Group-selective enrichment and determination of pyrethroid insecticides in aquaculture seawater via molecularly imprinted solid phase extraction coupled with gas chromatography-electron capture detection

Fluorometric assay of cyanophoric pyrethroids based on benzothiazole modified carbon quantum dots

A fluorometric assay based on benzothiazole carbon quantum dots (benzothiazole-CDs) was developed for the determination of cyanophoric pyrethroids (CPs, e.g., cypermethrin, deltamethrin and fenpropathrin).

Development of a time-resolved fluorescence microsphere Eu lateral flow test strip based on a molecularly imprinted electrospun nanofiber membrane for determination of fenvalerate in vegetables

Fenvalerate residues in fruits and vegetables may result in biological immune system disorders. Current sensor detection methods are harsh due to the shortcomings of antibody preparation and preservation conditions. Therefore, developing a recognition material with strong specificity, good stability, and low cost is of practical significance in designing a sensitive, simple, and rapid method. This study used precipitation polymerization to synthesize molecularly imprinted polymers (MIPs). The MIP was prepared into a fiber membrane using the electrostatic spinning method. After that, the fenvalerate hapten-mouse IgG-Eu fluorescent probe was synthesized, and the side flow chromatography strip was constructed to determine fenvalerate in vegetables using the immunocompetition method. The results showed that the adsorption capacity of MIP to fenvalerate was 3.65, and the adsorption capacity on MIPFM (an electrospinning membrane containing the fenvalerate MIPs) was five times that of free MIP. The test strip showed good linearity with R² = 0.9761 within the range of 50 μg/L-1,000 μg/L. In conclusion, substituting fenvalerate monoclonal antibodies with a molecularly imprinted electrospinning membrane is ideal for rapid onsite detection of pyrethroids.

Optimising factors affecting solid phase extraction performances of molecular imprinted polymer as recent sample preparation technique

Molecular imprinted solid-phase extraction is the technique that uses molecular imprinted polymer as the sorbent in solid phase extraction. Molecular imprinted solid-phase extraction is effective and efficient for the extraction process and cleaning as compared with solid phase extraction (SPE) without molecular imprinted polymer. The complexity of variables in molecular imprinted solid-phase extraction arise as problems in the analysis, therefore it is necessary to optimize the extraction conditions of molecular imprinted solid-phase extraction. To achieve the sorption equilibrium and achieve the shortest time, certain parameters such as contact time, ion strength of sample, pH of sample, amount of sorbent, sample flow rate, addition of salt and buffer solution, washing solvent, elution solvent, and loading solvent need to be optimized. The selection of suitable properties and quantities of each factor greatly affect the formation of appropriate interactions between the sorbent and analytes. Percentage recovery is also influenced by formation of the appropriate bonds, sample flow rates, extraction time, salt addition, and sorbent mass. Therefore, in the future, molecular imprinted solid-phase extraction optimization has to consider and adjust various factors reviewed in this paper to form appropriate interactions between the absorbent and target molecules which have an impact on the optimal results.

Residue Analysis of Insecticides in Potatoes by QuEChERS-dSPE/UHPLC-PDA

Insecticides are broadly applied in agriculture to defend crops from illnesses and pest attacks, consequently guaranteeing high production. However, their residual deposits in food products are becoming a main concern with regard to human consumption. As such, sensitive analytical methods should be developed to assess, prevent and control insecticide residues. In this research, an accurate, fast and reliable residual analytical method, that is quick, easy, cheap, effective, rugged and safe, combined with dispersive solid phase extraction (QuEChERS-dSPE), was developed for the determination of the most common insecticides used in potatoes cultivation (chlorpyrifos, λ-cyhalothrin, deltamethrin and acrinathrin), using an ultra-high performance chromatography photodiode array detector (UHPLC-PDA). The most influential extraction and instrumentation parameters that affect the method’s performance, such as extraction solvent, ratio salts, sorbents, stationary phases, gradient conditions and eluents, were assessed. Under the ideal conditions, good linearity (0.992–0.998), limits of detection (0.02–0.47 µg/kg) and quantification (0.06–1.58 µg/kg), recovery (94.1 to 112%) and precision (relative standard deviation <18%) were achieved for spiked levels between 2.5 and 50 µg/kg. The obtained results revealed that the potatoes analyzed do not represent any concern for human healthy, as the insecticide residues detected were lower than the maximum residue limits set by the European Union, Codex Alimentarius, and other organizations.

