Determination of imidacloprid in rice by molecularly imprinted-matrix solid-phase dispersion with liquid chromatography tandem mass spectrometry

A molecularly imprinted electrochemical sensor MIP/Cu-MOF/rGO/AuNPs/GCE for highly sensitive detection of electroneutral organophosphorus pesticide residues

A novel electrochemical sensor, MIP/Cu-MOF/rGO/AuNPs/GCE, was developed by depositing gold nanoparticles, coating Cu-MOF/GO on the surface of glassy carbon electrode (GCE) before electroreducing graphene oxide (GO) to rGO and covering molecularly imprinted membrane by electropolymerization for highly sensitive detection of electroneutral organophosphorus pesticide residues in agricultural product. Cyclic voltammetry, differential pulse voltametry, scanning electron microscopy, energy-dispersive spectroscopy, and atomic force microscopy were used to characterize the imprinted sensor. Several key factors such as chitosan concentration, suspension volume, pH of polymerization solution, and polymerization scanning rate during preparation of the imprinted sensor were optimized in detail. When electroneutral phosmet was used as a template, the linear range of MIP/Cu-MOF/rGO/AuNPs/GCE for detecting phosmet was 1.00 × 10-14-5.00 × 10-7 mol/L with the limit of detection of 7.20 × 10-15 mol/L at working potentials of - 0.2 to 0.6 V. The selectivity, reproducibility, and repeatability of MIP/Cu-MOF/rGO/AuNPs/GCE were all acceptable. The recoveries of this method for determining phosmet in real samples ranged from 94.2 to 106.5%. The MIP/Cu-MOF/rGO/AuNPs/GCE sensor could be applied to detect electroneutral pesticide residues in organisms and agricultural products.

Chitosan nanoparticles modified TLC-densitometry for determination of imidacloprid and deltamethrin residues in plants: greenness assessment

Two thin layer chromatography (TLC) methods have been developed for the determination of pesticides residues of imidacloprid (IMD) and deltamethrin (DLM) in thyme and guava leaves. In the two methods, the used stationary phase was silica gel 60 F₂₅₄ plates impregnated in chitosan nanoparticles (ChTNPs) 0.5% to improve separation using a green developing system consists of isopropyl alcohol for IMD and n-hexane-toluene-ethylacetate for DLM. The two pesticides were determined quantitatively, after TLC separation, at wavelengths 270.0 nm for IMD and 230.0 nm for DLM. Validation of both approaches was carried out in agreement with the guidelines of International Conference on Harmonization (ICH) and found to be selective, reliable and reproducible. Limits of detection of IMD and DLM were 0.002 and 0.00116 μg/spot, respectively. The newly developed TLC methods were used to monitor the pre-harvest interval estimation. Analytical eco-scaling depending on penalty points for IMD was calculated and showed that this method was eco-friendlier than the reported one.

Developing a DNA logic gate nanosensing platform for the detection of acetamiprid

This paper reports a novel fluorescence and colorimetric dual-signal-output DNA aptamer based sensor for the detection of acetamiprid residue. Acetamiprid is a new systemic broad-spectrum insecticide with high insecticidal efficiency that is widely used worldwide, but there is a risk of adverse neurological reactions in humans and animals. The dual-mode output principle designed in this paper, consisting of a fluorescence signal and colorimetric signal, is based on the relevant reaction of the special domain of a G-quadruplex, bidding farewell to a classical single-signal output, with a target-recognition cycle used to complete signal amplification through a hybridization chain reaction. Upgraded detection sensitivity and the qualitative and semi-quantitative detection of acetamiprid are achieved based on the fluorescence signal output and visual discrimination observations during colorimetric experiments. This model was applied to the determination of acetamiprid residue in fruits and vegetables. The dual-detection platform further reduced systematic error, with a detection limit of 27.7 pM. When applied in a comparative detection study using three different pesticides, the system shows excellent discrimination specificity and it performs well in actual sample detection and has a fast response time. Designing DNA logic gates that operate in the presence of targets and molecular-switch-based detection platforms also involves the intersection of biology and computational modeling, providing new ideas for biological platforms.

Synthesis, characterization and absorption evaluation of bifunctional monomer magnetic molecularly imprinted polymers nanoparticles for the extraction of 6-benzylaminopurine from vegetables

An adsorbent-magnetic molecularly imprinted polymers nanoparticles (MMIPs NPs) were synthesized for the extraction of 6-benzylaminopurine (6-BA) using Fe₃O₄ as magnetic core. The MIPs were prepared with methacrylic acid and sodium p-styrene sulfonate as bifunctional monomers. The adsorbents were characterized by transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffractometer, thermogravimetric analysis and vibrating sample magnetometer. The adsorption properties were evaluated by static, kinetic and selective adsorption experiments. The MMIPs NPs exhibit a high adsorption capacity (37.63 mg g^-1) and favorable imprinting factor (2.88) toward 6-BA. The chromatogram of 6-BA extraction using the MMIPs NPs as the adsorbent demonstrates that the matrix interference has been minimized. More importantly, MMIPs NPs can be applied to extracting 6-BA from mung bean sprout and cucumber with satisfactory recoveries (91.14-104.52%), and can be reused for at least five times. This work provides a new strategy to efficiently extract 6-BA from vegetables.

