Sensitive monitoring of benzoylurea insecticides in water and juice samples treated with multiple monolithic fiber solid-phase microextraction and liquid chromatographic analysis

Etched stainless steel wire modified with conjugated microporous polymers-F6 for jacket-free stir bar sorptive extraction of benzoylureas in juice sample

Benzoylurea (BU) insecticides have been widely used for pest control as third-generation insecticides. Considering that their residues in food may cause adverse effects on human health, the upper limits of BUs remaining in food have been set by the administration. Therefore, it is essential to develop a sensitive and efficient analytical method to determine the residues of BUs in food. Stir bar sorptive extraction (SBSE) is a novel sample preparation technique, and stainless steel wire (SSW) is an ideal substrate for an SBSE device. In this work, a novel SBSE device of SSW jacket-free stir bar with a dumbbell shape was designed and prepared. The conjugated microporous polymer CMP-F6, which possesses a porous structure, high hydrophobicity and rich fluorine-containing functional groups, was immobilized on the surface of SSW by the method of polyacrylonitrile glue adhesion. Compared with previous studies, which used SSW as a substrate, the method of etching partial SSW with hydrochloric acid, on the one hand, made the surface of SSW rough and easy to modify the extraction coating, and on the other hand, converted itself into a dumbbell-shaped structure, which is conducive to improving the extraction efficiency and stability of the SBSE device. The method of SBSE-HPLC-UV was established for determining five BUs. Owing to the hydrophobic interaction and F-F interaction between CMP-F6 and analytes, this method showed good extraction efficiency and had good linearity (R2 ≥ 0.9945) and high sensitivity (LODs in the range of 0.1-0.2 ng mL-1). It was used for the analysis of benzoylurea in an apple juice sample, and the recoveries were 74.3-117.9%.

In situ growth of ZIF-67 to construct core-shell mosaic structural composites for efficient extraction of benzoylurea insecticides

A novel mosaic structure Silica@C/Co@ZIF-67 composite was synthesized by successfully embedding Co nanoparticles on the surface of silica spheres with the help of thermoplastic polyethyleneimine by carbon-reduction. The ZIF-67 half-shell layer structure was synthesized by the in-situ growth of ZIF-67 on the surface of silica spheres through the coordination of 2-methylimidazole with Co metal nodes. The composite was used as a magnetic solid-phase extraction adsorbent combined with high performance liquid chromatography-ultraviolet detector (HPLC-UV) for the extraction and determination of benzoylurea insecticides (BUs) in vegetables and tea. Based on the presence of π-π, hydrophobic and hydrogen bonding interactions between Silica@C/Co@ZIF-67 and BUs, the BUs were rapidly captured by the composites resulting in high adsorption performance. Under the optimal extraction parameters, the linear ranges were 0.3-200 µg L-1 for diflubenzuron, 0.6-200 µg L-1 for chlorbenzuron, and 1.0-200 µg L-1 for triflumuron, teflubenzuron, and flufenoxuron, with correlation coefficients (R2) greater than 0.9991. The limits of detection (LODs) of the method were 0.1-0.3 μg L-1, and the relative standard deviations (RSDs) were 1.2-3.0% for intra-day and 2.6-4.6% for inter-day. In the spiked recovery experiments of vegetables and tea, the recoveries of the five kinds of BUs ranged from 75.8 to 112.9%. In addition, after 10 repetitions using Silica@C/Co@ZIF-67, the recoveries of the five kinds of BUs were still as high as 78.4 to 83.9%.

