Magnetic graphene solid-phase extraction for the determination of carbamate pesticides in tomatoes coupled with high performance liquid chromatography

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.

Graphene-based nanomaterials as potential candidates for environmental mitigation of pesticides

Over the years, bioaccumulation of hazardous chemicals in the food chain has become a critical issue, resulting in numerous health risks. Environmental mitigation aims to clean up contaminated sites and eliminate hazardous materials from the air, water, or soil to restore the site to its original and safe condition. Pesticides constitute one of the most dangerous environmental pollutants which are generally used to increase crop production. Addressing the removal or treatment of pesticides has become pivotal in mitigating environmental threats. Diverse remediation methods are employed to protect the environment and public health. Graphene-based materials have emerged as promising candidates with exceptional properties, including excellent adsorption capacity due to their high surface area, strong hydrophilicity, and tunable properties. Owing to these properties, they have been attracting major research attention in the field of design and fabrication of materials for the mitigation of pesticides from the environment such as from contaminated food, water and other samples. Various physical, chemical and biological extraction techniques are adopted to remove pesticides. This review article provides an insight into the potential role of graphene-based materials in the environmental remediation of pesticides. We have focused on the removal of Organophosphates, Organochlorines, Carbamates and Pyrethroids present in water, fruit, vegetable and other samples, highlighting the urgent need for environmental remediation. While graphene-based materials hold potential for pesticide remediation, addressing challenges in scalable production, assessing long-term sustainability, and mitigating potential environmental impacts are critical steps for successful large-scale applications.

Low transition temperature mixture-based extraction of 14 pesticides from tomato samples and their high-performance liquid chromatography-tandem mass spectrometry analysis

The extensive use of pesticides to control pest infestations has led to the development of analytical methods to determine pesticide residues in food matrices to prevent food exposure. However, most developed analytical methods do not consider impact on the environment in terms of the toxicity of the chemicals used and the amount of waste produced. An environmentally-friendly method, based on a miniaturized matrix solid-phase dispersion followed by high-performance liquid chromatography-tandem mass spectrometry, for the analysis of fourteen pesticides in tomatoes, was exploited. For the recovery of pesticides from tomato samples, a low transition temperature mixture (LTTM), containing choline chloride and sesamol 1:3 molar ratio, was employed. Extraction parameters like sample-to-dispersant ratio, extraction solvent volume and LTTM volume were optimized through a Box-Behnken design. The 1:4 sample-to-dispersant ratio, 900 µL of ethanol as extraction solvent and 50 µL of LTTM ensured the best result considering the pesticides' peak areas. The optimized analytical method was validated obtaining the following results: linearity range was between LOQ and 5 mg kg-1 with a minimum R2 of 0.9944 for tebufenozide, values in the range of 0.001-0.023 and 0.004-0.076 mg kg-1 were obtained for LOD and LOQ respectively, while peak areas intra-day and inter-day repeatability were maximum of 10.19 and 9.15 %, respectively. The analytical method was then applied to real samples studying whole, pulp and peel tomato pool. The analysis of whole and tomato pulp revealed the presence of seven and eight of the fourteen investigated pesticides, respectively. However, their concentration was lower than the limit of quantification. In tomato peel, five pesticides, namely dimethomorph, methoxyfenozide, pyraclostrobin, pyriproxyfen, and spiromesifen were quantified and their concentrations were below maximum residue levels.

