Nanomaterials-based electrochemical sensors for the detection of aroma compounds - towards analytical approach

Rhodamine and related substances in food: Recent updates on pretreatment and analysis methods

Rhodamine, a colorant prohibited in various consumer products due to its demonstrated carcinogenic, mutagenic, and toxic properties, necessitates the development of a straightforward, efficient, sensitive, environmentally friendly, and cost-effective analytical method. This review provides an overview of recent advancements in the pretreatment and determination techniques for rhodamine across diverse sample matrices since 2017. Sample preparation methods encompass both commonly used pretreatment techniques such as filtration, centrifugation, solvent extraction, and cloud point extraction, as well as innovative approaches including solid phase extraction, dispersive liquid-liquid microextraction, hollow fiber liquid phase microextraction, magnetic solid phase extraction, and matrix solid phase dispersion. The analytical techniques encompass high performance liquid chromatography, surface-enhanced Raman scattering, and sensor-based methods. Furthermore, a comprehensive examination is conducted to offer insights for future research on rhodamine regarding the advantages, disadvantages, and advancements in various pretreatment and determination methodologies.

Neodymium niobate nanospheres on functionalized carbon nanofibers: a nanoengineering approach for highly sensitive vanillin detection

Vanillin (VAN), the primary aroma compound in vanilla, contributes significantly to sensory delight; however, its unrestrained presence poses notable health risks. In response to the demanding concern regarding food safety, researchers have directed their efforts towards the detection of VAN, seeking sustainable strategies for contamination prevention. A groundbreaking solution has emerged in the form of a novel sensing platform, whose core lies on a finely tuned electrode, crafted through the incorporation of nano-sized NdNbO4 spheres onto carbon nanofibers (CNFs). This incorporation serves to augment the capabilities of a glassy carbon electrode (GCE), transforming it into a highly sensitive detector primed for vanillin detection. The NdNbO4/f-CNF nanocomposite embodies a paradigm of synergistic collaboration, wherein the nonlinear cumulative effects of synergism and quantum confinement impart exceptional performance characteristics. Notably, the sensor achieves a low detection limit of 6.3 nmol L-1, indicative of its remarkable sensitivity of 2.3 μA μ(mol L-1)-1 cm-2 and precision of 1.519 and 4.72%. Moreover, the sensor boasts a wide linear range spanning from 0.001 to 63.101 μmol L-1. These attributes, coupled with its discerning selectivity and robust stability, underscore its efficacy as a versatile tool for vanillin detection. Indeed, its successful deployment in monitoring food samples underscores its applicability across diverse culinary contexts, further cementing its status as a pivotal asset in safeguarding food quality and consumer well-being.

Detection and treatment of mono and polycyclic aromatic hydrocarbon pollutants in aqueous environments based on electrochemical technology: recent advances

Mono and polycyclic aromatic hydrocarbons are widely distributed and severely pollute the aqueous environment due to natural and human activities, particularly human activity. It is crucial to identify and address them in order to reduce the dangers and threats they pose to biological processes and ecosystems. In the fields of sensor detection and water treatment, electrochemistry plays a crucial role as a trustworthy and environmentally friendly technology. In order to accomplish trace detection while enhancing detection accuracy and precision, researchers have created and studied sensors using a range of materials based on electrochemical processes, and their results have demonstrated good performance. One cannot overlook the challenges associated with treating aromatic pollutants, including mono and polycyclic. Much work has been done and good progress has been achieved in order to address these challenges. This study discusses the mono and polycyclic aromatic hydrocarbon sensor detection and electrochemical treatment technologies for contaminants in the aqueous environment. Additionally mentioned are the sources, distribution, risks, hazards, and problems in the removal of pollutants. The obstacles to be overcome and the future development plans of the field are then suggested by summarizing and assessing the research findings of the researchers.

A novel electrochemical sensor based on phosphate-stabilized poly-caffeic acid film in combination with graphene nanosheets for sensitive determination of nitro-aromatic energetic materials

