Showing papers on "Amperometry published in 2023"

Competition between enzymatic and non-enzymatic electrochemical determination of cholesterol

Abstract: Cholesterol is considered an essential component in animal bodies that plays a vital role in hormone production and creating vitamin D. The elevated blood cholesterol level increases the possibility of heart disease. Consequently, the clinical diagnosis of cholesterol concentration is critical for human health care. The electrochemical sensor is one of the leading techniques for detecting cholesterol in biological fluids with high accuracy. Therefore, this review included comparative insights into the enzymatic and non-enzymatic techniques for electrochemical sensing. We discussed the recent progress in the electrochemical determination of cholesterol via various materials, e.g., metal composites, carbonaceous materials, ionic liquid crystals, and polymers. We explained electrochemical sensing techniques like amperometric, potentiometric, conductometric, and impedimetric methods. Furthermore, various enzyme-immobilization approaches were reported, like surface binding and encapsulation. The synergistic effect between the electrode surface and enzymes was demonstrated to clarify the detection mechanism. The review article summarized the outcome detection limits and linear range of detection for various surfaces for enzymatic and non-enzymatic electrochemical techniques within the last twenty years.

One-pot preparation of NiMn layered double hydroxide-MOF material for highly sensitive electrochemical sensing of glucose

Abstract: To rationally design and construct electrocatalytic nanomaterials is crucial for improving the sensitivity and selectivity of non-enzyme-based electrochemical sensors. Here, NiMn layered double hydroxide (LDH)-based MOF (NiMn-LDH-MOF) material was used as electrochemical electrode for highly sensitive assay of glucose. The NiMn-LDH-MOF was firstly synthesized by one-pot method via directly blending MOF-74, metal nodes and ammonia. The obtained NiMn-LDH-MOF has an excellent electrocatalytic activity for electrochemical oxidation of glucose and the NiMn-LDH-MOF/GCE sensor exhibits a wide linear detection range from 4.9 μM to 2.2 mM, a low detection limit (0.87 μM, S/N = 3), and high sensitivity (0.849 mA mM−1 cm−2). Meanwhile, the sensor has good selectivity and reliability for glucose detection in actual serum samples, suggesting the potential applicability of the sensor for glucose detection. The more exposed active sites, the introduction of LDHs subunit and the synergistic effect between Ni and Mn in the NiMn-LDH-MOF are the major factors to enhance the assay performance.

A paper chromatographic-based electrochemical analytical device for the separation and simultaneous detection of carbofuran and carbaryl pesticides

Abstract: We developed an electrochemical paper-based device (ePAD) for the online separation and simultaneous determination of structurally similar carbofuran (CBF) and carbaryl (CBR). Our device combined paper chromatography and an electrochemical sensor as a single system for increasing the selectivity to simultaneous detection of the two pesticides. During the simultaneous detection of CBF and CBR, the separation of the two carbamate compounds depends on the differences between the movements of the substances on the chromatographic paper in the moving phase flow. The isolated pesticides were electrochemically measured using an amperometric method. Under optimal conditions, which include the effect of the mobile phase, separation channel, and the applied potential, the proposed device provides a linear range for the simultaneous determination of CBF and CBR from 0.1 to 2.0 and 0.5–7.5 mg L−1, with the limits of detection at 0.06 and 0.40 mg L−1, respectively. Furthermore, we successfully used the developed device to determine CBF and CBR in water, cucumber, and cabbage samples. The obtained results correspond to results obtained from a standard method. This developed ePAD is low-cost and uses a low sample volume (2 µL). Moreover, it is disposable, portable, and a promising tool for the on-site quantification of pesticides in actual samples.