Exploration of anode candidacy of Ni0.2Co2.8O4 and integrated Ni0.2Co2.8O4/MWCNTs in supercapacitor and oxygen evolution reaction

In the current research work, Ni0.2Co2.8O4 and Ni0.2Co2.8/MWCNTs have been synthesized via facile sol-gel and wet impregnation method. The synthesized materials attained the crystalline structures as evident from X-ray diffraction analysis (XRD). The uniform morphology and well dispersion of Ni0.2Co2.8O4 onto MWCNTs was observed via scanning electron microscopy (SEM). The electrochemical investigations for supercapacitor application by cyclic voltammetry (CV), galvanostatic charge discharge (GCD), and electrochemical impedance spectroscopy (EIS) revealed that, among both materials, Ni0.2Co2.8O4/MWCNTs has high specific capacitance (CV; 505.8 Fg-1 at 5 mV/s, GCD; 1598 Fg-1 at 0.5 A/g), greater capacitance retention (85 %) at 1000 cycles and has lower charge transfer resistance (Rct; 3.48 Ω cm2). These findings reflected the potential candidacy of Ni0.2Co2.8O4/MWCNTs to be used as anode material in supercapacitor. Further investigations by CV and linear sweep voltammetry (LSV) for oxygen evolution reaction (OER) activity in 1.0 M KOH showed comparatively low over potential of 340 mV @100 mA/cm2 for the same integrated material. Additionally, the lower Tafel slope (47 mV/dec) and solution resistance authenticated it as an appropriate electrocatalyst for OER in water splitting. The CPE (controlled potential electrolysis) revealed the stability of both materials for OER in water oxidation.

Multifunctional Ni-NPC Single-Atom Nanozyme for Removal and Smartphone-Assisted Visualization Monitoring of Carbamate Pesticides

A multifunctional single-atom nanozyme, denoted as 3D Ni,N-codoped porous carbon (Ni-NPC), was devised that exhibits remarkable adsorption capabilities and a repertoire of enzyme mimetic functions (oxidase- and peroxidase-like). These attributes stem from the distinctive mesoporous thin-shell structure and well-dispersed Ni sites. The efficient adsorption capacity of Ni-NPC was assessed with respect to three carbamate pesticides (CMPs): metolcarb, carbaryl, and isoprocarb. Moreover, a colorimetric detection method for CMP was established based on its robust peroxidase-like catalytic activity and sequential catalytic interactions with acetylcholinesterase. Furthermore, a portable colorimetric sensor based on a hydrogel sphere integrated with a smartphone platform was devised. This sensor enables rapid, on-site, and quantitative assessment of CMP, boasting an extraordinarily low detection limit of 1.5 ng mL-1. Notably, this sensor was successfully applied to the analysis of CMP levels in lake water and vegetable samples (pakchoi and rape), propelling the progress of real-time detection technologies in food and environment monitoring.

Preparation of novel Zn-Al layered double hydroxide composite as adsorbent for removal of organophosphorus insecticides from water

In this work, a new and efficient composite LDH with high adsorption power using layered double hydroxide (LDH), 2,4-toluene diisocyanate (TDI), and tris (hydroxymethyl) aminomethane (THAM) was designed and prepared, which was used as an adsorbent to adsorb diazinon from contaminated water. The chemical composition and morphology of the adsorbent were evaluated using Fourier transform infrared (FTIR), X-ray diffraction (XRD), thermal gravimetric analysis (TGA), Energy dispersive X-ray (EDX) and Field emission scanning electron microscopy (FESEM) techniques. Also, the optimal conditions for adsorption of diazinon from water were determined by LDH@TDI@THAM composite. Various parameters like the effect of adsorbent dosage, pH, concentration and contact time of diazinon were studied to determine the optimal adsorption conditions. Then, different isotherm models and kinetic adsorption were used to describe the equilibrium data and kinetic. Also, the maximum adsorption capacity is obtained when the pH of the solution is 7. The maximum adsorption capacity for LDH@TDI@THAM composite was 1000 mg/g at 65 °C and the negative values of ΔG indicate that the adsorption process is spontaneous. After that, studying the reusability of LDH@TDI@THAM composite showed that the removal of diazinon by LDH@TDI@THAM was possible for up to four periods without a significant decrease in performance.