Residue changes of five pesticides during the production and storage of rice flour

The residue changes of five pesticides in samples from different steps of rice flour production and accelerated storage were systematically investigated. Rice flour was produced both by the extrusion process and the drying on roller process. The change of pesticide residues varied in different processing steps and storage time. The water adjusting step had little influence on the pesticide residues. The pesticide residues were decreased significantly in the extruding, soaking, and grinding steps with reduction from 21% to 76%. The drying step increased or decreased the pesticide residues in varying degrees through concentration due to water evaporation and thermal evaporation or thermal degradation. All the pesticide residues decreased during the accelerated storage, especially for methidathion and chlorpyrifos, neither was detected after accelerated stored for 14 days. The processing factors (PFs) for imidacloprid and isocarbophos in the drying step were greater than 1, and the others were all less than 1. The whole drying on roller process had lower PFs than the whole extrusion process, indicated that the drying on roller process had a greater effect on pesticide residues. The PFs of accelerated storage for five pesticides were all below 1. Overall, this study provides important references for monitoring pesticide residues in the processing and storage of rice flour. Moreover, the PFs obtained in this study could be useful in the dietary exposure and risk assessment of pesticides in rice flour.

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.

[Advances in application of molecularly imprinted polymers to the detection of polar pesticide residues]

Polar pesticides can be primarily classified as fungicides, herbicides, and insecticides; their rich variety and low cost have led to their extensive utilization in agriculture. However, the overuse of polar pesticides can lead to environmental contamination, such as water or soil pollution, which can also increase the risk of pesticide exposure among human life directly, or indirectly through contact with animal and plant-derived food. There are considerable differences in the physical and chemical properties of polar pesticides, as well as their trace amounts in complex food and environmental samples, posing immense challenges to their accurate detection. As a kind of artificially prepared selective adsorbent, molecularly imprinted polymers (MIPs) possess specific recognition sites complementary to template molecules in terms of the spatial structure, size, and chemical functional groups. With many advantages such as easy preparation, low cost, as well as good chemical and mechanical stability, MIPs have been widely applied in sample pretreatment and the analysis of polar pesticide residues. MIPs are typically used as adsorption materials in solid phase extraction (SPE) methods, including magnetic solid phase extraction (MSPE), dispersed solid phase extraction (DSPE), and stir bar sorptive extraction (SBSE). To rapidly detect polar pesticide residues with high sensitivity, MIPs are also used in the preparation of fluorescent sensors and electrochemical sensors. Furthermore, MIPs can be employed as the substrate in surface-enhanced Raman spectroscopy and as the substrate for the ion source in mass spectrometry for polar pesticide residue analysis. Thus far, various molecularly imprinted materials have been reported for the efficient separation and analysis of polar pesticide residues in various complex matrices. However, there is no review that summarizes the recent advances in MIPs for the determination of polar pesticides. This review introduces imprinting strategies and polymerization methods for MIPs, and briefly summarizes some new molecular imprinting strategies and preparation technologies. The application of MIPs in recent years (particularly the last five years) to the detection of polar pesticide residues including neonicotinoids, organophosphorus, triazines, azoles, and urea is then systematically summarized. Finally, the future development direction and trends for MIPs are proposed considering existing challenges, with the aim of providing reference to guide future research on MIPs in the field of polar pesticide residue detection.

Review of sample preparation methods for chromatographic analysis of neonicotinoids in agricultural and environmental matrices: From classical to state-of-the-art methods

This review specifically examines the development of sample preparation methods for residue analyses of neonicotinoid insecticides in agricultural and environmental matrices. Pesticide residue analysis is fundamentally important to ensure the safety of foods and processed foods of plant and animal origin, and to preserve the environment, particularly soil and water. For the development of pesticide residue analysis, the sample preparation process is an important key to maximizing the analytical performance of highly sensitive and accurate chromatographic instruments and to acquiring reliable analytical results. This review outlines sample preparation methods that have been proposed to date for extraction of neonicotinoids that might remain in a complicated sample matrix in quantitatively trace amounts, and for cleaning up, to the greatest extent possible, the interfering components that coexist in the sample extract.

