Magnetic nanoparticles coated with poly(p-phenylenediamine-co-thiophene) as a sorbent for preconcentration of organophosphorus pesticides

Paper-based SERS chips for the rapid detection of thiram

A simple one-pot method is developed to prepare positively charged aggregated silver nanoparticles (a-AgNPs). The obtained a-AgNPs show strong localized surface plasmon resonance (LSPR) absorption, whose wavelength can be easily tuned to match the commonly used lasers in surface enhanced Raman scattering (SERS). Furthermore, the obtained a-AgNPs can be easily fabricated into paper-based SERS chips by filtering against a negatively charged filter membrane. On the basis, a convenient SERS sensor has been developed for the detection of thiram using a 785 nm handheld Raman spectrometer.

Surface-Functionalized Magnetic Silica-Malachite Tricomposite (Fe-M-Si tricomposite): A Promising Adsorbent for the Removal of Cypermethrin

This study assessed the efficacy of adsorption for eliminating the agricultural pesticide cypermethrin (CP) from wastewater using various adsorbents: silica, malachite, and magnetite. Magnetic nanocomposites (NCs) (with varying amounts of Fe3O4 0.1, 0.25, 0.5, 1.0, and 1.5 wt/wt %) were synthesized, including Fe3O4 nanoparticles (NPs), bicomposites, and tricomposites, calcined at 300 and 500 °C, and then tested for CP removal. The study was conducted in two phases, with the objective of initially assessing how effectively each individual NP performed and then evaluating how effectively the NCs performed when used for the adsorption of CP. Notably, the Fe3O4-malachite combination exhibited superior CP removal, with the 0.25-Fe-M NC achieving the highest adsorption at 635.4 mg/g. This success was attributed to the large surface area, magnetic properties of Fe3O4, and adsorption capabilities of malachite. The Brunauer-Emmett-Teller (BET) isotherm analysis indicated that the NCs had potential applications in adsorption and separation processes. The scanning electron microscopy and transmission electron microscopy revealed the spherical, irregular shaped morphology of the synthesized NPs and NCs. However, the X-ray diffraction (XRD) pattern of surface functionalized materials such as surface functionalized malachite [Cu2CO3(OH)2] with Fe3O4 and SiO2 may be complicated by the specific functionalization method used and the relative amounts and crystallographic orientations of each component. Therefore, careful interpretation and analysis of the XRD pattern, along with other techniques, are necessary for accurate identification and characterization of the functionalized material. The originality of this study lies in its comprehensive investigation of several adsorbents and NCs for CP removal at neutral pH. The innovation stems from the synergistic action of Fe3O4 and malachite, which results in improved CP removal due to their combined surface properties and magnetic characteristics. The application of magnetic NCs in adsorption and separation, as validated by BET isotherm analysis, highlights the potential breakthrough in addressing pesticide contamination.

Voltammetric sensing of Cd(II) at ZIF-8/GO modified electrode: Optimization and field measurements

In this work, a metal-organic framework/graphene oxide (MOF(ZIF-8)/GO) nanocomposite was utilized for the electroanalysis of trace level of Cd(II) after modification of a cheap graphite rod electrode (GRE). After closed circuit process on the modified electrode, the differential pulse anodic stripping voltammetry (DPASV) technique was used for measuring of Cd(II). In optimal conditions, the sensor showed a linear dependence of current with concentration range 0.1-30 ppb for Cd(II). Moreover, limit of detection 0.03 ppb were obtained. Besides good selectivity, the sensor also indicated good reproducibility (below 5%). Moreover, the sensor showed satisfactory sensing performance in river, dam and wastewater samples with recovery ranging from 97.2% to 102.4%. Additionally, possible interfering cations were examined, but no significant interference was found. For the detection of trace Cd(II) in real matrices, this sensor illustrated other good merits like high stability, rapidity and simplicity.

Ionic-liquid-based effervescence-enhanced magnetic solid-phase extraction for organophosphorus pesticide detection in water samples

Herein, an ionic-liquid-based effervescence-enhanced magnetic solid-phase extraction (ILE-MSPE) approach for the extraction/concentration of organophosphorus pesticides in waters is reported with high stability and portability for rapid sample pretreatment in the field. The ionic-liquid-based magnetic effervescent tablet, composed of magnetic nanoparticles (Fe₃O₄), sodium carbonate (Na₂CO₃) as an alkaline source, and an ionic liquid ([C₆MIM][PF₆]), played triple functions: extractant, dispersant, and retrieving agent. Based on the one-factor-at-a-time method, the important variables for the ILE-MSPE approach were optimized as follows: as an extractant, 70 μL of [C₆MIM][PF₆]; molar ratio of alkaline to acidic sources (Na₂CO₃ : H₂C₄H₄O₆) as 1 : 1; and mass of magnetic nanoparticles (MNPs) of 30 mg. By integrating HPLC-DAD detection, the ILE-MSPE approach offered the limits of detection of 0.14-0.22 μg L^-1 and fortified recoveries of 81.4-97.6% for three representative species (methamidophos, phoxim, and parathion) in water samples. The relative standard deviations were lower than 4.9% for both the intra-day and inter-day precision. Overall, the newly developed method is environmentally benign, time-saving, and feasible for outdoor application.