In Silico Investigation of Selected Pesticides and Their Determination in Agricultural Products Using QuEChERS Methodology and HPLC-DAD

In this study, we considered some pesticides as active substances within formulations for the protection of plant-based food in the Republic of Serbia in silico, because these pesticides have not often been investigated in this way previously, and in an analytical way, because there are not very many available fast, cheap, and easy methods for their determination in real agricultural samples. Seven pesticides were detected in selected agricultural products (tomatoes, cucumbers, peppers, and grapes) using the QuEChERS methodology and HPLC-DAD. Standard curves for the investigated pesticides (chlorantraniliprole, methomyl, metalaxyl, thiacloprid, acetamiprid, emamectin benzoate, and cymoxanil) show good linearity, with R² values from 0.9785 to 0.9996. The HPLC-DAD method is fast, and these pesticides can be determined in real spiked samples in less than 15 min. We further characterized the pesticides we found in food based on physicochemical properties and molecular descriptors to predict the absorption, distribution, metabolism, elimination, and toxicity (ADMET) of the compounds. We summarized the data supporting their effects on humans using various computational tools to determine their potential adverse effects. The results of our prediction study show that all of the selected pesticides considered in this study have good oral bioavailability, and those with high toxicity, therefore, could be harmful to human health. Chlorantraniliprole was shown in a molecular docking study as a good starting point for a new Alzheimer's disease drug candidate.

A review on the pesticides in coffee: Usage, health effects, detection, and mitigation

Coffee is considered among the most popular beverages and is classified as the second most exported item worldwide. The presence of pesticides in this staple commodity is a challenge to import and export activities, in addition to the fact that pesticides are toxins of public health concern. Even if pesticides are applied properly and their residues are within the acceptable range, it is important to know the fate of these pesticides prior to their ingestion. A plethora of research has been done to optimize methods and thus to have valid procedures to test for the presence of pesticides in coffee. In this review, the analytical methods used in these articles to detect and quantify the pesticides in coffee beans, roasted coffee, and coffee infusion were identified. This review highlights as well the main factors that play a key role in having good separation, identification, and recovery of pesticide residues in the aforementioned items. In addition, the review explains the effect of pesticides on human health and the mitigation techniques for pesticide exposure.

Synthesis and Characterization of MWCNT-COOH/Fe3O4 and CNT-COOH/Fe3O4/NiO Nanocomposites: Assessment of Adsorption and Photocatalytic Performance

In this study the adsorption and photodegradation capabilities of modified multi-walled carbon nanotubes (MWCNTs), using tartrazine as a model pollutant, is demonstrated. MWCNT-COOH/Fe₃O₄ and MWCNT-COOH/Fe₃O₄/NiO nanocomposites were prepared by precipitation of metal oxides in the presence of MWCNTs. Their properties were examined by X-ray diffraction in powder (XRD), Fourier-transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), scanning electron microscopy (SEM), Raman spectroscopy, synchrotron-based Scanning PhotoElectron Microscopy (SPEM), and Brunauer-Emmett-Teller (BET) analysis. It was found that the optimal adsorption conditions were pH 4 for MWCNT-COOH/Fe₃O₄ and pH 3 for MWCNT-COOH/Fe₃O₄/NiO, temperature 25 °C, adsorbent dose 1 g L^-1, initial concentration of tartrazine 5 mg L^-1 for MWCNT-COOH/Fe₃O₄ and 10 mg L^-1 for MWCNT-COOH/Fe₃O₄/NiO and contact time 5 min for MWCNT-COOH/Fe₃O₄/NiO and 15 min for MWCNT-COOH/Fe₃O₄. Moreover, the predominant degradation process was elucidated simultaneously, with and without simulated sunlight irradiation, using thermal lens spectrometry (TLS) and UV-Vis absorption spectrophotometry. The results indicated the prevalence of the photodegradation mechanism over adsorption from the beginning of the degradation process.

