An ultrasensitive electroanalytical sensor based on MgO/SWCNTs- 1-Butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide paste electrode for the determination of ferulic acid in the presence sulfite in food samples

Monitoring of Specific Phytoestrogens by Dedicated Electrochemical Sensors: A Review

Phytoestrogens are non-steroidal estrogens produced from plants that can bind with the human body's estrogenic receptor site and be used as a substitute for maintaining hormonal balance. They are mainly classified as flavonoids, phenolic acids, lignans, stilbenes, and coumestans; some are resocyclic acids of lactones, which are mycotoxins and not natural phytoestrogen. Phytoestrogens have many beneficial medicinal properties, making them an important part of the daily diet. Electrochemical sensors are widely used analytical tools for analysing various pharmaceuticals, chemicals, pollutants and food items. Electrochemical sensors provide an extensive platform for highly sensitive and rapid analysis. Several reviews have been published on the importance of the biological and medicinal properties of phytoestrogens. However, this review provides an overview of recent work performed through electrochemical measurements with electrochemical sensors and biosensors for all the classes of phytoestrogens done so far since 2019.

Optimization of voltammetric parameters for sensitive and simultaneous determination of ferulic acid and vanillin using a glassy carbon electrode based on 2-aminonicotinic acid in the presence of surfactant media

The electrochemical sensor for simultaneous determination of ferulic acid (FA) and vanillin (VA) was prepared by electrochemical deposition of 2-aminonicotinic acid (2-ANA) on the glassy carbon (GC) electrode. The voltammetric determination of FA and VA was performed in the BR buffer solution in the presence of sodium dodecyl sulfate as a surfactant with SWV. The parameters of the SWV technique were optimized by response surface methodology experimental design. Under optimized conditions, the 2-ANA/GC modified electrode presented a linear working range of 2.8 × 10-8 M to 7.50 × 10-6 M and 7.50 × 10-6 M to 2.45 × 10-5 M for FA, 3.06 × 10-8 M to 1.27 × 10-5M for VA. The detection limit (LOD) values for FA and VA were 6.87 nM and 9.23 nM, respectively. Using the 2-ANA/GC sensor, concentrations of FA and VA in instant coffee and milk samples were determined with %recovery values between 103.40 and 97.07 and %RSD values between 0.76 and 4.40.

Voltammetric Investigation of Ferulic Acid at Disposable Pencil Graphite Electrode

Ferulic acid (FA), a monohydroxycinnamic acid, is an antioxidant with multiple beneficial effects on human health, presenting also importance in the food and cosmetics industry. Its electrochemical behavior was investigated at the disposable and cost-effective pencil graphite electrode (PGE). Cyclic voltammetry emphasized its pH-dependent, diffusion-controlled oxidation. Using the optimized conditions (HB type PGE, Britton Robinson buffer pH 4.56) differential pulse and square-wave voltammetric techniques were applied for its quantitative determination in the range 4.00 × 10-7-1.00 × 10-3 mol/L FA. The developed methods were employed for the rapid and simple assessment of the FA content from a commercially available powder designed for cosmetic use.

Enhanced photocatalytic performance of auto-combusted nanoparticles for photocatalytic degradation of azo dye under sunlight illumination and hydrogen fuel production

In this study, an innovative nanomaterial was synthesized for hydrogen production from methanolysis on sodium borohydride (NaBH₄) in order to be a solution for future energy problems. The nanocomposite containing FeCo, which does not contain noble metals, and whose support material is Polyvinylpyrrolidone (PVP), was synthesized by means of a thermal method. TEM, XRD and FTIR characterization methods were used for the analysis of the morphological and chemical structure of the nanocomposite. Nanocomposite particle size was 2.59 nm according to XRD and 5.45 nm according to TEM analysis for scale of 50 nm. For catalytic properties of nanomaterial in the methanolysis reaction of NaBH₄, temperature, catalyst, substrate, and reusability experiments were carried out and kinetic calculations were obtained. Among the activation parameters of FeCo@PVP nanoparticles, turnover frequency, enthalpy, entropy and activation energy were calculated as 3858.9 min^-1, 29.39 kJ/mol, -139.7 J/mol.K, and 31.93 kJ/mol, respectively. As a result of the reusability test of the obtained FeCo@PVP nanoparticles catalysts, which was carried out for 4 cycles, the catalytic activity was 77%. Catalytic activity results are given in comparison with the literature. In addition, the photocatalytic activity of FeCo@PVP NPs was evaluated against MB azo dye under solar light irradiation for 75 min and was found to be as 94%.

