New approach for the simultaneous determination fungicide residues in food samples by using carbon nanofiber packed microcolumn coupled with HPLC

Stirred discs from polycaprolactone nanofibers highly doped with graphene for straightforward preconcentration of pollutants in environmental waters

A novel sorbent for solid phase extraction (SPE) based on hybrid nanofibrous polycaprolactone containing graphene nanoparticles has been prepared. The preparation of hybrid polymer nanofibers with a very high 1:1 polymer/graphene ratio was achieved for the first time using alternating current electrospinning. The final appearance of these nanofibers was a thick porous layer that was cut into the shape of easy-to-handle extraction discs. Based on the preliminary study in which the graphene content varied, 30% graphene-doped nanofibers (w/w) exhibited the highest recoveries and enabled a significant increase in the retention of analytes, 2-25 times in comparison to PCL. The incorporation of graphene resulted in a higher surface area of 12 g/m2 compared to 2 g/m2 determined for the native polycaprolactone (PCL) nanofibers. This unique material was applied for a simple stirred disc sorptive extraction and preconcentration of trace levels of emerging organic environmental contaminants, bisphenols A, AF, AP, C, S, Z, 3-chlorophenol, and pesticides fenoxycarb, deltamethrin, and kadethrin from surface waters prior to HPLC-DAD determination. This was accomplished by stirring the unsupported nanofiber disc in a large-volume sample with RSD of five extractions of 3-15%. Recoveries yielded 87-120%, except 52% for bisphenol S due to its high polarity. Optimization of the extraction procedure included conditioning, sample volume, extraction time, and elution solvent. Our novel desorption procedure carried out in a vial used for the direct injection into the HPLC system significantly reduced sample handling and minimized potential human error.

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.

In Situ Self-Assembled Formation of Nitrogen-Rich Ag@Ti3C2 Film for Sensitive Detection and Spatial Imaging of Pesticides with Laser Desorption/Ionization Mass Spectrometry (LDI-MS)

Pesticide residues are hazardous to human health; thus, developing a rapid and sensitive method for pesticide detection is an urgent need. Herein, novel nitrogen-rich Ag@Ti₃C₂ (Ag@N-Ti₃C₂) was synthesized via an ecofriendly, ultraviolet-assisted strategy, followed by in situ formation of a highly homogeneous film on target carriers via a facile water evaporation-induced self-assembly process. Ag@N-Ti₃C₂ shows greater surface area, electrical conductivity, and thermal conductivity than Ti₃C₂. This Ag@N-Ti₃C₂ film overcomes the limitations of conventional matrixes and allows laser desorption/ionization mass spectrometry (LDI-MS) to provide fast and high-throughput analysis of pesticides (e.g., carbendazim, thiamethoxam, propoxur, dimethoate, malathion, and cypermethrin) with ultrahigh sensitivity (detection limits of 0.5-200 ng/L), enhanced reproducibility, extremely low background, and good salt tolerance. Furthermore, the levels of pesticides were quantified with a linear range of 0-4 μg/L (R² > 0.99). This Ag@N-Ti₃C₂ film was used for high-throughput analysis of pesticides spiked in traditional Chinese herbs and soft drink samples. Meanwhile, high-resolution Ag@N-Ti₃C₂ film-assisted LDI-MS imaging (LDI MSI) was used to successfully explore spatial distributions of xenobiotic pesticides and other endogenous small molecules (e.g., amino acids, saccharides, hormones, and saponin) in the roots of plants. This study presents the new Ag@N-Ti₃C₂ self-assembled film equably deposits on the ITO slides and provides a dual platform for pesticide monitoring and has the advantages of high conductivity, accuracy, simplicity, rapid analysis, minimal sample volume requirement, and an imaging function.

