Electroanalytical Properties Research Articles

The effect of magnetic nanoparticles and cetylpyridinium chloride on the electroanalytical properties of planar sensors sensitive to cefuroxime and cefotaxime

The effect of magnetic nanoparticles and cetylpyridinium chloride on the electroanalytical properties of planar sensors sensitive to cefuroxime and cefotaxime

Evaluation of electrochemical performance of antimony modified screen-printed carbon electrodes

This study compares the electrochemical performance of screen-printed carbon electrodes (SPCEs) modified with antimony (Sb/SPCEs) under different potentiostatic pre-plating conditions. Neutral Red (NR) was employed as a novel redox probe to evaluate the electrochemical performance of Sb/SPCEs. It was demonstrated that NR in the protonated form performs quasi-reversible redox transformations at bare SPCE and Sb/SPCEs in phosphate buffer solutions (pH 5.5±0.5) in the potential range of (−0.30)–(−0.75) V, where the antimony is not electroactive. Sb/SPCEs were studied electrochemically by cyclic voltammetry (CV) / electrochemical impedance spectroscopy (EIS), and morphologically by scanning electron microscopy (SEM). Cyclic voltammetry investigations revealed the dependence of the electrochemical performance of Sb/SPCEs on the degree of coverage of the substrate with the metal. The obtained CV, EIS, and SEM data are consistent. The lowest charge transfer resistance (Rct) value (6 Ω) was obtained at Sb/SPCE with the highest degree of antimony coverage. To investigate the electroanalytical performance of Sb/SPCEs, nickel (II) ions were utilized as a model analyte. A study of roughness factors and sensitivity towards nickel (II) ions for Sb/SPCEs using two-tailed Pearson's criterion revealed a high degree of correlation between their electrochemical and electroanalytical properties. The results show that using NR as a redox probe can help controlling modification processes during the development of innovative antimony-containing sensors.

Cooperative interaction of Ketjen black coating and electrical discharge post-treatment towards advanced screen-printed electrodes for hydroquinone and catechol

We report on the advanced electroanalytical properties towards hydroquinone (HQ) and catechol (CC) endowed to graphite screen-printed electrode (SPE) modified with EC-600JD Ketjen black (KB) after a short (9 s) and green (no liquids are involved) direct KB/SPE-to-graphite pin electrical discharge at ambient conditions. While KB coatings or spark discharge treatment on plain SPE alone endows low or moderate electrocatalytic properties, respectively, to otherwise inactive plain SPE, post-treatment of KB/SPE with graphite pin electrical discharge results in a remarkable increase of the response. The morphology and various physicochemical properties of the electrode surfaces were examined with scanning electron microscopy, contact angle measurements, Raman spectroscopy and different electrochemical techniques. Differential pulse voltammetric data demonstrated well-resolved oxidation peaks for HQ and CC, and good selectivity against possible interfering species. The response showed a linear relationship to the concentration of both HQ (from 0.050 to 1.0 μM) and CC (from 0.050 to 2.0 μM) while, based on the 3σ/m criterion, the detection limits were calculated 2 and 9 nM, respectively. The sparked KB/SPEs were successfully applied to real world samples spiked with sub-micromolar concentrations of the targets with satisfactory recoveries.

Pencil Graphite Electrocatalytic Sensors Modified by Pyrene Coated Reduced Graphene Oxide Decorated with Molybdenum Disulfide Nanoroses for Hydrazine and 4-Nitrophenol Detection in Real Water Samples.

