Voltammetric Techniques Research Articles

Phloroglucinol/activated carbon composite/multiwalled carbon nanotubes modified glassy carbon electrode for electrochemical quantification of caffeic acid

Waste-derived carbon materials and their composites have recently been utilized in electrochemical sensing of biologically important analytes due to their distinctive properties. Here, we present the electrochemical sensing of caffeic acid (CA) based on a phloroglucinol/ activated carbon composite (derived from mosquito repellent carbon rod)/multiwalled carbon nanotubes modified glassy carbon electrode (PL/AC/MWCNT/GCE). The hydrothermal process was employed to prepare activated carbon composite from waste carbon rods used in mosquito repellents. Thus obtained activated carbon composite was combined with multiwalled carbon nanotubes and electrochemically modified with phloroglucinol. Further, the prepared sensor was used effectively for electrochemical analysis of CA. The prepared electrodes are characterized using Field emission scanning electron microscope (FESEM), Fourier-transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD) and voltammetric methods. The PL/AC/MWCNT/GCE gives an enhanced electrochemical signal for CA in contrast to the lowest modified electrodes. Electrochemical studies such as impact of scan rate, pH, catalyst loading, coating cycles and concentration were performed using cyclic voltammetric (CV) technique. Under the optimized electrochemical conditions, the PL/AC/MWCNT/GCE was used to plot the calibration curve for CA using amperometry and square wave voltammetry (SWV) techniques in the analyte concentration ranging from 0.02 to 0.2 µM and 0.01 to 0.1 µM, which resulted in lesser Limit of detection (LOD) of 36.4 nM and 4.490 nM, respectively. Finally, the prepared sensor was applied for electrochemical quantification of CA in real-time analysis using commercially available coffee and wine samples with exceptional results.

Zeolite integrated carbon paste sensors for sensitive and selective differential pulse voltammetric determination of carprofen

The present research demonstrates the development and the electroanalytical performance of a novel carprofen (CAR) voltammetric carbon paste electrode (CPEs). Fortification of the electrode matrix with zeolite (ZY) nanostructures with an effective electrocatalytic activity catalyzes the oxidation of the CAR molecule at the ZY/CPEs surface in the universal buffer pH 5 with irreversible anodic oxidation peak at 0.954 V following a diffusion-electrode reaction mechanism. The postulated electrooxidation mechanism of CAR molecule undergoes through oxidation of the enamine N atom (N6) through the transfer of the delocalized lone pair of electrons in addition to the involvement of one proton as estimated from the electrochemical behavior of CAR at different scan rates, pH values and sustained with the molecular orbital calculations. Calibration graphs were linear within the CAR concentration ranged from 16.6 to 323.3 ng mL−1 recording a limit of detection (LOD) value of 5.6 ng mL−1. The cited ZY/CPEs showed enhanced performance, high measurement reproducibility, ease of construction and regeneration of the electrode surface, with a prolonged operational lifetime. Based on the recorded sensitivity and selectivity, ZY/CPEs were utilized for simultaneous quantification of CAR in the presence of various interferents and degradation products. The presented voltammetric analytical technique was tested for monitoring of CAR residues in veterinary and biological samples with acceptable recoveries values compared with the official chromatographic techniques.

Synthesis, characterization, electrochemical and antibacterial studies of MN4-type macrocyclic complexes of Ni(II)

Herein, we designed and synthesized two novel MN4-type macrocyclic complexes of NiII using a simple template-based strategy. The synthesized macrocyclic complexes were characterized by using several analytical techniques such as elemental analysis, FT-IR spectroscopy, UV-Vis spectroscopy, and mass spectrometry. The molar conductance was also measured to predict the electrolytic behavior of macrocyclic complexes. Furthermore, the complexes were subjected to electrochemical investigation utilizing cyclic voltammetric techniques. The results indicated a quasi-reversible peak for NiII/NiI redox couple with ∆Ep value is 0.195 V and E1/2 value of –0.749 V vs Ag/AgCl electrode. The complexes stabilized the unusual oxidation state of the central metal ion. In addition, both complexes were tested for their antibacterial activities against pathogens like E. coli, S. aureus, B. subtilis, C. albicans, and P. aeruginosa, and both complexes were shown to have comparable antibacterial activity with the standard drug Gentamycin.

