Electrochemical Determination Research Articles

Electrochemical determination of sorafenib by chronopotentiometry and ASDPV based on novel molecularly imprinted polymer and their applications in oncology patients

A promising selective and sensitive biosensor was fabricated for the first time to monitor trace amounts of sorafenib (SORF), a multi-target kinase inhibitor, based on the electropolymerization of pyrrole on a carbon paste electrode (CPE). To prepare a modified CPE, the prepared metal organic framework (NH2-MIL-101(Fe)) was mixed with graphite powder in the presence of an appropriate amount of paraffin oil before it was packed into a plastic tube containing a copper wire. Computational studies appreciate the use of pyrrole as the functional monomer for electropolymerization at the CPE surface using chronopotentiometry in the presence of SORF as a template. After the leaching of SORF, the imprinted sensor was characterized using FT-IR, SEM, and AFM, while NH2-MIL-101(Fe) was investigated by XRD, XPS, and SEM analysis. Under optimum conditions, SORF was detected using anodic stripping differential pulse voltammetric and chronopotentiometric techniques. High sensitivity (6.40 × 10−12 mol/L), excellent selectivity, and a wide linear range (4.20 × 10−11–7.10 × 10−3 mol/L) were recorded. Furthermore, the proposed sensor exhibited good repeatability (RSD = 2.40 % for n = 7) and high lifetime stability (∼7 weeks). Based on the above-mentioned merits, the designed electrochemical sensor was properly utilized for SORF determination in different oncology patients with satisfactory results (recovery = 94.40–99.90 %).

Electrochemical Behavior and Determination of Tolvaptan Using Glassy Carbon and Boron-Doped Diamond Electrodes

Tolvaptan (TOL), a vasopressin V2 receptor antagonists drug, is used to treat hyponatremia in people with heart failure. Herein, we report for the first time the electrochemical behavior of TOL and its oxidation metabolite TOL-oxo on glassy carbon and boron-doped diamond electrodes (GCE, BDDE) by cyclic voltammetry (CV). For both molecules, two-electron irreversible oxidation was observed in 0.5 M H2SO4, while single-electron irreversible oxidation occurred at pH 7.0. A sensitive and rapid electroanalytical technique for the detection of TOL has been developed, based on differential pulse voltammetry (DPV). Linearity was obtained with GCE within a concentration range between 1–1000 μM, using anodic currents appearing around 1397 mV. For BDDE, the concentration range was 8–1000 μM using anodic currents around 1490 mV.

A rapid and reliable electrochemical determination of 5- hydroxymethylfurfural in honey exploiting nickel oxide nanoparticles modified electrode

This study presents a novel approach for the rapid and reliable electrochemical determination of 5-hydroxymethylfurfural (5-HMF) in honey using a screen-printed carbon electrode modified with nickel oxide nanoparticles (NiONPs/SPCE). The NiONPs were synthesized using a simple method and characterized using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The NiONPs/SPCE demonstrated enhanced sensitivity and selectivity for 5-HMF detection. The electrochemical behavior of 5-HMF on the NiONPs/SPCE was investigated using techniques such as cyclic voltammetry (CV) and square wave voltammetry (SWV). The optimum experimental conditions were obtained including a 5 μL of 5.0 mg/mL NiONPs modifier, the voltammetric response of step potential 15 mV, amplitude 50 mV and frequency 50 Hz in 0.1 M BR buffer pH 13 as supporting electrolyte. The proposed method exhibited a linear relationship between the cathodic peak current and the concentration of 5-HMF in the concentration ranges of 0.5–5.0 ppm, with a limit of detection (LOD) of 0.24 ppm. The selectivity of the NiONPs/SPCE was evaluated by studying potential interferences commonly found in honey samples, and the results demonstrated excellent selectivity for 5-HMF detection. The reproducibility and stability of the NiONPs/SPCE were also assessed, with low relative standard deviations (RSD) obtained for both the cathodic peak current (2.94 %) and long-term stability (3.14 %). The developed NiONPs/SPCE method was successfully applied to the determination of 5-HMF in real honey samples, yielding comparable results to the standard HPLC method. This work showcases the potential of the NiONPs/SPCE as a practical and cost-effective electrochemical sensor for the accurate analysis of 5-HMF in honey samples.