Novel nanostructured platforms based on Pencil Graphite Electrodes (PGEs), modified with pyrene carboxylic acid (PCA) functionalized Reduced Graphene Oxide (rGO), and then decorated by chronoamperometry electrodeposition of MoS2 nanoroses (NRs) (MoS2NRs/PCA-rGO/PGEs) were manufactured for the electrocatalytic detection of hydrazine (N2H4) and 4-nitrophenol, pollutants highly hazardous for environment and human health. The surface morphology and chemistry of the MoS2NRs/PCA-rGO/PGEs were characterized by scanning electron microscopy (SEM), Raman, and X-ray photoelectron spectroscopy (XPS), assessing the coating of the PCA-rGO/PGEs by dense multilayers of NRs. N2H4 and 4-nitrophenol have been monitored by Differential Pulse Voltammetry (DPV), and the MoS2NRs/PCA-rGO/PGEs electroanalytical properties have been compared to the PGEs, as neat and modified by PCA-rGO. The MoS2NRs/PCA-rGO/PGEs demonstrated a higher electrochemical and electrocatalytic activity, due to their high surface area and conductivity, and very fast heterogeneous electron transfer kinetics at the interphase with the electrolyte. LODs lower than the U.S. EPA recommended concentration values in drinking water, namely 9.3 nM and 13.3 nM, were estimated for N2H4 and 4-nitrophenol, respectively and the MoS2NRs/PCA-rGO/PGEs showed good repeatability, reproducibility, storage stability, and selectivity. The effectiveness of the nanoplatforms for monitoring N2H4 and 4-nitrophenol in tap, river, and wastewater was addressed.

Metallic-like boron-modified bio-carbon electrodes for simultaneous electroanalysis for Cd2+, Pb2+ and Cu2+: Theoretical insight into the role of CxBOy(H)

It still remains challenges to develop efficient, sensitive yet low-cost electrochemical sensing platforms for quantification of heavy metal ions. Herein, by combining experiments and theoretical calculations, a novel boron-modified bio-carbon (B-bioC) electrode material prepared by ultrasonic-assisted hot impregnation with cotton stalk and inexpensive boric acid and subsequent pyrolysis strategy is initially proposed for simultaneous electroanalysis of cadmium (Cd), lead (Pb) and copper (Cu) using differential pulsed anodic stripping voltammetry (DPASV). The physico-chemical characterizations together with electrochemical characterizations suggested that a higher graphitization level for B-bioC was obtained by the catalytic graphitization effect of metalloid boron, thus rendering lower impedance and faster electron-transfer rate compared with pristine bio-carbon. Also, stronger electrocatalytic activity was observed as a results of the introduction of various boron-bonding electroactive sites (CxBOy(H)). These combined unique advantages make a great role for the enhanced electroanalytical properties of the modified electrodes (B-bioC/MEDs) with a linear response of Cd2+, Pb2+, and Cu2+ concentration range of 0.25–40 μM, 0.06–4.8 μM, and 0.125–20 μM, with sensibility of 10.54, 509.96, and 22.38 μA μM−1 cm−2, and detection limit low to 54, 4, and 24 nM (S/N = 3), respectively, which are comparable to certain reported metal-modified bio-carbons. Finally, through DFT calculations, it was concluded that C-BO2 on B-bioC was the optimum active site over seven B-bonding configurations. This work throws light on the pivotal roles of B configurations in electrochemical sensing and provides theoretical support for deliberately designing ultrasensitive bio-carbon based electrochemical sensing platforms toward heavy metal ions of interest.

Carbon nanomaterials and their composites for electrochemical glucose biosensors: A review on fabrication and sensing properties