Simple turn-off fluorescence sensor for determination of raloxifene using gold nanoparticles stabilized by chitosan hydrogel

It is essential to develop a simple, applicable, and reliable assay to anticancer drug raloxifene (RAF) because of its significant usage and side effect due to entering residue in the environment. Fluorescence sensors developed and widely used because of them high selectivity, fast-response, and highly-sensitivity. The gold nanoparticles using chitosan hydrogel was synthesized and applied as a fluorescence sensor to determine the trace amount of RAF. The characterization methods including DLS, FE-SEM, EDX, XRD, and FT-IR were performed to confirm the synthesized structure. This sensor turned off the fluorescent signals proportional to RAF concentrations at 400 nm. The RAF can be detected in the linear range from 5 × 10^-7 to 5 × 10^-5 M. Limits of detection and quantification were obtained as 34 × 10^-8 and 11 × 10^-7 M as well as the relative standard deviation calculated as 1.63% in RAF measuring. The effective parameters on quenching efficiency were studied by central composite design (CCD) with response surface methodology (RSM). The effective parameters in RAF determination, include analyte concentration, temperature, contact time, and pH, were obtained as 35 μM, 30 °C, 8 min, and pH = 8.5. The sensor was applied to determine the RAF concentrations in biological and environmental samples with satisfactory recoveries between 97.5% and 109%.

Novel Colorimetric and NIR Fluorescent Probe for Bisulfite/Sulfite Detection in Food and Water Samples and Living Cells Based on the PET Mechanism

Despite their status of being widely used as food additives, bisulfite (HSO₃^-)/sulfite (SO₃^2-) can pose serious health risks when they are excessively added. Therefore, it is vital to develop a new method for detecting HSO₃^-/SO₃^2- in foodstuff. In this paper, a benzopyran-benzothiazole derivative (probe DCA-Btl) with near-infrared emission was designed and synthesized by constructing a "push-pull" electronic system. DCA-Btl can selectively recognize HSO₃^-/SO₃^2- via a colorimetric and fluorescence dual channel in DMF/PBS (1:1, v/v, pH = 8.4), and the emission wavelength of DCA-Btl can reach 710 nm. The fluorescence quenching of DCA-Btl after recognition of HSO₃^- is attributed to the photoinduced electron transfer (PET) process of the adduct DCA-Btl-HSO₃^- as evaluated by the DFT/TD-DFT method. In addition, DCA-Btl has many advantages, including a large Stokes shift (95 nm), good anti-interference ability, and little cytotoxicity. What's more, DCA-Btl has been successfully applied for the detection of HSO₃^-/SO₃^2- in actual water samples and food samples such as sugar, red wine, and biscuits with satisfying results, as well as for fluorescent imaging of HSO₃^- in living MCF-7 cells.

Machine Learning Quantitative Structure–Property Relationships as a Function of Ionic Liquid Cations for the Gas-Ionic Liquid Partition Coefficient of Hydrocarbons

Ionic liquids (ILs) are known for their unique characteristics as solvents and electrolytes. Therefore, new ILs are being developed and adapted as innovative chemical environments for different applications in which their properties need to be understood on a molecular level. Computational data-driven methods provide means for understanding of properties at molecular level, and quantitative structure–property relationships (QSPRs) provide the framework for this. This framework is commonly used to study the properties of molecules in ILs as an environment. The opposite situation where the property is considered as a function of the ionic liquid does not exist. The aim of the present study was to supplement this perspective with new knowledge and to develop QSPRs that would allow the understanding of molecular interactions in ionic liquids based on the structure of the cationic moiety. A wide range of applications in electrochemistry, separation and extraction chemistry depends on the partitioning of solutes between the ionic liquid and the surrounding environment that is characterized by the gas-ionic liquid partition coefficient. To model this property as a function of the structure of a cationic counterpart, a series of ionic liquids was selected with a common bis-(trifluoromethylsulfonyl)-imide anion, [Tf2N]⁻, for benzene, hexane and cyclohexane. MLR, SVR and GPR machine learning approaches were used to derive data-driven models and their performance was compared. The cross-validation coefficients of determination in the range 0.71–0.93 along with other performance statistics indicated a strong accuracy of models for all data series and machine learning methods. The analysis and interpretation of descriptors revealed that generally higher lipophilicity and dispersion interaction capability, and lower polarity in the cations induces a higher partition coefficient for benzene, hexane, cyclohexane and hydrocarbons in general. The applicability domain analysis of models concluded that there were no highly influential outliers and the models are applicable to a wide selection of cation families with variable size, polarity and aliphatic or aromatic nature.