Chromatographic techniques for the analysis of organophosphate pesticides with their extraction approach: a review (2015-2020)

In agriculture, a wide range of OPPs has been employed to boost crop yield, quality, and storage life. However, due to the ever-increasing population and rapid urbanization, pesticide use has surged in recent years. These compounds are exceedingly poisonous to humans, and despite the fact that specific legislation prohibits their use, the frequency of toxic and/or fatal incidents, as well as current statistics, suggest that they are currently accessible. As a result, determining the exposure to these substances as well as their detection (and that of their metabolites) in different types of exposed samples has become a hot issue in terms of quality and safety concerns. However, developing tools for the evaluation of these substances is a critical challenge for laboratories. Various chromatographic-based methods reported in the period of 2015-2020 have been developed, which are summarized and critically reviewed in this article, including the extraction of the target OPPs from different kinds of matrices. A comparison among the extraction and analysis techniques has been made in the current review article.

Conductive Polymer-Based Nanocomposites as Powerful Sorbents: Design, Preparation and Extraction Applications

Conductive polymers as composite materials have been attracted tremendous attention due to their versatile and excellent features such as tunable conductivity, facile synthesis and fabrication, high chemical and thermal stability etc. These characteristics make them versatile and let them being used in numerous fields including microelectronics, optics and biosensors. Throughout the mentioned fields, conductive polymers particularly perform as effective sorbents. Although tremendous efforts have been put into this topic, to the best of our knowledge, a comprehensive up-to-date review on the applications of conductive polymers as efficient sorbents has not been reported. The main objective of this paper is to make a significant contribution to the recent literature toward the synthesis and extraction applications of conductive polymers as efficient sorbents.

Counter Current Salting-out Homogenous Liquid-liquid Extraction and Dispersion Liquid-liquid Microextraction Based on the Solidification of Floating Organic Drop Followed by High-performance Liquid Chromatography for the Isolation and Preconcentration of Pesticides from Fruit Samples

BACKGROUND

Pesticides are widely used to control pests and prevent diseases in crops, including cereals, vegetables, and fruits. Due to factors such as the persistence of pesticides, bioaccumulation, and potential toxicity, the pesticide residues monitoring in foodstuffs is very important.

OBJECTIVE

In the current research, we proposed a novel approach to counter current salting-out homogenous liquid-liquid extraction (CCSHLLE) combined with dispersive liquid-liquid microextraction based on the solidification of floating organic drop (DLLME-SFO) in pesticides from aqueous samples for the isolation and preconcentration, which were evaluated prior to analysis as real samples by high-performance liquid chromatography-ultraviolet detection (HPLC-UV).

METHODS

In brief, sodium chloride was applied as a separation reagent, which is filled in a small glass column, through which a combination of an aqueous solution (here we could say as juice of fruit) and passing of acetonitrile. In this process, the droplets rose through the column and a separated layer would be formed on what has remained from aqueous phase. Following that, acetonitrile as the organic phase combined with 50.0 µL of extraction solvent. To further enrich the analytes, the mixture was injected into five milliliters of a 4% sodium chloride solution and placed in a tube for the DLLME-SFO.

RESULTS

Under optimal conditions, the dynamic linear range of 0.5-500 μg/L, extraction recovery of 65-85%, enrichment factors of 108-142, and limit of detection as 0.2-0.4 μg/L were obtained for the organophosphorus pesticides. In addition, the repeatability and reproducibility in the five replicate of the pesticides measurements (100 μg/L) are within the ranges of 3.5-5.1% and 4.5-6.3%, respectively.