Direct solidification of switchable-hydrophilicity salicylic acid: A design for the on-site dispersive liquid-liquid microextraction of benzoylurea insecticides in water and honey samples

This study describes the development of a fully manual method for on-site dispersive liquid-liquid microextraction based on the direct solidification of switchable-hydrophilicity salicylic acid (on-site DLLME-DSSA) coupled with high-performance liquid chromatography with an ultraviolet detector (HPLC-UVD) and its utilization for the detection of benzoylurea insecticides (BUs) in water and honey samples. Salicylic acid (SA), a switchable hydrophilic aromatic acid, was used as an extraction solvent. It can be converted into the hydrophobic/hydrophilic forms in pH-changeable solutions, facilitating facile and effective dispersion and phase separation. Moreover, the melting point of SA (significantly higher than room temperature) enables its direct solidification without an ice-water bath, facilitating its collection by filtration. The dispersion, separation, and collection of the extraction solvent were carried out entirely in a plastic syringe without requiring special apparatus or additional energy. Univariate and response surface analyses were used to optimize various parameters of the on-site DLLME-DSSA method. Under optimal conditions, the limits of determination (LODs) were 1.50 µg L^-1 and 0.03-0.09 mg kg^-1 in water and honey, respectively. The relative standard deviations (RSDs) for inter-day (n = 5) and intra-day (n = 5) precision were ≤8.4%, whereas the extraction recoveries and enrichment factors for the BUs ranged from 67.0 to 97.1% and 29 to 34, respectively. Furthermore, the proposed method was used for the on-site extraction and laboratory detection of BUs from real water and honey samples. Theoretical analyses indicated non-covalent interactions (such as hydrogen bonds, electrostatic interactions, van der Waals forces, and π-π interactions) to be the main driving force for extraction. This study introduces a switchable hydrophilic aromatic acid capable of direct solidification into on-site DLLME for the first time, opening new frontiers in the development of on-site sample pretreatment methods.

Facile synthesis of magnetic hypercrosslinked polymer for the magnetic solid-phase extraction of benzoylurea insecticides from honey and apple juice samples

In this work, a novel knitting aromatic polymer (KAP) was fabricated for the first time by knitting ferrocene with 1,3,5-tris(bromomethyl)-2,4,6-trimethylbenzene via Friedel-Crafts reaction, and then the KAP was magnetically functionalized with Fe₃O₄ nanoparticles to produce a magnetic KAP (M-KAP). Combining M-KAP based magnetic solid-phase extraction with high performance liquid chromatography-ultraviolet detection, a simple and sensitive method was developed for simultaneous determination of six benzoylurea insecticides (BUs) in honey and apple juice samples. In the optimized conditions, a good linearity for the BUs existed in the range of 1.67-1000 ng g^-1 for honey sample and 0.500-100.0 ng mL^-1 for apple juice sample. The limits of detection were 0.500-1.50 ng g^-1 and 0.150-0.400 ng mL^-1 for honey and apple juice sample, respectively. Satisfactory recoveries were in the range of 85.5-105.5% with RSDs ≤ 8.3%. The developed method demonstrated an excellent practicability for sensitive analysis of the BUs.

Co-precipitation based on layered double hydroxides and anionic surfactants for preconcentration of six benzoylurea insecticides in soft drinks before simultaneous analysis by high-performance liquid chromatography

Layered-double hydroxides (LDHs) modified with anionic surfactants via a co-precipitation method were developed for preconcentrating and simultaneous analysis of six benzoylurea insecticides (BUs) by high-performance liquid chromatography (HPLC). The anionic surfactants with different chain lengths, including sodium dodecylbenzene sulfonate (SDBS), sodium dodecyl sulfate (SDS), sodium 1-nonane sulfonate (SNS), and sodium 1-hexane sulfonate monohydrate (SHS) were investigated to improve the extraction efficiency of LDHs. The SDBS-LDHs provided the highest efficiency for the enrichment of the BUs studied. Under the chosen conditions, enrichment factors in the range of 38-69 and detection limits in the range of 0.1-0.3 μg L^-1 were achieved. Good reproducibilities (RSD < 13.8%) and recoveries (71.4-118.7%) were also obtained. The proposed preconcentration method, used as an in situ procedure offers rapid and simple simultaneous preparation of LDHs and extraction of BUs. The method was successfully applied for residue analysis of BUs in fruit- and flower-derived soft drink samples.

