Electromembrane extraction and preconcentration of carbendazim and thiabendazole in water samples before capillary electrophoresis analysis

Synthesis of Carbon Dots from Peltophorum Pterocarpum Flowers for Selective Fluorescence Detection of Carbendazim

In this study, carbon dots (CDs) were synthesized from Peltophorum pterocarpum flowers as the precursor material using the hydrothermal method. The fluorescence emission spectra of the resulting Peltophorum pterocarpum CDs (PP-CDs) exhibited excitation-independent behavior, showing the fluorescence emission peak at 410 nm when excited at 330 nm. This method is simple, rapid and well consistent with the green chemistry and sustainable analytical method development. The as-synthesized PP-CDs acted as a promising fluorescent probe for detecting carbendazim (CBZ) via aggregation-induced emission mechanism, showing a linear response to CBZ concentrations ranging from 1 to 30 μM, with a detection limit of 5.41 nM. This method was successfully applied to quantify CBZ in food samples, achieving excellent recoveries of 99% with a relative standard deviation (RSD) of less than 2%.

A new coaxial flow-through probe for electromembrane extraction of methadone from clinical samples on-line coupled to capillary electrophoresis

BACKGROUND

A new design of a flow-through coaxial electromembrane extraction (EME) probe that can be on-line coupled with CE instrument is described and tested. The supporting base of the probe is a PDMS microchip with T-shaped channels into which two coaxially arranged capillaries for inlet and outlet solutions are inserted. The extraction part of the probe is a porous polypropylene hollow fiber, sealed at one end and modified with nitrophenyloctyl ether (NPOE) extraction fluid. The internal volume of the extraction probe is 1.1 μL.

RESULTS

The EME probe was tested on laboratory samples and methadone was extracted into 3.0 M AcOH as acceptor. The concentration dependence was linear in the range of 0.1-1.0 μg mL-1 at EME 300 s/150 V and in the range of 0.5-10.0 μg mL-1 at EME 100 s/150 V. The enrichment factor was greater than 30 and the LOD was 0.21 μg mL-1. The EME of methadone in clinical samples showed a linear concentration dependence in human urine and a nonlinear concentration dependence in serum. The distribution of methadone in each phase of the extraction system and the effect of extraction membrane thickness on the enrichment factor were studied. The EME probe can be applied repeatedly.

SIGNIFICANCE

The supporting base of EME probe and flow gating interface (FGI) are realized by a microfluidic PDMS microchips cast in the laboratory without the use of lithography. A supporting PDMS chip with coaxially arranged capillaries and extraction membrane forms a compact analytical instrument. The entire EME/CE analysis process is performed on a laboratory-made instrument and automated by LabView.

Highly sensitive fluorescent quantification of carbendazim by two-dimensional Tb-MOF nanosheets for food safety

Carbendazim (CBZ), a well-known benzimidazole pesticide, is utilized in agriculture to prevent and cure plant diseases caused by fungi. Residual CBZ in food poses serious threat to human health. Herein, a fluorescent two-dimensional terbium-based metal-organic framework (2D Tb-MOF) nanosheet sensor was developed for the rapid and ultrasensitive detection of CBZ. The 2D Tb-MOF nanosheets, prepared with Tb³⁺ ions and 5-borono-1,3-benzenedicarboxylic acid (BBDC) as the precursors, exhibited excellent optical properties. Upon the addition of CBZ, the fluorescence of Tb-MOF nanosheets was quenched because of the inner filter effect (IFE) and dynamic quenching. The fluorescence sensor offered two linear ranges of 0.06-4 and 4-40 µg/mL with a low detection limit of 17.95 ng/mL. Furthermore, the proposed sensing platform was successfully applied to assay CBZ in apples and tea, and satisfactory results were obtained. This study provides an effective alternative strategy for the qualitative and quantitative determination of CBZ to ensure food safety.

Environmental Applications of Electromembrane Extraction: A Review

Electromembrane extraction (EME) is a miniaturized extraction technique that has been widely used in recent years for the analysis and removal of pollutants in the environment. It is based on electrokinetic migration across a supported liquid membrane (SLM) under the influence of an external electrical field between two aqueous compartments. Based on the features of the SLM and the electrical field, EME offers quick extraction, effective sample clean-up, and good selectivity, and limits the amount of organic solvent used per sample to a few microliters. In this paper, the basic devices (membrane materials and types of organic solvents) and influencing factors of EME are first introduced, and the applications of EME in the analysis and removal of environmental inorganic ions and organic pollutants are systematically reviewed. An outlook on the future development of EME for environmental applications is also given.

