capability were studied and optimized, including the type of double extractant and its volume, salt addition, vortex time, and centrifugation time. Under optimum extraction conditions, this method provides high enrichment factors (EFs) of 73–318 with low limits of detection (LODs) of 0.3–1 μg L⁻¹ and limits of quantitation (LOQs) of 1–3 μg L⁻¹. In addition, the proposed method was prosperously applied for the determination of triazole fungicides in water, fruit juice, and soy milk samples.

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^-1, 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^-1. Under the optimized MSPE-HPLC conditions, the entire developed procedure provided a wide linear range between 0.015 and 1000 μg L^-1, low limits of detection, and limits of quantitation ranging from 0.005 to 0.090 and 0.015-0.300 μg L^-1, 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.

Multiclass Pesticide Residues in Fruits and Vegetables from Brazil: A Systematic Review of Sample Preparation Until Post-Harvest

Brazil annually produces around 43 million tons of fruits and vegetables. Therefore, large amounts of pesticides are needed to grow these foods. The use of unauthorized or indiscriminate pesticides can lead to the adherence of residues of these compounds to the product in a concentration above the maximum residue limit (MRL). Pesticide residues (PRs) monitoring is a continuous challenge due to several factors influencing the detection of these compounds in the food matrix. Currently, several adaptations to conventional techniques have been developed to minimize these problems. This systematic review presents the main information obtained from 52 research articles, taken from five databases, on changes and advances in Brazil in sample preparation methods for determining PRs in fruits and vegetables in the last nine years. We cover the preexisting ones and some others that might be suitable alternatives approaches. In addition, we present a brief discussion on the monitoring of PRs in different Brazilian regions, and we found that residues belonging to the organophosphate and pyrethroid classes were detected more frequently. Approximately 67% of the residues detected are of irregular use in 28 types of fruits and vegetables commonly consumed and exported by Brazil.