Sample Preparation Methods for Metal Containing Pesticides in Food and Environmental Samples

Metal-containing pesticides are used in many areas for purposes such as harvest efficiency and keeping pests away from the vegetable environment. Metal-containing pesticides are in the form of dithiocarbamate complexes and are named differently according to the type of metal they contain and are used for different purposes. Since the presence of these pesticides even at residue level threatens human and environmental health, their determination at trace level is important. In this review, studies on the determination of metal-containing dithiocarbamate pesticides in different matrices are discussed. This review on the analysis of dithiocarbamate pesticides with different techniques will shed light on the studies to be carried out for the determination of these pesticides one by one in different matrices.

Efficient Extraction and Determination of Carbamate Pesticides in Vegetables Based on a Covalent Organic Frameworks with Acylamide Sites

It is an important challenge to effectively extract and determine pesticides in complex samples. Covalent organic frameworks (COFs) are burgeoning porous crystalline organic materials with good environmental resistance, thus demonstrating great potential as adsorbents in contaminants detection. In this work, we design and synthesize a novel COF-TpDB via 1,3,5-triformylphloroglucinol (Tp) and 4,4'-diaminobenzoylanilide (DB) as well as its packed cartridge for solid phase extraction (SPE) of carbamate pesticides. Simulation calculations showed H-bonding facilitates the adsorption interactions between the carbamate pesticides and TpDB. A method was developed by coupling TpDB as SPE sorbents with high performance liquid chromatography-ultraviolet (HPLC-UV) detection to determine trace carbamate pesticides in vegetables. The established method showed a wide linear range of 0.1-200 ng mL^-1 and low limit of detections (0.005-0.05 ng mL^-1) for four carbamate pesticides. The applicability of TpDB as adsorbent was investigated for determination of trace carbamate pesticides residue in vegetables with satisfactory recoveries of four carbamates in the range of 80.4-101.2%. The results demonstrated that the COF-TpDB offer great potential for efficient extraction of carbamate pesticides from complicate matrices.

Iron nanoparticles decorated hierarchical carbon fiber forest for the magnetic solid-phase extraction of multi-pesticide residues from water samples

This study describes a versatile, robust and fast sample pre-concentration novel method based on chemical vapour deposition grown iron nanoparticles dispersed hierarchical carbon fiber forest (Fe-ACF/CNF) for the determination of multi-pesticide residue in water samples. This method was developed by the implementation of Fe-ACF/CNF to magnetic solid-phase extraction method (MSPE) for the adsorption of twenty-nine pesticides of various classes using gas chromatography equipped with an electron capture detector. Fe-ACF/CNF was grown via tip growth mechanism and Fe-nanoparticles are moved to the tip of CNF. The presence of Fe-nanoparticles is responsible for the magnetic property of proposed adsorbents. The Fe-ACF/CNF is competent enough to extract twenty-nine pesticides of different physico-chemical characteristics from water samples. All the predominant parameters including the amount of sorbent desorption time, temperature, sonication effect, regeneration, and reusability of Fe-ACF/CNF were thoroughly investigated. Acceptable linearity was obtained in the range of 20-500 μg/L with a correlation coefficient value ≥ 0.990 for all pesticides. The accuracy of the developed method was evaluated and the obtained recovery of the spiked samples was within 70-120% (standard deviation ≤ 15%) and reusability up to the 4th cycle. The limit of detection and quantification values was in the range of 1.44-5.15 and 4.76-17.0 μg/L, respectively. The obtained results are also cross verified with real water samples from the Gomti river (Lucknow, India) and shown the excellent extraction efficiency of Fe-ACF/CNF.

