Differential Pulse Stripping Voltammetry Research Articles

Transition metal doped ZIF‐8 for the detection of the heavy metal Hg(II)

AbstractThe effects of heavy metals such as Hg(II) and Pb(II) on the human body are profound. Moreover, they pose significant concerns due to industrial development. Thus, the rapid and stable detection of heavy metal ions and related chemicals has emerged as an urgent issue. The application of Differential Pulse Stripping Voltammetry (DPSV) facilitated accurate and rapid detection of Hg2+ utilizing MOF materials and ZIF‐8 as detection agents. Pure ZIF‐8 served as the substrate material. Copper or nickel ions were individually introduced into the substrate material. This process resulted in the formation of bimetallic MOF materials. These materials were designated as CuZn and NiZn, respectively. Transition metal‐doped materials were used to modify the glassy carbon electrode (GCE), resulting in a substantial enhancement in the detection performance of Hg2+. The CuZn/GCE configuration demonstrated the most significant enhancement. When compared to a GCE modified with pure ZIF‐8, both sensitivity and the detection limit for free Hg2+ in the environment experienced increases of 450% and 64%, respectively. Stability and repeatability tests were conducted on the CuZn‐modified GCE. Results indicated that the electrode proved to be very stable and showed strong selectivity in the presence of interfering ions. The sensor modified with CuZn shows promising potential for monitoring trace Hg2+ levels.

In-situ deposition of gold nanoparticles on screen-printed carbon electrode for rapid determination of Hg2+ in water samples

Herein, an electrochemical sensor for Hg2+ detection using in-situ deposited gold nanoparticles modified screen-printed carbon electrode (SPCE) was developed. The gold nanoparticles and Hg were co-deposited on the electrode during the enrichment process. Scanning electron microscope (SEM) and Energy dispersive X-ray (EDX) spectrum prove the successful modification of gold nanoparticles. After modification, the active surface area of the electrode enlarged, the electron transfer ability enhanced, and the detection of Hg2+ became possible. After comprehensive optimization of experimental parameters, the proposed sensor can achieve rapid detection of trace Hg2+ in drinking water through differential pulse stripping voltammetry (DPSV). The limit of detection reaches 0.33 μg/L, the linear range is 0.5–80 μg/L. The test can be completed within 5 min. This sensor does not require extra electrode modification before detection, which can simplify experimental steps and improve detection efficiency, holding great promise for the on-site detection of Hg2+ in environmental and food samples.

In situ bismuth ion exchange plating micro-electrochemical sensor based on laser-induced graphene for trace Cd2+ and Pb2+ detection

Rapid, sensitive, and on-site detection of heavy metal ions in the environment is of great significance for protecting human health and maintaining ecological balance. This work presents a novel approach for the synthesis of nitrogen and bismuth co-doped, homogeneous porous petaloid graphene on polyimide films through ion exchange plating and laser direct writing techniques. The electrochemical sensing platform constructed by this technique exhibits excellent detection performance for trace amounts of the heavy metals lead and cadmium ions. Particularly, the mild surface ion exchange and self-metallization strategy enables in situ incorporation of bismuth elements with ultra-low material consumption. At the same time, the laser direct writing method can be utilized to create multiple electrode patterns, enhancing the sensor’s versatility. The synergistic effect between the homogeneous porous structure of graphene and the abundant bismuth and nitrogen functional groups endows the new micro-electrochemical sensor with satisfactory sensing performance for simultaneous detection of Cd2+ and Pb2+ using differential pulse stripping voltammetry. The fabricated sensor exhibits superior performance with a linear range of 1.0–100.0 μg/L, a detection limit of 0.207 μg/L and 0.410 μg/L (S/N = 3) for Cd2+ and Pb2+, respectively, and demonstrates good anti-interference capability, stability, and repeatability. When applied to detecting Cd2+ and Pb2+ in actual porcelain applique and tea samples, it demonstrates good recovery rates ranging from 95.3% to 106.3%. Consequently, this portable and sensitive micro-electrochemical sensor based on laser-induced graphene shows promising potential for application in environmental monitoring and protection.

