Square Wave Anodic Stripping Voltammetry Research Articles

Thiol-based chemically modified carbon screen-printed electrode for simultaneous quantification of trace level Pb(II) and Cd(II).

Present work reports, the development of a novel electrochemical sensor based on a diazonium-coupling reaction and covalent attachment of the -NH2 group of cysteamine (Cyst) on screen-printed carbon electrode (SPCE), for simultaneous determination of Pb(II) and Cd(II). Initially, the in-situ generated 4-carboxyphenyl (4-CP) diazonium salt was electro-grafted to generate 4-CP/SPCE, followed by covalent bonding of terminal carboxylic group of 4-CP with -NH2 group of Cyst to give Cyst/4-CP/SPCE. The modified electrode showed an enhanced selectivity and sensitivity toward the quantification of Pb(II) and Cd(II) using square wave anodic stripping voltammetry (SWASV) without mutual interference. Under optimal experimental conditions, the newly designed sensor showed a wide linear range of 0.01µM to 0.7µM. The limit of detection (LOD) obtained was 0.882nM (0.09 ppb) and 0.65nM (0.134ppb) for Cd(II) and Pb(II), respectively. The modified SPCE exhibited good stability, selectivity, and reproducibility. Furthermore, the sensor was successfully applied for the determination of Pb(II) and Cd(II) ions in water samples which illustrated excellent recoveries in different spiked samples and the results were in line with the standard ICP-AES analysis.

Synthesis and application of bismuth nanoparticle-loaded longan porous carbon for simultaneous electrochemical determination of Pb(II) and cd(II) in seafoods

The discarded longan shell-derived porous carbon material (LPC) served as a scaffold for synthesizing bismuth nanoparticle-loaded longan porous carbon nanocomposite (BiNPs@LPC) via a hydrothermal method. Then BiNPs@LPC was utilized to modify screen-printed carbon electrodes (SPCE) for simultaneous detection of Pb(II) and Cd(II) by square wave anodic stripping voltammetry (SWASV). The material was thoroughly characterized by scanning electron microscopy, X-ray diffraction, Raman spectra, Brunauer-Emmett-Teller analysis, electrochemical impedance spectroscopy and cyclic voltammetry. BiNPs@LPC exhibited abundant porous structures, high surface area, and numerous active sites, which could improve significantly response sensitivity. Under optimal conditions, the peak currents of Pb(II) and Cd(II) exhibited favorable linear relationships with the concentration within a range of 0.1–150 μg L−1, with detection limits (S/N = 3) of 0.02 μg L−1 and 0.03 μg L−1, respectively. BiNPs@LPC/SPCE demonstrated remarkable selectivity, stability and repeatability. The proposed method was successfully applied for the detection of Pb(II) and Cd(II) in seafoods achieving satisfying recovery of 97.8%–108.3% and 96.7%–106.4%. These excellent test properties were coupled with convenience for batch preparation of the modified electrodes, highlighting its potential for practical applications in heavy metal detection of real samples.

Spectroscopic investigations of a commercial graphite screen printed electrode modified by bismuth oxide drop deposition and electrochemical reduction, for cadmium and lead ions simultaneous determination

A single use graphite screen-printed electrode (GSPE) was easily modified, to take advantage of the proven affinity of the nontoxic post-transition metal bismuth (Bi), for metal ions to be detected by Square Wave Anodic Stripping Voltammetry (SWASV). A bismuth oxide (Bi2O3) or a chitosan coated (CS@Bi2O3) nanopowder suspension was drop-casted on the graphite working electrode (WE) surface, giving rise to the precursor of a Bi-modified GSPE. After that, an electrochemical reduction was performed to obtain the Bi– or the CS@Bi–GSPE.X-ray photoelectron spectroscopy and micro-X-ray fluorescence investigations were performed on the graphitic structure pre and post modification. The bismuth oxide deposition amount was considered as critical parameter to sensor performance, indicating a minimum and maximum threshold. Under improved measurement conditions, with a 300 s pre-concentration time, the attained sensors exhibited a linearity in the range (2.0–20.0) μg L−1 in the simultaneous analysis of Pb(II) and Cd(II). The Bi–GSPE showed LODs of 1.7 and 0.5 μg L−1 for Cd(II) and Pb(II) respectively, while 1.5 μg L−1 for Cd(II) and 0.2 μg L−1 for Pb(II) were recorded by the CS@Bi–GSPE. As an applicative proof in real sample, a spike test was carried out in a ground water sample, without any preliminary sample treatment.