BackgroundWith the increasing prevalence of diabetes that increases the risk of cardiovascular diseases, kidney failure, nerve degeneration, eye damage, lower extremity amputations and birth defects, the demand for highly efficient glucose sensors has attracted significant attention worldwide. In this regard, carbon nanomaterials-based electrochemical glucose sensors have shown great potential in the detection and monitoring of glucose. MethodsDifferent forms of carbon such as carbon nanotubes, graphene, reduced graphene oxide, carbon nanofibers, activated and amorphous carbon, carbon spheres, carbon nanoparticles, carbon quantum dots, carbon nanorods, carbon nanocages etc. and their hybrids have been extensively researched for highly efficient glucose sensors due to their large surface area, porosity, lightweight, thermal stability, excellent mechanical properties, ease of fabrication, high electrical conductivity, excellent catalytic properties and fast electron transfer kinetics. Significant findingsDue to their large surface area and tunable porosity, carbon nanomaterials have been used as a scaffold for the immobilization of large quantities of bioreceptor units such as enzymes and highly catalytic metal or metal oxide nanostructures, which can enhance the electroanalytical properties of the biosensor. In this review paper, the fabrication and electroanalytical properties of carbon nanomaterials based enzymatic and nonenzymatic electrochemical glucose sensors have been reviewed and their sensing mechanisms are discussed.

METFORMIN-SENSITIVE ION-SELECTIVE ELECTRODE

Metformin in its protonated form as metformin hydrochloride is used worldwide as an advanced antidiabetic drug for type 2 diabetes. Hyperinsulinemia and insulin resistance of cells are the main causes of this disease. For patients with diabetes, metformin hydrochloride (MET) works by improving cell sensitivity to insulin.
 It has been shown that metformin with methyl orange (MO) forms an ionic associate that can be isolated in solid form and is suitable for the creation of plasticized membrane potentiometric metformin-sensitive sensors.
 The energy efficiency of IA formation is substantiated by the method of mathematical modeling. Molecular modeling of MO- + MET+ systems and related calculations were performed using the PM3 method for various initial variants of counter ion relative to each other (single point procedure). Geometric optimization of ions was performed by the method of molecular mechanics MM+. The standard enthalpy (ΔH0) of ion formation and the association “MET+ + MO-” was determined by the semi-empirical method PM3. The difference in the energy of formation of the ionic associate and the sum of the energies of formation of its components is 258 kJ/mol. Therefore, the process of IA formation is thermodynamically advantageous.
 Modeling and optimization of membrane composition is carried out. The results of the study of the influence of the nature of plasticizers on the electroanalytical properties of the developed sensors indicate that the best plasticizer for the system is TCP or DNF. For these solvents, the product of the dielectric constant and Rohrschneider polarity (ε × PR) is 123.5 and 175, respectively. For plasticizers that were less effective (DBF and DEF), these values are 235.6 and 326 respectively. For membranes with the same content of plasticizer of one homologous series (DEF, DBF, DOF, DNF), the slope of the Nernst function decreases with increasing dielectric constant of the plasticizer solvent. It is shown that the working pH range of the electrode is from 2 to 11. The drift potential does not exceed 1-3 mV/day. Stable values of electrode potentials are set for 5-15 s. The stability of the electroanalytical characteristics of the optimized membranes can be traced for at least three months. The developed sensors show satisfactory selectivity in relation to a number of substances and ions. The 300-1000 amount of glucose, starch, polyvinyl alcohol, Na+, K+, Mg2+, Ca2+, Ba2+ ions do not interfere with MET determination. This, in turn, allows the practical use of developed MET-sensitive sensors in a variety of objects.
 A method of potentiometric determination of metformin has been developed, which has been tested in its determination in dosage forms.

Disposable Paper-Based Biosensors: Optimizing the Electrochemical Properties of Laser-Induced Graphene