This work offers a novel approach and sensor electrode for electrocatalytic reduction of nitro-aromatic explosives (NAEs). This sensor was created by combining electrochemically reduced graphene nanosheets (GNSs) -through cyclic voltammetric reduction of a graphene oxide colloidal solution- with phosphate-stabilized poly-caffeic acid (pCAF) film-modified glassy carbon electrode (GCE). The poly-caffeic acid-modified nonconductive electrode was stabilized with a H2PO4-/HPO42- phosphate buffer at pH 7 and made conductive. The novel electrode, called phosphate stabilized-GC/GNSs/pCAF, was characterized by electrochemical methods and scanning electron microscopy (SEM). The sensor exhibited high performance for trinitrotoluene (TNT) detection with a linear response between 50 and 500 μg L- 1 and a detection limit of 6 μg L-1. In addition to TNT, precise determinations of NAEs such as 2,4-dinitrotoluene (2,4-DNT), tetryl (2,4,6-trinitrophenyl methyl nitramine), trinitro phenol (TNP or picric acid; PA), 2,4-dinitrophenol (2,4-DNP), and 4-amino dinitrotoluene (4A-DNT, an aerobic bacterial degradation product of TNT) were made using the developed sensor electrode and DPV technique. Simultaneous quantification of TNT and DNT was performed with the aid of a computational technique known as multiple linear regression (MLR). The optimized electrode was resistant to interference effects. Satisfactory results on real samples were obtained by applying the modified electrode to the determination of TNT, tetryl, and TNP in contaminated soil. The validation of the proposed method was made against a literature LC-MS/MS method. A statistical comparison of the obtained results was provided using F- and Student's t-tests.

A novel magneto-mediated electrochemical biosensor integrated DNAzyme motor and hollow nanobox-like Pt@Ni-Co electrocatalyst as dual signal amplifiers for vanilla detection

Herein, a novel magneto-mediated electrochemical aptasensor using the signal amplification technologies of DNAzyme motor and electrocatalyst for vanilla (VAN) detection was fabricated. The D/B duplex, formed by the DNAzyme motor that was each silenced by a blocker, and hairpin DNA1 (H1) containing adenosine ribonucleotide (rA) site were tethered on the sites of the gold nanoparticles@hollow porphyrinic-Metal-organic framework/polyethyleneimine-reduced graphene oxide (AuHPCN-222/PEI-rGO)-modified gold electrode (AuE). Then, after homogeneous and specific recognition in the presence of the VAN, trigger DNA was released and enriched by magnetic separation technique and introduced to the sensing platform to activate the DNAzyme motor, which efficiently improved target recognition capability and avoided the obstacle of multiple DNA strands tangling. More interestingly, the activated DNAzyme motor could repeatedly bind to and cleave H1 in the presence of Mg2+, leading to the exposure of a plethora of capture probes. The thionine (Thi) functionalized hairpin DNA2 (H2)-Pt@Ni-Co as signal probes could hybridize with capture probes. Additionally, the Pt@Ni-Co electrocatalysts presented catalytic activity towards Thi to obtain stronger electrochemical signals. VAN with concentrations ranging from 1 × 10-6 to 10 μM was determined and a detection limit was down to 0.15 pM. The designed electrochemical sensor was highly selective with specificity, stability, reproducibility, and reliable capability for monitoring the VAN in real samples.

Applications of Gas Sensing in Food Quality Detection: A Review

Food products often face the risk of spoilage during processing, storage, and transportation, necessitating the use of rapid and effective technologies for quality assessment. In recent years, gas sensors have gained prominence for their ability to swiftly and sensitively detect gases, making them valuable tools for food quality evaluation. The various gas sensor types, such as metal oxide (MOX), metal oxide semiconductor (MOS) gas sensors, surface acoustic wave (SAW) sensors, colorimetric sensors, and electrochemical sensors, each offer distinct advantages. They hold significant potential for practical applications in food quality monitoring. This review comprehensively covers the progress in gas sensor technology for food quality assessment, outlining their advantages, features, and principles. It also summarizes their applications in detecting volatile gases during the deterioration of aquatic products, meat products, fruit, and vegetables over the past decade. Furthermore, the integration of data analytics and artificial intelligence into gas sensor arrays is discussed, enhancing their adaptability and reliability in diverse food environments and improving food quality assessment efficiency. In conclusion, this paper addresses the multifaceted challenges faced by rapid gas sensor-based food quality detection technologies and suggests potential interdisciplinary solutions and directions.

Electrochemical Characterization of the Antioxidant Properties of Medicinal Plants and Products: A Review

Medicinal plants are an important source of bioactive compounds with a wide spectrum of practically useful properties. Various types of antioxidants synthesized in plants are the reasons for their application in medicine, phytotherapy, and aromatherapy. Therefore, reliable, simple, cost-effective, eco-friendly, and rapid methods for the evaluation of antioxidant properties of medicinal plants and products on their basis are required. Electrochemical methods based on electron transfer reactions are promising tools to solve this problem. Total antioxidant parameters and individual antioxidant quantification can be achieved using suitable electrochemical techniques. The analytical capabilities of constant-current coulometry, potentiometry, various types of voltammetry, and chrono methods in the evaluation of total antioxidant parameters of medicinal plants and plant-derived products are presented. The advantages and limitations of methods in comparison to each other and traditional spectroscopic methods are discussed. The possibility to use electrochemical detection of the antioxidants via reactions with oxidants or radicals (N- and O-centered) in solution, with stable radicals immobilized on the electrode surface, via oxidation of antioxidants on a suitable electrode, allows the study of various mechanisms of antioxidant actions occurring in living systems. Attention is also paid to the individual or simultaneous electrochemical determination of antioxidants in medicinal plants using chemically modified electrodes.