Construction of Stable Magnetic Vinylene-Linked Covalent Organic Frameworks for Efficient Extraction of Benzimidazole Fungicides

Covalent organic frameworks (COFs) have attracted impressive interest in separation on aqueous media. Herein, we integrated the stable vinylene-linked COFs with magnetic nanosphere via the monomer-mediated in situ growth strategy to construct a crystalline Fe₃O₄@v-COF composite for enrichment and determination of benzimidazole fungicides (BZDs) from complex sample matrices. The Fe₃O₄@v-COF has a crystalline assembly, high surface area, porous character together with a well-defined core-shell structure, and serves as progressive pretreatment materials for magnetic solid phase extraction (MSPE) of BZDs. Adsorption mechanism studies revealed that the extended conjugated system and numerous polar cyan groups on v-COF provides abundant π-π and multiple hydrogen bonding sites, which are conducive to interact with BZDs collaboratively. Fe₃O₄@v-COF also displayed enrichment effects to various polar pollutions with conjugated structures and hydrogen-bonding sites. Fe₃O₄@v-COF-based MSPE-high-performance liquid chromatography exhibited the low limit of detection, wide linearity, and good precision. Moreover, Fe₃O₄@v-COF showed better stability, enhanced extraction performance, and more sustainable reusability in comparison with its imine-linked counterpart. This work proposes a feasible strategy on constructing the crystalline stable magnetic vinylene-linked COF composite for the determination of trace contaminants in complex food matrices.

Determination of benzimidazoles in fruits by open-tubular capillary electrochromatography based on ionic liquids grafted covalent organic frameworks

A novel capillary electrochromatography method has been developed for the simultaneous quantification of ten benzimidazole fungicides in fruits. Herein, covalent organic frameworks (COFs) and ionic liquids (ILs) were successfully introduced to prepare open-tubular capillary column to improve the loading capacity and separation performance. The parameters effecting the analytical performance including pH and concentration of running buffer, separation voltage and the addition of organic solvent were investigated systematically. Under the optimized conditions, the method allowed the baseline separation of ten benzimidazole fungicides, and showed a good linearity in the range of 3.5-200 μg kg^-1 with the detection limits between 1.0 and 2.8 μg kg^-1. The intraday and interday precisions for recoveries were lower than 7.9% and 12.2%, respectively. Intraday and interday precisions for their retention times were lower than 3.2% and 6.6%, respectively. Satisfactory recoveries for grape, pear and orange samples at two concentrations were obtained ranging from 85.0 to 95.9% with RSDs lower than 7.8%, demonstrating the potential applications of the open-tubular capillary electrochromatography method for trace benzimidazole fungicides analysis in fruits.

Thiol-Yne Click Postsynthesis of a Sulfonate Group-Enriched Magnetic Microporous Organic Network for Efficient Extraction of Benzimidazole Fungicides

The lack of functional groups or binding sites largely hindered the broad application of microporous organic networks (MONs). Herein, we report the fabrication of the sulfonate group-enriched magnetic MON composite (MMON-SO₃H@SO₃Na) via the combination of the sulfonic acid group containing the monomer and thiol-yne click postmodification for efficient magnetic solid-phase extraction (MSPE) of benzimidazole fungicides (BZDs) from complex sample matrices. The well-defined core-shell-structured MMON-SO₃H@SO₃Na was obtained and served as an advanced adsorbent for MSPE for concentrating and monitoring trace BZDs. The MMON-SO₃H@SO₃Na with numerous sulfonate groups provides plenty of ion-exchange, hydrogen-bonding, and π-π sites, leading to the favorable affinity to BZDs via multiple interaction mechanisms. The MMON-SO₃H@SO₃Na-based MSPE-high-performance liquid chromatography method afforded a wide linear range, low limits of detection, large enrichment factors, good precisions, and reusability for BZDs. Trace BZDs in complex vegetables and fruit samples were successfully detected by the established method. The MMON-SO₃H@SO₃Na also exhibited good selectivity toward multiple types of polar contaminants containing hydrogen-bonding sites and aromatic structures. This work provided a new postsynthesis strategy for constructing novel and multifunctioned magnetic MONs for preconcentration of trace analytes in a complex matrix.