Laser-induced graphene (LIG) on paper substrates is a desirable material for single-use point-of-care sensing with its high-quality electrical properties, low fabrication cost, and ease of disposal. While a prior study has shown how the repeated lasing of substrates enables the synthesis of high-quality porous graphitic films, however, the process–property correlation of lasing process on the surface microstructure and electrochemical behavior, including charge-transfer kinetics, is missing. The current study presents a systematic in-depth study on LIG synthesis to elucidate the complex relationship between the surface microstructure and the resulting electroanalytical properties. The observed improvements were then applied to develop high-quality LIG-based electrochemical biosensors for uric acid detection. We show that the optimal paper LIG produced via a dual pass (defocused followed by focused lasing) produces high-quality graphene in terms of crystallinity, sp2 content, and electrochemical surface area. The highest quality LIG electrodes achieved a high rate constant k0 of 1.5 × 10–2 cm s–1 and a significant reduction in charge-transfer resistance (818 Ω compared with 1320 Ω for a commercial glassy carbon electrode). By employing square wave anodic stripping voltammetry and chronoamperometry on a disposable two-electrode paper LIG-based device, the improved charge-transfer kinetics led to enhanced performance for sensing of uric acid with a sensitivity of 24.35 ± 1.55 μA μM–1 and a limit of detection of 41 nM. This study shows how high-quality, sensitive LIG electrodes can be integrated into electrochemical paper analytical devices.

Novel covalent immobilization of cobalt (II) octa acyl chloride phthalocyanines onto phenylethylamine pre-grafted gold via spontaneous amidation

In this work, a gold electrode surface was pre-grafted with phenylethylamine (PEA) thin film for spontaneous covalent immobilization of cobalt (II) octa acyl chloride (CoOAClPc) via the nucleophilic addition reaction. Pre-grafting of PEA thin film was achieved by electrochemical reduction of 4-(2-aminoethyl) benzene diazonium (AEBD) salt. Cobalt (II) octa acyl chloride phthalocyanine (CoOAClPc) was successfully synthesized and covalently immobilized onto the pre-grafted gold electrode surface to form a thin monolayer of Au-PEA-CoOAClPc. Upon hydrolysis of the thin monolayer, the –COCl terminal functional groups were converted to -COOH to form Au-PEA-CoOCAPc. The presence of PEA and PEA-CoOCAPc was confirmed by electrochemical X-ray photoelectron spectroscopy surface characterization. The pH sensitivity of -COOH terminal groups was studied using a negatively charged [Fe(CN)6]3−/4− and a positively charged [Ru(NH3)6]2+/3+ redox probes. The Au-PEA-CoOCAPc was investigated for electrocatalytic and electroanalytical properties towards the detection of catecholamine neurotransmitters (dopamine, epinephrine, and norepinephrine). The electrocatalytic oxidation of the catecholamine neurotransmitters in PBS solution (pH 7.4) was studied using differential pulse voltammetry (DPV) in a linear range up to 50 μM. The limit of detection (LOD) was determined to be 64 nM, 0.22 μM and 0.17 μM for dopamine (DA), epinephrine (EP) and norepinephrine (NOR) respectively. The limit of quantification (LOQ) was determined to be 0.21 μM, 0.73 μM and 0.56 μM for DA, EP and NOR respectively. Stable and reproducible novel method of electrode fabrication to form Au-PEA-CoOCAPc was achieved. Excellent analytical properties (sensitivity, low detection limits and limit of quantification) were obtained by using the fabricated electrochemical sensors, Au-PEA-CoOCAPc, for the determination of catecholamine neurotransmitters and screening of ascorbic acid (AA).

Screen-Printed Carbon Electrodes with Macroporous Copper Film for Enhanced Amperometric Sensing of Saccharides.

