Oxidation Peak Current Research Articles

Heteroatom engineered graphene-based electrochemical assay for the quantification of high-risk abused drug oxytocin in edibles and biological samples

The naive detection of scheduled H drug oxytocin is a vital requisite, owing to its deleterious impact on societal affluence prompted by unconstrained usage. Therefore, a reliable, cost-effective, and quick-to-respond analytic technique for this drug is in ample demand. In this work, we report electrochemical detection of oxytocin employing novel nitrogen, phosphorus co-doped coke-derived graphene (NPG) modified electrode. The electro-oxidation behavior of oxytocin was investigated on the NPG modified electrode by square wave stripping voltammetry (SWSV) in 0.1 M phosphate buffer of pH 7. The oxidation peak current was linear in two ranges, spanning from 0.1 nM to 10 nM and 15 nM to 95 nM. The limit of detection at the NPG electrode was calculated to be 40 pM. The practical application of developed sensor for the determination of oxytocin was examined in edible products and body fluids, hence signifying the possibility of having real-time surveillance over its misusage.

Electrochemical detection of triamterene in human urine using boron-doped diamond electrodes

Urine is one of the most used biological fluids for screening drug delivery and the resultant metabolites. In sports, the use of diuretics such as triamterene is considered a violation of anti-doping rules and is stipulated to be present at less than 79 nM in urine by the World Anti-Doping Agency (WADA). It is therefore important to develop effective rapid and low-cost tests for this diuretic. Here we apply electrochemical analysis using boron-doped diamond (BDD) electrodes, which have superior properties such as low background current, a wide potential window, and high resistance to deactivation. Since real urine samples show clear oxidation current peaks in the potential range more positive than 0.5 V (vs. Ag/AgCl) due to the presence of bio-components such as protein, uric acid, and ascorbic acid, to detect triamterene effectively, the electrochemical protocol was optimized towards a potential range where the other components have limited effect. Our results show that reduced triamterene exhibits an oxidation peak at 0.1 V (vs. Ag/AgCl) in 0.1 M phosphate buffer (PB) and at 0.2 V (vs. Ag/AgCl) in pooled human urine. The peak current value increased according to the triamterene concentration. The limit of detection (LOD) was 3.15 nM in the PB and 7.80 nM in pooled human urine. Finally, triamterene detection was attempted in individual urine samples. Triamterene was electrochemically detectable in individual urine samples, excluding urine samples containing an excess amount of ascorbic acid. The limit of detection (LOD) in individual urine samples was determined to be 20.8 nM.

A Novel Electrochemical Aptasensor Based on a New Platform of Samarium Molybdate Flower-like Nanoparticles@Poly(pyrrole) for Non-Invasive Determination of Saliva CORTISOL.

Cortisol, a famous stress biomarker, can be considered a potential predictor of cardiac diseases in humans. The presence of cortisol in saliva has encouraged researchers to design point-of-care devices for cortisol concentration in biological fluids. Here, human salivary cortisol was analyzed through a new non-invasive voltammetric aptasensor. Although cortisol is an electroactive compound, generally, the reduction in the current peak has been considered; however, this does not show a strong signal on a bare electrode surface, especially at low concentration levels. Hence, in this study, cortisol concentration was measured electrochemically and indirectly by monitoring the difference between electrochemical probe signals in the presence and absence of cortisol. A new polymeric nanocomposite of samarium molybdate flower-like nanoparticles decorated in poly(pyrrole) was electro-synthesized on the surface of a glassy carbon electrode. Then, reduced graphene oxide was cast on the surface. Finally, the cortisol aptamer was immobilized covalently on the reduced graphene oxide. This platform was used to increase the oxidation current peak of the ferricyanide solution as a probe as well as its electrocatalyst. The novel designed polymeric has the potential ability for effective immobilization of aptamers on the electrode surface without decreasing their biological activities. Additionally, it can enhance the probe electrochemical signal. The differential pulse voltammetric method (DPV) was applied as the detection technique. By optimizing the effective parameters, a determination range of 5.0 × 10−14–1.5 × 10−11 mol/L and a limit of detection of 4.5 × 10−14 mol/L were obtained. Selectivity of the proposed aptasensor relative to β-estradiol, progesterone and also prednisolone was studied as well. Finally, cortisol in a healthy human saliva sample was successfully analyzed by the proposed biosensors.