Electrochemical Sensors Based on a Composite of Electrochemically Reduced Graphene Oxide and PEDOT:PSS for Hydrazine Detection

Abstract: In this study, hydrazine sensors were developed from a composite of electrochemically reduced graphene oxide (ErGO) and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), deposited onto a glassy carbon electrode (GCE). The structural properties, electrochemical characterization, and surface morphologies of this hydrazine sensor were characterized by Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy, electrochemical impedance spectroscopy (EIS), and scanning electron microscopy (SEM). In addition, the proposed hydrazine sensor also demonstrates good electrochemical and analytical performance when investigated using cyclic voltammetry (CV), differential pulse voltammetry (DPV), and amperometry techniques under optimal parameters. Using these investigated parameters, DPV and amperometry were chosen as techniques for hydrazine measurements and showed a linear range of concentration in the range of 0.2–100 μM. The obtained limits of detection and limits of quantitation for hydrazine measurements were 0.01 and 0.03 μM, respectively. In addition, the proposed sensor demonstrated good reproducibility and stability in hydrazine measurements in eight consecutive days. This fabricated hydrazine sensor also exhibited good selectivity against interference from Mg2+, K+, Zn2+, Fe2+, Na+, NO2–, CH3COO–, SO42–, Cl–, ascorbic acid, chlorophenol, and triclosan and combined interferences, as well as it depicted %RSD values of less than 5%. In conclusion, this proposed sensor based on GCE modified with ErGO/PEDOT:PSS displays exceptional electrochemical performance for use in hydrazine measurements and have the potential to be employed in practical applications.

Hydrogel-Coated Microelectrode Resists Protein Passivation of In Vivo Amperometric Sensors.

Abstract: Passivation of electrodes caused by nonspecific adsorption of protein can dramatically reduce sensing sensitivity and accuracy, which is a great challenge for in vivo neurochemical monitoring. However, most antipassivation strategies are not suitable to carbon fiber microelectrodes (CFMEs) for in vivo measurement, and these methods also do not work on electrochemical biosensors that fix biometric elements. In this study, we demonstrate that chitosan hydrogel-coated microelectrodes can avoid the current passivation caused by protein adsorption on the surface of carbon fiber because the chitosan hydrogel prepared by local pH gradient caused by hydrogen evolution reaction has three-dimensional networks containing large amounts of water. The highly hydrophilic three-dimensional structure of hydrogel not only forms a biocompatible interface to confine enzymes but also keeps the fast mass transfer of analytes, such as dopamine, ascorbic acid, and glucose. The consistency of the precalibration and postcalibration of the prepared sensor enables in vivo amperometric detection of both electroactive species based on their redox property and electroinactive species based on the enzyme. This study provides a simple and versatile strategy to constitute an amperometric sensor interface to resist passivation of protein adsorption in a complex biological environment such as the brain.

Polyaniline-Supported Nickel Oxide Flower for Efficient Nitrite Electrochemical Detection in Water

Abstract: Abstract A modified electrode with conducting polymer (Polyaniline) and NiO nanoflowers was prepared to detect nitrite ions in drinking water. A simple method was used to prepare the NiO nanoflower (NiOnF). Several techniques characterized the as-prepared NiOnF to determine the chemical structure and surface morphology of the NiO, such as XRD, XPS, FT-IR, and TGA. The activity of the electrode toward nitrite sensing was investigated over a wide range of pH (i.e., 2 to 10). The amperometry method was used to determine the linear detection range and limit. Accordingly, the modified electrode GC/PANI/NiOnf showed a linear range of detection at 0.1–1 µM and 1–500 µM. At the same time, the limit of detection (LOD) was 9.7 and 64 nM for low and high concentrations, respectively. Furthermore, the kinetic characteristics of nitrite, such as diffusion and transport coefficients, were investigated in various media. Moreover, the charge transfer resistance was utilized for nitrite electrooxidation in different pH values by the electrochemical impedance technique (EIS). The anti-interfering criteria of the modified surfaces were utilized in the existence of many interfering cations in water (e.g., K+, Na+, Cu2+, Zn2+, Ba2+, Ca2+, Cr2+, Cd2+, Pd2+). A real sample of the Nile River was spiked with nitrite to study the activity of the electrode in a real case sample (response time ~4 s). The interaction between nitrite ions and NiO{100} surface was studied using DFT calculations as a function of adsorption energy.