A porous layer of copper was formed on the surface of screen-printed carbon electrodes via the colloidal crystal templating technique. An aqueous suspension of monodisperse polystyrene spheres of 500 nm particle diameter was drop-casted on the carbon tracks printed on the substrate made of alumina ceramic. After evaporation, the electrode was carefully dipped in copper plating solution for a certain time to achieve a sufficient penetration of solution within the polystyrene spheres. The metal was then electrodeposited galvanostatically over the self-assembled colloidal crystal. Finally, the polystyrene template was dissolved in toluene to expose the porous structure of copper deposit. The morphology of porous structures was investigated using scanning electron microscopy. Electroanalytical properties of porous copper film electrodes were evaluated in amperometric detection of selected saccharides, namely glucose, fructose, sucrose, and galactose. Using hydrodynamic amperometry in stirred alkaline solution, a current response at +0.6 V vs. Ag/AgCl was recorded after addition of the selected saccharide. These saccharides could be quantified in two linear ranges (0.2–1.0 μmol L−1 and 4.0–100 μmol L−1) with detection limits of 0.1 μmol L−1 glucose, 0.03 μmol L−1 fructose, and 0.05 μmol L−1 sucrose or galactose. In addition, analytical performance of porous copper electrodes was ascertained and compared to that of copper film screen-printed carbon electrodes, prepared ex-situ by the galvanostatic deposition of metal in the plating solution. After calculating the current densities with respect to the geometric area of working electrodes, the porous electrodes exhibited much higher sensitivity to changes in concentration of analytes, presumably due to the larger surface of the porous copper deposit. In the future, they could be incorporated in detectors of flow injection systems due to their long-term mechanical stability.

Platinum nanoparticles loaded carbon black: reduced graphene oxide hybrid platforms for label-free electrochemical DNA and oxidative DNA damage sensing

• Rapid and effective synthesis of platinum nanoparticles on the carbon black:reduced graphene oxide hybrids were achieved. • Facile and efficient electrode modification was performed with the hybrids. • Characterization of the surfaces proved homogeneous and robust distribution of the structures. • Sensitive fsDNA detection was accomplished with a low detection limit. • DNA damage and protection monitoring were carried out successfully. Carbon black-based hybrid materials have attracted great attention in the design of electrochemical sensors due to their consistent electroanalytical properties. With this in mind, for the first time, we present the preparation of platinum nanoparticles loaded carbon black:reduced graphene oxide (PtNPs/CB:rGO) hybrid platforms for label-free electrochemical DNA and DNA damage sensing. Synthesis of different hybrids was performed via microwave-assisted reduction method for the impregnation of platinum nanoparticles efficiently. These materials were characterized with X-ray diffraction analysis (XRD), Raman spectroscopy, transmission emission spectroscopy (TEM) and subsequently they were used for pencil graphite electrode modification in order to improve the characteristics of the surface. Modified electrodes were firstly applied for fish sperm DNA (fsDNA) analysis. The effect of different ratios (wt.:wt. %) of CB and rGO was investigated and it was shown that the hybrid material with 50:50 ratio had better sensitivity with a low detection limit of 0.14 mg L −1 and a good linearity to fsDNA between 1 and 200 mg L −1 (n = 3) based on guanine (G) oxidation by using differential pulse voltammetry (DPV). In order to expand this comparison, PtNPs/CB and PtNPs/rGO modified electrodes were also incorporated. Furthermore, the electroanalytical response of the hybrid material modified electrode was investigated based on the oxidation of thymine (T). Later on, oxidative DNA damage detection in the presence of Cu(II)/H 2 O 2 reagents and protection studies in the presence of ascorbic acid were performed successfully by using electrochemical impedance spectroscopy (EIS). The study pointed out the remarkable reproducibility and sensitivity of the CB-based modification for nanoparticle decoration.

A New Electrochemical Sensor Based on Carbon Black Modified With Palladium Nanoparticles for Direct Determination of 17α‐Ethinylestradiol in Real Samples