Electroanalytical Investigation of 2‐(2‐Methylbenzyl)‐4(7)‐phenyl‐1H‐benzo[d]imidazole, a Novel Benzimidazole Derivative

AbstractElectrochemical analysis of 2‐(2‐methylbenzyl)‐4(7)‐phenyl‐1‐H‐benzo[d]imidazole (MPB), a new benzimidazole derivative with tyrosinase inhibitory effect and antioxidant activity, was performed in this study. The electro‐oxidation behavior of MPB was investigated by cyclic voltammetry (CV), differential pulse stripping voltammetry (DPSV), and square wave voltammetry (SWV) on glassy carbon electrode. The oxidation process of MPB showed an irreversible behavior. The highest peak current was obtained in 0.5 M H2SO4 containing 10 % methanol and used as the supporting electrolyte. As a result of the calibration study, two linear responses in the range of 0.06–1.00 μM and 2.00–100 μM were obtained with a detection limit of 10.4 nM by DPSV. Linearity for SWV was between 0.1 and 10.0 μM with a detection limit of 29.3 nM. Precision of the methods was obtained as relative standard deviation (RSD) and was below 2.0 %. Developed methods were applied for the recovery of MPB from spiked serum samples. Accordingly, recoveries of 100.39 % for DPSV and 100.07 % for SWV were obtained with RSD below 0.48 %. MPB was stable for at least 2 weeks as a result of retaining 97 % of the peak current when stored at +4 °C. Finally, the possible responsible group in MPB oxidation was proposed.

Nanoscale Ag2O decorated UiO-66 metal organic framework for simultaneous electrochemical sensing of heavy metals, Cd2+ and Hg2+

Herein, we come up with a new electrochemical sensing strategy for detecting heavy metal ions present in aqueous media using metal organic framework (MOF) electrode decorated with Ag2O nanoparticles (NPs). Post-synthesis modification route was followed to load the Ag2O NPs into zirconium-based MOF UiO-66 host. In the composite, the NPs were believed to act as the electric current enhancer while UiO-66 provided adsorption sites for heavy metal ions. The ITO electrodes were modified with as prepared composite for the electrochemical detection of Hg2+ and Cd2+ independently as well as simultaneously. The detection of heavy metals was performed by the modified electrodes through differential pulse stripping voltammetry (DPSV) which offered excellent selectivity and with sensitivity values up to 551 μA·μM−1·cm−2 for Cd2+ and 341.2 μA·μM−1·cm−2 for Hg2+. The limit of detection (LOD) for the respective cases, were estimated to be 0.008 μM and 0.003 μM. Technical viability of this approach can be further extended to real sample analysis in soil, river basin, waste land and even ground water for simultaneous detection of heavy metal ions as and when desired.

A novel sensor based on Ti3C2 MXene/Co3O4/carbon nanofibers composite for the sensitive detection of 4-aminophenol

A novel, sensitive Ti3C2 MXene/Co3O4/carbon nanofibers (Ti3C2 MXene/Co3O4/CNFs) composite was synthesized via a HF exfoliating Ti3AlC2 strategy, followed by doping Co3O4 and Ti3C2 MXene into the CNFs via a combination electrospinning and thermal annealing process. Ti3C2 MXene/Co3O4/CNFs composite exhibits higher catalytic effect, conductivity, chemical stability, and electrochemical performance than Co3O4 and Ti3C2 MXene in electrochemical impedance, differential pulse stripping voltammetry, chronocoulometry, and cyclic voltammetry tests. This Ti3C2 MXene/Co3O4/CNFs hybrid modified electrode provides fast analysis of 4-aminophenol (4-AP) with ultrahigh sensitivity, enhanced reproducibility and strong anti-interference capability. Furthermore, the level of 4-AP was quantified by this electrode with a wide linear range from 0.5 to 150 μM (R2 > 0.99) and a low detection limit about 0.018 μM was achieved. Finally, the fabricated electrode was used for fast and sensitive analysis of 4-AP spiked in tap water and blood serum samples. This work presents the new Ti3C2 MXene/Co3O4/CNFs electrode provides a platform for 4-AP monitoring and has the advantages of high selectivity, accuracy, simplicity, and rapid analysis.