A QuEChERS-HPLC-MS/MS Method with Matrix Matching Calibration Strategy for Determination of Imidacloprid and Its Metabolites in Procambarus clarkii (Crayfish) Tissues

We developed a method for determination of imidacloprid and its metabolites 5-hydroxy imidacloprid, olefin imidacloprid, imidacloprid urea and 6-chloronicotinic acid in Procambarus clarkii (crayfish) tissues using quick, easy, cheap, effective, rugged, and safe (QuEChERS) and high-performance liquid chromatography-triple quadrupole mass spectrometry. Samples (plasma, cephalothorax, hepatopancrea, gill, intestine, and muscle) were extracted with acetonitrile containing 0.1% acetic acid and cleaned up using a neutral alumina column containing a primary secondary amine. The prepared samples were separated using reverse phase chromatography and scanned in the positive and negative ion multiple reaction-monitoring modes. Under the optimum experimental conditions, spiked recoveries for these compounds in P. clarkii samples ranged from 80.6 to 112.7% with relative standard deviations of 4.2 to 12.6%. The limits of detection were 0.02-0.5 μg·L^-1, the limits of quantification were 0.05-2.0 μg·L^-1 and the method of quantification was 0.05-2.0 μg·kg^-1. The method is rapid, simple, sensitive and suitable for rapid determination and analysis of imidacloprid and its metabolites in P. clarkii tissues.

Capacitive sensor based on molecularly imprinted polymers for detection of the insecticide imidacloprid in water

This manuscript reports on the development of a capacitive sensor for the detection of imidacloprid (IMD) in water samples based on molecularly imprinted polymers (MIPs). MIPs used as recognition elements were synthesized via a photo-initiated emulsion polymerization. The particles were carefully washed using a methanol (MeOH) /acetic acid mixture to ensure complete template removal and were then dried. The average size of the obtained particles was less than 1 µm. The imprinting factor (IF) for IMD was 6 and the selectivity factor (α) for acetamiprid, clothianidin, thiacloprid and thiamethoxam were 14.8, 6.8, 7.1 and 8.2, respectively. The particles were immobilized on the surface of a gold electrode by electropolymerization. The immobilized electrode could be spontaneously regenerated using a mixture of MeOH/10 mM of phosphate buffer (pH = 7.2)/triethylamine before each measurement and could be reused for 32 times. This is the first-time that automated regeneration was introduced as part of a sensing platform for IMD detection. The developed sensor was validated by the analysis of artificially spiked water samples. Under the optimal conditions, the linearity was in the range of 5-100 µM, with a limit of detection (LOD) of 4.61 µM.

Development of rapid, sensitive and selective fluorimetric method for determination of 1-naphthalene acetic acid in cucumber by using magnetite-molecularly imprinted polymer

In this study, a novel method based on the determination of 1-naphthalene acetic acid with the usage of magnetite-molecularly imprinted polymer prior to fluorimetric detection has been developed. Magnetite-molecularly imprinted polymer has been used for the first time as selective adsorbent for the determination of 1-naphthalene acetic acid. The adsorption capacity of the synthesized polymer was found to be 2.18 ± 0.36 mg g^-1 (n = 3). Limit of detection (LOD) and limit of quantification (LOQ) of the method were found to be 0.75 and 2.50 μg L^-1, respectively. Linearity of the calibration graph for the proposed method was observed within the range of 20-700 μg L^-1. The proposed method seems to be rapid where the detection procedure for 1-naphthalene acetic acid can be completed within a total time of 1 h. The same imprinted polymer can be used for the determination of 1-naphthalene acetic acid with quantitative sorption and recovery values repeatedly for at least ten times. The effects of some potential organic interferences were investigated. Proposed method has been successfully applied to determine 1-naphthalene acetic acid in cucumber, where the recoveries of the spiked samples were found to be in the range of 93.7-104.5%. Characterization of the synthesized polymer was also evaluated. By combining the high capacity, cheapness, reusability and selectivity of the magnetic adsorbent with the dynamic calibration range, rapidity, simplicity, and sensitivity of fluorimetry, the proposed method seems to be an ideal method for the determination of trace levels of 1-naphthalene acetic acid.

Fast sensing of imidacloprid residue in tea using surface-enhanced Raman scattering by comparative multivariate calibration

This study focused on the fabrication of a rapid, highly sensitive and inexpensive technique for the quantification of imidacloprid residue in green tea, based on surface-enhanced Raman scattering (SERS) using highly roughned surface flower shaped silver nanostructure (as SERS substrate) coupled with the chemometrics algorithm. The basic principle of this method is imidacloprid yielded SERS signal after adsorption on Ag-NF under laser excitation by the electromagnetic enhancement and the intensity of the peak is proportional to the concentration ranging from 1.0 × 10³ to 1.0 × 10^-4 μg/mL. Among the models used, the GA-PLS (Genetic algorithm-partial least square) exhibited superiority to quantify imidacloprid residue in green tea. The model achieved Rp (correlation coefficient) of 0.9702 with RPD of 4.95% in the test set and RSD for precision recorded up to 4.50%. Therefore, the proposed sensor could be employed to quantify imidacloprid residue in green tea for the safeguarding of quality and human health.