Fabrication of a Magnetic Fluorinated Covalent Organic Framework for the Selective Capture of Benzoylurea Insecticide Residue in Beverages

Efficient capture of benzoylurea insecticide (BU) residue in food is a vital procedure for food safe monitoring. Herein, a core-shell structured magnetic fluorinated covalent organic framework with good magnetic responsiveness and abundant fluorine affinity sites was successfully synthesized, suitable for magnetic solid-phase extraction (MSPE) of BUs. Using a room-temperature synthesis strategy, the magnetic fluorinated covalent organic framework was fabricated by in situ polymerization of 1,3,5-tris(4-aminophenyl) triazine (TAPT) and 2,3,5,6-tetrafluoroterephthaldehyde (TFTA) on the surface of carboxylated Fe₃O₄ nanoparticles. The competitive adsorption experiment and molecular simulation verified that this magnetic fluorinated covalent organic framework possesses favorable adsorption affinity for BUs. This magnetic fluorinated covalent organic framework could be easily regenerated and reused at least eight times with no reduction of enrichment performance. Combining this magnetic fluorinated covalent organic framework-based MSPE with high-performance liquid chromatography-tandem mass spectrometry, a novel sensitive method for the analysis of BUs was developed. In yellow wine and fruit juice samples, good linear correlations were obtained for BUs in the range of 10-2000 and 20-4000 ng·L^-1, respectively. The limit of quantitation of the BUs ranged from 1.4 to 13.3 ng·L^-1 in the two beverage matrices. Desirable precision was achieved, with intraday and interday relative standard deviations lower than 11%.

Extraction and electrochemical sensing of pesticides in food and environmental samples by use of polydopamine-based materials

Polydopamine has high adsorption capacities for pollutants such as pesticides in food and environmental matrices. Consequently, it has found applications in some sorbent-based micro-extraction techniques such as solid phase micro-extraction and magnetic solid phase extraction. This paper gives a detailed review of the application of polydopamine-based adsorbents for the extraction of pesticides in food and environmental matrices using these techniques. The adhesive properties of polydopamine have made it to be a suitable material for the immobilisation of the components of electrochemical sensors used to detect pesticides in food and environmental matrices. This paper also gives a comprehensive review on the application of polydopamine in electrochemical sensors such as acetylcholinesterase sensors, molecularly imprinted sensors and aptasensors. The use of polydopamine-based adsorbents during the extraction and electrochemical sensing of pesticides in food and environmental matrices is not free of challenges. In this review, the challenges encountered during the use of polydopamine-based adsorbents are also discussed.

Room-temperature synthesis of magnetic covalent organic frameworks for analyzing trace benzoylurea insecticide residue in tea beverages

A novel magnetic covalent organic framework (NH₂-Fe₃O₄@COF) was prepared using a simple room-temperature synthesis in this study. These magnetic particles exhibited high adsorption performance with short adsorption time (10 min) for six benzoylurea insecticides (BUs) as magnetic solid-phase extraction (MSPE) adsorbents. Quantum chemistry calculation demonstrated that adsorption mechanism was primarily attributed to strong halogen bonds between electronegative O atoms of COF and electropositive F atoms of BUs as well as potential hydrophobic effect. Wide linearities (10-1000 ng·L^-1) and low limits of detection (0.06-1.65 ng·L^-1) for six analytes were obtained via liquid chromatography-tandem mass spectrometry. Applicability of the proposed method was further evaluated by analyzing four kinds of original tea beverages. Recoveries of six BUs in spiked samples ranged from 80.1% to 108.4%.

Dissolvable Mg/Al layered double hydroxides and surfactant as an extractant for trace analysis of benzoylurea insecticides by high performance liquid chromatography

A rapid and simple preconcentration method using dissolvable Mg/Al layered-double hydroxides (LDHs) and high performance liquid chromatography-photodiode array detection (HPLC-PDA) was developed for the analysis of benzoylurea insecticides (BUs) in water and honey samples. The proposed dissolvable LDHs for the extraction can be prepared in one step by the sequential addition of sodium hydroxide, magnesium chloride, aluminium chloride, and sodium dodecyl sulfate into the sample solution containing the target BUs. The co-precipitate phase was simply obtained after centrifugation, and the phase was then dissolved with formic acid before analysis by HPLC. The developed method provided an enrichment factor of 12.5-23.7. LODs were obtained in the range of 0.1-0.3 μg L^-1 for deionized water, 0.2-2.0 μg L^-1 for environmental waters, and 0.5-2.0 μg L^-1 for the analyzed honey samples. Good recoveries ranging from 78.4 to 117.8% and 72.7 to 117.9% for water and honey samples, respectively, were obtained.

