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Gadolinium (Gd) is an important material for advanced technology; hence, the development of a sensitive and efficient alternative for the Gd-detection method to reduce the dependency on complicated and expensive methods has been massively investigated. Furthermore, the combination of differential pulse voltammetry (DPV) and the experimental design to detect Gd provides a simple, effective, and efficient method. In this study, the Steepest Ascent and Box-Behnken designs were chosen to determine the maximum voltammetry responses. The optimum conditions used for this study showed an amplitude modulation of 0.0884 V, potential deposition of 1.4382 V, and deposition time was 60.3615 s with the obtained recovery value, accuracy, and precision values being 98.37, 95.91, and 5.12% in relative standard deviation (RSD), respectively. Meanwhile, the detection and quantization limit values are 3.46 and 11.53 mg/L, respectively. Under optimum conditions, the presence of Gd in acetonitrile is determined in a mixture with Eu and Sm. Based on the results, the DPV method is capable of determining the presence of Gd in acetonitrile.

Hierarchically bimetallic Zr-Cu metal–organic framework combined with 1,3,5-benzenetricarboxylic acid (Zr-CuBTC MOFs) was synthesized using hydrothermal reaction and used as modifier for investigation of non-electroactive glyphosate. These MOFs were dropcasted on a glassy carbon electrode (GCE) and non-electroactive glyphosate were tested by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and differential pulse voltammetry (DPV). Glyphosate in water was recognized by the difference of currents in spiked and non-spiked glyphosate samples. At the same time, CuBTC and Fe-CuBTC were investigated for the best material for sensor development. The results showed the bimetallic Zr-CuBTC MOF is the most promising for the determination of glyphosate. Morphological and structural studies showed the coordination of Cu2+ with the presence of Zr4+ ions with BTC ligands provided a highly porous framework with active surface area up to 1337 m2 g−1. The pore diameter and pore volume increased to 1.75 nm and 0.687 cm3 g−1, respectively. Under optimal conditions, Zr-CuBTC modified on GCE (Zr-CuBTC/GCE) sensor is able to indirectly detect glyphosate in a water environment at a detection limit as low as 9 × 10−13 M. The developed sensor was employed to determine glyphosate in the surface water samples collected from the Red River, North Vietnam. The results showed good recoveries (94.6–107.1%) which were in agreement with liquid chromatography coupled tandem mass spectrometry (LC-MS/MS) measurements. These results demonstrate the possibility of using this MOF material in sensor applications to determine trace pesticides in the contaminated water. [ABSTRACT FROM AUTHOR]

The main antioxidant compounds contained in cocoa are polyphenols, including flavonoids such as epicatechin, catechin, and procyanidin. This study aims to determine the antioxidant activity of three samples of cocoa powder using 1,1-diphenyl-2-picrylhydrazyl (DPPH) as a free radical by electroanalytical methods, namely cyclic voltammetry (CV) and differential pulse voltammetry (DPV). From the CV information obtained, the first anodic peak from DPPH appears at a potential of 0.33 V with an anodic current of 2.75 A/cm2, while the first anodic peak at DPPH after adding the chocolate sample which has the highest antioxidant activity appears at a potential of 0.43 V with an anodic current of 4.60 A/cm2. From the DPV information obtained, the anodic peak of DPPH appears at a potential of 0.19 V at an anodic current of 2.11 mA, while the anodic peak at DPPH after adding the chocolate sample which has the highest antioxidant activity appears at a potential of 0.02 V at an anodic current of 1.97 mA. The results show that the electroanalytical method has the potential to analyze the antioxidant activity of cocoa powder samples.