Eco-friendly electrochemical sensor for determination of conscious sedating drug “midazolam’’ based on Au-NPs@Silica modified carbon paste electrode

Benzodiazepines (BZDs) are a group of drugs prescribed for their sedating effect. Their misuse and addictive properties stipulate different authorities for developing simple, fast and accurate analytical methods for instantaneous detection. Differential pulse voltammetric technique (DPV) was utilized for the selective assay of midazolam hydrochloride (MDZ) in the pure, parenteral dosage forms and plasma samples. A chemically modified carbon paste electrode (CPE) was implemented during the study. The method depended on the electroreduction of MDZ on the surface of the electrode over a potential range of 0.0 V to −1.6 V. The electrode was fabricated using silica nanoparticles (Si-NPs) which were incorporated into the composition of the CPE and used to enhance the electrode performance. Then, to enhance the sensitivity of the method, a chronoamperometric modification step was applied for depositing gold nanoparticles (Au-NPs) on the carbon paste electrode surface. Modification with Au-NPs showed a higher reduction current peak for MDZ with well-defined peaks. Various parameters such as pH of the media and measurements scan rate were investigated and optimized to enhance the sensor sensitivity. The sensor showed a dynamic linear response over a concentration range of 4.0 × 10−7 M to 2.9 × 10−4 M of MDZ with a LOD of 2.24 × 10−8 M using 0.1 M acetate buffer (pH 5.6). The sensor was validated in accordance with the ICH guidelines regarding accuracy, precision and specificity for the selective assay of MDZ in the presence of excipients. A greenness evaluation was performed using three different assessment tools, namely, the “Green Analytical Procedure Index” (GAPI), the “Analytical Greenness metric” (AGREE) and the “Whiteness Analytical Chemistry tool” (WAC) using the RGB12 model.

Electrochemical sensor based on ZrO2/ionic liquid for ultrasensitive simultaneous determination of metoclopramide and paracetamol in biological fluids

A novel electrode, carbon paste electrode modified with a nanocomposite of zirconium dioxide nanoparticles and ionic liquid (ZrO2NP/IL/CPE), has been fabricated and used to determine both the paracetamol (PAR) and metoclopramide (MCP) mixture in bulk powder, pharmaceutical formulations, and biological fluids. Furthermore, it is the first reported method to determine the paracetamol in presence of its toxic impurities (i.e., p-aminophenol and p-chloroacetanilide) simultaneously. Square wave (SWV) and cyclic voltammetric (CV) techniques were used to investigate the effect of scan rate, concentration, and pH in order to optimize sensor’s response. The calibration curves were obtained in both low and wide concentration ranges from (0.1–200 nM) to (3.0–100.0 µM) for both drugs with limit of detection (LOD) as low as 28 and 29 pM and limit of quantification (LOQ) 93 and 97 pM for PAR and MCP, respectively. The proposed sensor was used to assess PAR, MCP, and paracetamol toxic impurities in human plasma, urine samples, and pharmaceutical formulations with satisfactory results showing a broad dynamic linear range from 100 pM to 100 µM with high sensitivity and good reproducibility.Graphical

Laser induced graphene (LIG) biosensors derived from chitosan: Towards sustainable and green electronics

Modern biosensors can provide real-time monitoring of individuals' health status, revolutionizing traditional healthcare diagnostics. As demand for these devices is continuously growing, the development of novel green materials and processes is mandatory to ensure sustainability. In this work, a simple laser direct writing approach was utilized to fabricate a novel green Laser Induced Graphene (LIG) glucose biosensor, whereby chitosan-based biofilms were used as writing feedstock material. Careful optimization of the biofilm composition was carried out in conjunction with the optimization of laser irradiation parameters to obtain bio-LIG structures with low sheet resistance and spectral characteristics of graphene-like materials. The surface of bio-LIG electrodes was modified with Prussian Blue nanoparticles and the electrocatalytic performance of bio-LIG sensors towards H2O2 was investigated using voltammetric techniques. The response of H2O2 was linear in the range 3 μM - 1 mM (sensitivity, 103.4 μA mM−1 cm−2 and the limit of detection (LOD), 1.9 μM). Following immobilization of glucose oxidase, the bio-LIG sensors showed a linear response of glucose in phosphate buffer (PBS) in the relevant physiological range of 25–300 μM (sensitivity, 457 nA mM−1 cm−2). The LOD was calculated as 9.6 μM. Additionally, the biosensor showed comparable results in artificial sweat.