Portable glucose meter-utilized label-free and washing-free telomerase assay

We herein describe a portable glucose meter (PGM)-utilized label-free and washing-free method for the facile determination of telomerase activity that relies on the kinase-catalyzed cascade enzymatic reaction (KCER) that transduces the telomerase activity to the glucose level. In the sensor, the telomerase that elongates telomere sequences ((TTAGGG)_n) from the 3'-terminus of telomerase substrate primer (TSP) consumes deoxynucleoside triphosphate (dNTP), which serves as a phosphate source for KCER promoted by hexokinase and pyruvate kinase. Thus, the presence of telomerase protects KCER from working effectively, resulting in the maintenance of an initial, high glucose level that is readily determined using hand-held PGM. With this strategy, the telomerase activities in various types of cell lines were successfully determined with high sensitivity. Furthermore, the ability of this method to screen candidate inhibitors for telomerase activity was also verified.

Simple and label-free strategy for terminal transferase assay using a personal glucose meter

We herein developed a simple personal glucose meter (PGM)-based method for terminal transferase (TdT) activity assay by utilizing the glucose oxidase (GOx)-mimicking activity of cerium oxide nanoparticles (CeO₂ NPs). Using this strategy, the TdT activity was reliably determined down to 0.7 U mL^-1 with high selectivity against other non-specific enzymes.

Recent Applications and Newly Developed Strategies of Solid-Phase Microextraction in Contaminant Analysis: Through the Environment to Humans

The present review aims to describe the recent and most impactful applications in pollutant analysis using solid-phase microextraction (SPME) technology in environmental, food, and bio-clinical analysis. The covered papers were published in the last 5 years (2014–2019) thus providing the reader with information about the current state-of-the-art and the future potential directions of the research in pollutant monitoring using SPME. To this end, we revised the studies focused on the investigation of persistent organic pollutants (POPs), pesticides, and emerging pollutants (EPs) including personal care products (PPCPs), in different environmental, food, and bio-clinical matrices. We especially emphasized the role that SPME is having in contaminant surveys following the path that goes from the environment to humans passing through the food web. Besides, this review covers the last technological developments encompassing the use of novel extraction coatings (e.g., metal-organic frameworks, covalent organic frameworks, PDMS-overcoated fiber), geometries (e.g., Arrow-SPME, multiple monolithic fiber-SPME), approaches (e.g., vacuum and cold fiber SPME), and on-site devices. The applications of SPME hyphenated with ambient mass spectrometry have also been described.

Green pre-concentration techniques during pesticide analysis in food samples

The ever-increasing demand for determining pesticides at low concentration levels in different food matrices requires a preliminary step of pre-concentration which is considered a crucial stage. Recently, the parameter of "greenness" during sample pre-concentration of pesticides in food matrices is as important as selectivity in order to avoid using harmful organic solvents during sample preparation. Developing new green pre-concentration techniques is one of the key subjects. Thus, to reduce the impact on the environment during trace analysis of pesticides in food matrices, new developments in pre-concentration have gone in three separate directions: the search for more environmentally friendly solvents, miniaturization and development of solvent-free pre-concentration techniques. Eco-friendly solvents such as supercritical fluids, ionic liquids and natural deep eutectic solvents have been developed for use as extraction solvents during pre-concentration of pesticides in food matrices. Also, miniaturized pre-concentration techniques such as QuEChERS, dispersive liquid-liquid micro-extraction and hollow-fiber liquid-phase micro-extraction have been used during trace analysis of pesticides in food samples as well as solvent-free techniques such as solid-phase micro-extraction and stir bar sorptive extraction. All these developments which are aimed at ensuring that pesticide pre-concentration in different food matrices is green are critically reviewed in this paper.