Sensitive electrochemical determination of riboflavin at simple and low-cost poly (valine) modified graphite paste electrode

• A modest, responsive, low-cost, and green electrochemically polymerised valine modified graphite paste electrode was developed. • FE-SEM, EI, and CV measurements are used for electrode materials characterisation. • Riboflavin electrochemical redox action was analysed using polymerised valine modified graphite paste electrode. • prepared electrochemical sensor provides a lower limit of detection with fine sensitivity and reproducibility. • The modified electrochemical sensor gives acceptable recoveries for riboflavin in medicinal sample. A sensitive electrochemical analysis of riboflavin (RFN) was done in 0.1 M phosphate buffer solution (PTBS) by constructing a modest and green electrochemically polymerised (EP) valine (VLN) modified graphite paste electrode (GPE). The electrochemical, morphological, resistive, and conductive characteristics of modified electrode (EP(VLN)MGPE) and bare graphite paste electrode (BGPE) surfaces were clarified through cyclic voltammetry (CV), field emission scanning electron microscopy (FE-SEM), and Electrochemical impedance (EI) methods. The EP(VLN) initiated electrode surface parades excellent sensitivity, steadiness, repeatability, and reproducibility for the redox action of RFN with enhanced peak currents as associated to BGPE. The oxidation peak currents of RFN are improved with increased concentrations of RFN in the range from 2.0 µM to 40.0 µM and the attained limit of detection (LOD) and limit of quantification (LOQ) are found to be about 28.69×10 -8 M and 95.66×10 -8 M, respectively. The prepared EP(VLN)MGPE was beneficial for the quantitative and qualitative investigation of RFN in medicinal samples.

Rapid and Sensitive Electrochemical Assay of Cefditoren with MWCNT/Chitosan NCs/Fe2O3 as a Nanosensor.

In this research, a glassy carbon electrode (GCE) modified by MWCNT/chitosan NCs/Fe2O3 was prepared for the determination of the cephalosporin antibiotic cefditoren (CFT) using adsorptive stripping differential pulse and cyclic voltammetry techniques. The effects of pH, the scan rate, the deposition potential, the accumulation time, and modification agents on the determination of CFT were analyzed. The results showed that the modified electrode significantly increased the oxidation peak current of CFT. Under optimized conditions, the MWCNT/chitosan NCs/Fe2O3/GCE nanosensor exhibited a linear response between 0.2 µM and 10 µM toward CFT. The limit of detection and quantification were determined to be 1.65 nM and 5.50 nM, respectively. Model drugs (cefdinir, cefpodoxime, cephalexin, and ceftazidime compounds) were used to enlighten the CFT oxidation mechanism. Moreover, the nanosensor was used to analyze CFT in a pharmaceutical dosage form and commercial deproteinated human serum samples. The accuracy of these methods was proven in the recovery studies, with values of 96.98 and 98.62% for the pharmaceutical dosage form and commercial deproteinated human serum sample, respectively.

Highly Sensitive Electrochemical Sensor for Sunset Yellow Based on Electrochemically Activated Glassy Carbon Electrode.

Electrochemically activated glassy carbon electrode (AGCE) was fabricated and applied for sensitive and selective detection of sunset yellow (SY). The electroanalysis of SY was investigated by square wave voltammetry (SWV). Owed to the specific oxygen-contained functional groups and the outstanding conductivity of AGCE, the proposed sensor exhibits an enhanced oxidation peak current of SY when compared with non-activated glass carbon electrode (GCE). Under the optimal analytical conditions, the oxidation peak current is linear with SY concentration in the range of 0.005–1.0 μM. The low limit of detection is 0.00167 μM (S/N = 3). This method is applied for the detection of SY in the actual samples. The recovery is between 96.19 and 103.47%, indicating that AGCE is suitable for the determination of SY in beverage sample.