Electrochemical Sensing of Vanillin Based on Fluorine-Doped Reduced Graphene Oxide Decorated with Gold Nanoparticles

4-hydroxy-3-methoxybenzaldehyde (vanillin) is a biophenol compound that is relatively abundant in the world’s most popular flavoring ingredient, natural vanilla. As a powerful antioxidant chemical with beneficial antimicrobial properties, vanillin is not only used as a flavoring agent in food, beverages, perfumery, and pharmaceutical products, it may also be employed as a food-preserving agent, and to fight against yeast and molds. The widespread use of vanilla in major industries warrants the need to develop simple and cost-effective strategies for the quantitative determination of its major component, vanillin. Herein, we explore the applications of a selective and sensitive electrochemical sensor (Au electrodeposited on a fluorine-doped reduced-graphene-oxide-modified glassy-carbon electrode (Au/F-rGO/GCE)) for the detection of vanillin. The electrochemical performance and analytical capabilities of this novel electrochemical sensor were investigated using electrochemical techniques including cyclic voltammetry and differential pulse voltammetry. The excellent sensitivity, selectivity, and reproducibility of the proposed electrochemical sensor may be attributed to the high conductivity and surface area of the formed nanocomposite. The high performance of the sensor developed in the present study was further demonstrated with real-sample analysis.

Rapid Sample Screening Method for Authenticity Controlling of Vanilla Flavours Using Liquid Chromatography with Electrochemical Detection Using Aluminium-Doped Zirconia Nanoparticles-Modified Electrode

A rapid and sensitive technique for frauds determination in vanilla flavors was developed. The method comprises separation by liquid chromatography followed by an electrochemical detection using a homemade screen-printed carbon electrode modified with aluminium-doped zirconia nanoparticles (Al-ZrO₂-NPs/SPCE). The prepared nanomaterials (Al-ZrO₂-NPs) were characterized by using X-ray diffraction (XRD), transmission electron microscopy (TEM) and energy dispersive X-ray (EDX). This method allows for the determination of six phenolic compounds of vanilla flavors, namely, vanillin, p-hydroxybenzoic acid, p-hydroxybenzaldehyde, vanillyl alcohol, vanillic acid and ethyl vanillin in a linear range between 0.5 and 25 µg g^-1, with relative standard deviation values from 2.89 to 4.76%. Meanwhile, the limits of detection and quantification were in the range of 0.10 to 0.14 µg g^-1 and 0.33 to 0.48 µg g^-1, respectively. In addition, the Al-ZrO₂-NPs/SPCE method displayed a good reproducibility, high sensitivity, and good selectivity towards the determination of the vanilla phenolic compounds, making it suitable for the determination of vanilla phenolic compounds in vanilla real extracts products.

A new electrochemical DNA biosensor for determination of anti-cancer drug chlorambucil based on a polypyrrole/flower-like platinum/NiCo2O4/pencil graphite electrode

In the current study, DNA immobilization was performed on pencil graphite (PG) modified with a polypyrrole (PPy) and flower-like Pt/NiCo2O4 (FL-Pt/NiCo2O4) nanocomposite, as a new sensitive electrode to detect chlorambucil (CHB). Energy dispersive X-ray (EDX) analysis, X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques were employed to characterize the synthesized FL-Pt/NiCo2O4 and PPy/FL-Pt/NiCo2O4 nanocomposites. Moreover, differential pulse voltammetry (DPV) was selected to assess the guanine and adenine electrochemical responses on the DNA sensor. The CHB determination was performed using the maximum currents towards adenine and guanine in the acetate buffer solution (ABS). According to the results, ds-DNA/PPy/FL-Pt/NiCo2O4/PGE was able to detect the different concentrations of CHB in the range between 0.018 and 200 μM, with a detection limit of (LOD) of 4.0 nM. The new biosensor was also exploited for CHB determination in real samples (serum, urine and drug), the results of which revealed excellent recoveries (97.5% to 103.8%). Furthermore, the interaction between ds-DNA and CHB was studied using electrochemistry, spectrophotometry and docking whose outputs confirmed their effective interaction.