AbstractElectrochemical sensors to quantify concentrations of emerging pollutants have attracted great attention from the industry and scientific community. Nanomaterials such as carbon black have been applied in sensors to identify substances that are toxic to the environment and human health due to their excellent electroanalytical properties. The aim of the study was to develop a novel electrochemical sensor for the endocrine disruptor hormone determination. To our knowledge, for the first time the synthesis of material based on carbon black containing immobilized palladium nanoparticles, with the application for the hormone ethinylestradiol, is reported in the literature. The material was synthesized, characterized, and applied to the determination in tap water and human urine of the synthetic hormone 17α‐ethinylestradiol (EE2), which is currently considered an emerging pollutant. The morphology, structure and electrochemical performance of the sensors were characterized by scanning electron microscopy (SEM) and cyclic voltammetry (CV). Differential pulse voltammetry (DPV) in sodium phosphate buffer solution at pH 5.0 allowed the generation of a method to quantify the concentration of 17α‐ethinylestradiol in a linear range of 0.5–119.0 μmol L−1, obtaining 81.0 nmol L−1 of calculated limit of detection (LOD). The system was efficient in detecting 17α‐ethinylestradiol in real urine samples and showed no interferences for ascorbic acid, uric acid, progesterone, and dopamine. It is noteworthy that the results obtained showed good recovery values, considering that the urine samples were not previously treated or pre‐concentrated, which suggests the development of an electrochemical sensor that works in situ and in real time to monitor relevant substances in the control clinical and environmental, with the possibility of point‐of‐care analyses.

Electrochemical sensor for isoniazid detection by using a WS2/CNTs nanocomposite

This paper presents a new modified electrode that combines the high electrical conductivity of carbon nanotubes (CNTs) with the catalytic sites of WS2 (named WS2/CNTs) for isoniazid detection. Electrochemical and electroanalytical properties of the WS2/CNTs/glassy carbon electrode (GCE)-modified electrodes were investigated by cyclic voltammetry and differential pulse voltammetry (DPV). The composite material was characterized by Raman spectroscopy, X-ray diffractometry (XRD), and scanning electron microscopy . The electrochemical performance of the WS2/CNTs/GCE sensor exhibited a limit of detection of 0.24 μM with a linear range from 10 to 80 μM of isoniazid using DPV. This sensor provided enhanced stability and electrocatalytic activity for isoniazid oxidation reactions. Recoveries ranging from 96.9 to 104.5% were calculated, demonstrating satisfactory accuracy of the proposed method. The improvement of electrochemical activity was assigned to synergic effects obtained by combining the catalytic sites from WS2 and the known electrical conductivity and large surface area of the CNTs, resulting in an anticipation of the oxidation peak of isoniazid in about 400 mV in comparison with bare GCE.

METFORMIN-SENSITIVE POTENTIOMETRIC SENSOR

Metformin (N,N-dimethylbiguanidine) in its protonated form as metformin hydrochloride is used worldwide as an advanced antidiabetic drug for type 2 diabetes. Hyperinsulinemia and insulin resistance of cells are the main causes of this disease. For patients with diabetes, metformin hydrochloride (hereinafter – MET) works by improving cell sensitivity to insulin. It has been shown that metformin with tropeolin 00 (T00) forms an ionic associate that can be isolated in solid form and is suitable for the creation of plasticized membrane potentiometric metformin-sensitive sensors. The energy efficiency of ionic associate formation is substantiated by the method of mathematical modeling. Molecular modeling of T00- + MET+ systems and related calculations were performed using the HyperChem 8.0 package for various initial variants of counter ion relative to each other (single point procedure). Geometric optimization of ions was performed by the method of molecular mechanics MM+. The standard enthalpy (ΔH0) of ion formation and the association “MET+ + T00-” was determined by the semi-empirical method PM3. The difference in the energy of formation of the ionic associate and the sum of the energies of formation of its components is 312 kJ/mol. Therefore, the process of ionic associate formation is thermodynamically advantageous. Modeling and optimization of membrane composition is carried out. The results of the study of the influence of the nature of plasticizers on the electroanalytical properties of the developed sensors indicate that the best plasticizer for the system is TCP or DNF. For these solvents, the product of the dielectric constant and Rorschneider polarity (ε × PR) is 123,5 and 175 respectively. For plasticizers that were less effective (DBF and DEF), these values are 235,6 and 326 respectively. For membranes with the same content of plasticizer of one homologous series (DEF, DBF, DOF, DNF), the slope of the Nernst function decreases with increasing dielectric constant of the plasticizer solvent. It is shown that the working pH range of the electrode is from 2 to 11. The drift potential does not exceed 1–3 mV/day. Stable values of electrode potentials are set for 5–15 s. The stability of the electroanalytical characteristics of the optimized membranes can be traced for at least three months. The developed sensors show satisfactory selectivity in relation to a number of substances and ions. The 300 and 1000 times the amount of glucose, starch, polyvinyl alcohol, Na+, K+, Mg2+, Ca2+, Ba2+ ions do not interfere with MET determination. This, in turn, allows the practical use of developed MET-sensitive sensors in a variety of objects. A method of potentiometric determination of metformin has been developed, which has been tested in its determination in dosage forms.