Dissipation Dynamics, Terminal Residues and Dietary Risk Assessment of Two Isomers of Dimethacarb in Rice by HPLC-MS/MS

Dimethacarb is a carbamate insecticide developed in China that contains 3,5-dimethylphenyl methylcarbamate (XMC) and 3,4-dimethylphenyl methylcarbamate (MPMC) isomers. Dimethacarb has been registered for use in rice in China, but no residue or degradation of dimethacarb in rice has been reported and the maximum residue limits (MRLs) for rice have not been established. A versatile high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method was developed with modified QuEChERS sample preparation to determine two isomers of dimethacarb in rice. The average recovery of XMC and MPMC in brown rice, rice husk, and rice straw ranged from 71.69 to 100.60%, with spike levels of 0.01 to 1 mg/kg and relative standard deviations (RSDs) of 0.21 to 8.41%. Field experiments showed that the half-lives of XMC and MPMC in rice straw were 4.08 to 4.23 days and 3.48 to 3.69 days, respectively. Final residues of XMC and MPMC in rice husk after 21 days of spraying at six sites ranged from 0.23-2.65 mg/kg and 0.06-1.10 mg/kg, and <0.01-0.16 mg/kg and <0.01-0.04 mg/kg in brown rice. The ratio of XMC to MPMC content in the rice husk differed from the original 50% dimethacarb EC, indicating the difference in the degradation rate of XMC and MPMC. The estimated risk quotient (RQ) for both XMC and MPMC was less than 30%. These data for residues from six representative locations could provide a reference for establishing the MRL of dimethacarb in rice.

Covalent organic framework-LZU1@PEI@Fe3O4-based magnetic dispersive micro-solid phase extraction of tetracyclines from environmental water prior to HPLC analysis

In this work, COF-LZU1@PEI@Fe₃O₄ was synthesized by immobilization of COF-LZU1 onto the surface of polyethyleneimine-functionalized Fe₃O₄ nanoparticles (PEI@Fe₃O₄) and employed as an adsorbent for magnetic dispersive micro-solid phase extraction of tetracyclines (TCs). COF-LZU1@PEI@Fe₃O₄ was characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction and nitrogen adsorption-desorption isotherms analysis. The optimal extraction and desorption conditions were as follows: 15.00 mL sample solution (pH 7.0) extracted with 5.0 mg of adsorbent for 30 min at 30 °C, and then desorbed with 1.50 mL methanol/acetonitrile/0.02 mol L^-1 oxalic acid solution (v/v, 1 : 2 : 7). Good linearities were obtained between the peak area and TC concentration ranging from 5-500 μg L^-1 with correlation coefficients (R²) higher than 0.9992 and limits of detection lower than 0.51 μg L^-1. The relative standard deviations (RSDs) of intra-day and inter-day were less than 5.7% and 7.4%, respectively. The developed method was successfully applied to the determination of TCs in environmental water samples with recoveries in the range of 87.0-113.8% and RSDs less than 5.1%, suggesting great potential of COF-LZU1@PEI@Fe₃O₄ for efficient extraction and analysis of trace TCs in water samples.

Current overview and perspectives in environmentally friendly microextractions of carbamates and dithiocarbamates

Carbamates and dithiocarbamates are two classes of pesticides widely employed in the agriculture practice to control and avoid pests and weeds, hence, the monitoring of the residue of those pesticides in different foodstuff samples is important. Thus, this review presents the classification, chemical structure, use, and toxicology of them. Moreover, it was shown the evolution of liquid- and solid-phase microextractions employed in the extraction of carbamates and dithiocarbamates in water and foodstuff samples. The classification, operation mode, and application of the microextractions of liquid-phase and solid-phase used in their extraction were discussed and related to the analytical parameters and guidelines of green analytical chemistry.

