Voltammetric detection of carbofuran determination using screen-printed carbon electrodes modified with gold nanoparticles and graphene oxide

Graphene derivatives-based electrodes for the electrochemical determination of carbamate pesticides in food products: A review

Graphene (GR) composites have great potential for the determination of carbamates pesticides (CPs) by electrochemical methods. Since the beginning of the 20th century, GR has shown remarkable promise as electrode material for various sensors. The contamination of food products with harmful CPs is a major problem as they do not always damage human health immediately, but can be harmful after prolonged exposure. A range of advantages can be gained from their electrochemical determination, such as high sensitivity, reasonably selectivity, rapid detection, low limit of detection, and easy electrode fabrication. Furthermore, these electrochemical techniques are robust, reproducible, user-friendly, and conform to both "green" and "white" analytical chemistry. This review is focused on results published in the last ten years in the field of electrochemical determination of CPs in food products using GR and its derivatives.

Current electroanalytical approaches in the carbamates and dithiocarbamates determination

Pesticides are a suitable tool for controlling plagues and disease vectors. However, their inappropriate use allows for contamination of the environment, soil, water, and foods. Carbamates and dithiocarbamates pesticides present accumulative effects in the human body resulting in hormonal, neurological and reproductive disorders, and some are still suspected or proven to give carcinogenic or mutagenic effects. This review provides a current electroanalytical approach in the carbamates and dithiocarbamates determination, showing the use of voltammetric techniques such as amperometry, cyclic and linear scan, differential pulse, and square wave voltammetry, indicating their advantages, disadvantages, and perspectives in electroanalytical detection of carbamates and dithiocarbamates in natural water and foods. Also are reported the different materials used in the preparation of working electrodes since their choice has an important impact on the success of the analytical applications, resulting in suitable sensitivity, selectivity, stability, and robustness.

Emerging Two-Dimensional Materials-Based Electrochemical Sensors for Human Health and Environment Applications

Two-dimensional materials (2DMs) have been vastly studied for various electrochemical sensors. Among these, the sensors that are directly related to human life and health are extremely important. Owing to their exclusive properties, 2DMs are vastly studied for electrochemical sensing. Here we have provided a selective overview of 2DMs-based electrochemical sensors that directly affect human life and health. We have explored graphene and its derivatives, transition metal dichalcogenide and MXenes-based electrochemical sensors for applications such as glucose detection in human blood, detection of nitrates and nitrites, and sensing of pesticides. We believe that the areas discussed here are extremely important and we have summarized the prominent reports on these significant areas together. We believe that our work will be able to provide guidelines for the evolution of electrochemical sensors in the future.

Electrochemical Synthesis of Reduced Graphene Oxide/Gold Nanoparticles in a Single Step for Carbaryl Detection in Water

In this study, an in situ synthesis approach based on electrochemical reduction and ion exchange was employed to detect carbaryl species using a disposable, screen-printed carbon electrode fabricated with nanocomposite materials. Reduced graphene oxide (rGO) was used to create a larger electrode surface and more active sites. Gold nanoparticles (AuNPs,) were incorporated to accelerate electron transfer and enhance sensitivity. A cation exchange Nafion polymer was used to enable the adhesion of rGO and AuNPs to the electrode surface and speed up ion exchange. Cyclic voltammetry (CV), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), electrical impedance spectroscopy (EIS), atomic force microscopy (AFM) and scanning electron microscopy (SEM) were performed to study the electrochemical and physical properties of the modified sensor. In the presence of differential pulse voltammetry (DPV), an rGO/AuNP/Nafion-modified electrode was effectively used to measure the carbaryl concentration in river and tap water samples. The developed sensor exhibited superior electrochemical performance in terms of reproducibility, stability, efficiency and selectivity for carbaryl detection with a detection limit of 0.2 µM and a concentration range between 0.5µM and 250 µM. The proposed approach was compared to capillary electrophoresis with ultraviolet detection (CE-UV).