Voltammetric Determination of Trace Amounts of Lead With Novel Graphite/Bleaching Earth Modified Electrode

Modified composite electrodes have gained considerable interest in the detection of heavy metal ions due to their excellent sensitivity, selectivity, stability, and rapid response. Generally, these sensors consist of binder, conductive substance, and modifier. This study examined into the performance of a novel modified electrode that used a graphite–bleaching earth (BE-MCPE) composite performed while detecting trace amounts of Pb(II) using a differential pulse voltammetric technique (DPASV). In order to investigate the properties of BE-MCPE, we employed several analytical techniques, including SEM, SEM-EDX, FTIR, and XRD. These techniques were used to characterize the physical, chemical, and elemental properties of BE-MCPE, as well as its Pb(II) adsorption capacity, providing a comprehensive understanding of its composition and structure. The electrochemical results showed that the modified electrode demonstrated superior sensitivity and selectivity, in detecting Pb(II) ions, with a linear response range of 2.10-7 M to 10.10-7 M, limit of detection (LOD) of 4,89x10-8 mol.L-1, and limit of quantification (LOQ) of 1,63x10-7 mol.L-1. This novel modified electrode can achieve the sensitive detection of trace amounts of Pb(II) in a wide range of wastewater applications.

ELECTROCHEMICAL INVESTIGATION OF OTILONIUM BROMIDE USING BORON-DOPED DIAMOND AND GLASSY CARBON ELECTRODES

Objective: Using cyclic (CV) and differential pulse (DPV) voltammetric techniques, the electrochemical research of otilonium bromide (OTB) was carried out over a wide pH range (0.3–12) at glassy carbon electrodes (GCE) and boron-doped diamond electrodes (BDDE). The typical electrochemical behavior of OTB was identified as being dependent on the type of working electrode and pH. This research aims to provide a brand-new electroanalytical technique for measuring OTB in buffer solutions. Material and Method: All experiments employed the typical three-electrode cell of 10 ml capacity in conjunction with a platinum wire counter electrode, a BDDE and GCE working electrode, and an Ag/AgCl reference electrode. NOVA 1.8 software and an AUTOLAB 204 potentiostat/galvanostat were used for electrochemical measurements. Result and Discussion: The electrochemical behavior of OTB, which belongs to a class of drugs called 'antispasmodics' (spasm and cramps reliever), primarily used to treat irritable bowel syndrome (IBS), and other gastrointestinal conditions characterized by motility problems, painful bowel spasms and distension (swelling and bloating in the belly area), was examined in 0.1 M H2SO4 at BDDE and GCE. The electrooxidation mechanism was also investigated by conducting CV investigations at various pH levels throughout a broad pH range (pH 0.3-12.0). Understanding the mechanism was aided by scan rate investigations, which revealed that diffusion was controlled for both electrodes. The proposed technique was successfully used to determine OTB under optimal conditions.

Voltammetric Detection of Explosive Nitroaromatic Compounds Using Boron-Doped Carbon Nanowall Electrodes

Nitroaromatic highly energetic explosive compounds were widely used during the I and II World Wars. Some of them, like 2,4,6-trinitrotoluene (TNT), are still used in military munitions or in industrial applications i.e., underwater blasting, mining, deep well or dye production. The worldwide use of nitroaromatic compounds led to widespread pollution of the environment causing a danger to living organisms due to their high toxicity and possible carcinogenicity. The most commonly used techniques for the detection of explosive nitroaromatics are high-performance liquid chromatography or high-resolution gas chromatography coupled with different detectors like mass spectrometers. Both methods require: expensive instrumentation, complex sample preparation which is crucial to analysis, and well-trained staff to perform the experiments. Therefore it is difficult to implement chromatography in the field. Electrochemical sensing is emerging as a fast, sensitive and relatively simple technique for detecting explosive materials. To date, various materials have been used as working electrodes for this purpose, however, carbon materials are particularly promising [1-2]. Among carbonaceous materials, boron-doped carbon nanowall (B:CNW) electrodes are particularly attractive for the sensitive and rapid detection of nitro-based compounds [3] due to the high content of sp2 phase, wide electrochemical working potential window (from -1.6 V to 1.2 V in 0.5 M KCl) and high values of heterogeneous electron transfer rate constant.In this work, we present electrochemical detection of chosen nitroaromatic explosive compounds like TNT on boron-doped carbon nanowall electrodes in aqueous solutions using voltammetric electrochemical techniques (differential pulse voltammetry, square-wave voltammetry, cyclic voltammetry). B:CNW electrodes were obtained using microwave plasma-assisted chemical vapour deposition in a one-step growth process. B:CNW electrode show enhanced electrocatalytic activity towards nitro moieties attached to aromatic rings, resulting in improved sensitivity toward detecting these groups. Hence, it is an attractive nanocarbon surface for nitroaromatic compound determination.