Preparation of a magnetic graphene/polydopamine nanocomposite for magnetic dispersive solid-phase extraction of benzoylurea insecticides in environmental water samples

A magnetic graphene/polydopamine (MG/PDA) nanocomposite has been prepared and used as sorbent for magnetic dispersive solid-phase extraction (MDSPE) of four benzoylurea insecticides in environmental water samples. The obtained nanocomposites were characterized by transmission electron microscopy, scanning electron microscopy, vibrating sample magnetometry, powder X-ray diffraction, fourier transform infrared spectroscopy, surface area and porosity analysis and thermogravimetric analysis. To investigate the adsorption performance of MG/PDA for target analytes, various parameters affecting the MG/PDA-based MDSPE procedure were optimized. Under the optimal conditions, the established method exhibits good linearity (R2 ≥ 0.9988) in the concentration range 2.5-500 µg L-1. A low limit of detection (0.75 µg L-1, signal/noise = 3:1), a low limit of quantification (2.50 µg L-1, signal/noise = 10:1), and good precision (intraday relative standard deviation ≤3.6%, interday relative standard deviation ≤4.5%) are also achieved. Finally, the simple, fast, and sensitive sample preparation technique was successfully used to determine benzoylurea insecticides in environmental water samples.

Polypyrrole coated ZnO nanorods on platinum wire for solid-phase microextraction of amitraz and teflubenzuron pesticides prior to quantitation by GC-MS

The authors describe a new sorbent for amitraz and teflubenzuron pesticides. It consists of a platinum wire coated with polypyrrole-coated ZnO nanorods. The nanocomposite was prepared by a two-step process. In the first step, oriented ZnO nanorods were hydrothermally grown in situ on a platinum wire. Subsequently, oxidative vapor phase polymerization of pyrrole was performed on FeCl₃-impregnated ZnO nanorods to give a porous polypyrrole film. The organic/inorganic nanocomposite synthesized through hydrothermal deposition and chemical vapor deposition polymerization yields material with attractive properties. The coated wire was applied to solid-phase microextraction of amitraz (in the form of 2,4-dimethylaniline resulting from the hydrolysis of amitraz) and teflubenzuron. The effects of extraction temperature, extraction time, sample pH value and salt concentration were optimized. The analytes 2,4-dimethylaniline and teflubenzuron were then quantified by GC-MS. Under optimum conditions, the LODs range between 0.1 and 0.15 ng.mL^-1. Relative standard deviations at two concentration are <8.3% for intraday precision and <10.3% for inter-day precision. In all cases, the fiber to fiber reproducibility is <12.2%. For both analytes the linear dynamic ranges are 0.5-300 ng.mL^-1. The procedure was successfully applied to the analysis of spiked agricultural water samples. Graphical abstract A novel inorganic/organic hybrid nanocomposite was synthesized through in situ hydrothermal deposition of ZnO nanorods and ten placing a thin layer of polypyrrole on them by chemical vapor deposition polymerization. This nanocomposite was applied to fabricate a solid-phase microextraction fiber for the extraction of amitraz and teflubenzuron pesticides residue from agricultural samples prior to their quantitation by GC-MS.

Ionic liquid-modified luffa sponge fibers for dispersive solid-phase extraction of benzoylurea insecticides from water and tea beverage samples

Ionic liquid-modified luffa sponge fibers were used as efficient and environmentally friendly sorbents in the dispersive solid-phase extraction method.

Using cobalt/chromium layered double hydroxide nano-sheets as a novel packed in-tube solid phase microextraction sorbent for facile extraction of acidic pesticides from water samples

Cobalt/chromium-layered double hydroxide (Co/Cr (NO₃⁻)-LDH) nano-sheets were employed as a packed in-tube solid phase microextraction sorbent for efficient extraction of acidic pesticides from water samples.