1-Octyl-3-methylimidazolium hexafluorophosphate-functionalised magnetic poly β-cyclodextrin for magnetic solid-phase extraction ofpyrethroids from tea infusions

In this study, a novel sorbent, 1-octyl-3-methylimidazolium hexafluorophosphate functionalised magnetic poly β-cyclodextrin, was successfully synthesised and applied to magnetic solid-phase extraction for the determination of pyrethroids in tea infusions. The sorbent was characterised by transmission electron microscopy, energy-dispersive spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, vibrating sample magnetometer and Brunauer-Emmett-Teller measurement. All factors affecting extraction efficiency, such as sorbent amount, extraction time, ionic strength and desorption conditions, were optimised individually. Under the chosen conditions, wide linearity (2.5-500 μg L^-1) with determination coefficients ranging from 0.9995 to 0.9999, low limits of detection of 0.32-0.54 μg L^-1 and good precision (intra-day: 2.6-7.0%; inter-day: 3.5-7.6%) were achieved for four pyrethroids in tea infusions. The relative recoveries of target analytes in real tea infusion samples were from 70% to 101% with relative standard deviations lower than 9.1%. We conclude that the proposed method is promising in the detection of pyrethroids in tea infusions.

Development of immunochromatographic strips for the detection of dicofol

In this study, a monoclonal antibody (mAb) against dicofol was developed to prepare immunochromatographic strips (ICAs) for the detection of dicofol residues in fruit and vegetables. The mAb exhibited high affinity and high sensitivity, with an affinity constant of 2.96 × 10¹⁰ and a limit of detection of 3.142 ng mL^-1. A cross reactivity test revealed that the mAb also had good specificity for dicofol. This ICA method gave a visible limit of detection of 50 ng g^-1, and a cut-off value of 500 ng g^-1 for the detection of dicofol in both apple and cucumber with the naked eye. Importantly, the results here are consistent with results obtained using liquid chromatography mass spectrometry and ic-ELISAs indicating that this ICA method is reliable and practical when used for the detection of dicofol in fruit and vegetables.

Determination of 12 Carbamate Insecticides in Typical Vegetables and Fruits by Rapid Multi-Plug Filtration Cleanup and Ultra-Performance Liquid Chromatography/Tandem Mass Spectrometry Detection

A multiresidue method for determining 12 carbamate pesticides in purple cabbage, orange, watermelon, cucumber, cowpea and Lactuca sativa L. employing multi-plug filtration cleanup (m-PFC) and ultra-performance liquid chromatography coupled with electrospray ionization tandem mass spectrometry (UPLC-ESI-MS/MS) was developed. M-PFC was carried out by cleanup at dispersive solid phase extraction (d-SPE), one m-PFC tip-filtration, two m-PFC tip-filtration and other methods (1-3 m-PFC cleanups). Results demonstrated that filtration simplified the cleanup method compared with d-SPE and other m-PFC methods (1-3 m-PFC cleanups). The method validation results showed that the method was linear, selective and accurate. The limits of quantification (LOQs) were 0.05-5.0 μg/kg, and the recoveries were in the range of 70.1-119.9% in different matrices. Although matrix effects were observed, they were successfully compensated using matrix-matched calibration. Finally, the developed method was successfully applied to detect pesticides in real samples.

Magnetic Graphene Dispersive Solid-Phase Extraction for the Determination of Phthalic Acid Esters in Flavoring Essences by Gas Chromatography Tandem Mass Spectrometry

In the present study, a sensitive, efficient and repeatable method for the simultaneous extraction and determination of 13 types of phthalic acid esters (PAEs) in flavoring essence samples using magnetic graphene solid-phase extraction coupled with gas chromatography tandem mass spectrometry was developed. Due to the unique structure of magnetic graphene, it has several advantages, such as large surface area and fast separation ability. This unique structure not only provided strong magnetic responsiveness for the separation but also prevented the self-aggregation of graphene. The large delocalized p-electron system of graphene can form strong π-stacking interactions with the benzene ring. Thus, graphene may be also a good candidate adsorbent for the adsorption of benzenoid-form compounds. Several magnetic soild-phase extraction parameters, such as elution solvents, amounts of sorbents, enrichment time and desorption time were optimized. The optimized procedures for this method were performed by ultrasonication using ethyl acetate as elution solvent for 5 min. Under the optimal conditions, the developed method provided spiked recoveries of 75.0–105.3% with relative standard deviations of ~5.6% and limits of detection were 0.011–0.091 mg/kg. Good linear relationships were observed with the coefficient of determination (R2) &gt; 0.993 for all the analytes. Finally, the validated method was successfully applied to the analysis of PAEs in real samples.