Cu2+ modified Zr-based metal organic framework-CTAB-graphene for sensitive electrochemical detection of sunset yellow.

A sensitive electrochemical sensor for sunset yellow (SY) was constructed based on cetyltrimethylammonium bromide (CTAB) functionalized graphene (Gr) and Cu/Zr-MOF electrode modified materials. The CTAB-Gr-Cu/Zr-MOF composites were synthesized by using a mild method and characterized by scanning electron microscopy, Fourier transform infrared spectroscopy and EDX spectrum. The combination of Cu/Zr-MOF and graphene exhibited synergetic effect of the strong accumulation efficiency, fast electron transfer rate and more sensing sites towards the oxidation of SY. The new modified materials remarkably increased the electrochemical response of SY to 6.53-fold when comparing with bare electrode. Under the optimized conditions, the oxidation peak currents of SY had a linear relationship with its concentration in a wide range from 0.10 to 8.00μM and 40.00-1000.00μM, and the limit of detection was 6.68nM (S/N=3). The electrochemical method shows high sensitivity, stability, reproducibility and is successfully applied in the determination of SY in soft drinks.

Electrochemical Determination of Vanillin in Cookies at Mediated AuNPs/GR Nanocomposites Modified Glassy Carbon Electrode

Background: Currently, carbon nanomaterials and carbon nanomaterials-based electrodes have illustrated significant electrocatalytic abilities. Methods: An electrochemical sensor was developed for vanillin using graphene (GR) decorated with gold nanoparticles (AuNPs) on a glassy carbon electrode (GCE) with two steps. AuNPs/GR/GCE, as the electrochemical sensor for determination of vanillin, included dropping GR onto the electrode and then electrodepositing AuNPs on GR/GCE. The structure and morphology of the synthesized nanocomposites (AuNPs/GR) on the electrode were confirmed by scanning electron microscopy (SEM). Results: Electrochemical studies revealed that modification of the electrode surface with AuNPs/GR nanocomposites significantly increases the oxidation peak currents of vanillin. The peak currents in differential pulse voltammetry (DPV) of vanillin increased linearly with their concentration in the range of 5-120 µM. The limit of detection was found to be 1.7 µM for vanillin. Also, the effect of some interfering compounds, such as NaCl, KCl, glucose, alanine, phenylalanine, glycine, and others, on the determination of vanillin was evaluated, and none of them had a significant effect on the assay recovery Conclusions: A new electrochemical biosensor was fabricated with AuNPs/GR nanocomposites. The sensor was successfully used to detect vanillin in cookie samples.

Phytochemicals of mustard (Brassica Campestris) leaves tuned the nickel‐cobalt bimetallic oxide properties for enzyme‐free sensing of glucose