An Investigation of the Intermolecular Interactions and Recognition Properties of Molecular Imprinted Polymers for Deltamethrin through Computational Strategies

Deltamethrin (DM) is a toxic pesticide that is nonetheless widely used to control insect pests in agricultural production. Although the number of DM molecularly imprinted polymers (MIPs) is increasing in many scientific applications, the theoretical aspects of the participating intramolecular forces are not fully understood. This paper aims to explore the intermolecular interactions between the template molecule DM and the functional monomer acrylamide (AM) through density functional theory (DFT), analysis of hydrogen nuclear magnetic resonance (¹H-NMR), Fourier transform infrared spectroscopy (FTIR), and adsorption thermodynamics. The results indicated that there is strong hydrogen bonding between O19 of DM and H9 of AM, suggesting that it is the preferable site for the binding of the target molecule. The existence of interaction sites was found to play an important role in the recognition process. The results from selective adsorption experiments showed that the DM MIPs exhibited the highest adsorption capacity for DM (Q = 75.72 mg g⁻¹) as compared to the five structural analogs. Furthermore, the recovery rates of spiked DM from various teas using the DM MIPs as solid-phase extraction filler also possessed a high value (all greater than 83.68%), which enables them to be used as separate and recognition functional materials.

A microtitre chemiluminescence sensor for detection of pyrethroids based on dual-dummy-template molecularly imprinted polymer and computational simulation

The residues of pyrethroids in foods of animal origin are dangerous to the consumers, so this study presented a chemiluminescence sensor for determination of pyrethroids in chicken samples. A dual-dummy-template molecularly imprinted polymer capable of recognizing 10 pyrethroids was synthesized. The results of computation simulation showed that the specific 3D conformations of the templates had important influences on the polymer' recognition ability. The polymer was used to prepare a sensor on conventional 96-well microplates, and the sample solution was added into the wells for direct absorption. The absorbed analytes were initiated with the bis(2,4,6-trichlorophenyl)oxalate-H₂ O₂ -imidazole system, and the chemiluminescence intensity was used for analyte quantification. Results showed that one assay was finished within 12 min, and this sensor could be reused four times. The limits of detection for the 10 analytes were in the range o0.3-6.0 pg/ml, and the recoveries from the standards of fortified blank chicken samples were in the range 70.5-99.7%.

Synthesis of molecularly imprinted nanoparticles for selective exposure assessment of permethrin: optimization by response surface methodology

BACKGROUND

Extensive use of high-efficiency pyrethroid pesticides as pest-control agents lead to remarkable adsorption and release of these materials in soil and aquatic environment which could have serious adverse effects on water and food chain quality as well as human health. In this study, a molecularly imprinted polymer was synthesized and used as a selective sorbent in the sample preparation procedure in order to facilitate sensitive and quantitative exposure assessment of insecticide permethrin.

METHODS

Molecular imprinted nanoparticles were prepared by precipitation polymerization technique using 1:4:20 mmol ratio of the template, functional monomer, and cross-linker, respectively, as well as 80 mL of chloroform as progen solvent. The obtained nanoparticles were characterized by field emission scanning electron microscopy (FESEM) and Fourier transform infrared spectrometry (FT-IR). The optimization of critical variables in the MISPE process was done using the central composite design (CCD) of the response surface methodology.