Electrocatalytic Properties of Ni(II) Schiff Base Complex Polymer Films.

Platinum electrodes were modified with polymers of the (±)-trans-N,N′-bis(salicylidene)-1,2-cyclohexanediaminenickel(II) ([Ni(salcn)]) and (±)-trans-N,N′-bis(3,3′-tert-Bu-salicylidene)-1,2-cyclohexanediaminenickel(II) ([Ni(salcn(Bu))]) complexes to study their electrocatalytic and electroanalytical properties. Poly[Ni(salcn)] and poly[Ni(salcn(Bu))]) modified electrodes catalyze the oxidation of catechol, aspartic acid and NO2−. In the case of poly[Ni(salcn)] modified electrodes, the electrocatalysis process depends on the electroactive surface coverage. The films with low electroactive surface coverage are only a barrier in the path of the reducer to the electrode surface. The films with more electroactive surface coverage ensure both electrocatalysis inside the film and oxidation of the reducer directly on the electrode surface. In the films with the most electroactive surface coverage, electrocatalysis occurs only at the polymer–solution interface. The analysis was based on cyclic voltammetry, EQCM (electrochemical quartz crystal microbalance) and rotating disc electrode method.

Electrodeposited palladium as efficient electrocatalyst for hydrazine and methanol electro-oxidation and detection

Electrodeposited palladium was used as an electrocatalyst for electrochemical oxidation of hydrazine and methanol and the development of a sensitive platform for their detection. The electrochemical behavior of the electrode was evaluated by cyclic voltammetry (CV) while electroanalytical properties were determined by means of differential pulse voltammetry (DPV). The electrodeposited Pd catalyst exhibited good electrocatalytic activity towards the oxidation of hydrazine in neutral solution and methanol oxidation in alkaline solution. Under optimized DPV conditions, the electrodeposited Pd electrode shows good sensing capability in hydrazine and methanol detection.

Highly Sensitive Electrochemical Sensor for Diagnosis of Diabetic Ketoacidosis (DKA) by Measuring Ketone Bodies in Urine.

In this report, we present an enzyme deposited Au electrode for an electrochemical measurement of acetylacetic acid (AcAc) in urine. The electrode has an immobilized layer of a mixture of D-β-hydroxybutyrate dehydrogenase (HBDH) and nicotinamide adenine dinucleotide (NADH) as sensing material to investigate its electroanalytical properties by means of cyclic voltammetry (CV). The modified electrodes are used for the detection of AcAc and present a linear current increase when the AcAc concentration increases. The electrode presents a limit of detection (LOD) of 6.25 mg/dL in the range of 6.25–100 mg/dL for investigation of clinical relevance. Finally, the electrode was evaluated using 20 patient samples. The measured results of urine ketone by the developed electrode were compared with the clinical results from a commercial kit, and the analysis showed good agreement. The proposed electrode was demonstrated to be a very promising platform as a miniaturized electrochemical analyzer for point-of-care monitoring of the critical biochemical parameters such as urine ketone.