AbstractThe fabrication of enzyme‐free glucose sensors is highly demanded for the biological, clinical, and food applications. In this study, we have developed a green method for tuning the surface properties of nickel‐cobalt bimetallic oxide (NiCo2O4) by adding mustard (Brassica Campestris) leaves extract during hydrothermal growth. The mustard (Brassica Campestris) leaves extract is rich with a variety of phytochemicals, which can easily tune the surface properties of NiCo2O4 nanostructures, thereby paving the way toward the development of sensitive and selective non‐enzymatic glucose sensors. The effect of various amounts of mustard (Brassica Campestris) leaves extract (0–20 ml) was also studied to find out the optimal conditions for growing surface‐modified NiCo2O4 nanostructures. The morphology and crystalline structure of the nanomaterials were studied by scanning electron microscopy (SEM) and powder X‐ray diffraction (XRD) techniques, respectively. The presence of an increasing quantity of mustard (Brassica Campestris) extract keeps the crystalline structure and the morphology of the NiCo2O4 nanostructures unaltered but changes their dimensions. All nanostructures show the same cubic spinel structure of NiCo2O4 and a morphology of spherical urchins composed of nanorods, but the diameter of the urchins decreases from ~10 μm to several nanometers, thus increasing the surface area of the nanomaterial. Furthermore, NiCo2O4 nanostructures were deposited onto glassy carbon electrodes (CGE), showing excellent catalytic properties toward the enzyme‐free detection of glucose using cyclic voltammetry. Importantly, the intensity of the oxidation current peak was linear over a wide range of glucose concentrations (from 0.1 to 10 mM) and the limit of detection (LOD) was estimated around 0.001 mM. Additionally, NiCo2O4 nanostructures grown in the presence of 20 ml of mustard leaf extract demonstrated good repeatability and excellent selectivity for glucose, without interference by other components such as urea, lactic acid, uric acid, ascorbic acid, as well as potassium and sodium ions. The combined results attest that mustard leaf extract has high potential as a green approach to improve the electrochemical properties of nanostructured materials, and could be useful for a wide range of materials for future electrochemical applications.

Electrochemical sensor based on Ca-doped ZnO nanostructured carbon matrix for algicide dichlone

As many new pollutants continue to be introduced into the environment, environmental pollution has become the biggest concern in the current era. It requires the development of a more sensitive, effective and selective, cost-efficient modified electrode. We designed a sensitive and effective voltammetric sensor with synthesized calcium-doped zinc oxide (Ca-ZnO/CPE). The cyclic voltammetry (CV) method was employed to determine the electrochemical behavior of dichlone (DCN), referred to as fungicide and algaecide. The surface morphology of the developed sensor's matrix was carried out employing SEM, TEM, and XRD techniques. The Ca-ZnO NPs as a modifier in the carbon paste efficiently enhanced both the oxidative and reduction peak current of DCN in CVs. The effect of electrolyte pH and scan rate variation investigation results were used to determine the total number of electrons in the DCN electro-oxidation mechanism, the number of protons, charge transfer coefficient, and heterogeneous rate constant. Additionally, kinetic and thermodynamic aspects of DCN were investigated. The square wave voltammetry technique (SWV) showed the lowest detection limit (DL) of 5.98 × 10–8 M and a wide linearity range (3.5 × 10–7 M to 7.2 × 10–4 M). The environmentally-based approach successfully quantifies DCN in water and soil samples.

Glycerol oxidation at Pd nanocatalysts obtained through spontaneous metal deposition on carbon substrates

Spontaneous deposition of Pd is carried out on five different carbon-based screen-printed electrodes (SPEs) in the absence of solute reductant species in the Pd ions solution. Pd nanoparticles (NPs) with mean sizes ranging between 11.2 and 17.9 nm and homogeneous distribution are obtained on the carbon supports. The NPs mean size and amount of available metal are found to depend on the type of the carbon SPE, i.e. carbon (C110), mesoporous carbon (MC), carbon nanofibers (CNF), single- or multi-walled carbon nanotubes (SWCNT or CNT). Overlapping and agglomerating particles are found only in the SWCNT case whereas for all other electrodes the individual NPs are well isolated. Glycerol oxidation is studied at the five types of Pd nanocatalysts and data for the mass activity are obtained for glycerol and KOH concentrations used in fuel cells applications. The data for the mass activity correlate with the electroactive surface area (EASA) of the metallic particles for three of the electrodes (C110, MC and CNF) whereas Pd NPs supported by multi walled CNTs show a very high mass activity not to be associated with increased EASA alone. In separate experiments the applicability of the Pd-carbon-based SPEs is studied in view of electroanalytical detection of glycerol. A stable electroanalytical response is found for the MC, CNT and CNF SPEs. The concentration dependence of the glycerol oxidation peak current is modeled by a Langmuir type function that allows for detection of glycerol in the 0.2 to 15 mmol/l concentration range. The ease of preparation of the Pd nanocatalysts and the use of disposable SPEs present a good prospect for practical applications.