Advancements of molecularly imprinted polymers in the food safety field

Molecularly imprinted technology (MIT) has been widely employed to produce stable, robust and cheap molecularly imprinted polymer (MIP) materials that possess selective binding sites for recognition of target analytes in food, such as pesticides, veterinary drugs, mycotoxins, illegal drugs and so on. Because of high selectivity and specificity, MIPs have drawn great attention in the food safety field. In this review, the recent developments of MIPs in various applications for food safety, including sample preparation, chromatographic separation, sensing, immunoassay etc., have been summarized. We particularly discuss the advancements and limitations in these applications, as well as attempts carried out for their improvement.

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.

Computational electronic structure of the bee killer insecticide imidacloprid

One conformer of imidacloprid in vacuum and three conformers in the aqueous phase were obtained by a DFT approach, and their structural and electronic properties were discussed.

Molecularly imprinted nanomicrospheres as matrix solid-phase dispersant combined with gas chromatography for determination of four phosphorothioate pesticides in carrot and yacon

An efficient, rapid, and selective method for sample pretreatment, namely, molecularly imprinted matrix solid-phase dispersion (MI-MSPD) coupled with gas chromatography (GC), was developed for the rapid isolation of four phosphorothioate organophosphorus pesticides (tolclofos-methyl, phoxim, chlorpyrifos, and parathion-methyl) from carrot and yacon samples. New molecularly imprinted polymer nanomicrospheres were synthesized by using typical structural analogue tolclofos-methyl as a dummy template via surface grafting polymerization on nanosilica. Then, these four pesticides in carrot and yacon were extracted and adsorbed using the imprinted nanomicrospheres and further determined by gas chromatography. Under the optimized conditions, a good linearity of four pesticides was obtained in a range of 0.05-17.0 ng·g(-1) with R varying from 0.9971 to 0.9996, and the detection limit of the method was 0.012~0.026 ng·g(-1) in carrot and yacon samples. The recovery rates at two spiked levels were in the range of 85.4-105.6% with RSD ≤9.6%. The presented MI-MSPD method combined the advantages of MSPD for allowing the extraction, dispersion, and homogenization in two steps and the advantages of MIPs for high affinity and selectivity towards four phosphorothioate pesticides, which could be applied to the determination of pesticide residues in complicated vegetal samples.

A novel core-shell magnetic nano-sorbent with surface molecularly imprinted polymer coating for the selective solid phase extraction of dimetridazole

A novel core-shell magnetic nano-sorbent with surface molecularly-imprinted polymer coating was prepared via a sol-gel process. Methyltrimethoxysilane and 3-aminopropyltriethoxysilane were used as functional monomers, tetraethyl orthosilicate as cross-linker, and Al(3+) as dopant to generate Lewis acid sites in the silica matrix for the metal coordinate interactions with the template dimetridazole (DMZ). The ratios of the monomers, the dopant, and the cross-linker, were optimised by a OA9 (3(4)) orthogonal array design. The resultant sorbent was characterised by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, powder X-ray diffraction, and magnetometry. The binding performances of the sorbent were evaluated by static, kinetic and selective adsorption experiments. The nano-sorbent was successfully applied to solid phase extraction followed by spectrophotometric determination of DMZ in real samples. Spiked recoveries ranged from 90.33% to 106.20% for egg, milk powder, and pig feed samples, with relative standard deviations of less than 4.54%.

Molecular imprinted photonic crystal hydrogels for the rapid and label-free detection of imidacloprid

A novel sensor for the rapid and label-free detection of imidacloprid was developed based on the combination of a colloidal crystal templating method and a molecular imprinting technique. The molecular imprinted photonic hydrogel film was prepared with methacrylic acid as monomers, ethylene glycol dimethylacrylate as cross-linkers and imidacloprid as imprinting template molecules. When the colloidal crystal template and the molecularly imprinted template was removed, the resulted MIPH film possessed a highly ordered three-dimensional macroporous structure with nanocavities. The response of the MIPH film to imidacloprid in aqueous solution can be detected through a readable Bragg diffraction red shift. When the concentration of imidacloprid increased from 10(-13) to 10(-7) g/mL, the Bragg diffraction peak shifted from 551 to 589 nm, while there were no obvious peak shifts for thiamethoxam and acetamiprid. This sensor which comprises of no label techniques and expensive instruments has potential application for the detection of trace imidacloprid.