Zeolitic imidazolate framework-8/polyaniline nanocomposite-based electrochemical sensor for sensitive detection of imidaclothiz

Imidaclothiz (IMZ) is a class of neonicotinoid insecticide which can pose potential threat to human health and be frequently detected in water and foods. Herein, a zeolitic imidazolate framework-8/polyaniline (ZIF-8/PANI) nanocomposite has been modified on the surface of glassy carbon electrode (GCE) for the electrochemical determination of IMZ, and the electrochemical detection performance of the modified electrode was investigated by cyclic voltammetry (CV) and square wave voltammetry (SWV). With the large surface area of ZIF-8 and great electric conductivity of PANI, the ZIF-8/PANI-modified electrode showed a high catalytic performance towards IMZ reduction in PBS. Under the optimized conditions, the linear range was from 1.0 × 10−7 to 1.0 × 10−5 mol/L and the limit of detection was as low as 2.5 × 10−8 mol/L (S/N = 3). In addition, the developed sensor displayed high reproducibility, excellent stability, and applicability in real vegetable sample analysis, indicating that the proposed method offered an alternative approach for IMZ residues analysis.Graphical abstract

Determination of Digoxin in Biological Samples and Medicinal Plants by Electrochemical and Chromatographic Methods

AbstractIn this study, the nanocomposite with FeS2 nanoparticles and sulfur‐doped reduced graphene oxide (SRGO) were synthesized and characterized with appropriate spectroscopic, crystallographic and morphological methods. The FeS2‐SRGO nanocomposite was coated on a glass‐carbon (GC) electrode as working electrode for the electrochemical determination of digoxin. The method was linear in the range of 3–25 μgL−1 with the detection limit of the method is 0.54 μgL−1. The plant‘s active ingredient was extracted from Leonurus cardiac and Valeriana officinalis. Three important types of real samples including plants extracted and urine samples were selected to measure the amounts of digoxin. The electrochemical sensing results were evaluated by studying the amount of spiked recovery and statistical test with comparison to the high‐performance liquid chromatography (HPLC) method results and the accuracy and precision of the method for digoxin determination in real samples were confirmed. The results show the plant extracted contained a significant amount of digoxin. The presence of digoxin in valerian was investigated for the first time in this study.

Magnetic perlite based molecularly imprinted polymer on screen printed carbon electrode as a new tyramine electrochemical sensor

This paper describes the design and fabrication of a sensitive electrochemical sensor using a new magnetic pearlite-based molecularly imprinted polymer (MPt/MIP) for the voltammetric determination of tyramine (Tyr). MPt/MIP nanocomposite was synthesized by direct surface-based imprinting procedure using methacrylic acid (MAA) as monomer for MIP and also functional group for magnetic perlite (MPt). The structural properties of MPt/MIP nanocomposite were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), FT-IR spectroscopy, vibrating sample magnetometry (VSM) and via adsorption kinetics and adsorption isotherms. The integrated analytical procedure consists of dispersion of synthesized MPt/MIPs for selective separation of target analyte from sample and their subsequent localization on the surface of a magnetic screen-printed carbon electrode (MSPCE) as a platform for determination of Tyr by differential pulse voltammetry (DPV). The experimental parameters which affect separation efficiency and electrochemical determination were optimized. The developed method provided a linear calibration range of 8.0 to 380.0 ng mL−1 (R2 = 0.998), and a detection limit of 3.8 ng mL−1. The intra-day and inter-day precision (%RSD) were in the range 3.1–4.4 %. The method was successfully applied to the determination of Tyr in real samples with recoveries ranging from 94.2 to 105.2 %.