Adsorptive stripping voltammetric determination of chloramphenicol residues in milk samples using reduced graphene oxide sensor

In this paper, the electrochemical response of chloramphenicol (CHL) was investigated on a bare glassy carbon electrode (GCE) and after modification with reduced graphene oxide (GCE/rGO). Preliminary studies by cyclic voltammetry demonstrated an adsorption-controlled mass transport regime of CHL species and a pH-dependent behavior on both electrode surfaces. An adsorptive stripping differential pulse voltammetry (AdSDPV) method was proposed and under optimized instrumental conditions, a comparison of the analytical characteristics of both sensors was performed. The GCE/rGO sensor showed an increase in sensitivity (10-fold), and an anticipation of the reduction potential (200 mV), compared to the bare electrode, due to the adsorptive character (pre-concentration of the CHL species) and the electrocatalytic effect of the nanomaterial. The method was applied to skimmed and whole milk samples, which were simply diluted (50-fold) in supporting electrolyte. The results by AdSDPV using GCE/rGO showed adequate detectability (0.22 μmol L^-1), good precision with a 6% relative standard deviation (RSD) and satisfactory recovery ranging from 93 to 108%. The obtained results were statistically similar (95% confidence level) with those performed through ultra-fast liquid chromatography (UFLC). Furthermore, the sensor showed an improvement in the analytical performance for CHL detection, when compared to other sensors reported in the literature. Therefore, the developed method is reliable and promising for implementation in monitoring CHL residues in milk samples.

Latest advances on the nanomaterials-based electrochemical analysis of azo toxic dyes Sunset Yellow and Tartrazine in food samples

Azo-dyes such as Allura Red, Carmoisine, Amaranth, Sunset Yellow (SY), Brilliant Blue, Tartrazine (Tz), etc., are popular as food coloring agents due to their low cost and stability. SY and Tz are the most used members of this group of dyes since they have similar colors and are usually used together in food products. Despite their advantageous industrial use, they exhibit a risk toxicity profile with adverse effects such as allergy, asthma, carcinogenicity, genotoxicity, cytotoxicity, anxiety, etc. Therefore, the United States Food and Drug Administration (FDA) and European Food Safety Authority (EFSA) regulate the permissions for using these compounds to provide safe food products for consumers and prevent adverse effects both short and long-term. Considering all of these, for the analysis of azo toxic dyes, highly sensitive, low-cost, simple, and rapid sensors are necessary. Electrochemical nanosensors, which combine the unique features of electrochemistry and nanotechnology, are devices with all these advantages and are widely used for the determination of azo dyes. SY and Tz step forth as the most used food dyes in the class of azo-toxic dyes. They are often preferred together in food products, increasing the occurrence and exposure risk. Therefore, the analysis of Sunset Yellow and Tartrazine in food products has significant importance. In this review, the latest nanomaterial-based approaches for the electrochemical sensors on the analysis of SY and Tz in food samples were evaluated in terms of used nanomaterials and applied food samples.

Surface Polymers on Multiwalled Carbon Nanotubes for Selective Extraction and Electrochemical Determination of Rhodamine B in Food Samples

In this study, we combine magnetic solid phase extraction (MSPE), with the screen-printed carbon electrode (SPCE) modified by a molecular imprinted polymer (MIP) for sensitive and selective extraction and electrochemical determination of Rhodamine B in food samples. A magnetic solid phase extraction (MSPE) was carried out using magnetic poly(styrene-co-divinylbenzene) (PS-DVB) and magnetic nanoparticles (MNPs) synthetized on the surface of multiwalled carbon nanotubes (MWCNTs). An MIP was prepared on the surface of MWCNTs in the presence of titanium oxide nanoparticles (TiO₂NPs) modifying the SPCE for the rapid electrochemical detection of Rhodamine B. The MIPs synthesis was optimized by varying the activated titanium oxide (TiO₂) and multiwalled carbon nanotubes (MWCNTs) amounts. The MSPE and electrochemical detection conditions were optimized as well. The present method exhibited good selectivity, high sensitivity, and good reproducibility towards the determination of Rhodamine B, making it a suitable method for the determination of Rhodamine B in food samples.