Hexa-peri-hexabenzocoronene (HBC) modified glassy carbon electrodes (HBC/GCEs) was fabricated by an electrochemical synthesis, solving the difficulty of the preparation of HBC films because of its poor solubility. HBC/GCE was used as a sensing electrode for the voltammetric investigation of imidacloprid (IDP). The presence of HBC increased the conductivity of GCE, and showed good electrocatalytic activity toward the reaction of IDP. Therefore, the HBC enhanced the electrochemical signal of IDP, which increased the sensitivity of the sensor. The best performance was obtained by optimizing the electrochemical synthesis time, pH and enrichment time. The linear response range and the limit of detection were 5 to 750 μmol·L−1 and 1.5 μmol·L−1, respectively. Moreover, the proposed sensor also exhibited good repeatability, selectivity and stability, and promising applications for real sample. [ABSTRACT FROM AUTHOR]

Hydroquinone (HQ) was used to catalyze Methanobactin (Mb) to reduce chlorauric acid to prepare Gold Nanoparticles (AuNPs). Mb@AuNPs was modified onto the surface of a bare gold electrode via electrodeposition to prepare the Mb@AuNPs/Au electrode. Subsequently, differential pulse voltammetry was conducted for the simultaneous determination of nitrite and ascorbic acid concentrations as well as condition optimization. For the electrode assembly, electrodeposition was performed with a 0.20 mol/L and pH6.5 PBS at a 100 mV/s scan rate for 40 cycles. In the linear range of 2~5600 μmol/L and 1~6000 μmol/L, the oxidation peak current of both nitrite and ascorbic acid detected by Mb@AuNPs/Au showed a good linear relationship with the concentration (R2>0.9928), and the limit of detection (LOD) was 0.31 and 0.57 μmol/L, respectively. The recovery rates of standard addition for the actual samples were 92.59%~109.26%, 90.01%~103.51%. The method has good reproducibility and stability and can be used for simultaneous determination of nitrite and ascorbic acid in fruits and vegetables.

A highly ultrafast and sensitive electrochemical sensor based on electrical potential-assisted hybridization was developed for the determination of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The electrode was modified with multi-walled carbon nanotubes (MWCNTs) and Au nanoparticles (AuNPs) for excellent electrochemical performance. The constant electric field was applied to rapidly and efficiently enrich the capture probes to the electrode surface in 60 s. Meanwhile, pyrene as the backfill reagent resulted in a significant reduction of nonspecific adsorption. The electrochemical properties of the modified electrode were investigated via electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The analytical response was measured by differential pulse voltammetry (DPV). The sensor achieved the ultrafast hybridization of nucleic acids at the electrode interface within 90 s, substantially reducing the reaction time from hours to minutes. Under optimal conditions, the sensor exhibited a superior detection limit of 60 fM and showed satisfactory specificity toward single-base mismatch. Additionally, the proposed sensor realized sensitive determination of SARS-CoV-2 in throat swabs. The enzyme-free and non-amplification sensing strategy showed promising potential for application in point-of-care testing (POCT). [ABSTRACT FROM AUTHOR]

The fabrication, optimization and validation of measurement using a modified carbon paste electrode (CPE) with dibenzo-18-crown-6 were carried out for the determination of paracetamol in commercial products. The pH, dibenzo-18-crown-6 concentration in carbon paste, and scan rate parameters were optimized. Validation of the measurement was observed from linear concentration range, LoD, LoQ, precision, and percentage of the recovery. The result showed that the optimum pH was at 2, the optimum concentration of dibenzo-18-crown-6 in carbon paste was 0.6%, optimum scan rates were 35 mV/s for CPE, and increased to 50 mV/s using modified CPE. The linear concentration range for CPE was obtained at 10-300 µM with LoD and LoQ of 28.88 and 96.28 µM, respectively. Meanwhile, CPE modified with dibenzo-18-crown-6 gave wider linear concentration range at 1–700 µM with LoD and LoQ of 52.36 and 174.53 µM, respectively. The CPE and modified CPE had good precision, with Horwitz ratio values of less than two. The percentage of recovery for two samples with three replicates measurements was obtained (89.81 ± 1.38)% and (108.02 ± 0.42)% for samples A and B, respectively. Dibenzo-18-crown-6 modified CPE was used for the determination of paracetamol in both samples yielding 97–98% compared with the paracetamol composition on its labels.