Development of a bio‐inspired magnetic nanocomposite synthesized through semi‐covalent imprinting for electrochemical determination of cholesterol in water samples

AbstractFecal pollution in aquatic environments by analysis of fecal coliforms along with the determination of sterol compounds, such as cholesterol (CHO) has been extensively investigated. Thus, the development of an easier, cheaper, selective, and sensitive method for CHO monitoring in aquatic environments can be a valuable tool in contributing to the analysis of fecal pollution mainly in developing countries. In the present study, a voltammetric method aiming at CHO determination in aqueous media based on a magnetic molecular imprinted polymer (MMIP) sensor is proposed. The MMIP was synthesized on the surface of silica‐coated magnetite, using CHO as a template covalently bound to 3‐(triethoxysilyl)propyl isocyanate (ICPTES). A suspension of MMIP was prepared in ethanol and used to modify a graphite‐epoxy composite magneto‐actuated electrode (m‐GEC). The indirect CHO determination was based on the decrease in the current of [Fe(CN)6]3−/4− redox probe in the presence CHO. Under optimized experimental conditions (Britton‐Robinson buffer 0.01 mol L−1 at pH 7.0), the parameters of square wave voltammetry were optimized through the Doehlert matrix (amplitude of 111.2 mV, potential increase of 10.8 mV and frequency of 5.54 Hz). An analytical curve ranging from 0.51 up to 11.0 μmol L−1 was obtained with a limit of detection of 0.15 μmol L−1. The developed method was applied to the analysis of the lake water sample, and the accuracy of the method was confirmed by HPLC‐DAD as a reference technique.

Poly(bis(2,2′-bipyridine) hydroxy Copper(II) iodide modified glassy carbon electrode for electrochemical determination of chloroquine in pharmaceuticals and biological samples

A new electrochemical sensor, poly(bis(2,2′-bipyridine)hydroxycopper(II) iodide modified glassy carbon electrode (poly([Cu(Bip)2OH]I)/GCE), was prepared by electropolymerization of bis(2,2′-bipyridine)chlorocopper(II) iodide ([Cu(Bip)2Cl]I) on glassy carbon electrode (GCE) for voltammetric determination of chloroquine (CQ). The synthesized complex (bis(2,2′-bipyridine)chlorocopper(II) iodide) was characterized using UV–Vis, CHN elemental analysis, atomic absorption spectroscopy (AAS), electrolytic conductivity, melting point and Fourier transform infrared spectroscopy (FT-IR) were used to characterize and confirm the synthesis of the desired complex (bis(2,2′-bipyridine)chlorocopper(II) iodide). The Uv-Vis, FTIR and electrochemical data of the synthesized polymer supports the replacement of chloro ligand by hydroxyl ligand during electropolymerization of the monomer in aqueous solution. The fabricated electrode (poly([Cu(Bip)2OH]I)/GCE) was characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The voltammetric behavior of CQ was examined using CV and square wave voltammetry (SWV). Compared to the bare GCE, poly(Bip)/GCE, and Cu/GCE, the current signal of CQ was significantly enhanced at poly([Cu(Bip)2OH]I)/GCE, which demonstrates excellent electrocatalytic behavior of poly([Cu(Bip)2OH]I)/GCE towards electrochemical oxidation of CQ. Under the optimum experimental conditions, the SWV current signal of poly([Cu(Bip)2OH]I)/GCE offered linearity on the concentration range of CQ between 0.5 and 250 μM with LOD and LOQ values of 4.22 ×10−2 and 1.4 × 10−1 μM, respectively. In the presence of possible interfering substances including glucose, paracetamol, adenine and guanine, the voltammetric determination of CQ was also considered, and their interventions were found to be insignificant, which evidenced the selectivity of the introduced electrode. The analytical application of the established sensor was successfully applied in the determination of CQ in pharmaceuticals, milk, serum, and urine samples. The detected amount of CQ in the tablet samples was in the range between 100.5 and 110.2% with RSD of 1.5 and 1.87%, respectively. The spiked recovery results in pharmaceuticals, milk, serum, and urine biological samples were in the range of 100.5 to 110.2%, 97.13 to 98.12, 103.7 to 103.6% and 95.50 to 97.05%, respectively. These results confirm that the developed method exhibits high applicability for electrochemical determination of CQ in various real samples.