New analytical strategies Amplified with 2D carbon nanomaterials for electrochemical sensing of food pollutants in water and soils sources

Pharmaceutical and food pollutants have threatened global health. Pharmacotherapy has left a positive impression in the field of health and life of people and animals. However, the many unresolved problems brought along with residues of pharmaceuticals in the environmental and food. Consumption of the world's freshwater resources, toxic chemicals, air pollution, plastic waste directly affects water and soil resources. Pesticides have a wide role in pollutants. Therefore, the determination of pesticides is significant to eliminate their negative effects on living things. Nowadays, there are many analytical methods available. However, new analysis methods are still being researched due to certain limitations of traditional methods. Electrochemical sensors have drawn attention because of their superior properties, such as short analysis time, affordability, high sensitivity, and selectivity. The development of new analytical strategies for assessing risks from pharmaceutical to food pollutants in water and soil sources is important for the measurement of different pollutants. Moreover, the 2D-carbon nanomaterials used in the development of electrochemical sensors are widely utilized to enlarge the surface area, increase porosity, and make easy immobilization. Graphene (graphene derivations) and carbon nanotubes integrated nanosensors are widely used for the determination of pesticides. 2D-carbon nanomaterials can be tailored according to the purpose of the study. The characterization and synthesis methods of 2D-carbon nanomaterials are widely explained. Furthermore, enzyme nanobiosensors, especially Acetylcholinesterase (AChE), are widely used to determine pesticides. The three main topics are focused on in this review: 2D-carbon nanomaterials, pesticides that threaten life, and the application of 2D-carbon nanomaterials-based electrochemical sensors. The various developed 2D-carbon nanomaterials-based electrochemical sensors were applied in pharmaceutical forms, fruits, tap/lake water, beverages, and soils sources. This work aims to indicate the recently published paper related to pesticide analysis and highlight the importance of 2D-nanomaterials on sensors.

A critical comparison between an ultra-high-performance liquid chromatography triple quadrupole mass spectrometry (UHPLC-QqQ-MS) method and an enzyme assay for anti-cholinesterase pesticide residue detection in cereal matrices

Analytical method development for the control of pesticide residues occurring in significant dietary foodstuffs is of utmost importance considering their potential impact on consumer health and food market sustainability. Depending on the purpose, either instrumental analysis, mainly chromatographic methods, or screening assays, mostly using biorecognition affinity, are commonly used, featuring different advantages and drawbacks. To practically compare these two different types of analytical strategies, we applied them for the detection of (i) 97 organophosphate (OP) and carbamate (CM) pesticide residues in wheat flour and (ii) carbofuran (a carbamate insecticide) in wheat, rye and maize flour samples. Regarding high-end analysis, an ultra-high-performance liquid chromatography coupled with triple quadrupole mass spectrometry (UHPLC-QqQ-MS) method was developed and validated achieving low limits of quantification (LOQs, from 0.002 to 0.040 mg kg^-1) and a short chromatographic run (12 min). In terms of bioanalytical methods, a fast (17 min) and cost-efficient (∼0.01€ per sample) acetylcholinesterase (AChE) microplate assay for carbofuran screening was utilized. Importantly, carbofuran was the strongest of the 11 OP and CM tested pesticides achieving a half maximal inhibitory concentration (IC₅₀) of 0.021 μM whilst the assay detectability was at the parts per billion level in all three cereal matrices. Based on the attained results, a critical discussion is presented providing the analytical merits and bottlenecks for each case and a wider outlook related to the application of analytical methods in the food safety control analytical scheme.