Reduced graphene oxide (rGO) and spherical barium molybdate (BaMoO4) crystal were prepared using hydrothermal method, respectively. The rGO-BaMoO4 composite was then formed by sonication mixing. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) were applied to characterize the microstructure of rGO-BaMoO4 composite. Moreover, cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and differential pulse voltammetry (DPV) techniques were utilized to investigate its electrochemical performance. Due to the synergistic effect of the two materials, the rGO-BaMoO4 composite modified glassy carbon electrode (rGO-BaMoO4/GCE) exhibits superior electroanalytical performance toward sunset yellow (SY) and tartrazine (TZ) assay, including wide linear range from 0.1 to 1.0 µmol/L and 1.0 to 80 µmol/L, low detection limits of 0.070 (for SY) and 0.078 µmol/L (for TZ), excellent selectivity, good reproducibility, and high stability. What is more, the constructed rGO-BaMoO4/GCE was applied for the assay of SY and TZ in commercial beverage samples. The satisfactory recoveries of 97-108% obtained in real samples reveal the potential of rGO-BaMoO4/GCE in practical applications. [ABSTRACT FROM AUTHOR]

An electrochemical aptasensor was established for the fast and sensitive determination of tetracycline based on the synergistic effect of MoS2-thionine nanocomposite and aptamer. The glassy carbon electrode was coated with MoS2 nanosheets of thionine to immobilize the tetracycline aptamer. In the absence of tetracycline, large quantities of thionin were loaded on the surface of the MoS2 nanosheet to serve as the electrochemical probe. After tetracycline was added to the surface of the electrode, an aptamer analyte complex was produced on the modified electrode. Through intercalation and electrostatic interactions, the complex was substantially adsorbed onto thionine, and the peak currents of the redox signal of thionine decreased. Therefore, the concentration of tetracycline was monitored by the change in signal intensity. Under optimized conditions, the developed electrochemical strategy with MoS2-thionine composite and aptamer exhibited an excellent linear detection range of 1.0 nM–1.0 μΜ and a low detection limit of 0.6 nM with suitable selectivity and stability. Therefore, the fabricated platform offers great potential for food safety, medical detection, and drug analysis. [ABSTRACT FROM AUTHOR]

Simultaneous determination of erythromycin (Ery) and hemoglobin (Hb) is of great significance for clinical diagnosis of many diseases. ZnO nanorods modified with Au nanoparticles were fabricated as an interface on the flexible carbon cloth (CC) and utilized to simultaneously determine Ery and Hb by a simple electrochemical method. The results demonstrated that Au/ZnO/CC displayed excellent analytical performance for Ery with a low detection limit of 3.38 × 10−7 mg/L and a linear range from 1 × 10−6 to 1 × 10−1 mg/L. At the same time, the sensor also showed a sensitive response to Hb with a low detection limit of 2.07 × 10−7 mg/L and a linear range from 1 × 10−6 to 1 × 10−1 mg/L. This work provides a viable approach for designing a flexible electrode and sensitive simultaneous determination of Ery and Hb. [ABSTRACT FROM AUTHOR]

While platinum electrode shows hyperactivity towards adsorption and surface processes, iodine-coated platinum electrode offers remarkable inertness toward them. Therefore, iodine-coated platinum electrodes lend themselves to probe chemical species in the bulk solution without intervention from adsorption and surface processes. The current work presents utilization of iodine-coated polycrystalline platinum electrode as a voltammetric sensor for determination of dopamine in serum and urine samples. Differential pulse voltammetry (DPV) at iodine coated polycrystalline platinum electrode is the technique of choice whenever higher sensitivity is sought. DPV with a scan rate of 5 mV/s was applied for determination of dopamine in PBS at pH 7. The anodic peak related to dopamine oxidation in the above-mentioned solution was centered at ~0.1V vs. Ag/AgCl quasi reference electrode. The linear range for the developed method was between 1.0 and 100 µM. The anodic peak current showed excellent linearity with dopamine concentration (R2 =0.9977) over the above-mentioned range. The limit of detection (LOD) and limit of quantitation (LOQ) were 0.29 µM and 0.96 µM respectively which attests to the high sensitivity of the developed method. The proposed method was successfully applied to the analysis of dopamine in serum and urine samples. The percent recovery values ranged from 94.4 to 104.5% attesting to the accuracy of the developed method and absence of determinate errors.