Development of a novel sensor with high sensitivity for electroanalytical determination of bisphenol A based on chitosan-3-mercaptopropyl trimethoxysilane modified glassy carbon electrode

In a facile synthesis process, a novel functionalized composite material was synthesized as precursors to the chitosan and 3-mercaptopropyl trimethoxysilane (CHMTS). The materials, chitosan (CH) and CHMTS were characterized using Fourier-transform infra-red, scanning electron microscope/energy dispersive X-rays, transmission electron microscopy, and Brunauer-Emmett-Teller surface area analyser techniques. The cyclic voltammetry (CV) studies showed that a 6-fold increase in oxidative peak current was recorded in CHTMS/GCE compared to bare GCE and 3-fold increase in peak current compared to CH/GCE. Similarly, EIS Nyquist plots showed a significant decrease in a semicircle for the CHMTS/GCE compared to the bare GCE and CH/GCE with the Rct value of 10814.0 Ω, 2639.0 Ω, and 663.7 Ω, respectively for the CHMTS/GCE, CH/GCE, and GCE. Further, the electrochemical behaviour of bisphenol A (BPA) showed an irreversible 2-electron process. Moreover, the differential anodic stripping voltammetry is found sensitive and selective for the trace detection of BPA under optimized experimental parameters such as pH 10.0, deposition potential 0.2 V (vs. Ag/AgCl), and deposition time 180 sec. The determination of BPA showed good linearity with BPA concentration against the oxidation peak current, within the studied concentration range of 140.0 µg/L to 200.0 µg/L, and the calculated limit of detection is 5.61 µg/L. The 10-fold increase in several co-existing ions not affect the detection of BPA, indicating the selectivity and sensitivity of the CHTMS/GCE toward BPA. The fabricated electrode showed reasonably good reproducibility with an RSD value of 0.35%. Furthermore, CHTMS/GCE showed long-term stability since the peak current was retained at 99.42% even after 48 hrs of repeated use. Real water samples using spring water and river water revealed the recovery percentage of Ca. 100% in the detection of BPA, which showed the practical applicability of the fabricated electrode.

Engineering MOFs derived metal oxide nanohybrids: Towards electrochemical sensing of catechol in tea samples

In this work, we have successfully developed Cu-MOF/CuO/NiO nanocomposites (NCs) and employed as a novel electrochemical sensing platform in catechol (CC) detection. The Scanning electron microscopy (SEM) along Energy dispersive X-ray Analysis (EDX), Transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) are carried out to characterize the as-fabricated Cu-MOF/CuO/NiO NCs. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques have used to obtain oxidation peak currents of CC. Glassy carbon electrode (GCE) modified with Cu-MOF/CuO/NiO has exposed the superb EC properties representing low limit of detection (LOD) of 0.0078 µM (S/N = 3). To assess the practicability of Cu-MOF/CuO/NiO based sensing medium, it has been used to detect CC from two varieties of tea, namely black and green. Thus, we anticipate that this structural integration strategy possesses encouraging application potential in sensing podium and material synthesis.

Screen-printed graphite electrode modified with Co3O4 nanoparticles and 2D graphitic carbon nitride as an effective electrochemical sensor for 4-aminophenol detection

We fabricated a new electrochemical 4-aminophenol sensor based on a nanocomposite of Co3O4 nanoparticles and graphite carbon nitride (Co3O4@g-C3N4), used for the modification of a screen-printed electrode (Co3O4@g-C3N4/SPE). The synthesized nanocomposite was characterized using field-emission scanning electron microscopy, energy-dispersive x-ray spectroscopy, x-ray diffraction and Fourier transform-infrared (FT-IR) techniques. The electro-oxidation of 4-aminophenol in phosphate buffer solution (pH = 7.0) was investigated via cyclic voltammetry, differential pulse voltammetry and chronoamperometry. The peak current of oxidation in the optimized conditions had a linear relationship with various 4-aminophenol contents (0.05–780.0 μM) with a correlation coefficient of 0.9996 and the limit of detection (S/N = 3) of 1.5 × 10−8 M. The developed method was successful to determine 4-aminophenol in real specimens, with acceptable outcomes.