Nano solid phase micro membrane tip and electrochemical methods for vanillin analysis in chocolate samples

A polymer-based nanosensor and electrochemical methods were developed for the quantitative analysis of vanillin. The sample preparation was done using nano solid phase micro membrane tip extraction (NSPMMTE). A novel poly(phenylalanine)/TiO2/CPE sensor was built as the working electrode for the first time for the analysis of the vanillin substance. The electrochemical behavior and analytical performance of vanillin were examined in detail by cyclic voltammetry (CV) and differential pulse stripping voltammetry (DPSV) techniques via the oxidation process. The optimized modules of the DPSV technique that affected the vanillin peak current and peak potential were pH, pulse amplitude, step potential, and deposition time. The electroactive surface areas of bare CPE, TiO2/CPE, and poly(phenylalanine)/TiO2/CPE electrodes were found to be 0.135 cm2, 0.155 cm2, and 0.221 cm2, respectively. The limit of detection (LOD) was 32.6 μg/L in the 0.25–15.0 mg/L working range at pH 7.0. The selectivity of the proposed DPSV method for the determination of vanillin on the modified electrode was investigated in the presence of various organic and inorganic substances, and the determination of vanillin with high recovery was achieved with less than 5% relative error. The analytical application was applied in chocolate samples and the DPSV method was found highly efficient, reproducible, and selective.

Highly Sensitive Electrochemical Determination of Luteolin Using Self-Assembled Titanium Carbide/Single-Walled Carbon Nanohorns (SWCNHs) and Differential Pulsed Stripping Voltammetry (DPV)

A novel electrochemical sensor based upon a Ti3C2/single-walled carbon nanohorn (SWCNH) composite was constructed using self-assembly for the determination of luteolin. The doping of SWCNHs avoids the restacking of Ti3C2 nanosheets, thus significantly improving the electrochemical properties of Ti3C2/SWCNHs. The Ti3C2/SWCNH nanocomposite was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The performance of the sensor was investigated by differential pulse stripping voltammetry (DPV). The Ti3C2/SWCNH-modified glassy carbon electrode exhibits enhanced electrocatalytic activity for luteolin. The composite electrode demonstrates excellent conductivity and high catalysis due to the synergistic properties of Ti3C2 with SWCNHs, which provides high selectivity, good reproducibility, and a low detection limit. Under the optimal conditions, the peak current of the sensor increases linearly with the luteolin concentration from 0.5 to 20 μM, with a detection limit of 0.0086 μM. The sensor was employed for the determination of luteolin in chrysanthemum tea with recoveries between 101.6% and 104.9%. Therefore, the electrochemical sensor based upon the Ti3C2/SWCNH composite is expected to have applications in food and pharmaceutical analysis.

A facile electrochemical sensor based on amino-functionalized magnetic nanoparticles for simultaneous detection of lead and mercuric ions

The development of a facile analytical way for detecting toxic heavy metal ions is highly desirable due to their serious toxicity to human health. In this work, amino-functionalized magnetic nanoparticles (Fe3O4@SiO2-NH2) were prepared by hydrothermal and sol-gel method for electrochemical detection of lead ions (Pb2+) and mercuric ions (Hg2+). All prepared materials were characterized by four kinds of technologies. The proposed sensor was fabricated by the compound of Fe3O4@SiO2-NH2 with metal ions added to the working electrode surface. Pb2+ and Hg2+ could be easily absorbed by Fe3O4@SiO2-NH2 through coordination, and differential pulse stripping voltammetry was applied to detect Pb2+ and Hg2+ directly. Several parameters, such as deposition potential, deposition time, volume, and incubation time, were optimized to obtain better sensitivity for the electrochemical determination of Pb2+ and Hg2+. Under optimal conditions, Pb2+ and Hg2+ were detected simultaneously by the developed electrochemical sensor with detection limits of 6.06 and 9.09 nmol/L, respectively. The recoveries of Pb2+ and Hg2+ in milk ranged from 95.1% to 114%. Hence, the developed electrochemical sensor presented great potential for detecting Pb2+ and Hg2+ in milk.