Exploring the Impact of Oligomerization on Redox Flow Cell Performance

The redox flow battery (RFB) is a promising stationary energy storage technology due to its inherent decoupling of energy and power, long service lifetime, and potential for low-cost manufacturing.1 While current embodiments are constrained by high upfront cost, nonaqueous RFBs may offer a pathway to cost-competitive energy storage systems through higher energy densities;2 however, this concept is at an early stage and several challenges must be overcome. In particular, the development of stable, high-voltage redox chemistries in conjunction with low-cost, selective membranes is needed to mitigate difficult-to-reverse capacity fade and reduced efficiencies. As such, a range of redox-active organic macrostructures, including oligomers (RAOs),3 polymers (RAPs),4 and colloids (RACs),5 have been described in the peer-reviewed literature. Of specific interest are RAOs, which, like the other macrostructures, can be paired with size-exclusion membranes but exhibit electrochemical and fluid dynamic properties that more closely align with monomers. While this proof-of-concept has been demonstrated,6,7 to our knowledge, few studies have systematically evaluated how the molecular properties of RAOs influence their performance in flow cells.In this presentation, we will describe our efforts to understand how the molecular properties of different oligomers influence their behavior in redox flow cells. To this end, we synthesize and characterize a set of model compounds, ranging from monomers to tetramers, that utilize TEMPO as the redox-active unit. We then assess the thermodynamic, kinetic, and transport properties of these compounds using a suite of voltammetric techniques. Subsequently, we characterize the performance and durability of these compounds in symmetric flow cells via electrochemical impedance spectroscopy, DC polarization, and durational cycling. We perform post-test characterization after the cycling experiments to disaggregate molecular- and cell-level sources of capacity fade. We find that, in general, oligomers with increased size exhibit lower diffusivities while maintaining the facile charge transfer characteristics afforded by the appended monomer. These size-dependent variations in mass transport rates directly translate to differences in cell polarization and cycling performance. Time-dependent capacity fade observed during cycling is confirmed by post-mortem analysis. Broadly, these results align with previously developed relationships between molecular size, electrochemical properties, and flow cell performance; we posit that the principles for functionalization and testing utilized here can be applied to other RAOs with improved stability. Acknowledgements This work was supported as part of the Joint Center for Energy Storage Research, an Energy Innovation Hub funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences. B.J.N gratefully acknowledges the NSF Graduate Research Fellowship Program under Grant Number 1122374. Any opinion, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the NSF. The authors thank Jeffrey Kowalski and Katharine Greco of the Brushett Group as well as Yu Cao and Jeffrey Moore of the Moore Group at the University of Illinois for their contributions to conceptualizing the framework and preliminary testing for this work.

Optimization of arsenic detection conditions using copper ferrite nanocomposite in aqueous medium via response surface methodology

Arsenic (As) element is considered a toxic and carcinogenic pollutant in the environment. Therefore, effective technology for its detection in drinking water is crucial. In this study, a modified electrode with copper ferrite and multiwall carbon nanotubes (MWCNTs) has been used as a simple, high-sensitivity electrochemical sensor for detection of As(III) ion in water. After preparation of the modified electrode, the electrochemical behavior of arsenic was investigated by voltammetric technique. The prepared nanostructures were characterized by different techniques including Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), field emission scanning electron microscopes (FESEM), and electrochemical impedance spectroscopy (EIS). The effects of chemical and instrumental variables on the process efficiency were evaluated through multivariate optimization. The optimal conditions were obtained at pH = 5.00, modifier percentage 18.37 %, time 52.53 s, scan rate 0.062 Vs−1, and pulse height 0.036 V. Thus, the modified electrode with copper ferrite and MWCNTs nanostructures can be used for sensitive detection of arsenic in water samples under the optimal conditions designed through response surface methodology (RSM).