Sensitive and selective determination of imidacloprid with magnetic molecularly imprinted polymer by using LC/Q-TOF/MS

In this paper, magnetic-molecularly imprinted polymer was used for the preconcentration of trace levels of imidacloprid in water and apple samples prior to liquid chromatography-quadrupole-time-of-flight mass spectrometric determination. The selectivity of the magnetic polymer was united with the sensitivity and the high resolving power of the chromatographic system. The developed method showed a linear range from 10.0 to 500.0 µg/L. The quantitative recoveries were obtained for water and apple samples in the range of 92.0%–99.0 %. The relative standard deviations of intra-day and inter-day tests were found to be in the range of 0.8%–1.2% and 1.2%–1.6 %, respectively. In addition, the same magnetic-molecularly imprinted polymer (MMIP) can be used at least ten cycles for the determination of imidacloprid. The preconcentration factor of the method was found to be 2.5, and the total preconcentration procedure can be completed in 1 h. Characterization of synthesised particles were executed with various techniques. Due to its suitable limit of detection, dynamic linear range, sensitivity and selectivity, the developed method seemed to be ideal for the determination and preconcentration of imidacloprid in water and fruit samples.

Simultaneous determination of organophosphorus pesticides residues in vegetable, fruit juice, and milk samples with magnetic dispersive micro solid-phase extraction and chromatographic method; recruitment of simplex lattice mixture design for optimization of novel sorbent composites

Dispersive micro solid-phase extraction procedure using a novel and selective sorbent prepared from four components was developed as a sample preparation strategy for extracting five organophosphorus pesticides, including fenitrothion, malathion, ethion, and chlorpyrifos, and diazinon in several vegetables, fruit juices, and cow's milk samples. Due to the high importance of the sorbent in the microextraction process, the percentages of sorbent components, including metal-organic framework (ZIF-67), chitosan, magnetic Fe₃O₄ nanoparticles, and silica nanoparticles, were optimized by a simplex lattice mixture design. After optimizing the sorbent composite, effective parameters on the extraction of organophosphorus pesticides were optimized using a definitive screening design and Box-Behnken design, respectively. A surfactant (Triton X100) as a dispersion agent with a low volume (10 μL) was utilized in the microextraction procedure to reduce the sorbent dispersion time and increase the sorbent dispersion efficiency. Under the optimal conditions, linearity for the determination of fenitrothion, malathion, ethion, chlorpyrifos, and diazinon was in the concentration ranges of 0.13-1100, 0.27-1000, 0.38-1000, 0.21-1200, and 0.11-1100 ng mL^-1 with a determination coefficient higher than 0.9906, respectively. The quantitation limits, detection limits, and relative standard deviations (n = 5) were lower than 0.38 ng mL^-1, 0.11 ng mL^-1, and 4.59% for the determination of organophosphorus pesticides. The method application for measuring OPPs on cucumber, carrot, tomato, apple juice, orange juice, and cow's milk indicated the presence of residual amounts of malathion in a cucumber sample, diazinon in a carrot sample, and chlorpyrifos in a tomato sample.

Fabrication of Co3O4 quantum dot incorporated polyacrylamide ethylene glycol dimethacrylate as a new fiber for solid phase microextraction and trace determination of organophosphorus pesticides in environmental water samples

In this paper, a novel solid phase microextraction fiber based on Co₃O₄ quantum dot incorporated polyacrylamide-co-ethylene glycol dimethacrylate followed by corona discharge ion mobility spectrometry is presented for the trace determination of organophosphorus pesticides in environmental water samples. Ion mobility spectrometry is a comparatively inexpensive, well-known, robust, and easy to operate analytical instrument. This combination would provide a low-cost, fast, selective, and sensitive quantitative system for detection of organophosphorus pesticides. In order to obtain the best extraction efficiency, the optimization of parameters affecting this method was carried out. After optimization, a solution pH of 7.0, extraction temperature of 60 °C, adsorption temperature of 260 °C, extraction time of 30 min, stirring speed of 750 rpm, and ionic strength of 10% w/w were obtained. Consequently, the presented method showed low limits of detection (0.3-0.6 ng mL^-1), excellent enrichment factors (PF = 221-263), good linearity (R² > 0.995), and repeatabilities (intra-day: 3.4 to 4.8%) and (inter-day: 4.7 to 6.1%). The reproducibility (RSD% of fiber to fiber) was also investigated by analyzing three as-prepared fibers under the same conditions and was found to be less than 7.6%. Finally, the developed fiber was used for determination of organophosphorus pesticides in the field samples.