Electrochemical detection of methyl-paraoxon based on bifunctional cerium oxide nanozyme with catalytic activity and signal amplification effect

A new electrochemical sensor for organophosphate pesticide (methyl-paraoxon) detection based on bifunctional cerium oxide (CeO₂) nanozyme is here reported for the first time. Methyl-paraoxon was degraded into p-nitrophenol by using CeO₂ with phosphatase mimicking activity. The CeO₂ nanozyme-modified electrode was then synthesized to detect p-nitrophenol. Cyclic voltammetry was applied to investigate the electrochemical behavior of the modified electrode, which indicates that the signal enhancement effect may attribute to the coating of CeO₂ nanozyme. The current research also studied and discussed the main parameters affecting the analytical signal, including accumulation potential, accumulation time, and pH. Under the optimum conditions, the present method provided a wider linear range from 0.1 to 100 μmol/L for methyl-paraoxon with a detection limit of 0.06 μmol/L. To validate the proof of concept, the electrochemical sensor was then successfully applied for the determination of methyl-paraoxon in three herb samples, i.e., Coix lacryma-jobi, Adenophora stricta and Semen nelumbinis. Our findings may provide new insights into the application of bifunctional nanozyme in electrochemical detection of organophosphorus pesticide.

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A new electrochemical method for methyl-paraoxon detection by using bifunctional nanozyme was presented.

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The cerium oxide nanozyme modified glassy carbon electrode was prepared to improve the sensitivity.

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The developed method has been successfully applied in three herbal plant samples.

Paper and Other Fibrous Materials-A Complete Platform for Biosensing Applications

Paper-based analytical devices (PADs) and Electrospun Fiber-Based Biosensors (EFBs) have aroused the interest of the academy and industry due to their affordability, sensitivity, ease of use, robustness, being equipment-free, and deliverability to end-users. These features make them suitable to face the need for point-of-care (POC) diagnostics, monitoring, environmental, and quality food control applications. Our work introduces new and experienced researchers in the field to a practical guide for fibrous-based biosensors fabrication with insight into the chemical and physical interaction of fibrous materials with a wide variety of materials for functionalization and biofunctionalization purposes. This research also allows readers to compare classical and novel materials, fabrication techniques, immobilization methods, signal transduction, and readout. Moreover, the examined classical and alternative mathematical models provide a powerful tool for bioanalytical device designing for the multiple steps required in biosensing platforms. Finally, we aimed this research to comprise the current state of PADs and EFBs research and their future direction to offer the reader a full insight on this topic.

Recent Trends in the Improvement of the Electrochemical Response of Screen-Printed Electrodes by Their Modification with Shaped Metal Nanoparticles

Novel sensing technologies proposed must fulfill the demands of wastewater treatment plants, the food industry, and environmental control agencies: simple, fast, inexpensive, and reliable methodologies for onsite screening, monitoring, and analysis. These represent alternatives to conventional analytical methods (ICP-MS and LC-MS) that require expensive and non-portable instrumentation. This needs to be controlled by qualified technicians, resulting moreover in a long delay between sampling and high-cost analysis. Electrochemical analysis based on screen-printed electrodes (SPEs) represents an excellent miniaturized and portable alternative due to their disposable character, good reproducibility, and low-cost commercial availability. SPEs application is widely extended, which makes it important to design functionalization strategies to improve their analytical response. In this sense, different types of nanoparticles (NPs) have been used to enhance the electrochemical features of SPEs. NPs size (1–100 nm) provides them with unique optical, mechanical, electrical, and chemical properties that give the modified SPEs increased electrode surface area, increased mass-transport rate, and faster electron transfer. Recent progress in nanoscale material science has led to the creation of reproducible, customizable, and simple synthetic procedures to obtain a wide variety of shaped NPs. This mini-review attempts to present an overview of the enhancement of the electrochemical response of SPEs when NPs with different morphologies are used for their surface modification

Highly Selective Electrochemical Sensor Based on Gadolinium Sulfide Rod-Embedded RGO for the Sensing of Carbofuran