Calibration-Free, Seconds-Resolved In Vivo Molecular Measurements using Fourier-Transform Impedance Spectroscopy Interrogation of Electrochemical Aptamer Sensors.

Electrochemical aptamer-based (EAB) sensors are capable of measuring the concentrations of specific molecules in vivo, in real time, and with a few-second time resolution. For their signal transduction mechanism, these sensors utilize a binding-induced conformational change in their target-recognizing, redox-reporter-modified aptamer to alter the rate of electron transfer between the reporter and the supporting electrode. While a variety of voltammetric techniques have been used to monitor this change in kinetics, they suffer from various drawbacks, including time resolution limited to several seconds and sensor-to-sensor variation that requires calibration to remove. Here, however, we show that the use of fast Fourier transform electrochemical impedance spectroscopy (FFT-EIS) to interrogate EAB sensors leads to improved (here better than 2 s) time resolution and calibration-free operation, even when such sensors are deployed in vivo. To showcase these benefits, we demonstrate the approach's ability to perform real-time molecular measurements in the veins of living rats.

Green Prospective Approach of Chromium Zinc Oxide Nanoparticles for Highly Ultrasensitive Electrochemical Detection of Anti-hypotensive Medication in Various Matrices.

A highly ultrasensitive sensor that relied on Cr/ZnO-NPs was developed to detect etilefrine hydrochloride (ETF) in different matrices via a particular green voltammetric technique. The X-ray diffraction pattern showed the nanomaterials of the polycrystalline hexagonal structure. The energy-dispersive X-ray spectrum approved the presence of Cr3+ inside the host zinc oxide framework. The morphological and topological characteristics were visualized using transmission electron microscopy and atomic force microscopy micrographs describing the nanoparticles in spherical-like shape with large-surface area. The energy gap (Eg) was evaluated from transmittance (T %) and reflectance (R %) spectra within the visible region. The optimization study indicated that the Cr/ZnO-NP/CPE sensor has high sensitivity, thanks to the distinctive physical and chemical properties of the fabricated electrode. A new approach showed a great selectivity for determining ETF in different matrices in the presence of other interferents like levodopa. Under optimal circumstances, the square-wave voltammetry revealed a linear response to ETF from 0.01 to 10 μmol L-1 (r = 0.9996) with quantification and detection limits of 9.11 and 2.97 nmol L-1, respectively. Finally, the proposed approach was effectively applied to estimate ETF in pharmaceutical dosage forms and biological fluids using simple, accurate, and selective electrochemical electrode. The greenness profile assessment of the developed method was performed using the Eco-Scale and green analytical procedure index. These tools indicated that the proposed method is an eco-friendly technique for the determination of ETF in different matrices.

Fe3O4 nanochips loaded MXenes/g-C3N4 nanocomposite for ultrasensitive electrochemical detection of zinc (II), cadmium (II), lead (II), copper (II) and mercury (II) metal ions

The present work demonstrates a highly sensitive and efficient nanosensor for the simultaneous detection of zinc (II), cadmium (II), lead (II), copper (II) and mercury (II) metal ions using Ti3C2/Fe3O4/g-C3N4 nanocomposite. The Ti3C2/Fe3O4/g-C3N4 nanocomposite was prepared using co-prcepitation method followed by ultrasonication treatment containing Ti3AlC2, ferrous sulfate, ferric chloride and melamine as precursors. The as-prepared nanocomposites were successfully examined using XRD, FTIR, SEM and cyclic voltammetric techniques. Differential pulse anodic stripping voltammetry (DPASV) technique was applied for the simultaneous detection of Zn (II), Cd (II), Cu (II), Pb (II) and Hg (II) ions. The electrochemical variables including pH of the solution, amount of Ti3C2/Fe3O4/g-C3N4 on the GCE surface, supporting electrolyte and deposition time were optimized to get maximum sensitivity. Under optimal conditions, Ti3C2(HF)/Fe3O4/g-C3N4 sensor exhibited excellent performance for Zn (II), Cu (II), Cd (II), Pb (II) and Hg (II) in a range from 0.5 to 0.005 μM with detection limits 0.26 nM for Zn (II), 0.21 nM for Cd (II), 0.10 nM for Pb (II), 0.11 nM for Cu (II) and 0.12 nM for Hg (II) which are lower than the permissible limit recommended by the WHO guidelines. The sensor also shown outstanding selectivity in the presence of various foreign species (Ca2+, Mg2+, Na1+, Cl1-, NO31-, and 4-nitrophenol) and high resolution for simultaneous detection of Zn (II), Cd (II), Cu (II), Pb (II) and Hg (II) ions. The good electroanalytical performance and excellent selectivity and sensitivity of developed nanosensor can be attributed to the heterostructure and the coordination provided by MXene and Fe3O4/g-C3N4, resulting in enhanced interfacial charge transfer and number of adsorption sites. In addition, the developed sensor was applied for the detection of metal ions in tap water samples and satisfactory results were obtained. This study highlights a facile approach for designing MXene-supported magnetic NPs/ N containing carbon materials as sensing platform for the detection of other toxic heavy metal ions.