AbstractA rapid and simple solid-state microwave method was used for the synthesis of a ternary nanocomposite comprising nickel sulfide/nickel oxide/carbon nanotubes (NiSx/NiO/CNT). This nanocomposite was subsequently utilized for the electrochemical determination of melamine. Various techniques, including scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive spectroscopy (EDX), X-ray diffraction (XRD), and Raman spectroscopy, were employed to characterize the structure and morphology of the material. Additionally, cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were utilized to investigate the electrochemical properties. The results indicated that the NiSx/NiO/CNT nanocomposite electrode demonstrated a favorable electrochemical reactivity toward melamine. It displayed a linear range from 10 to 2000 μg/L, a detection limit (DL) as low as 0.017 μg/L, and a sensitivity of up to 83.5 μA/(μM·cm2). The NiSx/NiO/CNT composite demonstrated the ability to detect trace melamine in milk samples, demonstrating its practical application. [ABSTRACT FROM AUTHOR]

An electrochemical sensor based upon a poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT-PSS) co-polymer film with gold nanoparticles (AuNPs) modified microelectrode is reported for the determination of Fe(III). Scanning electron microscopy images showed that the AuNPs were immobilized on gold (Au) microelectrode by formation of a nanofilm with PEDOT-PSS. The individual particles and their cluster-like aggregates provide a larger active electrochemical area and higher conductivity, which facilitates the determination of Fe(III). Electrochemical impedance spectroscopy (EIS) shows the AuNPs/PEDOT-PSS/Au microelectrode possesses high conductivity. A low detection limit of 0.01 µM Fe(III) was obtained using the modified microelectrode by differential pulse voltammetry (DPV) due to its large specific surface area, high conductivity, and the presence of more active sites. The optimized pH of the supporting acetate buffer was 2.0. The AuNPs/PEDOT-PSS/Au provided a linear range from 0.0119 μM to 7.14 μM. The modified electrode was successfully employed for the the determination of total dissolved iron in river water from Three Gorges with satisfactory results. [ABSTRACT FROM AUTHOR]

A simple and reliable method based on a composite of Nafion (Naf), multiwalled carbon nanotubes (MWCNTs), and mesoporous silica (SBA-15) modified glassy carbon electrode (GCE) is reported for individual and simultaneous determination of indigo carmine (IC, dye) and carbendazim (CBZ, pesticide). SBA-15 was synthesized and characterized and used to design a GCE/Naf/MWCNTs/SBA-15 sensor, which was characterized by electrochemical techniques and used for the determination of IC and CBZ. Using the optimum conditions for differential pulse voltammetry (DPV), the peak currents were linear from 1.0 µM to 11.0 µM. The limits of detection for individual measurements were 0.50 µM and 0.57 µM for IC and CBZ, respectively, while those for simultaneous detection were 0.28 µM and 0.30 µM. The interferences studies show that GCE/Naf/MWCNTs/SBA-15 exhibited excellent selectivity. The developed procedure was successfully applied to determine IC and CBZ in spring, tap, and lake water. [ABSTRACT FROM AUTHOR]