Nowadays, a lot of pesticides have been used in the agriculture field due to the global demand for food production. Carbofuran (CF) is the most commonly used carbamate compound that is responsible for the highest toxicity to humans compared to any other pesticide used in agricultural settings. Thus, rapid, portable, and low-cost sensors are needed for the detection of CF in the environment and food samples. Herein, we have successfully developed an electrochemical sensor using a glassy carbon electrode (GCE) modified with gadolinium sulfide (Gd₂S₃) and reduced graphene oxide (RGO) composite for the detection of carbofuran (CF). A novel Gd₂S₃/RGO composite was prepared by the facile hydrothermal route and confirmed by morphological and structural analyses such as field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray (EDX), powder X-ray diffraction (XRD), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS), and also the formation mechanism of Gd₂S₃/RGO composite was discussed. The desired electrical conductivity of Gd₂S₃ was enhanced by the RGO, which was estimated from the electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). Electrochemical studies demonstrated that the developed Gd₂S₃/RGO sensor was highly sensitive and selective to CF. In addition, the Gd₂S₃/RGO sensor exhibits a low detection limit (LOD) and the linear ranges were 0.0128 and 0.001-1381 μM, respectively, for CF detection under optimized experimental conditions. Moreover, we also investigated the practical applicability of the sensor for CF detection in the environment and food samples.

Exploring carbon particle type and plasma treatment to improve electrochemical properties of stencil-printed carbon electrodes

Stencil-printing conductive carbon inks has revolutionized the development of inexpensive, disposable and portable electrochemical sensors. However, stencil-printed carbon electrodes (SPCEs) typically suffer from poor electrochemical properties. While many surface pretreatments and modifications have been tested to improve the electrochemical activity of SPCEs, the bulk composition of the inks used for printing has been largely ignored. Recent studies of other carbon composite electrode materials show significant evidence that the conductive carbon particle component is strongly related to electrochemical performance. However, such a study has not been carried out with SPCEs. In this work, we perform a systematic characterization of SPCEs made with different carbon particle types including graphite particles, glassy carbon microparticles and carbon black. The relationship between carbon particle characteristics including particle size, particle purity, and particle morphology as well as particle mass loading on the fabrication and electrochemical properties of SPCEs is studied. SPCEs were plasma treated for surface activation and the electrochemical properties of both untreated and plasma treated SPCEs are also compared. SPCEs displayed distinct analytical utilities characterized through solvent window and double layer capacitance. Cyclic voltammetry (CV) of several standard redox probes, FcTMA+, ferri/ferrocyanide, and pAP was used to establish the effects of carbon particle type and plasma treatment on electron transfer kinetics of SPCEs. CV of the biologically relevant molecules uric acid, NADH and dopamine was employed to further illustrate the differences in sensing and fouling characteristics of SPCEs fabricated with different carbon particle types. SEM imaging revealed significant differences in the SPCE surface microstructures. This systematic study demonstrates that the electrochemical properties of SPCEs can be tuned and significantly improved through careful selection of carbon particle type and plasma cleaning with a goal toward the development of better performing electrochemical point-of-need sensors.

Determination and Extraction of Carbofuran Pesticide in Different Matrices using Cloud Point Extraction Method

Background:

Pesticides are increasingly used in agriculture and households, but they are also considered a major pollutant to the environment. Carbofuran (CAR; 2,3-dihydro-2,2- dimethylbenzofuran-7-yl methylcarbamate) is a widely used pesticide due to its effectiveness on soybean aphids.

Objectives:

A simple and green method was suggested for the extraction and determination of CAR in different matrices.

Methods:

A diazotization reaction involving the use of the drug compound metoclopramide was utilized in this study. A red dye product, which was formed from the diazotization coupling between CAR and diazotized metoclopramide (DMCP), was extracted using cloud point extraction with the nonionic surfactant Triton X-114 and measured at a wavelength of 515 nm.

Results:

The linearity of the extracted method was over a concentration range of 0.1-0.5 µg/mL (r2 = 0.996) for CAR with a detection limit of 0.064 µg/mL and enrichment factors of about 148 folds for CAR. The mean recovery percentage was in the range of 99-102% for water and soil samples with precision (RSD%) of less than 0.4%.

Conclusion:

The described method was effectively utilized in the simultaneous extraction of CAR from water and soil samples.