Latest Advances in Determination of Bisphenols with Nanomaterials, Molecularly Imprinted Polymers and Aptamer Based Electrochemical Sensors

Contamination of environmental sources such as soils, sediments and rivers and human exposure caused by several endocrine disrupting compounds (EDCs) are considered as the most challenging issues of today's world. EDCs cover a wide variety of compounds ranging from phthalates to parabens and bisphenols (BPs) are the leading group among them. BPs are widely used during the production of different plastic materials such as food and beverage containers, toys, medical equipment and baby bottles that we use in every aspect of our lives. BPs may migrate from those products to different media under certain conditions and this situation causes chronic exposure for humans and other creatures in the environment. Especially bisphenol A (BPA) and its other analogues such as bisphenol F, bisphenol S and tetrabromobisphenol that have similar structures and are preferred as alternatives to BPA cause harmful adverse effects such as endocrine disruption, neurotoxicity, genotoxicity and cytotoxicity. There are legal restrictions and prohibitions by the European Union (EU) in order to prevent possible harmful effects. Therefore, it is important to develop highly sensitive, fast, easy to use and cheap sensors for the determination of BPs in biological, environmental and commercial samples. Electrochemical sensors, which are one of the most widely, used analytical techniques, provide these conditions. Additionally, it is possible to enhance the performance of electrochemical sensors with nanomaterials, molecularly imprinted polymers or aptamer based technologies. This review aims to give comprehensive information about BPs with summarizing most recent applications of electrochemical sensors for their determination in different samples.

Application of biosynthesized metal nanoparticles in electrochemical sensors

Recently, the development of eco-friendly, cost-effective and reliable methods for synthesis of metal nanoparticles has drawn a considerable attention. The so-called green synthesis, using mild reaction conditions and natural resources as plant extracts and microorganisms, has established as a convenient, sustainable, cheap and environmentally safe approach for synthesis of a wide range of nanomaterials. Over the past decade, biosynthesis is regarded as an important tool for reducing the harmful effects of traditional nanoparticle synthesis methods commonly used in laboratories and industry. This review emphasizes the significance of biosynthesized metal nanoparticles in the field of electrochemical sensing. There is increasing evidence that green synthesis of nanoparticles provides a new direction in designing of cost-effective, highly sensitive and selective electrode-catalysts applicable in food, clinical and environmental analysis. The article is based on 157 references and provided a detailed overview on the main approaches for green synthesis of metal nanoparticles and their applications in designing of electrochemical sensor devices. Important operational characteristics including sensitivity, dynamic range, limit of detection, as well as data on stability and reproducibility of sensors have also been covered.

Application of Electrochemical Sensors Based on Carbon Nanomaterials for Detection of Flavonoids

Flavonoids have a variety of physiological activities such as anti-free radicals, regulating hormone levels, antibacterial factors, and anti-cancer factors, which are widely present in edible and medicinal plants. Real-time detection of flavonoids is a key step in the quality control of diverse matrices closely related to social, economic, and health issues. Traditional detection methods are time-consuming and require expensive equipment and complicated working conditions. Therefore, electrochemical sensors with high sensitivity and fast detection speed have aroused extensive research interest. Carbon nanomaterials are preferred material in improving the performance of electrochemical sensing. In this paper, we review the progress of electrochemical sensors based on carbon nanomaterials including carbon nanotubes, graphene, carbon and graphene quantum dots, mesoporous carbon, and carbon black for detecting flavonoids in food and drug homologous substances in the last four years. In addition, we look forward to the prospects and challenges of this research field.

Selective determination of non-organophosphorus insecticide using DNA aptamer-based single-use biosensors

In the present study, we developed a disposable aptamer-based biosensor for rapid, sensitive, and reliable detection of acetamiprid (ACE). To improve the sensitivity of the aptasensor, poly-5-amino-2-mercapto-1,3,4-thiadiazole [P(AMT)] and gold nanoparticles (AuNPs) were progressively electrodeposited on the screen-printed electrode (SPE) surface by using cyclic voltammetry (CV) technique. For the determination of ACE, thiol-modified primary aptamer (Apt1) was selected by using the SELEX method and immobilized on the surface of the P(AMT) and AuNPs-modified SPE (SPE/P(AMT)/AuNPs) via AuS bonding. Then, the surface-bound aptamer was incubated with ACE for 45 Min. After that, the biotin-labeled aptamer 2 (Apt2) was interacted with the ACE, then the enzyme-labeled step was performed. In this step, alkaline phosphatase (ALP) was bound to the surface through the interaction between Apt2 labeled with biotin and streptavidin (strep)-ALP conjugate. The determination of ACE was achieved by measuring the oxidation signal of α-naphthol, which is formed on the electrode surface through the interaction of ALP with α-naphthyl phosphate. The working range of the developed aptasensor was determined as 5 × 10^-12 -5 × 10^-10  mol L^-1 with a low limit of detection (1.5 pmol L^-1 ). It was also found that the proposed aptasensor possessed great advantages such as low cost, good selectivity, and good reproducibility.