A Planar Disk Electrode Chip Based on MWCNT/CS/Pb2+ Ionophore IV Nanomaterial Membrane for Trace Level Pb2+ Detection.

Unlike conventional lead ion (Pb2+) detecting methods, electrochemical methods have the attractive advantages of rapid response, good portability and high sensitivity. In this paper, a planar disk electrode modified by multiwalled carbon nanotube (MWCNTs)/chitosan (CS)/lead (Pb2+) ionophore IV nanomaterial and its matched system are proposed. This system presented a good linear relationship between the concentration of Pb2+ ions and the peak current in differential pulse stripping voltammetry (DPSV), under optimized conditions of -0.8 V deposition potential, 5.5 pH value, 240 s deposition time, performed sensitive detection of Pb2+ within sensitivity of 1.811 μA · μg-1 and detection limit of 0.08 μg · L-1. Meanwhile, the results of the system in detecting lead ions in real seawater samples are highly similar to that of inductively coupled plasma emission spectrometer (ICP-MS), which proved a practicability for the system in detection of trace-level Pb2+.

Voltammetric Measurement of Antioxidant Activity by Prevention of Cu(II)-Induced Oxidative Damage on DNA Bases Using a Modified Electrode.

The protective effect of antioxidants using electrochemical techniques can be evaluated by examining the oxidative changes in deoxyribonucleic acid (DNA) nucleobases. In this study, a gold nanoparticle (AuNP)-decorated and multiwalled carbon nanotube (MWCNT)-Nafion-modified glassy carbon electrode (GCE/AuNP/MWCNT-Nafion) was developed to evaluate the preventive ability of antioxidants on oxidative DNA damage. A modified working electrode was prepared and characterized by cyclic voltammetry, electrochemical impedance spectroscopy, and scanning electron microscopy. The developed electrochemical method relies on two phenomena: (i) reactive species (RS) produced by dissolved oxygen in the presence of copper(II) partially damage the DNA immobilized on the electrode surface and (ii) antioxidant compounds prevent this damage by scavenging the formed RS. Changes in guanine, adenine, and cytosine oxidation signals resulting from DNA damage were measured using differential pulse stripping voltammetry before/after the interaction of dsDNA with Cu(II) while antioxidants were absent or present. The DNA protective ability of antioxidants was assessed for a number of antioxidant compounds (i.e., ascorbic acid, gallic acid, epicatechin, catechin, epicatechin gallate, glutathione, chlorogenic acid, N-acetyl cysteine, rosmarinic acid, quercetin, and rutin). Quercetin was found to show the highest antioxidant effect, and its limit of detection was determined as 1 μM. The manufactured biosensor was put in an application for the determination of antioxidant activity of herbal teas.

Comparison of carbon paste and boron-doped diamond electrodes for determination of cefepime in pharmaceutical dosage forms and biological samples