Niobium Oxide Nanorods Obtained by Hydrothermal Synthesis—Structure, Morphology, and Electrochemical Detection of Oxygen Via Oxygen Reduction Reaction

Niobium oxides are promising materials for applications within various research fields, especially as electrocatalysts for various chemical reactions. The tuning of the synthetic parameters can achieve a successful compromise between morphology and structure, aiming to obtain certain properties. Hence, this study aimed to investigate the influence of hydrothermal synthesis parameters on the morphology and structure of niobium oxide growth on a niobium metallic plate. The effect of annealing on the material performance was also evaluated. Afterward, the most crystalline sample was tested for the electrochemical determination of dissolved oxygen, a fundamental reaction in corrosion, biomedicine, and environmental monitoring. This is the first work using this material configuration as an electrochemical sensor. The hydrothermal synthesis produced nanorods formed by poorly crystalline, acidic, hydrated Nb2O5. Increasing the mineralizer concentration could increase the crystallinity and the nanorod growth rate, but it could also promote a lack of structural and morphological uniformity throughout the surface. Heat treatment allowed the increase in crystallinity and favored orthorhombic Nb2O5. Raman spectroscopy revealed that, at the first moment, acidic, hydrated niobium oxide structures were formed as precursors of crystalline niobium oxide that would be developed with longer reaction times and a higher mineralizer concentration. The obtained niobium oxide showed electrocatalytic activity toward the oxygen reduction reaction, with comparable performance between the samples with and without heat treatment. At all analyzed pH values, the amperometric response was linearly correlated with the dissolved oxygen concentration. pH influenced the sensitivity of the material; a maximum sensitivity of 0.0417 mA/cm2·mg/L O2 was achieved at pH = 6. The participation of the acidic functionalities of the surface in the ORR reaction was confirmed by Raman spectroscopy.

Comparison of colorimetric and electrochemical (Easy Touch GCU Meter) methods for determination of blood uric acid in clinical practice in patients with gout and hyperuricemia (data from a pilot study)

Hyperuricemia (HU) is a condition caused by an increase in serum uric acid (UA) levels above 360 μmol/l. Often HU is asymptomatic, but under the influence of genetic and environmental factors, attacks of peripheral arthritis (gout) may occur. Remission of gout is achieved by normalization of UA serum levels, which can be determined by a colorimetric or electrochemical method, although the latter is not currently commonly used in clinical practice to control UA levels. Objective: to compare the standard colorimetric and electrochemical methods (Easy Touch GCU Meter) for monitoring UA levels. Material and methods. 30 gout patients were included in the study. This group included subjects with current/anamnestic asymptomatic HU andpatients with a confirmed diagnosis of gout (ACR/EULAR 2015 criteria). The examination included a general examination, history taking, and laboratory testing. The determination of UA level by the colorimetric method in venous blood serum was performed no later than 5 minutes after collection, and the determination of UA level in fresh whole capillary blood from the fingertip by the electrochemical method (Easy Touch GCU Meter) – immediately after collection. Results and discussion. The average values of UA blood level determined by the two compared methods differed by 13.9 μmol/l (3.9 % with respect to the colorimetric method). The high value of the correlation coefficient (r = 0.86) indicates a close linear relationship between the compared results and their good agreement. The method is also applicable in patients with achieved normouricemia. Conclusions. The method of electrochemical determination of UA level in subjects with HU and gout can be used in real clinical practice for self-monitoring.