Sol-gel fabrication and performance evaluation of graphene-based hydrophobic solid-phase microextraction fibers for multi-residue analysis of pesticides in water samples

Widespread use of organophosphorus pesticides poses serious environmental threats, and hence calls for effective analysis methods for these classes of compounds. In this study, a lab-made graphene-based solid-phase microextraction (SPME) fiber was fabricated by the sol-gel method and combined with a gas chromatography-flame photometry detector (GC-FPD) to realize the detection of trace OPPs in water samples. Compared to the commercial fiber coatings, the new sol-gel graphene fiber coatings showed advantages of good durability and solvent resistance, which were attributed to the hydrophobic and antibacterial properties of the functionalized graphene and 3-(trimethoxysilyl)propyldimethyloctadecylammonium chloride (QAS). A headspace SPME method in combination with a GC-FPD was established to evaluate the performance of the novel fibers. The proposed method showed a good linear relationship for the eight OPPs (R²≥ 0.9957) in the concentration range of 1 to 1000 μg L^-1, with limits of quantification of 0.11-3.37 μg L^-1 and limits of detection of 0.03-1.01 μg L^-1. Furthermore, the developed method also exhibited good recoveries for the analysis of OPPs both in rainwater and lake water, which demonstrates that this method is an alternative choice for multi-residue analysis of OPPs, and it has the potential for broader applications in the future.

Self-Assembled Three-Dimensional Microporous rGO/PNT/Fe3O4 Hydrogel Sorbent for Magnetic Preconcentration of Multi-Residue Insecticides

The purpose of this work was to develop a highly selective, sensitive, and reliable method for multi-residual analysis. A three-dimensional microporous reduced graphene oxide/polypyrrole nanotube/magnetite hydrogel (3D-rGOPFH) composite was synthesized and utilized as a magnetic solid-phase extraction (MSPE) sorbent to preconcentrate thirteen insecticides, including five organophosphorus (isocarbophos, quinalphos, phorate, chlorpyrifos, and phosalone), two carbamates (pirimor and carbaryl), two triazoles (myclobutanil and diniconazole), two pyrethroids (lambda-cyhalothrin and bifenthrin), and two organochlorines (2, 4′-DDT and mirex), from vegetables, followed by gas chromatography-tandem mass spectrometry. This method exhibited several major advantages, including simultaneous enrichment of different types of insecticides, no matrix effect, high sensitivity, and ease of operation. This is ascribed to the beneficial effects of 3D-rGOPFH, including the large specific surface (237 m2 g−1), multiple adsorption interactions (hydrogen bonding, electrostatic, π–π stacking and hydrophobic interaction force), appropriate pore size distribution (1–10 nm), and the good paramagnetic property. Under the optimal conditions, the analytical figures of merit were obtained as: linear dynamic range of 0.1–100 ng g−1 with determination coefficients of 0.9975–0.9998; limit of detections of 0.006–0.03 ng g−1; and the intra-day and inter-day relative standard deviations were 2.8–7.1% and 3.5–8.8%, respectively. Recoveries were within the range of 79.2 to 109.4% for tomato, cucumber, and pakchoi samples at the fortification levels of 5, 25, and 50 ng g−1. This effective and robust method can be applied for determining multi-classes of insecticide residues in vegetables.