The electrochemical analysis of cefepime, a fourth-generation cephalosporin, was investigated in the direction of oxidation using a carbon paste (CP) electrode and a boron-doped diamond (BDD) electrode. The optimum paste composition was determined as 25 % mineral oil-75 % graphite powder for the CP electrode. The effects of different pHs and scan rates on the anodic peak potential and peak current of cefepime were investigated. Scan rate studies were carried out in the range of 5–200 mV s −1 (vs. Ag/AgCl). It was found that the CP electrode had an adsorption-controlled process and the BDD electrode had a diffusion-controlled process under some adsorption effect. The linear ranges of cefepime obtained for the CP electrode were determined as 0.08–10 μM (correlation coefficient; r = 0.998) for differential pulse stripping voltammetry with a detection limit of 3.73 nM and 0.4–10 μM ( r = 0.998) for square wave stripping voltammetry with a detection limit of 22.1 nM. For the BDD electrode, cefepime gave a linear range of 0.04–10 μM ( r = 0.999) for differential pulse voltammetry with a detection limit of 1.58 nM and 0.4–60 μM ( r = 0.998) for square wave voltammetry with a detection limit 11.0 nM. The precision of the proposed methods was examined by repeatability studies and presented by relative standard deviation (RSD) values below 1.76 %. Quantitative analysis of cefepime from pharmaceutical dosage forms and human serum samples using the developed methods was performed for both electrodes without any separation or filtering pretreatment. Recoveries were between 99.41 and 102.07 % for pharmaceutical dosage forms and between 99.79 and 100.50 % for human serum samples, with RSD ranging from 0.70 % to 0.98 %. • Sensitive detection of cefepime helps to increase the effectiveness of treatment. • Side effects in the treatment can be reduced by the determination of cefepime. • Oxidative determination of cefepime can be done using non-toxic solid electrodes. • Carbon paste and boron doped diamond electrodes offer advantages over each other. • Voltammetric methods enable determination from serum samples without pretreatment.

Highly sensitive detection of arsenic in groundwater by paper-based electrochemical sensor modified with earth-abundant material

The toxicity of arsenic and its hazards to the human body are well known and its timely, accurate, and cost-effective detection in water and foodstuffs and other environmental matrices is highly essential. Herein, we present a simple and easy method for the synthesis of reduced graphene oxide-ceria (rGO-CeO2) nanocomposite and its use for low-level detection of As(III) in water up to 0.93 μg/L. The presence of CeO2 on rGO surface is attributed to the enhanced electron transfer rate. The material characterization was performed with different analytical techniques including scanning electron microscopy (SEM), Raman spectroscopy, and X-ray diffraction (XRD), Infrared spectroscopy (FTIR) and Electrochemical Impedance Spectroscopy (EIS). The electrochemical behaviour of the rGO-CeO2 modified screen-printed electrodes (SPE) has been investigated by using Cyclic Voltammetry (CV) and Differential Pulse Stripping Voltammetry (DPSV). A highly linear response with a correlation coefficient of 0.9986 is achieved with a detection limit of 0.39 μg/L. Finally, the sensor was also tested with real-world groundwater samples collected from the arsenic-contaminated areas and acceptable recoveries were observed in the range of 85–95% as compared to Inductively Coupled Plasma Mass Spectrometer (ICP-MS) analysis. The electroanalytical performances of rGO-CeO2 modified SPE confirm that the as prepared sensor can be used for practical applications owing to its high sensitivity, good selectivity, robustness, low cost, high reproducibility, reusability, and ease of high scale production.

Trace Level Quantification of Lead in Michigan Lake Water Using Differential Pulse Stripping Voltammetry: A Comparative Study on the Usage of Mercury Based Electrodes Vs Solid State Gold Electrodes

The concentration of lead in fresh-water samples from the southern shoreline of Lake Michigan was analysed and compared using two different cell-stands: Controlled Growth Mercury Electrode (CGME) and voltammetry cell stand with disk type gold electrode. Clearly visible Lead (II) peaks at -395 mV and 130 mV were obtained with CGME and Au electrodes respectively using anodic stripping voltammetry (ASV) technique. Sensitivity, reproducibility, and ease of usage were differentiated for each method. While the measured lead concentration was 2.4 ppb using CGME set-up a closely similar concentration of 2.7 ppb was obtained with the gold disk electrode set-up and thereby confirms the availability of Hg-free detection of lead. The sensitivity obtained from the standard addition curve using the gold electrode was also over twice that of the CGME. The difference in background currents was attributed to the different electrode materials, bulk diffusion in electrolyte of lead ions, electrode-electrolyte interface and the relative surface areas of the electrode surface. Even after repeated polishing of gold electrodes in each run, its inherent sensitivity makes it an ideal candidate for lead determinations with no further requirement of handling the hazardous mercury wastes.