Integrating catalytic role of gold nanoparticles with in-situ confinement effect of zirconium-based metal-organic frameworks for electrochemical determination of methylmercury

Catalytic redox reactions and size matching effect between the target molecule and sensing material are reliable methods for highly efficient determination of heavy metal ions. In this work, the electrochemical determination of methylmercury (CH3Hg+) was carried out gold nanoparticles (AuNPs) incorporated into four zirconium-based metal organic frameworks (MOF) with different pore diameters, namely MOF-801, (University of Oslo) UiO-66, UiO-67, UiO-68. The work relates the role of dicarboxylic ligands of different lengths to the AuNPs load capacity and the adsorption and reduction of CH3Hg+. The voltammetric properties of CH3Hg+ at different modified electrodes were studied by differential pulse anodic stripping voltammetry (DPASV). It was found that the CH3Hg+ electrochemical behavior was greatly influenced by the pore confinement effect of MOFs. Under the optimal conditions, the pore sizes of Au/UiO-67 are matched to CH3Hg+ molecule and they showed the highest response current. The possible reduction process of CH3Hg+ at the sensitive interface was explored by X-ray photoelectron spectroscopy (XPS) and chronoamperometry (CA). These four Au/MOFs modified GCE can also be used in detection of CH3Hg+ spiked in river water, confirming their potential application in the rapid detection of methylmercury in environmental samples.

Exonuclease III‑assisted and target-induced conformational change of DNA hairpins for electrochemical detection of mercury (II)

Here, we report a DNA hairpin strategy for electrochemical determination of Hg2+ based on T-Hg2+-T pairs and exonuclease III (Exo III) assistance. The innovation of this work lies in the designed DNA structure and detection principles. Unlike the previously reported DNA hairpin structure, the ring portion of the hairpin DNA we designed consisting of T bases serves as a recognition probe, forming a T-Hg-T complex with Hg2+. The stem is composed of 5 pairs of complementary bases, which is conducive to the stability of the hairpin structure. After the formation of T-Hg-T in the ring, with the help of Exo III, Exo III can digest more DNA than the T bases designed in the stem. In this event, the shorter the length of the remaining DNA strand on the electrode, the weaker the repulsive force against [Fe(CN)6]3−/4−, and the stronger the differential pulse voltammetry (DPV) current signal, achieving “signal-on” transitions. Under the optimal conditions, the DPV current response increases with increasing Hg2+ concentration and is linear with the logarithm of Hg2+ concentration (1 nM–10 μM). The limit ofdetection is 0.16 nM. The electrochemical sensor was successfully applied to the determination of Hg2+ in river water.

Electrochemical Determination of Rutin on a Gold Microsphere—Taro Stalk Porous Carbon Modified Carbon Ionic Liquid Electrode (CILE)

As an abundant, inexpensive, and renewable biomass raw material, taro [Colocasia esculenta (L.) Schott] stalks were employed as a simple biochar template due to their porous structure. A composite composed of gold microsphere and taro stalk derived porous carbon (Au-MS@TSPC) was used to construct an electrochemical sensor for the sensitive determination of rutin. Under the optimized conditions, the sensor exhibited a wide linear range from 0.12 to 10.0 μmol·L−1 with a detection limit of 0.0265 μmol·L−1. The sensor demonstrated good selectivity and was applied to the determination of rutin in human serum with recoveries from 94.0% to 105.8%. The fabrication of Au-MS@TSPC in this study provides a promising approach for the subsequent utilization of taro stalks.

A Selective and Sensitive Electrochemical Sensor for Pyridoxine Hydrochloride (Vitamin B6) in Pharmaceutic Tablet