Copper foam in situ loaded with precious metal nanoparticles as transmission SEIRAS substrate for rapid detection of dithiocarbamate pesticides

A transmission surface-enhanced infrared absorption spectroscopy (SEIRAS) substrate based on copper foam (CF) was developed for the rapid detection of dithiocarbamate (DTC) pesticides. The transmission SEIRAS substrate was prepared by immersing CF in a mixed solution of a precious metal solution and a polyvinyl pyrrolidone (PVP) solution. Then CF could be in situ loaded with precious metal nanoparticles (MNPs) by PVP-modified displacement reaction in seconds. PVP could be helpful for the uniform distribution of MNPs. Experimental parameters were evaluated with 11-mercaptoundecanoic acid (MUA) as a probe molecule, including the concentration of the precious metal solution, the amount of PVP, and the reaction time. Taking CF loaded with gold nanoparticles (Au NPs-CF) as an example, the signal intensity of DTC pesticide (Ziram) could be enhanced by two orders of magnitude, and the R² of the calibration curve was 0.999. In addition, the Pt NPs-CF substrate was applied to the rapid detection of other DTC pesticides (Ferbam). In summary, we have developed a new method to prepare the transmission SEIRAS substrate and apply it to the rapid detection of DTC pesticides in liquid.

Magnetic amino-functionalized hollow silica-titania microsphere as an efficient sorbent for extraction of pesticides in green and roasted coffee beans

This study describes the synthesis and application of a magnetic amino-functionalized hollow silica-titania microsphere as a new sorbent for magnetic dispersive micro-solid phase extraction of selected pesticides in coffee bean samples. The sorbent was fully characterized by Fourier-transform infrared spectroscopy, field emission scanning electron microscopy, transition electron microscopy, energy-dispersive X-ray spectroscopy, and vibrating sample magnetometry techniques. Significant extraction parameters affecting the proposed method, such as extraction time, sorbent amount, sample solution pH, salt amount, and desorption conditions (desorption solvent and time) were investigated and optimized. All the figures of merits were validated in coffee bean samples under the matrix-matched calibration method. Linear dynamic ranges were 5-250 µg/kg with the determination coefficients (R² ) > 0.9980. The limits of detection for the pesticides of chlorpyrifos, malathion, hexaconazole, and atrazine were 1.42, 1.43, 1.35, and 1.33 µg/kg, respectively. Finally, the method was successfully applied for the determination of the pesticides in green and roasted coffee bean samples, and the obtained recoveries were in the range of 74-113% for spiked samples. The prepared sorbent could be used for the magnetic dispersive micro-solid phase extraction of pesticides in the plant-derived food matrix.

Pt-Ni(OH)2 nanosheets amplified two-way lateral flow immunoassays with smartphone readout for quantification of pesticides

Excessive use of herbicide and insecticide causes bioaccumulation in the environment and increases potential toxicity for people and animals. Portable systems for rapid assays of herbicide and insecticide residues have attracted prominent interests. Here, we developed a two-dimensional (2D) Pt-Ni(OH)₂ nanosheets (NSs) amplified two-way lateral flow immunoassay (LFI) with a smartphone-based readout for simultaneous detection of acetochlor and fenpropathrin. The 2D Pt-Ni(OH)₂ NSs were synthesized and used as the enhanced signal label in the immunoassay due to their high peroxidase-like activity and low migration speed. The two-way LFI was designed to eliminate potential cross-reaction between two targets. Portable detection system was developed based on a smartphone-based readout, which scans the LFI and provides the accurate testing result. The universal use of smartphones makes the developed platform suitable for cheap and on-site applications. Using the integrated platform, detection of acetochlor and fenpropathrin simultaneously was successfully achieved with the detection limits of 0.63 ng/mL and 0.24 ng/mL, respectively. To confirm the performance of the on-site application, we detected 10 non-spiked samples and 3 spiked samples. The obtained detection results were consistent with the data from gas chromatography analysis. The estimated recoveries ranged from 97.12% to 111.46%, indicating the practical reliability of our developed assay. The developed smartphone-based platform exhibits enhanced sensitivity, which provides a promising technique for on-site, multiplex, highly sensitive detection of pesticides.