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.

Bilirubin determination at the electrified liquid-liquid interface supported with a 3D printed capillary

In this work, we have studied the behavior of bilirubin at the electrified liquid-liquid interface using two voltammetric techniques - cyclic and differential pulse voltammetry. The effect of bilirubin concentration as the analyte, and the influence of the aqueous phase pH on the interfacial behavior were investigated. Our focus was to optimize the electroanalytical determination protocol of bilirubin at the electrified liquid-liquid interface with the buffered aqueous phase (physicochemical study) and/or artificial urine formulation (analytical study). In this respect, we have extracted a number of electroanalytical parameters concerning bilirubin covering limits of detection and quantification and sensitivities. To push the optimized protocol towards applicability, we have designed and fabricated a 3D printed polyamide based tube finished with an aperture supporting a soft junction. Liquid-liquid interface placed in a fabricated support was characterized using voltammetry and scanning electron microscopy. With 3D printed platform we have significantly reduced the amount of consumed chemicals (from a few mL to a few tens of µL) and obtained a few times lower limit of determination as compared with the macroscopic apparatus.

Unveiling the Remarkable Antioxidant Activity of Plant-Based Fish and Seafood Analogs through Electrochemical Sensor Analysis.

The global consumption of vegan foods is experiencing an expressive upward trend, underscoring the critical need for quality control measures based on nutritional and functional considerations. This study aimed to evaluate the functional quality of caviar and salmon analog food inks based on pulses combined with nano ingredients and produced in our laboratory (LNANO). The primary objective of this work was to determine the total antioxidant compounds contained in these samples using a voltammetric technique with a glassy carbon electrode. The samples underwent ethanolic extraction (70%) with 1 h of stirring. The voltammograms were acquired in a phosphate buffer electrolyte, pH 3.0 with Ag/AgCl (KCl 3 mol L-1) as the reference electrode and platinum wire as the auxiliary electrode. The voltammograms revealed prominent anodic current peaks at 0.76-0.78 V, which are attributed to isoflavones. Isoflavones, known secondary metabolites with substantial antioxidant potential commonly found in pulses, were identified. The total isoflavone concentrations obtained ranged from 31.5 to 64.3 mg Eq genistein 100 g-1. The results not only validated the efficacy of the electrochemical sensor for quantifying total antioxidant compounds in the samples but also demonstrated that the concentration of total isoflavones in caviar and salmon analogs fell within the expected limits.

Facile immobilization of cholesterol oxidase on Pt,Ru-C nanocomposite and ionic liquid-modified carbon paste electrode for an efficient amperometric free cholesterol biosensing.

