Application of Hydrophobic Magnetic Nanoparticles as Cleanup Adsorbents for Pesticide Residue Analysis in Fruit, Vegetable, and Various Soil Samples

Determination of Cyazofamid and Its Metabolite in Rice Based on Magnetic Zirconia Nanoparticles Sample Cleanup and Its Application to a Dissipation and Residue Study

An analytical method was developed for the determination of cyazofamid (CZFM) and its metabolite CCIM in rice, employing magnetic zirconia nanoparticles (MZNPs) for sample cleanup. MZNPs were synthesized through a one-step hydrothermal process and characterized by multiple techniques. Samples of rice plant, rice hull, and brown rice were extracted using acetonitrile/water, followed by salting out. MZNPs removed the most coextract compared with primary secondary amine (PSA) and zirconia-coated silica (Z-Sep). Satisfactory recoveries (79.6-95.7%; n = 5) of the analytes were acquired with RSDs less than 9.6%. The linearity was good (r > 0.999) over 0.001-1 mg L-1. The LOQs were 0.01 mg kg-1. The dissipation and residues of CZFM were studied as the method application. Half-lives of CZFM in rice plants were calculated to be 4.5-9.8 days. At harvest, residues of CZFM > LOQ were not detected in brown rice, indicating a low dietary risk.

Application of electrospun composite nanofibers as an efficient sorbent for extraction of pesticides from food samples

Herein, the composite of polylactic acid (PLA)/ Iron-based metal-organic framework (r-MIL-88A)/ Cellulose electrospun nanofibers was fabricated; and then, applied as a novel sorbent for thin-film micro-extraction (TFME) of four selected pesticides followed by GC-FID analysis. From the evaluation of scanning electron microscopy, Fourier transform infrared spectroscopy energy dispersive X-ray spectroscopy and X-ray diffraction, the successful fabrication of composite nanaofibers was approved. The presence of r-MIL-88A/Cellulose with large surface area and plenty of OH-functional groups results in improving PLA extraction efficiency. The effect of various main parameters on extraction efficiency was evaluated. The LODs (based on S/N = 3) were in the range of 1.0 to 1.5 ng mL^-1. Intra-day and inter-day relative standard deviations (RSDs) were in the range of 4.8% - 5.6% and 5.2%-6.4%, respectively. In addition, the fiber to fiber relative standard deviations were observed in the range of 5.2%-12.3%. By using the optimized factors, acceptable linearity ranges were obtained in the range of 3.0-1900.0 ng mL^-1 for metribuzin and ethofumasate, and 5.0-2000.0 for atrazine and ametryn (R² = 0.9913-0.9967). The developed method was investigated in fruit juice, vegetables, milk and honey samples, and recoveries (79.3-95.6%) indicate that the PLA/r-MIL-88A/Cellulose can be a prominent composite film for the extraction of the target analytes in various samples.

Fabrication of a label-free electrochemical cell-based biosensor for toxicity assessment of thiram

Thiram has been widely used in agriculture and may invades the food chain, posing a threat to human health. In this research, a label-free electrochemical cell-based biosensor was presented for in vitro toxicity assessment of thiram. HepG2 cells were cultured on poly-l-lysine@gold nano-flowers functionalized indium tin oxide coated glass electrode (PLL@AuNFs/ITO) to serve as biorecognition elements. AuNFs were electrodeposited on ITO to provide an enlarged specific surface area and benefited the output signal amplification. PLL was selected as an effective biocompatible coating material to facilitate cell adhesion and proliferation, thereby realizing one-step recording of electrochemical signals from thiram-treated cells. With the aid of the differential pulse voltammetry method, the fabricated biosensor was applied to assess the cytotoxicity of thiram. Results showed that the cytotoxicity measured by the fabricated biosensor exhibited a linear relationship related to thiram concentration ranging from 5 to 50 μM with a detection limit of 2.23 μM. The IC₅₀ of thiram obtained by the biosensor was 29.5 μM, which was close to that of conventional MTT assay (30.8 μM). The effects of thiram on HepG2 cells were also investigated via SEM and flow cytometry. Meanwhile, the proposed biosensor was used to evaluate the toxicity of thiram in fruit samples. Results indicated that the toxicity of thiram cannot be ignored even at a low residual concentration in food (≤5 mg/kg). In conclusion, the developed sensor showed excellent sensitivity, stability, and reliability, which provided a great capacity for the convenient toxicity evaluation of thiram residue in food.

Novel Magnetically-Recoverable Solid Acid Catalysts with a Hydrophobic Layer in Protecting the Active Sites from Water Poisoning

Three novel magnetically-recoverable solid acid catalysts (hydrophobic catalysts Fe3O4@SiO2-Me&PrSO3H, Fe3O4@SiO2-Oc&PrSO3H and hydrophilic catalyst Fe3O4@SiO2-PrSO3H) were synthesized by introducing organic propylsulfonic acid and alkyl groups to Fe3O4@SiO2 nanocomposites. We characterized these catalysts by FT-IR, EDS, XRD, VSM and SEM, and found that they had excellent core-shell structure and magnetic responsiveness. We also explored the impact of surface hydrophobicity on activity and stability of catalysts in ethyl acetate (EAC) synthesis reaction. The results indicated that: for reactivity and reusability, Fe3O4@SiO2-Oc&PrSO3H > Fe3O4@SiO2-Me&PrSO3H > Fe3O4@SiO2-PrSO3H. This was because octyl and methyl groups could build a hydrophobic layer on the surfaces of Fe3O4@SiO2-Oc&PrSO3H and Fe3O4@SiO2-Me&PrSO3H, and this could effectively prevent water molecules from poisoning active sites; the hydrophobicity of octyl was stronger than methyl. Fe3O4@SiO2-Oc&PrSO3H also showed higher catalytic activity in the external aqueous reaction system, which indicated that it had good water toleration. Moreover, we could easily separate Fe3O4@SiO2-Oc&PrSO3H from the reaction mixture with an external magnetic field, in the meanwhile, its reactivity could still remain above 80% after reusing 6 times.