MWCNTs and ZnO-based Ce-MOF nanocomposites as enhanced sensing platform for electrochemical detection of carbendazim in Chinese traditional herbs samples

A facile and novel Ce-MOF@MWCNTs@ZnO-modified glassy carbon electrode was prepared through drop coating and used for accurate and sensitive electrochemical detection of carbendazim. The modification of ZnO nanospheres and Ce-based metal-organic frameworks (Ce-MOFs), which possess vast surface/bulk ratio, large surface area, and excellent catalytic ability, provided more active sites for reaction. The combination of multi-walled carbon nanotubes endowed the modified electrode with excellent conductivity and greatly accelerated the electron transfer. The promotion of electrochemical response and the significant improvement of peak current indicated the outstanding electrocatalytic ability of the modified electrode. The oxidation peak current of carbendazim which was measured by DPV in a potential range from 0.5 to 1.0 V produced a good linear relationship in the concentration ranges 0.05-10.0 μM and 10.0-50.0 μM under  optimized experimental conditions. The detection limit was 13.2 nM (S/N = 3). The constructed electrode was successfully applied to the detection of carbendazim in Lithospermum and Glycyrrhiza uralensis real samples and exhibited satisfactory RSD (2.7-3.6% and 1.6-4.8%, respectively) and recovery (102-106% and 97.7-107%, respectively).

Review of Characteristics and Analytical Methods for Determination of Thiabendazole

Thiabendazole (TBZ) is a fungicide and anthelmintic drug commonly found in food products. Due to its toxicity and potential carcinogenicity, its determination in various samples is important for public health. Different analytical methods can be used to determine the presence and concentration of TBZ in samples. Liquid chromatography (LC) and its subtypes, high-performance liquid chromatography (HPLC) and ultra-high-performance liquid chromatography (UHPLC), are the most commonly used methods for TBZ determination representing 19%, 18%, and 18% of the described methods, respectively. Surface-enhanced Raman spectroscopy (SERS) and fluorimetry are two more methods widely used for TBZ determination, representing 13% and 12% of the described methods, respectively. In this review, a number of methods for TBZ determination are described, but due to their limitations, there is a high potential for the further improvement and development of each method in order to obtain a simple, precise, and accurate method that can be used for routine analysis.

Intelligent analysis of carbendazim in agricultural products based on a ZSHPC/MWCNT/SPE portable nanosensor combined with machine learning methods

A nano-ZnS-decorated hierarchically porous carbon (ZSHPC) was mixed with MWCNTs to obtain ZSHPC/MWCNT nanocomposites. Then, ZSHPC/MWCNTs were used to modify a screen-printed electrode, and a portable electrochemical detection system combined with machine learning methods was used to investigate carbendazim (CBZ) residues in rice and tea. The electrochemical performance of the constructed electrode showed that the electrode had good electrocatalytic ability, large effective surface area, strong stability and anti-interference ability. Support Vector Machine (SVM), Least Square Support Vector Machine (LS-SVM) and Back Propagation-Artificial Neural Network (BP-ANN) were used to establish the prediction model for CBZ residues in rice and tea, and the traditional linear regression was developed. The investigated results showed that the LS-SVM model had the best prediction performance and the lowest prediction error compared with the traditional linear regression, BP-ANN and SVM models. The R², RMSE, and MAE for the training set samples were 0.9969, 0.3605 and 0.2968, respectively. The R², RMSE, MAE and RPD for the prediction set samples were 0.9924, 0.6190, 0.5360 and 10.3097, respectively. The average recovery range of CBZ in tea and rice was 98.77-109.32% and that of RSD was 0.47-2.58%, indicating that the rapid analysis of CBZ pesticide residues in agricultural products based on a portable electrochemical detection system combined with machine learning was feasible.