Towards Electrochemical Sensor Based on Molecularly Imprinted Polypyrrole for the Detection of Bacteria—Listeria monocytogenes

Abstract: Detecting bacteria—Listeria monocytogenes—is an essential healthcare and food industry issue. The objective of the current study was to apply platinum (Pt) and screen-printed carbon (SPCE) electrodes modified by molecularly imprinted polymer (MIP) in the design of an electrochemical sensor for the detection of Listeria monocytogenes. A sequence of potential pulses was used to perform the electrochemical deposition of the non-imprinted polypyrrole (NIP-Ppy) layer and Listeria monocytogenes-imprinted polypyrrole (MIP-Ppy) layer over SPCE and Pt electrodes. The bacteria were removed by incubating Ppy-modified electrodes in different extraction solutions (sulphuric acid, acetic acid, L-lysine, and trypsin) to determine the most efficient solution for extraction and to obtain a more sensitive and repeatable design of the sensor. The performance of MIP-Ppy- and NIP-Ppy-modified electrodes was evaluated by pulsed amperometric detection (PAD). According to the results of this research, it can be assumed that the most effective MIP-Ppy/SPCE sensor can be designed by removing bacteria with the proteolytic enzyme trypsin. The LOD and LOQ of the MIP-Ppy/SPCE were 70 CFU/mL and 210 CFU/mL, respectively, with a linear range from 300 to 6700 CFU/mL.

Amperometric Measurements by a Novel Aerosol Jet Printed Flexible Sensor for Wearable Applications

Abstract: In the last years, increasing interest has been addressed on wearable devices for the continuous monitoring of biochemical profiles of patients and athletes. Among various markers, lactate represents one of the most interesting to deepen the knowledge on fatigue processes, in combination with traditional electromyographic features. In this work, we propose a new, low-cost, rapid, and flexible electrochemical amperometric lactate carbon biosensor fabricated by the novel technique of aerosol jet printing (AJP). The developed biosensors were combined with a paper-based microfluidic system and a chitosan-based stable functionalization to allow a long-term continuous monitoring of human daily activities. The sensor performances were evaluated by static and dynamic electrochemical tests in buffered media. The limit of detection is 11 ± 2 mM for the static setup and of 15 ± 6 mM for the dynamic setup, while sensitivity is 0.02 and 0.04 $\mu \text{A}$ /mM, respectively, with single sigma standard deviation lower than 8%. Increasing and decreasing concentration steps of lactate induces comparable response times below 30 s. These results obtained in vitro under controlled laboratory conditions represent a promising starting point to pursue with ex-vivo and in vivo validation for the future development of stand-alone wearable patches for noninvasive lactate measurements.

Optimizing the sensing performance of amperometric creatinine detection based on creatinine deiminase/Nafion®-nanostructured polyaniline composite film by mixture design method

Abstract: Nafionࣨ-nanostructured polyaniline (nsPANi) composite film is prepared using cyclic voltammetry (CV) and immobilized with creatinine deiminase (CD) enzyme and is used to sense creatinine in a buffer phosphate solution. The conditions for preparing Nafionࣨ-nsPANi composite film are optimized by using a mixture design for which the sensitivity is the response. The relationship between the sensitivity of the amperometric creatinine biosensor (y) and the normalized aniline concentration (Y1), HCl concentration (Y2) and scanning rate (Y3) is y = 119.44Y1 + 45.23Y2 + 100.93Y3 + 255.69Y1Y2 + 313.16Y1Y3 + 430.56Y1Y2Y3 The maximum sensitivity of an amperometric creatinine biosensor that is constructed using Nafionࣨ-nsPANi composite film in 0.0943 M aniline, 0.9024 M HCl and using a scanning rate of 27.88 mV s−1 is 2013.2 μA mM−1 cm−2, which is 54.9% better than the sensitivity of a conventional experimental technique. The amperometric creatinine biosensor is 6.60% less sensitive after sensing 0.15 mM creatinine 240 times. The amperometric creatinine biosensor incurs insignificant interference in 0.138 mM urea, 0.085 mM ascorbic acid (AA) and 5.54 mM glucose.