In present work, the enzyme cholesterol oxidase (ChOx) was immobilized by Nafion® (Naf) on Pt,Ru-C nanocomposite and an ionic liquid (IL)-modified carbon paste electrode (CPE) in order to create cholesterol biosensor (Naf/ChOx/Pt,Ru-C/IL-CPE). The prepared working electrodes were characterized using scanning electron microscopy-energy-dispersive spectrometry, while their electrochemical performance was evaluated using electrochemical impedance spectroscopic, cyclic voltammetric, and amperometric techniques. Excellent synergism between IL 1-allyl-3-methylimidazolium dicyanamide ([AMIM][DCA]), Pt,Ru-C, and ChOx, as modifiers of CPE, offers the most pronounced analytical performance for improved cholesterol amperometric determination in phosphate buffer solution pH 7.50 at a working potential of 0.60V. Under optimized experimental conditions, a linear relationship between oxidation current and cholesterol concentration was found for the range from 0.31 to 2.46µM, with an estimated detection limit of 0.13µM and relative standard deviation (RSD) below 5.5%. The optimized amperometric method in combination with the developed Naf/ChOx/Pt,Ru-C/IL-CPE biosensor showed good repeatability and high selectivity towards cholesterol biosensing. The proposed biosensor was successfully applied to determine free cholesterol in a human blood serum sample via its enzymatic reaction product hydrogen peroxide despite the presence of possible interferences. The percentage recovery ranged from 99.08 to 102.81%, while RSD was below 2.0% for the unspiked as well as the spiked human blood serum sample. The obtained results indicated excellent accuracy and precision of the method, concluding that the developed biosensor can be a promising alternative to existing commercial cholesterol tests used in medical practice.

Highly sensitive amperometric food sensor for Sudan-I dye using nanocomposites modified working electrode

Sudan-I dye (1-phenyl azo-2-naphthol) is commonly used as a coloring agent in the food and textile industries. The excessive use of Sudan-I dye has ill effects on human health. A sensitive and selective electrochemical detection is required for sensing Sudan-I dye in food products. An electrochemical sensor based on a modified working electrode using ternary mixed metal oxide (Ti/Fe/CuO) nanocomposites was developed for sensing Sudan-I dye. Using a modified Sol-gel technique, Ti/Fe/CuO mixed metal nanocomposites were synthesized. FT-IR, UV–Visible, SEM, and XRD techniques were used to characterize the Ti/Fe/CuO nanocomposites. Different voltammetric techniques, such as Cyclic voltammetry (CV), Differential Pulse Voltammetry (DPV), and Linear Sweep Voltammetric (LSV) were used for qualitative and quantitative estimation of Sudan-I dye. Electrochemical Impedance Spectroscopy (EIS) was used for structural information of interface. The specially designed working electrode acted as a sensor and shows good sensing ability toward Sudan-I dye in real food samples. A linear range of 0–160 µM and 0–200 µM for red chili sauce and powder (real samples), respectively was observed. Under the optimized condition, the current response was linear with a detection limit of 0.02 µM/L. A characteristic oxidation peak of 7263.36 µA at 0.2606 V and a reductive peak of − 1465 μA at − 0.3714 V are the characteristic peaks for Sudan-I dye. The effect of change in pH, scan rate, storage, stability behavior, and concentration of Sudan-I dye was evaluated. A comparative study was done between glassy carbon electrodes, bare Copper metal, and ternary metal oxide NCs modified electrodes. The developed electrochemical sensor demonstrated reliability, reproducibility, stability, speed, and non-specificity, making it suitable for both quantitative and qualitative analysis of food additives, preservatives, coloring agents, and flavoring agents.

Construction of a novel sensor based on activated nanodiamonds, zinc oxide, and silver nanoparticles for the determination of a selective inhibitor of cyclic guanosine monophosphate in real biological and food samples

In the present work, we developed a highly sensitive and selective method for the determination of sildenafil (SIL) using a modified glassy carbon electrode (GCE) with activated nanodiamonds, zinc oxide, and silver nanoparticles nanocomposite (AND@ZnO-Ag/GCE). Various voltammetric techniques, including CV, DPV, and EIS, were employed to investigate the electrochemical process of SIL on the modified electrode. The resulting AND@ZnO-Ag/GCE electrode exhibited enhanced electron transfer between the electrode and the analyte, resulting in an excellent electrocatalytic performance for SIL oxidation under optimized conditions. The analytical performance of the AND@ZnO-Ag/GCE sensor demonstrated two linear responses within the concentration range of 0.01–0.08 μM and 0.08–14.6 μM, with a remarkably low detection limit of 7.08 nM. Moreover, the modified sensor (AND@ZnO-Ag/GCE) exhibited high selectivity and anti-interference capacity. It successfully detected trace amounts of SIL in biological and food samples, yielding satisfactory results. Furthermore, this work provides insights into the potential adulteration of energy drinks with sildenafil, addressing an area that has received limited attention in previous research.