Evaluation of Dissipation Behavior, Residues, and Dietary Risk Assessment of Fludioxonil in Cherry via QuEChERS Using HPLC-MS/MS Technique

The chemical fungicide fludioxonil is widely used to control post-harvest fungal disease in cherries. This study was implemented to investigate the dissipation behaviours and residues of fludioxonil on cherries. A reliable and efficient analytical method was established. Cherry samples from four product areas were analyzed by QuEChERS and HPLC-MS/MS methods with acceptable linearity (R² > 0.99), accuracy (recoveries of 81–94%), and precision (relative standard deviation of 2.5–11.9%). The limits of quantification (LOQs) and limits of detection (LODs) of cherries were 0.01 mg/kg and 0.005 mg/kg. The dissipation of fludioxonil on cherries followed first order kinetics with half-lives of 33.7–44.7 days. The terminal residues of fludioxonil were all lower than 5.00 mg/kg, which is the MRL recommended by the European Commission. According to Chinese dietary patterns and terminal residue distributions, the risk quotient (RQs) of fludioxonil was 0.61%, revealing that the evaluated cherries exhibited an acceptably low dietary risk to consumers.

Chromatographic Methods for Detection and Quantification of Carbendazim in Food

Carbendazim (CBZ), which is a fungicide widely used for the management of plant diseases, has been detected in a number of food products. The negative effects of CBZ to human health have stimulated the reduction of the maximum residue limits (MRLs), and subsequently the development of reliable and sensitive detection methods. Here, we are reviewing for the first time all reported chromatographic methods for the detection and quantification of CBZ in food. Several techniques, including liquid chromatography (LC), thin layer chromatography (TLC), micellar electrokinetic chromatography (MEKC), and supercritical fluid chromatography (SFC), were used for the separation and detection of CBZ, showing diverse characteristics and sensitivity. Some methods allowed the specific determination of CBZ, whereas other methods were successfully applied for the simultaneous quantification of a huge number of pesticides. Most reported methods showed limits of detection (LOD) and quantification (LOQ) lower than the MRLs. Relevant efforts in the field have been directed toward the simplification and optimization of the extraction steps prior to the chromatographic separation to increase the recovery and reduce the matrix effects. In this Review, the matrices, extraction procedures, and separation and detection parameters are detailed and compared in order to provide new insights on the development of new reliable methods for the detection of CBZ in food.

Dissipation behavior, residues distribution and dietary risk assessment of tembotrione and its metabolite in maize via QuEChERS using HPLC-MS/MS technique

The dissipation and residues of tembotrione in corn field application were investigated using liquid chromatography tandem mass spectrometry (LC-MS/MS) method. The average recoveries of tembotrione in maize, corncob, and straw were in the ranges of 98-107% with relative standard deviations (RSDs ≤9.3%), respectively. The recoveries of M5 was in the ranges of 90-108% in all three matrices of maize, with RSDs were 3.3-12.8%. The LODs for tembotrione and M5 in maize were 0.85 μg/L and 1.0 μg/L, 0.84 μg/L and 0.43 μg/L in corncob, 0.94 μg/L and 1.5 μg/L in straw, respectively. The LOQs of the method in maize grain, corncob and straw were 0.01, 0.01 and 0.05 mg/kg for both analytes, respectively. The dissipation of tembotrione in straw was in compliance with the first-order dynamic equation, with half-lives of 1.18-1.23 days at Beijing and Heilongjiang. Total residue of tembotrione in maize grain and corncob matrix were both below 0.02 mg/kg, lower than the max residue limit (MRL) recommended by european food safety authority (EFSA). Risk quotients (RQs) of this pesticide was assessed via comparing national estimated daily intake with acceptable daily intake. The dietary intake risk of tembotrione residue in maize was very low for all groups of Chinese residents. These data could provide scientific data and strategies and facilitate Chinese government to establish the MRLs of tembotrione.