Zinc Nanocomposite Supported Chitosan for Nitrite Sensing and Hydrogen Evolution Applications

Abstract: Nanoparticles of ZnO-Chitosan (Zn-Chit) composite were prepared using precipitation methods. Several analytical techniques, such as scanning electron microscope (SEM), transmitted electron microscope (TEM), powder X-ray diffraction (XRD), infrared spectroscopy (IR), and thermal analysis, were used to characterize the prepared composite. The activity of the modified composite was investigated for nitrite sensing and hydrogen production applications using various electrochemical techniques. A comparative study was performed for pristine ZnO and ZnO loaded on chitosan. The modified Zn-Chit has a linear range of detection 1–150 µM and a limit of detection (LOD) = 0.402 µM (response time ~3 s). The activity of the modified electrode was investigated in a real sample (milk). Furthermore, the anti-interference capability of the surface was utilized in the presence of several inorganic salts and organic additives. Additionally, Zn-Chit composite was employed as an efficient catalyst for hydrogen production in an acidic medium. Thus, the electrode showed long-term stability toward fuel production and enhanced energy security. The electrode reached a current density of 50 mA cm−2 at an overpotential equal to −0.31 and −0.2 V (vs. RHE) for GC/ZnO and GC/Zn-Chit, respectively. Electrode durability was studied for long-time constant potential chronoamperometry for 5 h. The electrodes lost 8% and 9% of the initial current for GC/ZnO and GC/Zn-Chit, respectively.

Carbon Nanotube Fiber-Based Flexible Microelectrode for Electrochemical Glucose Sensors

Abstract: Electrochemical sensors are gaining significant demand for real-time monitoring of health-related parameters such as temperature, heart rate, and blood glucose level. A fiber-like microelectrode composed of copper oxide-modified carbon nanotubes (CuO@CNTFs) has been developed as a flexible and wearable glucose sensor with remarkable catalytic activity. The unidimensional structure of CNT fibers displayed efficient conductivity with enhanced mechanical strength, which makes these fibers far superior as compared to other fibrous-like materials. Copper oxide (CuO) nanoparticles were deposited over the surface of CNT fibers by a binder-free facile electrodeposition approach followed by thermal treatment that enhanced the performance of non-enzymatic glucose sensors. Scanning electron microscopy and energy-dispersive X-ray analysis confirmed the successful deposition of CuO nanoparticles over the fiber surface. Amperometric and voltammetric studies of fiber-based microelectrodes (CuO@CNTFs) toward glucose sensing showed an excellent sensitivity of ∼3000 μA/mM cm2, a low detection limit of 1.4 μM, and a wide linear range of up to 13 mM. The superior performance of the microelectrode is attributed to the synergistic effect of the electrocatalytic activity of CuO nanoparticles and the excellent conductivity of CNT fibers. A lower charge transfer resistance value obtained via electrochemical impedance spectroscopy (EIS) also demonstrated the superior electrode performance. This work demonstrates a facile approach for developing CNT fiber-based microelectrodes as a promising solution for flexible and disposable non-enzymatic glucose sensors.

Gold Nanoparticle-Modified Tungsten Oxide Flakes as Nitric Oxide Sensor Electrodes for Fruit Quality Monitoring

Abstract: Development of low-cost, handheld nitric oxide (NO) sensors is very much important due to its major role in environmental pollution, biomedical research, and food safety applications. In this study, an electrochemical NO sensor has been fabricated using gold nanoparticle (Au NP)-modified tungsten oxide (WO3) nanoflakes. WO3 nanoflakes were grown hydrothermally on fluorine doped tin oxide (FTO) substrates, and Au NPs were attached by a photoreduction method. The sensing characteristics of pristine WO3 and Au NP-coated WO3 electrodes have been studied by amperometric techniques. The sensor performance has been optimized at various Au NP loadings. The optimized sensor demonstrated a high sensitivity (∼39.37 μA cm–2 mM–1) over a wide linear range (∼10 μM to 5.78 mM) with a low detection limit (∼0.12 μM). The Au NP-coated WO3 sensing electrode demonstrated high stability. The sensor current only decreases 7.54% after 31 days of continuous measurements. The sensor also showed fast response (1.7 s) and high selectivity toward NO detection. NO detection in fruit samples (apple and orange) has been studied with the Au NP-modified WO3 electrode for fruit quality monitoring application.