Electrochemical Investigation of Porosity in Core-Shell Magnetoplasmonic Nanoparticles.

Porous core-shell nanoparticles (NPs) have emerged as a promising material for broad ranges of applications in catalysts, material chemistry, biology, and optical sensors. Using a typical Ag core-Fe3O4 shell NP, a.k.a., magnetoplasmonic (MagPlas) NP, two porous shell models were prepared: i.e., Ag@Fe3O4 NPs and its SiO2-covered NPs (Ag@Fe3O4@SiO2). We suggested using cyclic voltammetry (CV) to provide unprecedented insight into the porosity of the core-shell NPs caused by the applied potential, resulting in the selective redox activities of the core and porous shell components of Ag@Fe3O4 NPs and Ag@Fe3O4@SiO2 NPs at different cycles of CV. The porous and nonporous core-shell nanostructures were qualitatively and quantitatively determined by the electrochemical method. The ratio of the oxidation current peak (μA) of Ag to Ag+ in the porous shell to that in the SiO2 coated (nonporous) shell was 400:3.2. The suggested approach and theoretical background could be extended to other types of multicomponent NP complexes.

HAP-TiO2 nanocomposites based electrochemical sensor for selective and simultaneous detection of para-aminohippuric acid and uric acid

Kidney diagnosis by p-aminohippuric acid (PAH) test indicates the ability of the kidney to combine benzoic acid with PAH by determination of the latter eliminated in urine or blood serum. Hippuric acid synthesis also occurs in both the liver and cortical cells of the kidney. However, the PAH test did not become popular because of the non-availability of a simple method for quick and accurate determination of the PAH at an affordable cost. Here, we report a novel electrochemical sensor based on hydroxyapatite-titanium dioxide (HAP-TiO2) nanocomposite for quantifying specific biomarkers PAH and uric acid (UA). Nanostructured HAP and TiO2 powders have been synthesized independently by microwave irradiation and hydrolysis methods respectively and the composites are prepared by mixing the appropriate amounts of HAP and TiO2 under sonication. Voltammetric studies of HAP-TiO2 modified glassy carbon electrodes exhibited improved electrocatalytic activity towards the oxidation of PAH and UA in a phosphate buffer saline (pH7.0). Under the optimized conditions, the oxidation peak currents are linearly proportional to PAH and UA concentrations over wide linear ranges of 50 nM to 5.760 mM, and the corresponding lowest detection limits are estimated to be 37 nM and 43 nM (S/N = 3). The fabricated electrode has been successfully implemented for the determination of PAH and UA in human urine samples. Performance of the device in terms of sensitivity, specificity, and linear range fulfills the requirement for screening the chosen biomarkers simultaneously making it suitable for clinical non-invasive liver and kidney diagnoses.

Highly sensitive and disposable electrochemical nano sensor for simultaneous analysis of caffeic acid and uric acid based on halloysite nanotubes and magnetite nanoparticles

Simultaneous quantitative analysis of caffeic acid (CAFA) and uric acid (UA) in biological samples was carried out using a pencil graphite electrode (PGE) coated with a mixture of halloysite (a clay mineral) nanotubes (HNTs) and magnetite (Fe3O4) nanoparticles. Surface morphology and electrochemical characterization of the sensor were investigated by field emission scanning electron microscopy (FE-SEM), Energy dispersive X-ray analysis (EDX), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The sensor prepared has an effective surface area 1.75 times larger than that of the corresponding bare PGE electrode. Oxidation peak currents for CAFA and UA obtained by the sensor increased by 1.4 and 2.0 times, respectively, compared to the values found with bare PGE. Under the optimal conditions, linear working ranges for CAFA and UA were found in the ranges (0.027–70.0 µM) and (0.009–70.0 µM), respectively. The respective detection limits were 0.008 µM and 0.003 µM. The sensor developed was shown to be applicable to quantifying the analytes simultaneously in human serum and urine.