Analysis of As(III) By Anodic Stripping Voltammetry Using Disc and Screen Printed Electrodes

Determination of arsenic is possible by various methods such as spectrophotometry, atomic absorption (as arsine), atomic emission, and neutron activation analysis are common. High levels of interference and the high costs of these methods are major drawbacks. Anodic stripping voltammetry (ASV) has proved to be a sensitive, precise, and cost-effective electroanalytical technique for determining trace metals. It is routinely used for detecting Pb (II) and Cd (II). The general procedure of this technique involves depositing metal(s) at a reductive potential into Hg electrodes for a certain time and stripping them back into the solution by scanning the potential in the oxidative direction. In this work, the analysis of As (III) by ASV has been investigated using solid and Screen Printed Gold electrodes. Improved detection limits up to 10 ppb could be achieved with relative ease. A highly optimized procedure has been presented for the BASi Epsilon users that automatically provides electrochemical pretreatment in automated fashion along with the built-in differential pulse stripping voltammetry in the next step.

Electrochemical Analysis of Antipsychotic Drug Quetiapine Fumarate Using Multi‐walled Carbon Nanotube Modified Glassy Carbon Electrode

AbstractElectrochemical properties of quetiapine fumarate were examined on the anodic direction with multi‐walled carbon nanotube modified glassy carbon electrode using voltammetric methods. The ratio of multi‐walled carbon nanotube has been optimized using its various concentrations. The oxidation process was found to be irreversible, and adsorption controlled. The linear ranges were determined as 4×10−9–2×10−6 M for differential pulse stripping voltammetry and 2×10−9–2×10−6 M for square‐wave stripping voltammetry with detection limits of 8.07×10−10 and 2.71×10−10 M, respectively. The methods were validated and successfully applied for the analysis of quetiapine fumarate tablets. The groups responsible for the oxidation reaction of quetiapine fumarate were investigated with model substances.

A new voltammetric sensor for penicillin G using poly(3-methylthiophene)-citric acid modified glassy carbon electrode

In this study, an effective voltammetric sensor was developed for determination of penicillin G by electropolymerization of 3-methylthiophene with citric acid on glassy carbon electrode. Penicillin G selective electrode was prepared in water:acetonitrile (1:1) mixture containing 0.1 M sodium perchlorate as electrolyte medium with cyclic voltammetry. Then, the electrochemical behavior of penicillin G on poly(3-methylthiophene) based membrane modified electrode was investigated by cyclic voltammetry, differential pulse voltammetry and differential pulse stripping voltammetry techniques. When the penicillin G responses of the modified glassy carbon electrode were compared with the bare glassy carbon electrode responses, it was seen that the selectivity and sensitivity of the penicillin G responses of the modified electrode significantly increased. A linear calibration graph for penicillin G was obtained in the concentration range of 0.07 to 4.0 mM with the prepared electrode. The R2 value was calculated as 0.9999 from the linear calibration curve. The limit of detection and limit of quantitation of the poly(3-methylthiophene)-citric acid modified glassy carbon electrode for penicillin G were calculated as 8 μM and 28 μM, respectively. In addition, the developed electrode for the detection of PeG was applied to milk samples. The recovery efficiency of the poly(3-methylthiophene)-citric acid modified glassy carbon electrode was obtained in the range of 93 % and 103 % for three different milk samples. As a result; the modified electrode can be used for residue penicillin detection in food and biological samples.