Properties and Recent Advantages of N,N’-dialkylimidazolium-ion Liquids Application in Electrochemistry

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N,Nʹ-dialkylimidazolium-ion liquids is one of the important ionic liquids with a wide range of application as conductive electrolyte and in electrochemistry. The modified electrodes create a new view in fabrication of electroanalytical sensors. Many modifiers have beeen suggested for modification of electroanalytical sensor since many years ago. Over these years, ionic liquids and especially room temperature ionic liquids have attracted more attention due to their wide range of electrochemical windows and high electrical conductivity. N,Nʹ-dialkylimidazolium-ion liquids are one of the main important ionic liquids suggested for modification of bare electrodes and especially carbon paste electrodes. Although many review articles have reported onthe use of ionic liquids in electrochemical sensors, no review article has been specifically introduced so far on the review of the advantages of N,Nʹ-dialkylimidazolium ionic liquid. Therefore, in this review paper we focused on the introduction of recent advantages of N,Nʹ-dialkyl imidazolium ionic liquid in electrochemistry.

Electroanalytical performance of a β-cyclodextrin and ionic liquid modified carbon paste electrode for the determination of verapamil in urine and pharmaceutical formulation

The analytical performance of sensitive and cost-effective electrochemical sensors based on ionic liquids (ILs) with the bis(trifluoromethylsulfonyl)imide anion, [NTf2]-, and the imidazolium cation with different alkyl chain lengths for electrochemical oxidation of verapamil (VER) was investigated. 1-Ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM][NTf2]), 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([BMIM][NTf2]) and 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([HMIM][NTf2]) were studied as possible materials for modification of a carbon paste electrode (CPE) for trace-level determination of VER. The experimental parameters including selection of the working electrode, the pH of working media, and the amount of CPE modifiers were investigated. Among them, the [EMIM][NTf2]-CPE with 4.3 wt% of IL was selected as the most appropriate for the square wave voltammetric (SWV) determination of VER at pH 5.0. Cyclic voltammetric studies showed that the electrochemical oxidation of VER was adsorption controlled. Consequently, the square wave adsorptive stripping voltammetric (SW-AdSV) parameters were optimized with Eacc = -0.4 V and tacc = 180 s as the most suitable for accumulation of VER on the electrode surface. The electroanalytical performance of the [EMIM][NTf2]-CPE was further improved by its in situ electrochemical modification with β-cyclodextrin (β-CD) and the linear concentration range of VER was from 0.006 to 0.129 μg mL-1; the relative standard deviation did not exceed 0.7%, and the evaluated limit of detection in model solution was 0.002 μg mL-1. The β-CD/[EMIM][NTf2]-CPE showed adequate selectivity towards VER in the presence of inorganic ions and interferents usually found in human urine. The proposed sensor was successfully applied for VER determination in a spiked human urine sample and pharmaceutical formulation with good repeatability and recovery.

Determination of sulfite in food and beverages using a reliable ratiometric AIE probe

The feasibility of using an “AIE + ICT” probe for a highly accurate and reliable determination of the sulfite level in food and beverages is demonstrated.

Simple synthesis of a clew-like tungsten carbide nanocomposite decorated with gold nanoparticles for the ultrasensitive detection of tert-butylhydroquinone

The excessive use of food additives in manufactured food products negatively affects their quality and potentially impacts human health. In the present study, a composite consisting of gold nanoparticles decorated on tungsten carbide (AuNP-WC) was successfully fabricated using a facile and cost-effective ultrasonication technique. Compared to a bare glassy carbon electrode (GCE), AuNP-GCE, and WC-GCE, the AuNP-WC-GCE demonstrated excellent sensing performance for tert-butylhydroquinone (TBHQ) when used as an electrocatalyst in 0.05 M phosphate buffer solution (PBS), with a low working potential and a high peak current. In particular, the composite was able to detect the oxidation of TBHQ within a linear concentration range of 5 to 75 nM, with an extremely low detection limit of 0.20 nM. The practicability of the sensor was also assessed in the analysis of TBHQ in real samples of soybean oil, blended oil, and red wine, with satisfactory recovery rates obtained.

