Determination of carbendazim residues in fruit juices by liquid chromatography-tandem mass spectrometry

Smartphone-assisted colorimetric aptasensor for rapid detection of carbendazim residue in agriculture products based on the oxidase-mimicking activity of octahedral Ag2O nanoparticles

Carbendazim (CBZ) is a widely used pesticides, and its excessive intake is serious damage to humans and animals. Herein, a stable and sensitive colorimetric aptasensor for rapid detection of CBZ residue has been established based on the enhancement of CBZ-specific aptamer (CZ-13) on oxidase-mimicking activity of octahedral Ag2O nanoparticles (NPs). The CZ-13 aptamer can significantly increase the catalytic activity by promoting the production of superoxide anion (·O2-) on the surface of Ag2O NPs and enhancing the affinity of octahedral Ag2O NPs to 3,3',5,5'-tetramethylbenzidine (TMB) molecules. In the presence of CBZ, the quantity of CZ-13 aptamer will be exhausted due to the specific binding to CBZ pesticide. Thus, the rest CZ-13 aptamer no longer enhanced the catalytic activity of octahedral Ag2O NPs, which leads to the change in color of sensing solution. The color change of sensing solution can be easily converted to the corresponding RGB value by a smartphone for quantitative and rapid detection of CBZ. The designed aptasensor has excellent sensitivity and specificity, and the limit of detection was determined as low as 7.35 μg L-1 for CBZ assay. Besides, the aptasensor exhibited good recoveries in the spiked cabbage, apple and cucumber, showing that it may have broad application prospects for detecting CBZ residues in agriculture products.

Sensitive dual-mode detection of carbendazim by molecularly imprinted electrochemical sensor based on biomass-derived carbon-loaded gold nanoparticles

A dual-mode electrochemical sensor was fabricated for carbendazim (CBD) detection. Biomass-derived carbon loaded gold nanoparticles (AuNPs/BC) were firstly coated on a glassy carbon electrode (GCE), and then molecularly imprinted polymer (MIP) of o-aminophenol was prepared on the resulting AuNPs/BC/GCE through electrochemical method in the presence of CBD. The AuNPs/BC had excellent conductivity, large surface and good electrocatalysis, while the imprinted film presented good recognition. Thus, the obtained MIP/AuNPs/BC/GCE exhibited sensitive current response to CBD. Furthermore, the sensor displayed good impedance response to CBD. Hence, a dual-mode detection platform for CBD was established. Under optimum conditions, the linear response ranges were as wide as 1.0 nM - 15 μM (by differential pulse voltammetry, DPV) and 1.0 nM - 10 μM (by electrochemical impedance spectroscopy, EIS), and the detection limits for these two methods were as low as 0.30 nM (S/N = 3) and 0.24 nM (S/N = 3), respectively. The sensor also had high selectivity, stability and reproducibility. The sensor was applied to detect CBD in spiked real samples, including cabbage, peach, apple and lake water, and the recoveries were 85.8-108% (by DPV) and 91.4-110% (by EIS); the relative standard deviations (RSD) were 3.4-5.3% (by DPV) and 3.7-5.1% (by EIS), respectively. The results were consistent with that obtained by high-performance liquid chromatography. Therefore, this sensor is a simple and effective tool for CBD detection, and it has good application potential.

Vertically-Ordered Mesoporous Silica Films Grown on Boron Nitride-Graphene Composite Modified Electrodes for Rapid and Sensitive Detection of Carbendazim in Real Samples

Carbendazim (CBZ), a kind of widely used pesticide, is harmful to human health and environmental ecology. Therefore, it is of great importance to detect CBZ in real samples. Herein we report the stable growth of vertically-ordered mesoporous silica films (VMSF) on the glassy carbon electrode (GCE) using boron nitride-reduced graphene oxide (BN-rGO) nanocomposite as an adhesive and electroactive layer. Oxygen-containing groups of rGO and 2D planar structure of BN-rGO hybrid favor the stable growth of VMSF via the electrochemically assisted self-assembly (EASA) method. Combining the good electrocatalytic activity of BN-rGO and the enrichment effect of VMSF, the proposed VMSF/BN-rGO/GCE can detect CBZ with high sensitivity (3.70 μA/μM), a wide linear range (5 nM–7 μM) and a low limit of detection (2 nM). Furthermore, due to the inherent anti-fouling and anti-interference capacity of VMSF, direct and rapid electrochemical analyses of CBZ in pond water and grape juice samples are also achieved without the use of complicated sample treatment processes.