Electrochemical (Bio)Sensors for Pesticides Detection Using Screen-Printed Electrodes

Pesticides are among the most important contaminants in food, leading to important global health problems. While conventional techniques such as high-performance liquid chromatography (HPLC) and mass spectrometry (MS) have traditionally been utilized for the detection of such food contaminants, they are relatively expensive, time-consuming and labor intensive, limiting their use for point-of-care (POC) applications. Electrochemical (bio)sensors are emerging devices meeting such expectations, since they represent reliable, simple, cheap, portable, selective and easy to use analytical tools that can be used outside the laboratories by non-specialized personnel. Screen-printed electrodes (SPEs) stand out from the variety of transducers used in electrochemical (bio)sensing because of their small size, high integration, low cost and ability to measure in few microliters of sample. In this context, in this review article, we summarize and discuss about the use of SPEs as analytical tools in the development of (bio)sensors for pesticides of interest for food control. Finally, aspects related to the analytical performance of the developed (bio)sensors together with prospects for future improvements are discussed.

The benefits of carbon black, gold and magnetic nanomaterials for point-of-harvest electrochemical quantification of domoic acid

Gold nanostars (GNST), gold nanospheres (GNP) and carbon black (CB) are chosen as alternative nanomaterials to modify carbon screen-printed electrodes (c-SPEs). The resulting three kinds of modified c-SPEs (GNP-SPE, CB-SPE and GNSP-SPE) were electrochemically and microscopically characterized and compared with standardized c-SPEs after pretreatment with phosphate buffer by pre-anodization (pre-SPE). The results show outstanding electrochemical performance of the carbon black-modified SPEs which show low transient current, low capacitance and good porosity. A competitive chronoamperometric immunoassay for the shellfish toxin domoic acid (DA) is described. The performances of the CB-SPE, GNP-SPE and pre-SPE were compared. Hapten-functionalized magnetic beads were used to avoid individual c-SPE functionalization with antibody while enhancing the signal by creating optimum surface proximity for electron transfer reactions. This comparison shows that the CB-SPE biosensor operated best at a potential near - 50 mV (vs. Ag/AgCl) and enables DA to be determined with a detection limit that is tenfold lower compared to pre-SPE (4 vs. 0.4 ng mL-1). These results show very good agreement with HPLC data when analysing contaminated scallops, and the LOD is 0.7 mg DA kg-1 of shellfish. Graphical abstractSchematic representation of the magnetic bead-based immunoassay for the quantification of domoic acid (DA) in shellfish with nanomaterial-modified screen-printed electrodes. CB, carbon black; GNP, gold nanospheres; GNST, gold nanostars; MB, magnetic beads; DA-mAb, anti-DA monoclonal mouse antibody; HRP-pAb, horseradish conjugated polyclonal goat anti-mouse antibody; DA-BSA, bovine serum albumin conjugated DA; HQ, hydroquinone; BQ, benzoquinone.

Screen-Printed Electrodes Modified with Metal Nanoparticles for Small Molecule Sensing

Recent progress in the field of electroanalysis with metal nanoparticle (NP)-based screen-printed electrodes (SPEs) is discussed, focusing on the methods employed to perform the electrode surface functionalization, and the final application achieved with different types of metallic NPs. The ink mixing approach, electrochemical deposition, and drop casting are the usual methodologies used for SPEs' modification purposes to obtain nanoparticulated sensing phases with suitable tailor-made functionalities. Among these, applications on inorganic and organic molecule sensing with several NPs of transition metals, bimetallic alloys, and metal oxides should be highlighted.

Noble Metal Nanostructured Materials for Chemical and Biosensing Systems

Nanomaterials with unique physical and chemical properties have attracted extensive attention of scientific research and will play an increasingly important role in the future development of science and technology. With the gradual deepening of research, noble metal nanomaterials have been applied in the fields of new energy materials, photoelectric information storage, and nano-enhanced catalysis due to their unique optical, electrical and catalytic properties. Nanostructured materials formed by noble metal elements (Au, Ag, etc.) exhibit remarkable photoelectric properties, good stability and low biotoxicity, which received extensive attention in chemical and biological sensing field and achieved significant research progress. In this paper, the research on the synthesis, modification and sensing application of the existing noble metal nanomaterials is reviewed in detail, which provides a theoretical guidance for further research on the functional properties of such nanostructured materials and their applications of other nanofields.