Acetaminophen (AP) is one of the most commonly used antipyretics. Accurate and efficient determination of its concentration is of great significance to human health. In this work, FeNi alloy nanoparticles and reduced graphene oxide (rGO) were compounded by an ultrasonic method to obtain FeNi/rGO nanocomposites. The nanocomposites were analyzed by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), and cyclic voltammetry (CV). Due to the catalytic activity of FeNi alloy nanoparticles and the synergy between the high specific surface area and conductivity of reduced graphene oxice (rGO), a FeNi/rGO nanocomposite showed excellent electrocatalysis for acetaminophen determination. With differential pulse voltammetry (DPV) as the analytical method, the linear range for acetaminophen is from 1 to 100 and 100 to 3,000 μM with a limit of detection (LOD) equal to 0.3 μM. Moreover, the sensor also has good reproducibility and selectivity with high recoveries in practical analysis. [ABSTRACT FROM AUTHOR]

Many voltammetry methods have been developed to monitor brain extracellular dopamine levels. Fewer approaches have been successful in detecting serotonin in vivo. No voltammetric techniques are currently available to monitor both neurotransmitters simultaneously across timescales, even though they play integrated roles in modulating behavior. We provide proof-of-concept for rapid pulse voltammetry coupled with partial least squares regression (RPV-PLSR), an approach adapted from multi-electrode systems (i.e., electronic tongues) used to identify multiple components in complex environments. We exploited small differences in analyte redox profiles to select pulse steps for RPV waveforms. Using an intentionally designed pulse strategy combined with custom instrumentation and analysis software, we monitored basal and stimulated levels of dopamine and serotonin. In addition to faradaic currents, capacitive currents were important factors in analyte identification arguing against background subtraction. Compared to fast-scan cyclic voltammetry-principal components regression (FSCV-PCR), RPV-PLSR better differentiated and quantified basal and stimulated dopamine and serotonin associated with striatal recording electrode position, optical stimulation frequency, and serotonin reuptake inhibition. The RPV-PLSR approach can be generalized to other electrochemically active neurotransmitters and provides a feedback pipeline for future optimization of multi-analyte, fit-for-purpose waveforms and machine learning approaches to data analysis.

Herein the synergistic properties of electrochemically reduced graphene oxide–antimony nanoparticles (ERGO-SbNPs) were leveraged for the ultrasensitive determination of bisphenol A (BPA) in water samples using disposable pencil graphite rods. A novel pencil-graphite multi-electrode array was utilized as the coating tool resulting in the production of highly reproducible and disposable single-use ERGO-SbNP-coated pencil graphite rods. This coating method effectively mitigated the fouling caused by BPA by-products during oxidation. The analytical determination of BPA oxidation on the single-use ERGO-SbNP-coated pencil graphite rods demonstrated an impressive 0.0,125 µM detection limit, surpassing the USEPA drinking water standard of 0.087 µM. Furthermore, the developed electrochemical sensor exhibited exceptional reproducibility for BPA in tap water samples from Western Cape, South Africa with few interferences. The study's findings not only highlight the sensor's superior performance but also present a promising alternative to existing anti-fouling measures. [ABSTRACT FROM AUTHOR]

Dysprosium has gained global interest due to its key application in renewable technology, such as wind power technology. The presence of this rare earth element (REE) can be determined by several spectroscopic methods. Recently, a voltammetry method has provided an alternative method for the simple and fast detection of REEs. However, to the best of our knowledge, this experiment is usually carried out in an aqueous solvent, and the response of the REE in an organic solvent by the voltammetry method has rarely been investigated. In this research, the quantitative detection of dysprosium and dysprosium mixtures with samarium, europium and gadolinium in acetonitrile is reported by differential pulse voltammetry. A Box-Behnken design was applied to predict the optimum condition of the measurements. Three factors, namely potential deposition, deposition time and amplitude modulation, were found to significantly influence the signal under optimal conditions, which are -1.0 V, 83.64 s and 0.0929 V, respectively. The surface characterization of dysprosium deposited on a Pt surface shows better deposition under 100% acetonitrile compared to a lower concentration of acetonitrile. The evaluation in this study shows a detection limit of 0.6462 mg•L-1 and a quantitation limit of 2.1419 mg•L-1, with a precision value and recovery value of 99.97% and 93.62%, respectively.