Impact of gadolinium oxide with functionalized carbon nanosphere: A portable advanced electrocatalyst for pesticide detection in aqueous environmental samples

In this study, we developed a portable electrochemical sensor for realizing the pesticide residue in biological, environmental, and vegetable samples. A lower concentration of carbendazim pesticide (CBZ) was electrochemically exposed by newly developed gadolinium oxide/functionalized carbon nanosphere modified glassy carbon electrode (Gd₂O₃/f-CNS/GCE). The Gd₂O₃/f-CNS composite was prepared by two-pot ultrasonic-assisted co-precipitation method and characterized by various physicochemical analytical techniques. In addition, the electrocatalytic activity of the composite was investigated by cyclic voltammetry (CV) towards the detection of CBZ. Besides, the Gd₂O₃/f-CNS/GCE exhibited excellent electrocatalytic capability and sensitivity towards the oxidation of CBZ due to its high electrochemical active surface area, good conductivity, and fast electron transfer ability. A wide linear range of CBZ (0.5-552 μM) was attained with a low level of detection (LOD) of 0.009 μM L^-1 and exceptional stability of 93.41%. The proposed sensor exemplifies practical feasibility in blood serum, water, and vegetable samples with an remarkable recovery range of 96.27-99.44% and primary current response of ∼91% after 15 days.

Fast and Sensitive Determination of the Fungicide Carbendazim in Fruit Juices with an Immunosensor Based on White Light Reflectance Spectroscopy

Carbendazim is a systemic benzimidazole-type fungicide with broad-spectrum activity against fungi that undermine food products safety and quality. Despite its effectiveness, carbendazim constitutes a major environmental pollutant, being hazardous to both humans and animals. Therefore, fast and reliable determination of carbendazim levels in water, soil, and food samples is of high importance for both food industry and public health. Herein, an optical biosensor based on white light reflectance spectroscopy (WLRS) for fast and sensitive determination of carbendazim in fruit juices is presented. The transducer is a Si/SiO₂ chip functionalized with a benzimidazole conjugate, and determination is based on a competitive immunoassay format. Thus, for the assay, a mixture of an in-house developed rabbit polyclonal anti-carbendazim antibody with the standards or samples is pumped over the chip, followed by biotinylated secondary antibody and streptavidin. The WLRS platform allows for real-time monitoring of biomolecular interactions carried out onto the Si/SiO₂ chip by transforming the shift in the reflected interference spectrum caused by the immunoreaction to effective biomolecular adlayer thickness. The sensor is able to detect 20 ng/mL of carbendazim in fruit juices with high accuracy and precision (intra- and inter-assay CVs ≤ 6.9% and ≤9.4%, respectively) in less than 30 min, applying a simple sample treatment that alleviates any "matrix-effect" on the assay results and a 60 min preincubation step for improving assay sensitivity. Excellent analytical characteristics and short analysis time along with its small size render the proposed WLRS immunosensor ideal for future on-the-spot determination of carbendazim in food and environmental samples.

Disposable pipette extraction using a selective sorbent for carbendazim residues in orange juice

In this work, a selective sorbent for carbendazim was prepared by the thermal immobilization of the poly(glycidoxypropylmethyl-co-dimethylsiloxane), PGDMS, on silica. The lab-made Si(PGDMS) sorbent was physicochemically and morphologically characterized and was used into the pipette tip for the disposable pipette extraction (DPX) of carbendazim residues of orange juice. The DPX method was optimized from a central composite design and validated according to the SANTE/11813/2017 document recommended by the European Union. The proposed method presented recoveries between 93 and 110% with RSD <16% and the limit of quantification below the MRL for carbendazim in citrus. The whole sample preparation process was carried out at less than 3 min, with good accuracy and precision without the need of any cleanup step or electrical equipment, allowing its portability for the extraction of carbendazim residues in orange juice.

An ultra-sensitive aptasensor based on carbon nanohorns/gold nanoparticles composites for impedimetric detection of carbendazim at picogram levels

We reported a carbon nanohorns/gold nanoparticles composites-based impedimetric aptasensor for carbendazim (CBZ) detection in lettuce and orange juice at picogram levels. The increased electron-transfer resistance, resulting from the formation of CBZ-aptamer complex, was recorded by electrochemical impedance spectroscopy as the aptasensor response for CBZ. Under the optimal conditions, the proposed aptasensor displayed a linear response for CBZ ranging from 1 to 1000 pg mL^-1 with a detection limit of 0.5 pg mL^-1. Noteworthy, the as-developed aptasensor displayed the lowest detection limit for CBZ among the previously reported methods. Common pesticides (atrazine, thiamethoxam, etc.) with 100-fold concentration did not interfere the CBZ detection. For CBZ detection in lettuce and orange juice, satisfactory recoveries were obtained with standard addition method. Statistics demonstrated that no significant differences were found between the data provided by standard HPLC-MS reference method and developed aptasensing method in term of accuracy and precision. We believe that the proposed aptasensor possesses a potential application for CBZ monitoring in agricultural product and food.