Highly sensitive electrochemical detection of carbendazim residues in water by synergistic enhancement of nitrogen-doped carbon nanohorns and polyethyleneimine modified carbon nanotubes

Carbendazim (CBZ) can protect crops from pathogens, but it is also easy to cause pesticide residues, threatening human health. In our work, an electrochemical sensor based on nitrogen-doped carbon nanohorns (N-CNHs) and polyethyleneimine-modified carbon nanotubes (PEI-CNTs) was developed for the detection of CBZ content in water. The results showed that N-doping provided the CN bonds for CNHs and improved the electrochemical reaction performance of N-CNHs surface. With the participation of PEI, the surface of CNTs was positively charged and contained a large number of NH bonds, which not only promoted the electrostatic assembly of N-CNHs and PEI-CNTs but also was beneficial to further enriching CBZ. After further ultrasound-assisted assembly of N-CNHs and PEI-CNTs, the electron transfer capacity, electrochemical active surface area, and catalytic activity of N-CNHs/PEI-CNTs were significantly improved. The sensor performed a wider linear range (15 nmol/L ~ 70 μmol/L), low detection limit (4 nmol/L) and satisfactory recovery (87.33 % ~ 117.67 %) under the optimal conditions. In addition, the sensor had good anti-interference, reproducibility, and stability. Our work provided a new strategy for quantification of CBZ in environment.

Electromembrane extraction of polar substances - Status and perspectives

In this article, the scientific literature on electromembrane extraction (EME) of polar substances (log P < 2) is reviewed. EME is an extraction technique based on electrokinetic migration of analyte ions from an aqueous sample, across an organic supported liquid membrane (SLM), and into an aqueous acceptor solution. Because extraction is based on voltage-assisted partitioning, EME is fundamentally suitable for extraction of polar and ionizable substances that are challenging in many other extraction techniques. The article provides an exhaustive overview of papers on EME of polar substances. From this, different strategies to improve the mass transfer of polar substances are reviewed and critically discussed. These strategies include different SLM chemistries, modification of supporting membranes, sorbent additives, aqueous solution chemistry, and voltage/current related strategies. Finally, the future applicability of EME for polar substances is discussed. We expect EME in the coming years to be developed towards both very selective targeted analysis, as well as untargeted analysis of polar substances in biomedical applications such as metabolomics and peptidomics.

A multicolor enzyme-linked immunoassay method for visual readout of carbendazim

Enzyme-linked immunosorbent assay (ELISA) with high specificity and sensitivity is one of the most popular techniques for detecting carbendazim (CBD), a commonly used benzimidazole fungicide in agriculture. However, the traditional ELISA based on the horseradish peroxidase (HRP)-3,3',5,5'-tetramethylbenzidine (TMB) system for CBD only displays the yellow color of TMB²⁺ from deep to light, making it difficult for the naked eye to judge whether CBD in fruits and vegetables exceeds the maximum residue limit. In this article, we intend to improve the traditional ELISA method to establish a multicolor signal output ELISA to achieve visual semiquantitative detection of CBD. This method is based on the optical properties of gold nanorods (AuNRs). After introducing AuNRs into TMB²⁺ solution, which was produced by the HRP-TMB system of traditional ELISA, AuNRs were quickly etched by TMB²⁺. Consequently, the longitudinal localized surface plasmon resonance peak of AuNRs shows a clear blue shift and a vivid color change. Different concentrations of CBD generate different amounts of TMB²⁺, which in turn leads to different etching degrees of AuNRs, and ultimately results in a rainbow-like color change. As a result, CBD from 0.08 to 100 ng mL^-1 can be easily distinguished by the naked eye, which does not require any large instruments. Moreover, the colors displayed by 0.49 ng mL^-1 (purple) and 0 ng mL^-1 (pink) are significantly different from each other. It should be noted that 0.49 ng mL^-1 is far below the most stringent maximum residue limit of CBD in the world. Additionally, the quantitative determination of CBD spiked in canned citrus, citrus fruits, chives, and cabbage samples showed satisfactory recoveries. The good performance of the AuNR-based ELISA makes it have a wide range of application prospects in food safety and international trade.

Chitosan biofilms: Insights for the selective electromembrane extraction of fluoroquinolones from biological samples

A selective electromembrane extraction procedure for the extraction of Enrofloxacin, Marbofloxacin and Flumequine, usually employed as antibiotic in veterinarian use, is proposed by using a chitosan biofilm, composed by 60% (w/w) chitosan and 40% (w/w) Aliquat®336, as active biopolymeric support. The interaction mechanism occurring between the target drugs and the biopolymer has been deeply studied using the Quantum Theory of Atoms in Molecules. The obtained results show the interaction between the extracted fluoroquinolones and the biomembrane is stabilized by two hydrogen bonds formed between both the carboxyl and keto groups of the drugs with both the amine and hydroxyl groups of glucosamine in the biopolymer. The energetic results agree with the high extraction efficiency obtained for Marbofloxacin, Enrofloxacin and Flumequine in terms of enrichment factors (83, 82 and 58, respectively) in presence of other fluoroquinolones. Under optimum conditions, the proposed electromembrane extraction method exhibits wide linear ranges of 4.2-200 μg L^-1, 5.6-200 μg L^-1 and 5.1-200 μg L^-1, respectively; low limits of detection close to 1.3 μg L^-1 and appropriate repeatability (relative standard deviation values 4-7%).