The Preparation, Morphological Characterization and Possible Electroanalytical Application of a Hydroxyapatite-Modified Glassy Carbon Electrode

By simple modification of a GC electrode with biofunctional material, hydroxyapatite (HAp), an efficient electroanalytical tool, was designed and constructed. Modification of the GC surface includes two steps in synthesis: electrochemical deposition and chemical conversion. The properties, structure, and morphology of a nanosized material formed on a surface and absorbability were studied by electrochemical impedance spectroscopy, Fourier-transform infrared spectroscopy and scanning electron microscopy with energy-dispersive spectroscopy analysis. Numerous methods in this work confirmed that the developed method for controlled HAp deposition results in a HAp open structure and uniform morphology, which is capable of the selective absorption of the target species. The main goal of this study was the possibility of using a HAp-modified electrode for the fast screening of copper, cadmium, and lead content in honey and sugar samples. The electrochemical behavior and potential of the electroanalytical determination of heavy metals using the HAp/GC electrode were studied using cyclic voltammetry and square wave anodic stripping voltammetry. The HAp/GC electrode exhibited great performance in the determination of heavy metals, based on the reduction of target metals, because of the high absorbability of the HAp film and the electroanalytical properties of GC. A linear response between 10 and 1000 μg/L for Cu and Pb and 1 and 100 μg/L for Cd, with an estimated detection limit of 2.0, 10.0, and 0.9 μg/L, respectively, was obtained.

Determination of levamisole using ion-selective electrode

Current development of applied ionometry requires focusing of theoretical studies both on revealing the nature of the selectivity of electrode membranes and on the developing the new methods of membrane synthesis and their modification with the goal of obtaining more perfect structural units with improved functional properties. Elucidation of the relationship between the structural characteristics of the membranes and their effect on the electro-analytical properties is a rather important task. The interaction of organic cation levamisole with bromophenol blue was studied to meet the goals. Levamisole-selective sensor with a plasticized polyvinyl chloride (PVC) membrane has been developed. The electrode contains an ionic associate of levamisole with bromophenol blue. PVC was used as a matrix to model the membrane composition. Membranes plasticized with dibutyl phthalate (DBP), diethyl phthalate (DEP), dioctyl phthalate (DOP), dinonyl phthalate (DNP), dibutyl sebacate (DBP), tricresyl phosphate (TCP) were studied. It was shown that the nature of the plasticizer insignificantly affected the analytical characteristics of the electrode. The response is linear within the concentration range of 1 × 10–5 – 1 ×10–1 mole/liter with the slope of the electrode function 52.1 ± 1.0 mV/pC. The sensor has a quick response (10 sec) and can be used for at least 8 weeks without any divergence in the long run. The operation life of the membranes with a high plasticizer content is much longer. The electrode can be used within pH range of 3.0 – 8.0. Potentiometric selectivity coefficients of the electrode relative to a number of potentially interfering ions were determined. The developed electrode was tested in determination of levamisole in model solutions and pharmaceuticals («Decaris» and «Levamisole-Zdorovye»).

Nanomaterials Based Electrochemical Sensors for Serotonin Detection: A Review

The present review deals with the recent progress made in the field of the electrochemical detection of serotonin by means of electrochemical sensors based on various nanomaterials incorporated in the sensitive element. Due to the unique chemical and physical properties of these nanomaterials, it was possible to develop sensitive electrochemical sensors with excellent analytical performances, useful in the practice. The main electrochemical sensors used in serotonin detection are based on carbon electrodes modified with carbon nanotubes and various materials, such as benzofuran, polyalizarin red-S, poly(L-arginine), Nafion/Ni(OH)2, or graphene oxide, incorporating silver-silver selenite nanoparticles, as well as screen-printed electrodes modified with zinc oxide or aluminium oxide. Also, the review describes the nanocomposite sensors based on conductive polymers, tin oxide-tin sulphide, silver/polypyrole/copper oxide or a hybrid structure of cerium oxide-gold oxide nanofibers together with ruthenium oxide nanowires. The presentation focused on describing the sensitive materials, characterizing the sensors, the detection techniques, electroanalytical properties, validation and use of sensors in lab practice.