Screening of Carbamate and Organophosphate Pesticides in Food Matrices Using an Affordable and Simple Spectrophotometric Acetylcholinesterase Assay

Carbamates (CMs) and organophosphates (OPs) are widely used pesticides with known neurotoxicity arising from the inhibition of acetylcholinesterase (AChE). When AChE is active, in vitro, it can hydrolyze certain substrates to colored products while in the presence of an inhibitor this color development is decreased. Based on this principle, an AChE assay for CM and OP compounds was optimized and validated for carbofuran, carbofuran-3-hydroxy and dichlorvos in lettuce and strawberry extracts. The analytical performance of the assay was confirmed by an accredited liquid chromatography tandem mass spectrometry (LC–MS/MS) method. The developed AChE assay achieved low limits of detection (LODs) at the part per billion (ppb) level, depending the analyte inhibitory strength, recovery rates higher than 70% and good repeatability. Moreover, the toxic unit (TU) approach was applied, for extracts containing the validated analytes, and antagonism was noticed in all cases. Overall, the developed method is rapid, simple, cost-effective and may find application as a low-cost pre-screening tool of AChE inhibitors presence. Last but not least, this study can be considered a guide on development, validation and benchmarking of bioassays in food safety, a topic, which is commonly mispresented in the available literature.

Evaluation of single and combined toxicity of bisphenol A and its analogues using a highly-sensitive micro-biosensor

Bisphenol analogues have been developed as alternatives to bisphenol A (BPA), a common chemical with potential adverse effects on human health. It is imperative to perform a fast and sensitive evaluation for the toxicity of these bisphenol analogues. This study introduces a label-free electrochemical biosensor based on a screen-printed electrode modified with the carboxylated multi-walled carbon nanotube/rhodamine B/gold nanoparticle. Ctenopharyngodon idella kidney (CIK) cells were used as the biological recognition agent to detect changes in electrochemical signals and indicate the cell viability. Only 20 μL of sample was required for detection, which was much lower than that of other conventional electrochemical methods (≥ 1 mL). This biosensor was examined for the cytotoxicity of BPA, bisphenol AF (BPAF), bisphenol B (BPB), bisphenol F (BPF), and bisphenol S (BPS) to CIK cells. The half inhibition concentration (IC₅₀) values after 48 h of exposure indicated that the rank order of cytotoxicities was BPAF > BPB > BPA > BPF > BPS. The morphological changes in CIK cells after treatment with various bisphenols were investigated, and the combined toxicities of the binary bisphenol mixtures were determined. Potentially synergistic and additive effects were observed. These findings provide new insights into the cytotoxicity of bisphenol analogues.

A Hybrid Lab-on-a-Chip Injector System for Autonomous Carbofuran Screening

Securing food safety standards is crucial to protect the population from health-threatening food contaminants. In the case of pesticide residues, reference procedures typically find less than 1% of tested samples being contaminated, thus indicating the necessity for new tools able to support smart and affordable prescreening. Here, we introduce a hybrid paper-lab-on-a-chip platform, which integrates on-demand injectors to perform multiple step protocols in a single disposable device. Simultaneous detection of enzymatic color response in sample and reference cells, using a regular smartphone, enabled semiquantitative detection of carbofuran, a neurotoxic and EU-banned carbamate pesticide, in a wide concentration range. The resulting evaluation procedure is generic and allows the rejection of spurious measurements based on their dynamic responses, and was effectively applied for the binary detection of carbofuran in apple extracts.