Selectivity and efficiency of electromembrane extraction of polar bases with different liquid membranes-Link to analyte properties

In the present fundamental study, selectivity and efficiency of electromembrane extraction of 50 polar basic substances (-6.7 < log P < +1.0) was systematically studied for ten different supported liquid membranes. For each model substance, 23 molecular descriptors were collected and these were investigated as potential parameters for understanding of extraction efficiency and selectivity by means of partial least squares regression. Overall, a highly aromatic deep eutectic solvent composed of coumarin and thymol with addition of 2% ionic carrier (di(2-ethylhexyl) phosphate) provided the highest extraction efficiency with an average extraction yield of 69% from pure water samples, 55% from plasma, and 62% from urine. With this solvent system, ionic, cation-π, and π-π interactions between the supported liquid membrane and analytes were dominant. Supported liquid membranes without aromaticity, however, operated primarily based on hydrogen-bonding interactions. This is the first time the relationship between analyte properties, solvent composition, and extraction yield has systematically been studied for polar bases in electromembrane extraction. This new knowledge represents a first step toward enabling future development and optimization of electromembrane extraction systems for polar bases based on rational design, rather than trial-and-error approaches.

A highly sensitive detection of carbendazim pesticide in food based on the upconversion-MnO2 luminescent resonance energy transfer biosensor

Carbendazim (CBZ) pesticide residues in food products have become a growing concern in recent years. Herein, a sensitive biosensor for detecting CBZ was developed based on luminescent resonance energy transfer (LRET) from aptamer labeled upconversion nanoparticles (UCNPs, donor) to manganese dioxide (MnO₂, acceptor) nanosheets. The strong overlap between the absorption spectrum of MnO₂ and the UCNPs fluorescence emission allowed the luminescence quenching. With the addition of CBZ, it tended to bind with specific aptamers, which culminated in the UCNPs-aptamer dropping off MnO₂ nanosheets and restoring the fluorescence. A linear calibration plot between logarithmic CBZ concentration and fluorescence intensity was acquired in the range of 0.1-5000 ng·mL^-1, with a limit of detection 0.05 ng·mL^-1, indicating that the UCNPs- MnO₂ aptasensor is a rapid, sensitive and specific quantitative detection platform for CBZ. Furthermore, the precision and accuracy of the developed LRET biosensor was validated by HPLC method with no significant differences.

Fluorescence enhancement of fungicide thiabendazole by van der Waals interaction with transition metal dichalcogenide nanosheets for highly specific sensors

Many molecules quench their fluorescence upon adsorption on surfaces. Herein we show that the interaction of thiabendazole, a widespread used fungicide of the benzimidazole family, with nanosheets of transition metal dichalcogenides, particularly of WS2, leads to a significant increase, more than a factor of 5, of the fluorescence yield. This surprising effect is rationalized by DFT calculations and found to be related to the inhibition of the intramolecular rotation between the benzimidazole and thiazole groups due to a bonding rigidization upon interaction with the MoS2 surface. This non-covalent adsorption leads to a redistribution of the molecular LUMO that blocks the non-radiative energy dissipation channel. This unusual behaviour does not operate either for other molecules of the same benzimidazole family or for other 2D materials (graphene or graphene oxide). Moreover, we found that a linear dependence of the emission with the concentration of thiabendazole in solution, which combined with the specificity of the process, allows the development of a highly sensitive and selective method towards thiabendazole determination that can be applied to real river water samples. An excellent detection limit of 2.7 nM, comparable to the best performing reported methods, is obtained with very good accuracy (Er ≤ 6.1%) and reproducibility (RSD ≤ 4.1%) in the concentration range assayed.

