A novel approach based on capillary liquid chromatography for the simultaneous determination of neonicotinoid residues in cereal samples

A Dimode Scattering Method for Ultratrace Dinitrofuran Detection with Nanopalladium Molecularly Imprinted Polymer Nanocatalytic Probe

With four nanoparticles as the nanomatrix, dinotefuran (DNF) as the template molecule, N-isopropylacrylamide as the functional monomer, trimethylolpropane and trimethacrylate as the cross-linker, four nanosurface molecularly imprinted polymer (MIP) bifunctional probes were prepared by microwave synthesis. It was found that palladium nanosurface MIP (Pd@MIP) not only recognized DNF but also had the strongest catalytic effect on the new nanogold indicator reaction of acrylic acid-HAuCl4, which was evaluated quickly with the slope procedure developed by us. The generated gold nanoparticles (AuNPs) not only possessed the resonance Rayleigh scattering (RRS) effect but also strong surface-enhanced Raman scattering (SERS) activity. The combination of Pd@MIP with DNF enhanced the catalytic effect by coupling the nanosurface electrons with π-electrons, thus enhancing both scattering signals. A new Pd@MIP nanoprobe catalytic-SERS/RRS dual-mode analytical platform was developed for the specific and sensitive detection of DNF. The linear ranges of the SERS and RRS methods were 0.075-0.75 and 0.1-0.75 nmol/L, and the limits of detection were 0.03 and 0.06 nmol/L, respectively. The standard deviations were 0.54-2.39%, and the recoveries were 93-105%.

A chitin-based magnetic hyper-cross-linked polymer for highly efficient enrichment of neonicotinoids in lemon juice and tomatoes

A chitin-based magnetic hyper-cross-linked polymer (labeled as Ch-MHCP) has been successfully synthesized and utilized for highly-effective solid-phase extraction of neonicotinoid insecticides (NEOs). The extraction capability of Ch-MHCP for four common NEOs is higher than that of four commercial sorbents including octadecyl-silane C18, oasis hydrophilic/lipophilic balanced sorbent, oasis mixed anion sorbent and poly-phenylacetic mixed anion sorbent. The large number of hydroxyl and amide groups as well as benzene rings in Ch-MHCP allow the H-bond and π-π* interaction to be the principal adsorption mechanism of Ch-MHCP for NEOs. Besides, polar interaction was also involved in the adsorption process. In combination of Ch-MHCP based extraction technique with high-performance liquid chromatography, a novel analytical method for sensitive detection of NEOs in lemon juice and tomatoes has been established. At optimal conditions, wide linear ranges were obtained to be 0.20-100 ng mL-1 for lemon juice and 0.80-1000 ng g-1 for tomatoes. The detection limits were 0.06-0.12 ng mL-1 for lemon juice and 0.24-0.60 ng g-1 for tomatoes. This work not only provides a powerful tool for simultaneously detecting four NEOs in lemon juice and tomatoes, but also offers a new insight into the preparation of bio-based magnetic sorbents for adsorption/removal of pollutants.

Analytical Methods Based on Liquid Chromatography and Capillary Electrophoresis to Determine Neonicotinoid Residues in Complex Matrices. A Comprehensive Review

Neonicotinoids (NNIs) are neuro-active and systemic insecticides widely used to protect crops from pest attack. During the last decades, there has been an increase concern about their uses and toxic effects, especially to beneficial and non-target insects such as pollinators. To assess potential health hazards and the environmental impacts derived from NNIs uses, a great variety of analytical procedures for the determination of their residues and their metabolites at trace level in environmental, biological and food samples have been reported. Due to the complexity of the samples, efficient sample pretreatment methods have been developed, which include mostly clean-up and preconcentration steps. On the other hand, among the analytical techniques used for their determination, high-performance liquid chromatography (HPLC) coupled to ultraviolet (UV) or mass spectrometry (MS) detection is the most widely used, although capillary electrophoresis (CE) has also been employed in the last years, considering some improvements in sensitivity when coupling with new MS detectors. In this review, we present a critical overview of analytical methods based on HPLC and CE reported in the last decade, discussing relevant and innovative sample treatments for the analysis of environmental, food and biological samples.

Nanofibrous Online Solid-Phase Extraction Coupled with Liquid Chromatography for the Determination of Neonicotinoid Pesticides in River Waters

Polymeric nano- and microfibers were tested as potential sorbents for the extraction of five neonicotinoids from natural waters. Nanofibrous mats were prepared from polycaprolactone, polyvinylidene fluoride, polystyrene, polyamide 6, polyacrylonitrile, and polyimide, as well as microfibers of polyethylene, a polycaprolactone nano- and microfiber conjugate, and polycaprolactone microfibers combined with polyvinylidene fluoride nanofibers. Polyimide nanofibers were selected as the most suitable sorbent for these analytes and the matrix. A Lab-In-Syringe system enabled automated preconcentration via online SPE of large sample volumes at low pressure with analyte separation by HPLC. Several mat layers were housed in a solvent filter holder integrated into the injection loop of an HPLC system. After loading 2 mL sample on the sorbent, the mobile phase eluted the retained analytes onto the chromatographic column. Extraction efficiencies of 68.8–83.4% were achieved. Large preconcentration factors ranging from 70 to 82 allowed reaching LOD and LOQ values of 0.4 to 1.7 and 1.2 to 5.5 µg·L⁻¹, respectively. Analyte recoveries from spiked river waters ranged from 53.8% to 113.3% at the 5 µg·L⁻¹ level and from 62.8% to 119.8% at the 20 µg·L⁻¹ level. The developed methodology proved suitable for the determination of thiamethoxam, clothianidin, imidacloprid, and thiacloprid, whereas matrix peak overlapping inhibited quantification of acetamiprid.