Rapid, on-site and quantitative paper-based immunoassay platform for concurrent determination of pesticide residues and mycotoxins

Mycotoxins and pesticides are prevalent in cereal food. It is difficult to detect these two kinds of hazard factors simultaneously in rapid assay. In order to find a solution to the problem, carbamates and aflatoxins were selected in this study to establish a rapid, on-site, and quantitative paper sensor. Two novel monoclonal antibodies (mAbs) against carbaryl and carbofuran (1D2 and G11) were developed. The IC50 values (half maximal inhibitory concentration) were 0.8 ng/mL and 217.6 ng/mL for carbaryl and carbofuran, respectively. Based on the sensitive and specific mAbs, a multi-TRFICA (time-resolved fluorescence) paper sensor was developed, which simultaneously detected six types of hazardous chemicals, including AFB1, AFB2, AFG1, AFG2, carbaryl, and carbofuran. A universal sample pretreatment method for mycotoxins and pesticides was explored to apply on established competitive indirect enzyme-linked immunosorbent assay (icELISA) and multi-TRFICA-paper sensor. The established paper sensor can be easily observed with naked eyes, qualitatively under a UV lamp, and quantitated using a home-made device. It exhibited a calculated limit of quantity for AFTs, carbaryl, and carbofuran of 0.03, 0.02, and 60.2 ng/mL in corn samples, respectively. The spiking-recoveries and real sample studies proved that multi-TRFICA-paper sensor is an accurate, sensitive, and high throughput detection method for simple and low-cost analysis in corn samples.

Direct competitive immunosensor for Imidacloprid pesticide detection on gold nanoparticle-modified electrodes

A direct competitive immunosensor for the electrochemical determination of Imidacloprid (IMD) pesticide on gold nanoparticle-modified screen-printed carbon electrodes (AuNP-SPCE) is here reported for the first time. Self-obtained specific monoclonal antibodies are immobilized on the AuNP-SPCE taking advantage of the AuNPs biofunctionalization abilities. In our biosensor design, free IMD in the sample competes with IMD conjugated with horseradish peroxidase (IMD-HRP) for the recognition by the antibodies. After that, 3,3',5,5'-Tetramethylbenzidine (TMB) is enzymatically oxidized by HRP, followed by the oxidized TMB reduction back at the surface of the SPCE. This process gives an associated catalytic current (analytical signal) that is inversely proportional to the IMD amount. The main parameters affecting the analytical signal have been optimized, reaching a good precision (repeatability with a RSD of 6%), accuracy (relative error of 6%), stability (up to one month), selectivity and an excellent limit of detection (LOD of 22 pmol L^-1), below the maximum levels allowed by the legislation, with a wide response range (50-10000 pmol L^-1). The detection through antibodies also allows to have an excellent selectivity against other pesticides potentially present in real samples. Low matrix effects were found when analysing IMD in tap water and watermelon samples. The electrochemical immunosensor was also validated with HPLC-MS/MS, the reference method used in official laboratories for IMD analysis, through statistical tests. Our findings make the electrochemical immunosensor as an outstanding method for the rapid and sensitive determination of IMD at the point-of-use.

Promising post-consumer PET-derived activated carbon electrode material for non-enzymatic electrochemical determination of carbofuran hydrolysate

In this work, activated carbon (AC) materials, prepared from polyethylene terephthalate (PET) waste bottles were used as the sensing platform for the indirect detection of carbofuran. The morphology and surface properties of the PET-derived AC (PET-AC) were characterized by N₂ adsorption/desorption isotherm, X-ray diffraction (XRD), field-emission scanning/transmission electron microscopy (FE-SEM/TEM) and Raman spectroscopy. The electrochemical activity of the PET-AC modified glassy carbon electrode (GCE) (PET-AC/GCE) was measured by cyclic voltammetry and amperometry. The enhanced surface area and desirable porosities of PET-AC are attributed for the superior electrocatalytic activity on the detection of carbofuran phenol, where, the proposed sensor shows low detection limit (0.03 µM) and remarkable sensitivity (0.11 µA µM⁻¹ cm⁻²). The PET-AC/GCE holds high selectivity towards potentially interfering species. It also provides desirable stability, repeatability and reproducibility on detection of carbofuran phenol. Furthermore, the proposed sensor is utilized for the detection of carbofuran phenol in real sample applications. The above mentioned unique properties and desirable electrochemical performances suggest that the PET-derived AC is the most suitable carbonaceous materials for cost-effective and non-enzymatic electrochemical sensor.