Multiple Pulse Amperometry—An Antifouling Approach for Nitrite Determination Using Carbon Fiber Microelectrodes

Abstract: Nitrite is a ubiquitous pollutant in modern society. Developing new strategies for its determination is very important, and electroanalytical methods present outstanding performance on this task. However, the use of bare electrodes is not recommended because of their predisposition to poisoning and passivation. We herein report a procedure to overcome these limitations on carbon fiber microelectrodes through pulsed amperometry. A three-pulse amperometry approach was used to reduce the current decay from 47% (after 20 min under constant potential) to virtually 0%. Repeatability and reproducibility were found to have an RSD lower than 0.5% and 7%, respectively. Tap water and synthetic inorganic saliva samples were fortified with nitrite, and the results obtained with the proposed sensor were in good agreement with the amount added.

Synthesis, Characterization, and Electrochemical Evaluation of Copper Sulfide Nanoparticles and Their Application for Non-Enzymatic Glucose Detection in Blood Samples

Abstract: Glutathione-capped copper sulfide (CuxSy) nanoparticles with two different average sizes were successfully achieved by using a simple reduction process that involves only changing the reaction temperature. Temperature-induced changes in the size of CuxSy nanoparticles resulted in particles with different optical, morphological, and electrochemical properties. The dependence of electrochemical sensing properties on the sizes of CuxSy nanoparticles was studied by using voltammetric and amperometric techniques. The spherical CuxSy nanoparticles with the average particle size of 25 ± 0.6 nm were found to be highly conductive as compared to CuxSy nanoparticles with the average particle size of 4.5 ± 0.2 nm. The spherical CuxSy nanoparticles exhibited a low bandgap energy (Eg) of 1.87 eV, resulting in superior electrochemical properties and improved electron transfer during glucose detection. The sensor showed a very good electrocatalytic activity toward glucose molecules in the presence of interference species such as uric acid (UA), ascorbic acid (AA), fructose, sodium chloride, and sucrose. These species are often present in low concentrations in the blood. The sensor demonstrated an excellent dynamic linear range between 0.2 to 16 mM, detection limit of 0.2 mM, and sensitivity of 0.013 mA/mM. The applicability of the developed sensor for real field determination of glucose was demonstrated by use of spiked blood samples, which confirmed that the developed sensor had great potential for real analysis of blood glucose levels.

Layer-By-Layer Films of Silsesquioxane and Nickel(II) Tetrasulphophthalocyanine as Glucose Oxidase Platform Immobilization: Amperometric Determination of Glucose in Kombucha Beverages

Abstract: This paper describes the development of a novel glucose biosensor through the layer-by-layer technique (LbL). The self-assembled architectures were composed of a positive-charged silsesquioxane polyelectrolyte, 3-n-propylpyridinium silsesquioxane chloride (SiPy+Cl−), nickel (II) tetrassulphophthalocyanine (NiTsPc), and a conductive surface of FTO (fluor tin oxide). The construction of the biosensor was influenced by the isoelectric point (pI) of the glucose oxidase enzyme (GOx), which allowed electrostatic interaction between the outer layer of the silsesquioxane film and the enzyme. The architecture of modified electrode GOx/(SiPy+Cl−/NiTsPc)5.5/FTO was confirmed by UV-Vis, FTIR, and chronoamperometry techniques using different immobilization methods of GOx. Among the studied methods, a higher variation of current was observed for the modified electrode formed by mixed LbL films of SiPy+Cl− and NiTsPc and the enzyme immobilized by drop coating. The stability and reproducibility of the biosensor were verified when the last layer containing the enzyme was coated with 0.2% Nafion® polymer. Under these conditions, a linear response for glucose was obtained in the concentration range of 0.2 to 1.6 mmol L−1 (R2 = 0.991) with a limit of detection of 0.022 mmol L−1. The proposed biosensor was applied to quantify glucose in two different samples of kombucha juices with accuracy, allowing the glucose content of the healthy beverages to be estimated.