AbstractIn this study, a copper (II) oxide‐glutardialdehyde modified boron doped diamond electrode was used as a sensor for the electroanalysis of pyridoxine hydrochloride (vitamin B6) for the first time. A copper oxide‐glutardialdehyde modified boron doped diamond electrode (CuO‐GA2/BDDE) was prepared by a simple drop casting method on boron diamond electrode (BDDE) by suspending CuO with glutardialdehyde (CuO‐GA2). The electrochemical behavior of vitamin B6 was examined using cyclic voltammetry (CV) and its electrochemical determination was found by differential pulse voltammetry (DPV). Under optimum experimental conditions, the linear working range of vitamin B6 on CuO‐GA2/BDDE via the DPV method was calculated as 5.96×10−6–3.75×10−4 mol.L−1. The limit of detection (LOD) was calculated as 1.99×10−7 mol.L−1. In order to demonstrate the selectivity of the method improved for the quantitative determination of vitamin B6 on the CuO‐GA2/BDDE, the interference effect of some cations (Zn2+, Cu2+, Pb2+) and anions (NO3−, Cl−) was investigated via the DPV method. The improved electrode was successfully used for the electroanalysis of vitamin B6 in a tablet sample of the commercial Tribeksol® (deva) (250/250/1 mg B1+B6+B12).

Submicromolar electrochemical sensing platform for fast Fluoxetine quantification based on Nb2CTx MXene and nitrogen-doped graphene oxide nanocomposites

A facile and novel electrochemical determination of Fluoxetine (FLX) at submicromolar concentration Niobium carbide (Nb2CTx) and Nitrogen-doped Reduced Graphene Oxide (NRGO) hybridized electrodes as sensing platform is demonstrated. Herein, Niobium carbide (Nb2CTx) was successfully prepared by etching Nb2AlC and then ultrasonically compounded with Nitrogen-doped Reduced Graphene Oxide (NRGO), to form a well-dispersed Nb2CTx/NRGO composite, which was modified onto a glassy carbon electrode (GCE). The morphology, structure and electrochemical property of the Nb2CTx/NRGO/GCE was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The electrocatalytic activity of the Nb2CTx/NRGO/GCE for FLX oxidation was studied in detail. The peak currents showed two good linear relationships (R2 = 0.9962 and 0.9949) with FLX concentrations (1.0–10 µM and 10–100 µM) and a detection limit of 0.34 µM (S/N = 3). The sensor has good selectivity, repeatability, reproducibility and stability, and is capable of sensitively determining FLX in human serum and urine samples of clinical biological fluids. This work is believed to be of great significance and of broad interest for research on innovative MXene materials development and biomedical sensing applications.

An electrochemical sensor for sub-attomolar determination of aluminum ion with an ultra-wide response range

In this work, an electrochemical sensor was developed for ultra-sensitive determination of aluminum ion (Al3+) using poly(3-aminophenylboronic acid)-gold nanoparticles (PAPBA-AuNPs) modified electrode. The proposed PAPBA-AuNPs modified electrode was prepared by two steps including electrodeposition of gold chloride hydrate and electropolymerization of 3-aminophenylboronic acid. The peak current for PAPBA reduction was recorded by square-wave voltammetry and employed for electrochemical determination of Al3+ based on the coordination reaction between them. With the increasing concentration of Al3+, the peak current for PAPBA reduction diminished. Under the optimized conditions, the proposed electrochemical sensor exhibited a wide response range of 0.10 aM to 10.00 μM and a low limit of detection of 0.019 aM, which is much superior to those of conventional methods. Moreover, this electrochemical sensor was successfully used for Al3+ detection in tap water and instant noodle samples.

A novel approach of flow system with a 3D-printed Direct Injector Detector for electrochemical determination of cadmium and lead

A simple approach based on a flow system equipped with a novel 3D-printed Direct Injection Detector (DID), first time working in an electrochemical mode, is proposed to simultaneously determine cadmium and lead cations in water and food samples. The use of flow DID combined with electrochemical detection for the first time allowed to significantly reduce the volume of dosed reagents and waste generation and increase the automation of the determination, which perfectly fits into the principles of “Green Analytical Chemistry”. For voltammetric detection, the screen-printed carbon electrodes (SPCEs) modified with carbonized halloysite (C_Hal) and multi-walled carbon nanotubes (MWCNTs) were used (MWCNTs/C_Hal/Nafion/SPCE). The tested sensor exhibited linear response in concentration ranges: 15 – 3000 nmol L–1. The limits of detection were estimated as LODCd = 4.30 nmol L–1 (0.48 ng mL−1) and LODPb = 0.97 nmol L–1 (0.20 ng mL−1). Thus, the use of DID, as well as the Signal Increment Standard Addition Method, allowed to determine the cadmium and lead in tap, well, mineral waters and also in honey and rice samples with a recovery in the range of 95–103% and with a precision error of less than 7%.