Selection and Characterization of DNA Aptamers for Electrochemical Biosensing of Carbendazim

This article reports a novel aptamer-based impedimetric detection of carbendazim, a commonly used benzimidazole fungicide in agriculture. High affinity and specificity DNA aptamers against carbendazim were successfully selected using systematic evolution of ligand by exponential enrichment (SELEX). The dissociation constants (K_ds) of the selected DNA aptamers after 10 in vitro selection cycles were characterized using fluorescence-based assays showing values in the nanomolar range. The aptamer which showed the highest degree of affinity and conformation change was used to fabricate an electrochemical aptasensor via self-assembly of thiol-modified aptamer on gold electrodes. The aptasensor exploits the specific recognition of carbendazim by the aptamer immobilized on the gold surface which leads to conformational changes in the aptamer structure. This conformational change alters the access of a ferrocyanide/ferricyanide redox couple to the aptasensor surface. The aptasensor response is thus measured by following the increase in the electron transfer resistance of the redox couple using Faradaic electrochemical impedance spectroscopy. This method allowed a selective and sensitive label-free detection of carbendazim within a range of 10 pg/mL-10 ng/mL with a limit of detection of 8.2 pg/mL. The aptasensor did not show cross reactivity with other commonly used pesticides such as fenamiphos, isoproturon, atrazine, linuron, thiamethoxam, trifluralin, carbaryl, and methyl parathion. Moreover, the aptasensor has been applied in different spiked food matrixes showing high recovery percentages. We believe that the proposed aptasensor is a promising alternative to the currently used methods for carbendazim monitoring.

Determination of Imidacloprid, Carbendazim and Thiabendazole Residues in Vegetables and Fruits by HPLC

The aim of this work was to establish a method that the residues of imidacloprid,carben-dazim and thiabendazole in fruits and vegetables were determined by HPLC.Acetonitrile was edded in the sample for extraction solvent, and using sodium chloride for absorbing water of the sample,then purified by NH2 solid phase extraction cartridge, the sample was detected by HPLC.Under the selected conditions,the detection limits of imidacloprid, carbendazim, thiabendazole were 0.002 mg/kg,0.003 mg/kg and 0.003 mg/kg respectively.Tests for recovery were made by addition of three pesticidess standards at three different concentration levels (0.1, 0.5 and 1.0 mg/kg) to the blank sample.The mean recovery rates of imidacloprid, carbendazimand thiabendazole were87.0%~99.2%,82.0%~96.0% and 80.0%~95.0% respectively , and the relative standard deviations were 0.52%~6.80%.The sensitivity, accuracy and precision of this method were able to meet the requirements for pesticide residue analysis.

Determination of several pesticides in water by solid-phase extraction, liquid chromatography and electrospray tandem mass spectrometry

The analysis of pesticides in water samples is a problem of primary concern for quality control laboratories due to the toxicity level of these compounds and their public health risk. In order to evaluate the impact of pesticides in the Lisbon drinking water supply system, following the requirements of the European Union Directive 98/83/EC, we developed and validated an analytical method based on the combination of solid-phase extraction with liquid chromatography and tandem mass spectrometry. In this work, several pesticides were studied: imidacloprid, dimethoate, cymoxanil, carbendazime, phosmet, carbofuran, isoproturon, diuron, methidathion, linuron, pyrimethanil, methiocarbe, tebuconazole and chlorpyrifos. Several parameters of the electrospray source were optimized in order to get the best formation conditions of the precursor ion for each pesticide, namely capillary and extractor voltage, cone voltage, cone gas flow rate and desolvation gas flow rate. After optimization of the collision cell energy of the triple quadrupole, two different precursor ion-product ion transitions were selected for each pesticide, one for quantification and one for qualification, and these ions were monitored under time-scheduled multiple reaction monitoring (MRM) conditions. The selection of specific fragment ions for each pesticide guarantees a high degree of selectivity as well as additional sensitivity to quantify trace levels of these pesticides in water samples. This method showed excellent linearity ranges for all pesticides, with correlation coefficients greater than 0.9989. Determination limits (between 0.0041 and 0.0480 microg/L), precision (RSD <9.18%), accuracy and recovery studies in several water samples using solid-phase extraction were also performed.

Current trends in solid-phase-based extraction techniques for the determination of pesticides in food and environment

Solid-phase extraction (SPE) procedures for pesticide residues in food and environment are reviewed and discussed. The use of these procedures, which include several approaches such as: matrix solid-phase dispersion (MSPD), solid-phase micro-extraction (SPME) and stir-bar sorptive extraction (SBSE), represents an opportunity to reduce analysis time, solvent consumption, and overall cost. SPE techniques differ from solvent extraction depending on the interactions between a sorbent and the pesticide. This interaction may be specific for a particular pesticide, as in the interaction with an immunosorbent, or non-specific, as in the way a number of different pesticides are adsorbed on apolar or polar materials. A variety of applications were classified according to the method applied: conventional SPE, SPME, hollow-fiber micro-extraction (HFME), MSPD and SBSE. Emphasis is placed on the multiresidue analysis of liquid and solid samples.

Pesticides analysis by liquid chromatography and capillary electrophoresis

Nowadays, a wide range of pesticides are used in agricultural production, and their monitoring in samples of environmental and alimentary interest is of extreme importance to ensure, among others, the safety of consumption of foods. The aim of this work is to provide updated information about the major developments in CE and HPLC in pesticide analysis, covering relevant publications between 2004 and early 2006. The use of different sample pretreatment steps to provide a suitable extraction of these compounds from the different matrices as well as to increase the sensitivity of the determination is also discussed.