RESULTS

Quadratic regressional models were developed to correlate the response and independent variables and the analysis of variance (ANOVA) verified the excellent fitting of proposed models for experimental data. Optimum conditions for the highest MISPE yield were selected as follow: sorbent mass of 7.71 mg, sample pH 5.58 and 5.68 for cis and trans-permethrin, respectively, sample flow rate of 0.6 mL/min, as well as 5 and 3.94 mL of methanol/acetic acid at the flow rate of 2 mL/min as elution solvents for cis and trans-permethrin, respectively. Under optimized conditions, the linear range was obtained 20-120 μg/L (R2 = 0.99) and the detection limits were 5.51 and 5.72 μg/L for cis and trans-permethrin, respectively. Analysis of real samples demonstrated the high extraction efficiency of designed protocol ranging from 93.01 to 97.14 with the relative standard deviation (RSD) less than 4.51%.

CONCLUSIONS

The satisfactory results confirmed the reliability and efficiency of the proposed method for trace analysis of permethrin isomers in biological and environmental samples.

A high-performance SERS-imprinted sensor doped with silver particles of different surface morphologies for selective detection of pyrethroids in rivers

Ag-MIPs were prepared through a multistep procedure, in which MPS and LC were selected as the template molecules. These materials could selectively rebind the templates and could be detected using Raman spectroscopy.

A fluorescent molecularly imprinted polymer sensor synthesized by atom transfer radical precipitation polymerization for determination of ultra trace fenvalerate in the environment

In this study, novel fluorescence molecularly imprinted polymers (FMIPs) were prepared via atom transfer radical precipitation polymerization (ATRPP) for the optical detection of trace fenvalerate (FE).

Molecular imprinting: perspectives and applications

This critical review presents a survey of recent developments in technologies and strategies for the preparation of MIPs, followed by the application of MIPs in sample pretreatment, chromatographic separation and chemical sensing.

Optical detection of λ-cyhalothrin by core-shell fluorescent molecularly imprinted polymers in Chinese spirits

In this study, fluorescent molecularly imprinted polymers (FMIPs), which were for the selective recognition and fluorescence detection of λ-cyhalothrin (LC), were synthesized via fluorescein 5(6)-isothiocyanate (FITC) and 3-aminopropyltriethoxysilane (APTS)/SiO2 particles. The SiO2@FITC-APTS@MIPs were characterized by Fourier transform infrared (FT-IR), UV-vis spectrophotometer (UV-vis), fluorescence spectrophotometer, thermogravimetric analysis (TGA), confocal laser scanning microscope (CLSM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The as-synthesized SiO2@FITC-APTS@MIPs with an imprinted polymer film (thickness was about 100 nm) was demonstrated to be spherically shaped and had good monodispersity, high fluorescence intensity, and good selective recognition. Using fluorescence quenching as the detection tool, the largest fluorescence quenching efficiency (F0/F - 1) of SiO2@FITC-APTS@MIPs is close to 2.5 when the concentration of the LC is 1.0 μM L(-1). In addition, a linear relationship (F0/F - 1= 0.0162C + 0.0272) could be obtained covering a wide concentration range of 0-60 nM L(-1) with a correlation coefficient of 0.9968 described by the Stern-Volmer equation. Moreover, the limit of detection (LOD) of the SiO2@FITC-APTS@MIPs was 9.17 nM L(-1). The experiment results of practical detection revealed that the SiO2@FITC-APTS@MIPs as an attractive recognition element was satisfactory for the determination of LC in Chinese spirits. Therefore, this study demonstrated the potential of SiO2@FITC-APTS@MIPs for the recognition and detection of LC in food.

Detection of nonfluorescent cyhalothrin in honey by a spheral SiO2-based particle coating with thin fluorescent molecularly imprinted polymers film

In this study, we report a general protocol for making core–shell SiO₂@KH570-MIP based on the surface modification of SiO₂ beads for the selective fluorescence detection of ultra trace cyhalothrin.

Synthesis and characterization of molecularly imprinted polymer embedded composite cryogel discs: application for the selective extraction of cypermethrins from aqueous samples prior to GC-MS analysis

Molecularly imprinted particles embedded composite cryogel discs specific for α-cypermethrin and β-cypermethrin were prepared.