A highly efficient NiCo2O4 decorated g-C3N4 nanocomposite for screen-printed carbon electrode based electrochemical sensing and adsorptive removal of fast green dye.

Herein, we demonstrate the preparation and application of NiCo2O4 decorated over a g-C3N4-based novel nanocomposite (NiCo2O4@g-C3N4). The prepared material was well characterized through several physicochemical techniques, including FT-IR, XRD, SEM, and TEM. The electrochemical characterizations via electrochemical impedance spectroscopy show the low electron transfer resistance of NiCo2O4@g-C3N4 owing to the successful incorporation of NiCo2O4 nanoparticles on the sheets of g-C3N4. NiCo2O4@g-C3N4 nanocomposite was employed in the fabrication of a screen-printed carbon electrode-based innovative electrochemical sensing platform and the adsorptive removal of a food dye, i.e., fast green FCF dye (FGD). The electrochemical oxidation of FGD at the developed NiCo2O4@g-C3N4 nanocomposite modified screen-printed carbon electrode (NiCo2O4@g-C3N4/SPCE) was observed at an oxidation potential of 0.65V. A wide dual calibration range for electrochemical determination of FGD was successfully established at the prepared sensing platform, showing an excellent LOD of 0.13µM and sensitivity of 0.6912 µA.µM-1.cm-2 through differential pulse voltammetry. Further, adsorbent dose, pH, contact time, and temperature were optimized to study the adsorption phenomena. The adsorption thermodynamics, isotherm, and kinetics were also investigated for efficient removal of FGD at NiCo2O4@g-C3N4-based adsorbents. The adsorption phenomenon of FGD on NiCo2O4@g-C3N4 was best fitted (R2 = 0.99) with the Langmuir and Henry model, and the corresponding value of Langmuir adsorption efficiency (qm) was 3.72mg/g for the removal of FGD. The reaction kinetics for adsorption phenomenon were observed to be pseudo-second order. The sensitive analysis of FGD in a real sample was also studied.

The Theoretical Description for Fructose Fermentation Product Hydroxyquinol and its Ether Sesamol Amperometric Determination in Tahini Halva and Lokum

For the first time, hydroxyquinol and sesamol electrochemical amperometric determination in tahini halva and lokum Turkish delights has been described. The electroanalytical process is given by amavadin-modified conducting polymer, in which both monomer and dopant may be natural compounds. Taking into account the ionic nature of the modifier, even in neutral medium the oscillatory behavior will be more probable in this system than in the simplest cases. Nevertheless, the amavadin-modified conducting polymer may be efficient electrode modifier for hydroxyquinol and sesamol electrochemical determination in Turkish delights like lokum and tahini halva.

Bimetallic cobalt–nickel supported on carbon fiber for electrochemical simultaneous determination of dopamine and hydroquinone

Bimetallic cobalt–nickel supported on carbon fiber (Co-Ni@CF) was synthesized by a straightforward homogeneous co-precipitation approach. Electrochemical results demonstrated that the modified Co-Ni@CF electrode demonstrated excellent electrooxidation activity toward dopamine (DA) and hydroquinone (HQ) without any other activating treatments, which could be modified as an electrochemical biosensor for DA and HQ detection simultaneously. The as-proposed biosensor was developed for simultaneous detection of DA and HQ, featuring low detection limits (LODs) of 0.4698 μM for DA and 0.2388 mM for HQ, respectively. The sensor also offers broad linear ranges for DA (5.0–30 μM), and HQ (0.5–5.0 mM). Along with these attractive features, the Co-Ni@CF electrode also performed good long-term stability and reproducibility, making it a promising candidate for electrochemical biosensing of DA and HQ.