Development of a Novel Electrochemical Biosensor Based on Carbon Nanofibers-Gold Nanoparticles-Tyrosinase for the Detection of Ferulic Acid in Cosmetics

The present paper deals with the electrochemical behavior of three types of sensors based on modified screen-printed electrodes (SPEs): a sensor based on carbon nanofibers (CNF/SPE), a sensor based on nanofibers of carbon modified with gold nanoparticles (CNF-GNP/SPE) and a biosensor based on nanofibers of carbon modified with gold nanoparticles and tyrosinase (CNF-GNP-Ty/SPE). To prepare the biosensor, the tyrosinase (Ty) was immobilized on the surface of the electrode already modified with carbon nanofibers and gold nanoparticles, by the drop-and-dry technique. The electrochemical properties of the three electrodes were studied by cyclic voltammetry in electroactive solutions, and the position and shape of the active redox peaks are according to the nature of the materials modifying the electrodes. In the case of ferulic acid, a series of characteristic peaks were observed, the processes being more intense for the biosensor, with the higher sensitivity and selectivity being due to the immobilization of tyrosinase, a specific enzyme for phenolic compounds. The calibration curve was subsequently created using CNF-GNP-Ty/SPE in ferulic acid solutions of various concentrations in the range 0.1-129.6 μM. This new biosensor allowed low values of the detection threshold and quantification limit, 2.89 × 10-9 mol·L-1 and 9.64 × 10-9 mol·L-1, respectively, which shows that the electroanalytical method is feasible for quantifying ferulic acid in real samples. The ferulic acid was quantitatively determined in three cosmetic products by means of the CNF-GNP-Ty/SPE biosensor. The results obtained were validated by means of the spectrometric method in the infrared range, the differences between the values of the ferulic acid concentrations obtained by the two methods being under 5%.

Electrochemical Voltammogram Recording for Identifying Varieties of Ornamental Plants

An electrochemical voltammogram recording method for plant variety identification is proposed. Electrochemical voltammograms of Vistula, Andromeda, Danuta, Armandii 'Apple Blossom,' Proteus, Hagley Hybrid, Violet Elizabeth, Kiri Te Kanawa, Regina, and Veronica's Choice were recorded using leaf extracts with two solvents under buffer solutions. The voltametric data recorded under different conditions were derived as scatter plots, 2D density patterns, and hot maps for variety identification. In addition, the voltametric data were further used for genetic relationship studies. The dendrogram deduced from the voltammograms was used as evidence for relationship study. The dendrogram deduced from voltametric data suggested the Andromeda, Danuta, Proteus, Regina, and Hagley Hybrid were closely related, while Violet Elizabeth and Veronica's Choice were closely related. In addition, Vistula and Armandii 'Apple Blossom' could be considered outliers among the varieties.

Development of Electrochemical Oscillation Method for Identification of Prunus persica, Prunus davidiana, and Prunus armeniaca Nuts

In this work, an electrochemical oscillation system has been developed using the Belousov-Zhabotinsky reaction. The effect of the combination of each reagent, reaction temperature, and stirring speed on the induction period, oscillating period, and oscillating life were optimized. The nuts of Prunus persica, Prunus davidiana, and Prunus armeniaca have been widely used for medical purposes. The proposed electrochemical oscillation system was then used for the identification of P. persica, P. davidiana, and P. armeniaca. Three nuts exhibited very different electrochemical oscillation profiles. The dendrogram was divided into three main principal infrageneric clades. Each cluster only contains one species, suggesting that no outlier was observed in this study. Based on the discussed results, we proposed a simple method for herbal medicine identification.

Biosensors and Sensing Systems for Rapid Analysis of Phenolic Compounds from Plants: A Comprehensive Review

Phenolic compounds are secondary metabolites frequently found in plants that exhibit many different effects on human health. Because of the relevant bioactivity, their identification and quantification in agro-food matrices as well as in biological samples are a fundamental issue in the field of quality control of food and food supplements, and clinical analysis. In this review, a critical selection of sensors and biosensors for rapid and selective detection of phenolic compounds is discussed. Sensors based on electrochemistry, photoelectrochemistry, fluorescence, and colorimetry are discussed including devices with or without specific recognition elements, such as biomolecules, enzymes and molecularly imprinted materials. Systems that have been tested on real matrices are prevalently considered but also techniques that show potential development in the field.