Applications of Hollow-Fiber and Related Microextraction Techniques for the Determination of Pesticides in Environmental and Food Samples—A Mini Review

Pesticides represent one of the most important groups of analytes in environmental analysis. Moreover, their levels are very frequently determined in food and beverages due to the concern over their possible adverse health effects. Their concentration in samples is usually very low; thus, they have to be preconcentrated. Conventional solvent and solid-phase extractions are mainly used for this purpose, but miniaturized approaches are also being applied more and more often. The present review covers solvent microextractions that use a semi-permeable membrane barrier between the sample and the solvent. The main representatives of this approach are hollow-fiber microextraction (HFME), solvent bar microextraction (SBME), electromembrane extraction (EME), and different variations of those, such as combinations with other sorbent or solvent microextractions, electromigration, etc. The relevant research from the last decade, dealing with the application of these microextractions to the isolation of pesticides from various environmental and food samples, is critically discussed with emphasis on their strengths and weak points.

Green synthesized carbon dots embedded in silica molecularly imprinted polymers, characterization and application as a rapid and selective fluorimetric sensor for determination of thiabendazole in juices

An eco-friendly method was used to synthesize carbon dots (CDs) from Rosemary leaves, as a carbon source. The as-synthesized CDs was applied as a fluorophore in an optical sensor after modification with molecularly imprinted polymers (MIPs) for determination of thiabendazole (TBZ). For this purpose, a silica shell using tetraethoxysilane (TEOS), as a Si source, was stabilized on the surface of CDs via reverse microemulsion technique. Following, MIPs were synthesized in the presence of TBZ as a template, using 3-aminopropyl triethoxysilane and TEOS as a functional monomer and a crosslinker, respectively. After optimization of the experimental parameters, a linear dynamic range of 0.03-1.73 μg/mL TBZ with a detection limit as 8 ng/mL were obtained for the suggested method. Finally, the proposed sensor was successfully applied for the determination of TBZ in apple, orange, and tomato juices. This sensor is a simple, rapid, selective, and non-expensive method for TBZ measurement.

A novel electrochemical sensor based on molecularly imprinted polymer modified hollow N, S-Mo2C/C spheres for highly sensitive and selective carbendazim determination

A novel electrochemical sensor based on nitrogen and sulfur doped hollow Mo₂C/C spheres (N, S-Mo₂C) and molecularly imprinted polymer (MIP) was proposed for carbendazim (CBD) determination. The N, S-Mo₂C were prepared by first nitrogen and sulfur doping via one-pot method and subsequent carbonization at high temperature. A film of MIP was then fabricated in situ on the N, S-Mo₂C surface by electropolymerization, with CBD acting as template molecule and o-phenylenediamine as functional monomer. The N, S-Mo₂C were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and electrochemical behaviors of CBD on differently modified electrodes were explored by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Under the optimal conditions, a calibration curve of current shift versus the logarithm of CBD concentration was obtained in the range of 1×10^-12 ∼ 8×10^-9 M with a detection limit of 6.7×10^-13 M (S/N=3). Moreover, the proposed sensor exhibited favorable stability and selectivity, and was applied to analyze pesticide residues in fruits and vegetables with decent accuracy.

Quantitation of zolpidem in biological fluids by electro-driven microextraction combined with HPLC-UV analysis

In this study, for the first time, an electro-driven microextraction method named electromembrane extraction combined with a simple high performance liquid chromatography and ultraviolet detection was developed and validated for the quantitation of zolpidem in biological samples. Parameters influencing electromembrane extraction were evaluated and optimized. The membrane consisted of 2-ethylhexanol immobilized in the pores of a hollow fiber. As a driving force, a 150 V electric field was applied to facilitate the analyte migration from the sample matrix to an acceptor solution through a supported liquid membrane. The pHs of donor and acceptor solutions were optimized to 6.0 and 2.0, respectively. The enrichment factor was obtained >75 within 15 minutes. The effect of carbon nanotubes (as solid nano-sorbents) on the membrane performance and EME efficiency was evaluated. The method was linear over the range of 10-1000 ng/mL for zolpidem (R² >0.9991) with repeatability ( %RSD) between 0.3 % and 7.3 % (n = 3). The limits of detection and quantitation were 3 and 10 ng/mL, respectively. The sensitivity of HPLC-UV for the determination of zolpidem was enhanced by electromembrane extraction. Finally, the method was employed for the quantitation of zolpidem in biological samples with relative recoveries in the range of 60-79 %.