Organophosphorus pesticides extraction with polyvinyl alcohol coated magnetic graphene oxide particles and analysis by gas chromatography-mass spectrometry: Application to apple juice and environmental water

In this study, we synthesized, characterized the magnetic graphene oxide coated with polyvinyl alcohol (PVA@MGO), and used it as an adsorbent for the magnetic solid-phase extraction (MSPE) of organophosphorus pesticides (OPPs) residue in the apple juice and environmental water samples followed by gas chromatography-mass spectrometry (GC-MS) analysis. Effective factors on the extraction efficiency, including the adsorbent dosage, desorption conditions, sample pH, extraction and desorption time, and ionic strength were optimized. The dynamic range of the MSPE-GC-MS method was obtained in the concentration range of 0.07-500 ng mL^-1 OPPs with the limits of detection (LODs) in the range of 20-80 pg mL^-1. Also, the intra- and inter-day precisions were determined to be in the range of 3.3-5.7% and 5.9-8.2%. The relative recoveries of pesticides for spiked real water samples and apple juice were in the range of 94.5 and 107.1%, with relative standard deviations between 2.6 and 6.5%. These results propose that the PVA@MGO is appropriate for simultaneous determination and high throughput analysis of OPPs residues.

Greenness of magnetic nanomaterials in miniaturized extraction techniques: A review

Green analytical chemistry principles should be followed, as much as possible, and particularly during the development of analytical sample preparation methods. In the past few years, outstanding materials such as ionic liquids, metal-organic frameworks, carbonaceous materials, molecularly imprinted materials, and many others, have been introduced in a wide variety of miniaturized techniques in order to reduce the amount of solvents and sorbents required during the analytical sample preparation step while pursuing more efficient extraction methods. Among them, magnetic nanomaterials (MNMs) have gained special attention due to their versatile properties. Mainly, their ability to be separated from the sample matrix using an external magnetic field (thus enormously simplifying the entire process) and their easy combination with other materials, which implies the inclusion of a countless number of different functionalities, highly specific in some cases. Therefore, MNMs can be used as sorbents or as magnetic support for other materials which do not have magnetic properties, the latter permiting their combination with novel materials. The greenness of these magnetic sorbents in miniaturized extractions techniques is generally demonstrated in terms of their ease of separation and amount of sorbent required, while the nature of the material itself is left unnoticed. However, the synthesis of MNMs is not always as green as their applications, and the resulting MNMs are not always as safe as desired. Is the analytical sample preparation field ready for using green magnetic nanomaterials? This review offers an overview, from a green analytical chemistry perspective, of the current state of the use of MNMs as sorbents in microextraction strategies, their preparation, and the analytical performance offered, together with a critical discussion on where efforts should go.

Immobilization of synthesized phenyl-enriched magnetic nanoparticles in a fabricated Y-Y shaped micro-channel containing microscaled hedges as a microextraction platform

In this survey, a reliable and applicable Y-Y shaped micro-channel in a microfluidic device was designed and manufactured. A number of micro-scaled hedges were precisely fabricated inside the micro-channel to facilitate the immobilization of synthesized core-shell Fe₃O₄@SiO₂ magnetic nanoparticles (MNPs), functionalized by triethoxyphenylsilane (TEPS) by sol-gel technique. Both sample and reagents were introduced into the microfluidic device by a syringe pump to perform the extraction and desorption steps. The functionalized MNPs were characterized by transmission electron microscopy, X-ray diffraction spectroscopy and Fourier transform infrared spectroscopy. By adopting the strategy of extraction-on-chip using this microfluidic device, we were benefited from implementing the entire analyses with the minimum amount of desorbing solvent, MNPs, and aqueous/fruit juice samples. In contrast to dispersive solid phase extraction, dispersion of MNPs during experiment is prevented by fabrication of micro-scaled hedges in the micro-channel. Consequently the stabilized MNPs are reused for the entire runs. The microfluidic device was successfully exploited as an efficient extracting plateau to evaluate the extraction/desorption capability in analysis of some organophosphorus pesticides (OPPs) as model compounds. Our results indicate that the functionalization of Fe₃O₄@SiO₂ with TEPS, improved their extraction capability due to the existence of phenyl and hydroxyl groups for more efficient π-π and hydrogen bonding interactions. Eventually, μL-scale of the organic solvent was injected into a gas chromatography-mass spectrometry system. The limits of detection (3S_b) and quantification (10S_b) for the OPPs were 0.03-0.1 and 0.1-0.35 ng mL^-1, respectively. In addition, the interday and intraday precisions were lower than 5.3% (n = 3). The obtained recovery was 95-99% for water samples and 88-96% for fruit juice samples while satisfactory regression coefficients of 0.9949-0.9991, could be achieved.