Recent uses of carbon nanotubes & gold nanoparticles in electrochemistry with application in biosensing: A review

The innovation of nanoparticles assumes a critical part of encouraging and giving open doors and conceivable outcomes to the headway of new era devices utilized as a part of biosensing. The focused on the quick and legitimate detecting of specific biomolecules using functionalized gold nanoparticles (Au NPs), and carbon nanotubes (CNTs) has turned into a noteworthy research enthusiasm for the most recent decade. Sensors created with gold nanoparticles or carbon nanotubes or in some cases by utilizing both are relied upon to change the very establishments of detecting and distinguishing various analytes. In this review, we will examine the current utilization of functionalized AuNPs and CNTs with other synthetic mixes for the creation of biosensor prompting to the location of particular analytes with low discovery cutoff and quick reaction.

A microfluidic chip containing a molecularly imprinted polymer and a DNA aptamer for voltammetric determination of carbofuran

An electrochemical microfluidic chip is described for the determination of the insecticide carbofuran. It is making use of a molecularly imprinted film (MIP) and a DNA aptamer as dual recognition units. The analyte (carbofuran) is transported to the MIP and captured at the identification site in the channel. Then, carbofuran is eluted with carbinol-acetic acid and transported to the DNA aptamer on the testing position of the chip. It is captured again, this time by the aptamer, and detected by differential pulse voltammetry (DPV). The dual recognition (by aptamer and MIP) results in outstanding selectivity. Additionally, graphene oxide-supported gold nanoparticles (GO-AuNPs) were used to improve the sensitivity of electrochemical detector. DPV response is linear in the 0.2 to 50 nM carbofuran concentration range at a potential of -1.2 V, with a 67 pM detection limit. The method has attractive features such as its potential for high throughput, high degree of automation, and high integration. Conceivably, the method may be extended to other analytes for which appropriate MIPs and aptamers are available. Graphical abstract Schematic of an electrochemical microfluidic chip for carbofuran detection based on a molecularly imprinted film (MIP) and a DNA aptamer as dual recognition units. In the chip, targets were recognized by MIP and aptamer, respectively. It shows promising potential for the design of electrochemical devices with high throughput, high automation, and high integration.

Voltammetric sensing based on the use of advanced carbonaceous nanomaterials: a review

This review (with 210 references) summarizes recent developments in the design of voltammetric chemical sensors and biosensors based on the use of carbon nanomaterials (CNMs). It is divided into subsections starting with an introduction into the field and a description of its current state. This is followed by a large section on various types of voltammetric sensors and biosensors using CNMs with subsections on sensors based on the use of carbon nanotubes, graphene, graphene oxides, graphene nanoribbons, fullerenes, ionic liquid composites with CNMs, carbon nanohorns, diamond nanoparticles, carbon dots, carbon nanofibers and mesoporous carbon. The third section gives conclusion and an outlook. Tables are presented on the application of such sensors to voltammetric detection of neurotransmitters, metabolites, dietary minerals, proteins, heavy metals, gaseous molecules, pharmaceuticals, environmental pollutants, food, beverages, cosmetics, commercial goods and drugs of abuse. The authors also describe advanced approaches for the fabrication of robust functional carbon nano(bio)sensors for voltammetric quantification of multiple targets. Graphical Abstract Featuring execellent electrical, catalytic and surface properies, CNMs have gained enormous attention for designing voltammetric sensors and biosensors. Functionalized CNM-modified electrode interfaces have demonstrated their prominent role in biological, environmental, pharmaceutical, chemical, food and industrial analysis.