Simultaneous determination of pyridaben, dinotefuran, DN and UF in eggplant ecosystem under open-field conditions: Dissipation behaviour and residue distribution

A sensitive method for simultaneous determination of pyridaben, dinotefuran, DN and UF in eggplant ecosystem was established and validated through rapid resolution liquid chromatography triples quadrupole tandem mass spectrometry (RRLC-QqQ-MS/MS). Matrix-matched external calibrations were introduced to check matrix effects. Limits of quantification (LOQs) of pyridaben, dinotefuran, DN and UF in eggplant were 0.2, 0.2, 1.0 and 1.0 μg kg^-1, and 0.2, 0.2, 5.0 and 1.0 μg kg^-1 in soil, respectively. Limits of detection (LODs) of four pesticides were below 0.41 μg L^-1. The mean recoveries (n = 5) of these insecticides varied from 79.4% to 103%, and the relative standard deviations (RSDs) ranged from 2.1% to 15.3% at three levels. This method was applied to Chinese open-field samples from two representative locations, which were previously treated with these insecticides at the doses of 210-315 g a.i. ha^-1 twice or three times. The dissipations of pyridaben and dinotefuran in eggplant and soil followed first-order kinetics with the half-lives of 3.65-11.4 d. The residues of pyridaben and total dinotefuran (calculated as sum of dinotefuran parent, DN and UF) in eggplant were below 0.0311 mg kg^-1 at the pre-harvest interval (PHI, 7 d). Presently, no maximum residue limit (MRL) of pyridaben and dinotefuran in eggplant was recommended by China, Codex Alimentarius Commission (CAC) or European Union (EU). This study was important for evaluation of environmental fate and food safety of pyridaben and dinotefuran in eggplant ecosystems, and facilitated China to establish maximum residue limits (MRLs) of pyridaben and dinotefuran in eggplant.

Simultaneous Electrochemical Detection of Benzimidazole Fungicides Carbendazim and Thiabendazole Using a Novel Nanohybrid Material-Modified Electrode

In this work, a novel ZnFe₂O₄/SWCNTs nanohybrid was successfully synthesized as electrode material and applied to the simultaneous quantitative determination of carbendazim (CBZ) and thiabendazole (TBZ). The electrochemical behaviors of CBZ and TBZ on the ZnFe₂O₄/SWCNTs/GCE were investigated using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The electrochemical active area of modified electrode was calculated, which is nearly 5.5 times that of the bare electrode. The influence of various factors such as accumulation time, pH and scan rates, type of surfactant, and the electrochemical reaction mechanism was studied. The results showed that the reaction of CBZ/TBZ was controlled by adsorption/diffusion and was a quasi-reversible/an irreversible process at the ZnFe₂O₄/SWCNTs/GCE. In the pH 7.0 phosphate-buffered saline (PBS) containing 10.0 μg/mL CTAB, the electrochemical responses of CBZ and TBZ were separately investigated and were linearly dependent on their concentrations ranging from 0.5 to 100.0 μM, with relatively low detection limits of 0.09 and 0.05 μM, respectively. The concentration range for the simultaneous determination of CBZ and TBZ was 1.0-100.0 μM. Furthermore, with satisfactory results, the proposed electrochemical sensor was successfully applied to the determination of CBZ and TBZ in the real samples.

Automated Multiplug Filtration Cleanup for Pesticide Residue Analyses in Kiwi Fruit (Actinidia chinensis) and Kiwi Juice by Gas Chromatography-Mass Spectrometry

To reduce labor-consuming manual operation workload in the cleanup steps, an automated multiplug filtration cleanup (m-PFC) method for QuEChERS (quick, easy, cheap, effective, rugged, and safe) extracts was developed. It could control the volume and speed of pulling and pushing cycles accurately. In this study, m-PFC was based on multiwalled carbon nanotubes (MWCNTs) mixed with primary-secondary amines (PSA) and anhydrous magnesium sulfate (MgSO4) in a packed column for analysis of pesticide residues followed by gas chromatography-mass spectrometry (GC-MS) detection. It was validated by analyzing 33 pesticides in kiwi fruit and kiwi juice matrices spiked at two concentration levels of 10 and 100 μg/kg. Salts, sorbents, m-PFC procedure, 4 mL of automated pulling and pushing volume, 6 mL/min automated pulling speed, and 8 mL/min pushing speed were optimized for each matrix. After optimization, spike recoveries were within 71-120% and <20% RSD for all analytes in kiwi fruit and kiwi juice. Matrix-matched calibrations were performed with the coefficients of determination >0.99 between concentration levels of 10 and 1000 μg/kg. The developed method was successfully applied to the determination of pesticide residues in market samples.