Trace Analysis of Lead in Michigan Lake Water Using Differential Pulse Stripping Voltammetry: A Comparative Study on the Usage of Controlled Growth Mercury Electrodes Vs Solid State Gold Electrodes

The concentration of lead in fresh-water samples from the southern shoreline of Lake Michigan was analyzed and compared using two different cell-stands: Controlled Growth Mercury Electrode (CGME) and voltammetry cell stand with disk type gold electrode. Clearly visible Lead (II) peaks at -395 mV and 130 mV were obtained with CGME and Au electrodes respectively using anodic stripping voltammetry (ASV) technique [1-4]. Sensitivity, reproducibility, and ease of usage are compared and reported for each method. While the measured lead concentration was 2.4 ppb using CGME set-up a closely similar concentration of 2.7 ppb was obtained with the gold disk electrode set-up. The sensitivity obtained from the standard addition curve using the gold electrode was over twice that of the CGME. The difference in background currents was attributed to the different electrode materials, bulk diffusion in electrolyte of lead ions, electrode-electrolyte interface and the relative surface areas of the electrode surface. The main convenience associated with the CGME was the fresh electrode surface provided by each new drop, so no further electrochemical cleaning was needed. However, even after repeated polishing of gold electrodes in each run, its inherent sensitivity makes it an ideal candidate for lead determinations with no further requirement of handling the hazardous mercury wastes. Figure 1

Using Carbon Paste Electrode Modified with Ion Imprinted Polymer and MWCNT for Electrochemical Quantification of Methylmercury in Natural Water Samples.

Methylmercury (MeHg) is one of the most toxic organic mercury compounds found in the environment. The continuous exposure of human beings to this highly toxic compound may damage their nervous system. The present work reports the development and application of a novel electrochemical sensing technique for the quantification of MeHg using a modified carbon paste electrode with multi-walled carbon nanotubes (MWCNTs) combined with ion imprinted polymer, which is highly selective toward MeHg (CPE/MWCNTs/IIP-MeHg) detection. The ion imprinted polymer was synthesized using 2-mercaptobenzothiazole (MBT), acrylic acid (AA) and MeHg employed as ligand, functional monomer and template ion, respectively, and the synthesized material was characterized by Raman spectroscopy and SEM-EDX. Both the proposed and control sensors were characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The electrochemical measurements were carried out using differential pulse stripping voltammetry (DPSV), and a well-defined anodic peak observed at about +0.138 V (vs. Ag/AgCl) was recorded for MeHg. The application of the CPE/MWCNTs/IIP-MeHg sensor (which increased the charge transfer on the electrode surface) under the DPSV-based electrochemical method (which enhanced the signal intensity) made the detection technique highly sensitive and selective for the quantification of methylmercury. Under optimum experimental conditions, the proposed sensor exhibited a linear response range of 560–610 µg L−1 and a detection limit of 0.538 µg L−1, with acceptable relative error values ≤1% when applied for the detection of MeHg in real water samples.

Use of electrochemical methods to determine the effect of brewing techniques (Espresso, Turkish and Filter coffee) and roasting levels on the antioxidant capacity of coffee beverage.

Coffee is a complex mixture of chemicals, which provide biologically active compounds with various health benefits. The some biologically active compounds arising from both its natural structure and formed after processing were determined as an antioxidant capacity of coffee beverages. In this study, we aimed to determine how roasting levels of Arabica coffee seed (light, medium, dark) and three brewing techniques-decoction methods (Turkish coffee), infusion method (filter coffee) and pressure methods (Espresso)-affect total antioxidant capacity in a cup of coffee beverage by electrochemical methods such as square wave stripping voltammetry (SWSV), differential pulse stripping voltammetry (DPSV) and cyclic voltammetry (CV). Antioxidant capacities of the coffee samples in terms of the equivalent amounts were determined according to standard oxidation peaks of rutin and caffeic acid. The highest antioxidant capacity was found in espresso coffee prepared at light roasting coffee seeds as equivalent the routine and caffeic at 9.4 ± 0.2g/L and 19.7 ± 0.7g/L, respectively with SWSV on a carbon paste electrode. As a result, SWSV, DPSV and CV voltammetric methods, fast, reliable, fully validated and without any pretreatment are alternative to conventional analytical methods to evaluation antioxidant values in any food samples.