Porphyrin based porous organic polymer modified with Fe3O4 nanoparticles as an efficient adsorbent for the enrichment of benzoylurea insecticides

Porphyrin-based porous organic polymers (P-POPs) are amorphous polymers linked by strong covalent bonds between the porphyrin subunits that act as building blocks. The authors describe a magnetic P-POP that possesses high surface area, a highly porous structure, and strong magnetism. The MP-POP was employed as a magnetic sorbent for the extraction of benzoylurea insecticides from cucumber and tomato samples prior to their determination by HPLC. The sorbent has a typical sorption capacity of 1.90-2.00 mg∙g^-1. The method exhibits a good linear range (0.8-160 ng·g^-1), low limits of detection (0.08-0.2 ng·g^-1), and high method recoveries (81.8-103.5%) for cucumber and tomato samples. The MP-POP has different adsorption capabilities for the benzoylurea insecticides, phenylurea herbicides and phenols compounds, and the adsorption mechanism is found to be based on π-stacking, hydrogen-bonding, and hydrophobic interactions. Graphical abstract A novel magnetic porphyrin-based porous organic polymer was fabricated and used as the adsorbent for the efficient extraction of benzoylurea insecticides.

Rapid analysis of fungicides in tea infusions using ionic liquid immobilized fabric phase sorptive extraction with the assistance of surfactant fungicides analysis using IL-FPSE assisted with surfactant

A green, simple, inexpensive, and sensitive ionic liquid immobilized fabric phase sorptive extraction method coupled with high performance liquid chromatography was developed for rapid screening and simultaneous determination of four fungicides (azoxystrobin, chlorothalonil, cyprodinil and trifloxystrobin) residues in tea infusions. This IL modified extraction fiber is capable of extracting target analytes directly from complicated tea water matrices with the addition of surfactant. A series of extraction conditions were investigated by one-factor-at-a-time approach and orthogonal test. After a series experiments, the optimum conditions were found to be 10% [HIMIM]NTf₂ as coating solution, 2min vortex time, 500μL acetonitrile as dispersive solvent and 2min desorption time. Under the above conditions, the proposed technique was applied to detect fungicides from real tea water samples with satisfactory results.

Freezing temperature controlled deep eutectic solvent dispersive liquid–liquid microextraction based on solidification of floating organic droplets for rapid determination of benzoylureas residual in water samples with assistance of metallic salt

A hydrophobic deep eutectic solvent worked as an extractant to extract benzoylureas with assistance of FeCl₃ contained dispersive-demulsified solvent.

Rapid and label-free strategy for the sensitive detection of Hg2+ based on target-triggered exponential strand displacement amplification

A rapid and label-free strategy for sensitive detection of Hg²⁺ is developed based on target-triggered exponential strand displacement amplification (eSDA).

Crosslinked polymeric ionic liquids as solid-phase microextraction sorbent coatings for high performance liquid chromatography

Neat crosslinked polymeric ionic liquid (PIL) sorbent coatings for solid-phase microextraction (SPME) compatible with high-performance liquid chromatography (HPLC) are reported for the first time. Six structurally different PILs were crosslinked to nitinol supports and applied for the determination of select pharmaceutical drugs, phenolics, and insecticides. Sampling conditions including sample solution pH, extraction time, desorption solvent, desorption time, and desorption solvent volume were optimized using design of experiment (DOE). The developed PIL sorbent coatings were stable when performing extractions under acidic pH and remained intact in various organic desorption solvents (i.e., methanol, acetonitrile, acetone). The PIL-based sorbent coating polymerized from the IL monomer 1-vinyl-3-(10-hydroxydecyl) imidazolium chloride [VC10OHIM][Cl] and IL crosslinker 1,12-di(3-vinylbenzylimidazolium) dodecane dichloride [(VBIM)2C12] 2[Cl] exhibited superior extraction performance compared to the other studied PILs. The extraction efficiency of pharmaceutical drugs and phenolics increased when the film thickness of the PIL-based sorbent coating was increased while many insecticides were largely unaffected. Satisfactory analytical performance was obtained with limits of detection (LODs) ranging from 0.2 to 2 μg L(-1) for the target analytes. The accuracy of the analytical method was examined by studying the relative recovery of analytes in real water samples, including tap water and lake water, with recoveries varying from 50.2% to 115.9% and from 48.8% to 116.6%, respectively.