Pesticide-Residue Analysis in Soils by the QuEChERS Method: A Review

Pesticides are among the most important contaminants worldwide due to their wide use, persistence, and toxicity. Their presence in soils is not only important from an environmental point of view, but also for food safety issues, since such residues can migrate from soils to food. However, soils are extremely complex matrices, which present a challenge to any analytical chemist, since the extraction of a wide range of compounds with diverse physicochemical properties, such as pesticides, at trace levels is not an easy task. In this context, the QuEChERS method (standing for quick, easy, cheap, effective, rugged, and safe) has become one of the most green and sustainable alternatives in this field due to its inherent advantages, such as fast sample preparation, the minimal use of hazardous reagents and solvents, simplicity, and low cost. This review is aimed at providing a critical revision of the most relevant modifications of the QuEChERS method (including the extraction and clean-up steps of the method) for pesticide-residue analysis in soils.

Simultaneous analysis of multiple pesticide residues in tobacco by magnetic carbon composite-based QuEChERS method and liquid chromatography coupled to quadrupole time-of-flight mass spectrometry

Magnetic carbon composite (Fe3O4@C) was synthesized and applied as a reversed-dispersive solid-phase extraction sorbent for the simultaneous analysis of 40 pesticide residues in tobacco by ultrahigh-performance liquid chromatography coupled to quadrupole time-of-fight mass spectrometry. Compared to the traditional QuEChERS method, the optimized Fe3O4@C simplified clean-up process and exhibited better clean-up capability than conventional sorbents. The pesticides were qualitatively identified by accurate mass of protonated molecules, fragment ions, isotopic peak clusters, and retention time, and quantitatively determined by matrix-matched external standard method. Good linearity of the proposed method was obtained with R value greater than 0.997 for all target pesticides at concentration levels of 2-200 µg/L. The limit of detection ranged from 0.14 to 2.67 µg/kg. The recoveries and relative standard deviations of all target pesticides at three spiked concentrations of 20, 50 and 200 µg/kg were in the ranges of 80.8%-113.3% and 0.6%-16.3%, respectively. Compared with the reported methods for the analysis of multiple pesticide residues in tobacco, the proposed method has the advantages of simple to operate, high clean-up ability and less time-consuming in clean-up process.

PVA/Stevia/MIL-88A@AuNPs composite nanofibers as a novel sorbent for simultaneous extraction of eight agricultural pesticides in food and vegetable samples followed by HPLC-UV analysis

Herein, an electrospun composite from poly(vinyl alcohol) (PVA) and Stevia extract as a cross-linked nanofibrous was prepared with incorporating Fe-metal organic framework@Au nanoparticles (MIL-88A@AuNPs). The final composite was characterized, and then used as an efficient sorbent in pipette-tip micro solid-phase extraction (PT-µSPE) of eight selected pesticides in food samples followed by HPLC-UV analysis. Under the opted conditions, the linearity was in the range of 1.0-1000.0 ng mL^-1 for atrazine and ametryn, 3.0-1500.0 ng mL^-1 for tribenuron-methyl, metribuzin, profenofos and chlorpyrifos, 5.0 to 1500.0 ng mL^-1 for phosalone, and 5.0-2000.0 ng mL^-1 for malation with coefficient of determination (r²) ≥ 0.9943. The LODs (based on S/N = 3) ranged from 0.3 to 1.5 ng m L^-1. The relative standard deviations (RSDs) were between 5.2% and 6.6% (intra-day, n = 5) and 5.9%-7.4% (inter-day, n = 3) for three consecutive days. Ultimately, the capability of the method in various food samples was appraised with good recoveries (79.3 to 97.6%).

Design, Preparation, and Application of Magnetic Nanoparticles for Food Safety Analysis: A Review of Recent Advances

This review (with 126 references) aims at providing an updated overview of the recent developments and innovations of the preparation and application of magnetic nanoparticles for food safety analysis. During the past two decades, various magnetic nanoparticles with different sizes, shapes, and surface modifications have been designed, synthesized, and characterized with the prospering development of material science. Analytical scientists and food scientists are among the ones who bring these novel materials from laboratories to commercial applications. Powerful and versatile surface functional groups and high surface to mass ratios make these magnetic nanoparticles useful tools for high-efficiency capture and preconcentration of certain molecules, even when they exist in trace levels or complicated food matrices. This is why more and more methods for sensitive detection and quantification of hazards in foods are developed based on these magic magnetic tools. In this review, the principles and superiorities of using magnetic nanoparticles for food pollutant analysis are first introduced, like the mechanism of magnetic solid phase extraction, a most commonly used method for food safety-related sample pretreatment. Their design and preparation are presented afterward, alongside the mechanisms underlying their application for different analytical purposes. After that, recently developed magnetic nanoparticle-based methods for dealing with food pollutants such as organic pollutants, heavy metals, and pathogens in different food matrices are summarized in detail. In the end, some humble outlooks on future directions for work in this field are provided.