EDTA salt modified carbon paste electrode for square wave voltammetric determination of theophylline in pharmaceutical tablet formulation.

In this study, a square wave voltammetric method for determination of theophylline in tablet formulation based on EDTA salt modified carbon paste electrode is presented. CV, FT-IR, and EIS results confirmed modification of the carbon paste with EDTA salt. In contrast to the unmodified carbon paste electrode, the modified carbon paste electrode showed irreversible oxidation of theophylline with considerable current enhancement. Investigation of the effect of scan rate on the Ip and Ep response of the modified electrode for theophylline revealed predominantly diffusion controlled oxidation kinetics. Under the optimized conditions, square wave oxidative peak current of theophylline in pH 7.0 PBS showed linear dependence on concentration in the range 10–200 μM with determination coefficient (R2), limit of detection, and limit of quantification of 0.99782, 0.0257 μM, and 0.0857 μM, respectively. Detection of an amount of theophylline in the analyzed tablet formulation with 1.85% error from its nominal content (120 mg/tablet) confirmed the accuracy of the developed method. Spike and interference recovery results of 98.59%, and 95.7–100%, respectively validated the applicability of the developed method for determination of theophylline content in tablet samples.

A sensitive aflatoxin B1 electrochemical aptasensor based on ferrocene-functionalized hollow porous carbon spheres as signal amplifier

Due to the high toxicity and carcinogenicity of Aflatoxin B1 (AFB1), a sensitive, low-cost and simple method to accurately detect AFB1 in foodstuffs is highly desirable. Herein, a sensitive and selective AFB1 electrochemical aptasensor was developed by using ferrocene immobilized hollow porous carbon spheres (HPCS-Fc) as the electrochemical signal tag. Attributed to the large surface and high conductivity of HPCS, the prepared Fc-HPCS showed the high load amount of Fc and HPCS-Fc labelled GC electrode displayed large oxidation peak current. To further improve the biosensing ability, tetrahedral DNA nanostructures (TDNs) was attached on the biosensing interface to control the orientation of HPCS-Fc-cDNA. Based on the above advantages, the HPCS-Fc labelled electrochemical aptasensor exhibited high sensitivity towards AFB1 in a wide linear range from 1.0 × 10−2 pg mL−1 to 100.0 μg mL−1 and a low detection limit down to 3.3 × 10−5 ng mL−1. Furthermore, the developed aptasensor was applied to detect AFB1 in wheat powder samples with satisfactory recoveries of 91.7%∼107.7%, demonstrating its potential application in testing AFB1 in food samples.

Economical Voltammetric Sensor for Sensitive Rapid Determination of Ondansetron in the Presence of Opioid Antagonist Naltrexone

The electrochemical actions of ondansetron (OND) were investigated on the modified electrode with Polyvinyl Pyrollidone (PVP) and multi-walled carbon nanotube (MWCNTs). The oxidation peak current was enhanced to be doubled when compared to the bare electrode as a result of the synergistic effect of nanomaterial and cation-exchange polymer on the electron transfer rate. Following optimization of the experimental conditions, the Square Wave Voltammograms (SWV) method was employed to determine ondansetron in pharmaceutical formulations. Moreover, the modified electrode MWCNTs/PVP/CPE displayed high selectivity in the voltammetric measurements of ondansetron and co-administrated opioid antagonist drug naltrexone (NAL) with strong potential separation (422 mV). The response peak currents had a linear relationship with drug concentration in the range of (2.00–200.0 nmolL−1) with detection limits 430 pmolL−1 and 456 pmolL−1 for ondansetron and naltrexone, respectively. The electrode was successfully used to detect both medications electrochemically in human plasma samples.Graphical abstract