Rapid colorimetric determination of the pesticides carbofuran and dichlorvos by exploiting their inhibitory effect on the aggregation of peroxidase-mimicking platinum nanoparticles

A novel and highly sensitive enzyme inhibition assay was developed for the rapid detection of the organophosphate pesticide dichlorvos and the carbamate pesticide carbofuran. It achieves signal amplification by the secondary catalysis of platinum nanoparticles. Acetylcholinesterase (AChE) is capable of catalyzing the hydrolysis of acetylthiocholine to form thiocholine. Thiocholine causes the aggregation of citrate-capped platinum nanoparticles which then lose their peroxidase-mimicking properties. After addition of pesticides, the activity of AChE is inhibited, less thiocholine is produced, less aggregation occurs, and the peroxidase-mimetic properties are increasingly retained. In the presence of tetramethylbenzidine and H₂O₂, a deep blue coloration with an absorption maximum at 650 nm will be formed. The assay was applied to the determination of dichlorvos and carbofuran, and detection limits of 2.3 μg·L^-1 and 1.4 μg·L^-1 were obtained, respectively. Recovery experiments with spiked tap water and pears gave satisfactory relative standard deviations. Graphical abstract The blue product formed by platinum nanoparticle-catalyzed oxidation of 3,3'5,5'-tetramethylbenzidine (TMB) by H₂O₂ is reduced if acetylthiocholine (ATCh) is hydrolyzed by acetylcholinesterase (AChE) to form thiocholine. However, if AChE is inhibited by pesticides, color formation will recover.

A highly sensitive and low-background fluorescence assay for pesticides residues based on hybridization chain reaction amplification assisted by magnetic separation

Due to the concern over food safety, it is important to detect the pesticides residues in agricultural products. Here, a highly sensitive and low background fluorescent strategy for the detection of pesticides residues has been developed. The fluorescence intensity of N-methyl mesoporphyrin IX (NMM) binding G-quadruplex could be turn off because of inhibiting effect of the pesticides on the acetylcholinesterase (AChE) activity. For that, four single-stranded DNAs (named linker, trigger, H1 and H2, respectively) are rational designed and T-Hg-T mismatches duplex DNAs as a recognizer combined with the separation of magnetic beads. The design of hybridization chain reaction (HCR) amplification strategy assisted by magnetic separation has been adopted to improve the detection sensitivity. In the presence of pesticides, the amount of the thiol group generated by hydrolysis reaction of acetylcholine (ACh) is reduced, lead to release of less trigger DNA. Therefor subsequent HCR process is retarded with decreased fluorescence intensity. The reduced fluorescence intensity has a quantitative relationship with the pesticide concentration. The limit of detection of chlorpyrifos was estimated to be 2.0 ng ml-1. It has been applied to detect the pesticides residues in real samples.

Porous magnetized carbon sheet nanocomposites for dispersive solid-phase microextraction of organophosphorus pesticides prior to analysis by gas chromatography-ion mobility spectrometry

Carbon sheets were attached to magnetite (Fe₃O₄) nanoparticles. The resulting nanocomposite is shown to be a viable sorbent for use in magnetic dispersive solid-phase microextraction of three organophosphorus pesticides. The sorbent was synthesized via the sol-gel process followed by calcination and was characterized by an X-ray diffractometer, field emission scanning electron microscopy and energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, and Raman spectrometry techniques. The affecting parameters in the adsorption and desorption steps were assessed and optimized via response surface methodology. Following desorption with dichloromethane, the OPPs were quantified by gas chromatography along with ion mobility spectrometry detection. Under optimized conditions, the limits of detection were 1.00, 0.46 and 0.85 μg L^-1 for fenthion, malathion and chlorpyrifos, respectively. Response is linear in the concentration range of 2-500 μg L^-1 for fenthion and malathion, and 2-1000 μg L^-1 for chlorpyrifos with the determination coefficient larger than 0.9969. The intra-day and inter-day precision were from 3 to 9% and 5 to 16%, respectively. The enrichment factor was greater than 142 for all the studied pesticides. The sorbent was used for analyze spiked water and vegetable samples and gave relative recovery higher than 82%. Graphical abstract A flowchart of the synthesis of porous magnetized carbon sheet nanocomposites and the process of the magnetic dispersive solid-phase microextraction (MD-μ-SPE) of three organophosphorus pesticides prior to analysis by gas chromatography-ion mobility spectrometry (GC-IMS).

Poly(pyrrole-co-aniline)@graphene oxide/Fe3O4 sorbent for the extraction and preconcentration of polycyclic aromatic hydrocarbons from water samples

In this work, the extraction of polycyclic aromatic hydrocarbons (PAHs) with an efficient poly(pyrrole-co-aniline)@graphene oxide/Fe₃O₄ [poly(Py-co-Ani)@GO–Fe₃O₄] nanocomposite followed by GC-FID is presented.