New methodological approach for deep penetrating geochemistry and environmental studies part 2: field determination of Co(II) /Ni(II) and Pb(II) /Zn(II) of on-site soil extractions by electrochemical stripping techniques

In the framework of deep penetrating geochemistry for mineral exploration, we report a field electroanalytical method using disposable screen-printed working electrodes able to quantify metal pathfinders in partial extracts of soil samples at the nanomolar level on site. Four metal pathfinders (Co, Ni, Pb, Zn) were chosen due to their geological interest and suitability of electrochemical detection. Square Wave Anodic Stripping Voltammetry (SW-ASV) was developed for the simultaneous detection of Pb(II) and Zn(II) providing limits of detection (LODs) of 1.2 nM and 5.3 nM respectively. A linear scan-cathodic stripping voltammetry (LS-CSV) methodology was developed for the joint detection of Co(II) and Ni(II) yielding LODs of 1.8 nM and 3.5 nM respectively. Method validation was carried out on 14 upper B-horizon soil samples during a field survey. Two wet extraction procedures were applied for soil samples - a strong extraction using HNO 3 and a weak extraction with CaCl 2 . Excellent agreement between electroanalytical methods and ICP-MS was found for Pb(II) while a small underestimation was observed for Zn(II). For Co(II) and Ni(II), the LS-CSV measurements in the HNO 3 extractions were impossible due to the change from low pH to pH to 7.15 which induces precipitation of the Fe and Al. For the CaCl 2 extractions, the Co(II)/Ni(II) results obtained by LS-CSV were in excellent agreement with ICP-MS measurements. Supplementary material: https://doi.org/10.6084/m9.figshare.c.7188747

Superior performance of N-doped carbon Nanoonions/Nafion based microfluidic electrochemical Cd2+ sensor when compared to Screen-Printed Carbon-Based electrode devices

The sensing of cadmium is important due to its highly toxic effects on various organs of humans and animals. Commonly employed are screen-printed carbon-based electrodes (SPCE) as suitable low-cost sensing platform. Microfluidic electrochemical sensor (μCS) can also be portable, highly sensitive, and low-cost but are up to now only seldom studied and applied. Here we demonstrate the superior performance of μCS over SPCE arrangements for sensing ultra-trace of Cd2+. Additionally, N-doped carbon nanoonions (N-CNOs) are introduced as sustainable non-metallic modifier and employed for both sensing arrangements. The study depicted that employing the modifier the electrochemically active surface area and the electron transfer rate in both arrangements is improved together with improve sensitivity. Both arrangements were compared using cyclic voltammetry and electrochemical impedance spectroscopy in [Fe(CN)6]3−/4−, and also square-wave anodic stripping voltammetry (SWASV) for Cd2+ sensing. The µCS arrangement clearly outperforms the SPCE arrangement in signal strength. For the final device (μCS modified with N-CNOs) a linear concentration range from 1.0 to 100 μg L−1 was achieved. The limit of detection and sensitivity resulted to 0.25 μg L−1 and 1.02 μA µg−1 L cm−2, respectively. Besides this excellent sensitivity combines with high stability, which was tested for 8 repetitive measurements with a single device resulting in high reproducibility. Additionally, this procedure was favorably employed for measurements of Cd2+ in different real samples, which demonstrated the excellent applicability of the device for the adsorption and detection of heavy metal ions.

Decentralized touch-based micronutrition sensor towards personalized nutrition: Parallel detection of sweat ascorbic acid and zinc ions

The zinc (Zn) and ascorbic acid (AA) micronutrient duo has received a considerable attention in individual’s nutrition plans, particularly after the recent pandemic, owing to its distinct beneficial impact on boosting the immune system. Accordingly, there are growing needs for frequent and decentralized measurements of the trace element and micronutrient levels towards well-balanced personalized nutrition. Leveraging natural sweat sampling from the fingertip, we describe here a disposable electrochemical sensor array, consisting of neighboring Zn ion (Zn(II)), and AA electrodes, towards parallel touch-based on-site monitoring of dynamically-changing sweat Zn(II), and AA levels, following the intake of the corresponding nutrition supplements.. A highly permeable poly (vinyl alcohol) (PVA) hydrogel, placed on the dual-electrode sensor array, served for transferring the sweat from the fingertip onto the electrode surface. Zn(II) measurements were performed on a bismuth/Nafion modified screen printed electrode (SPE) with square-wave anodic stripping voltammetry (SWASV), while the AA detection relied on recording of the open circuit potential (OCP) change, on the tetrathiafulvalene-7,7,8,8-tetracyanoquinodimethane (TTF-TCNQ) immobilized SPE. Rapid decentralized measurements of sweat Zn(II) and AA temporal profiles were carried out on the fingertip sweat of healthy subjects after consuming pill supplements in connection to the disposable strip along with hand-held electrochemical analyzer. The utility of the touch-based disposable Zn(II)/AA multisensory platform for parallel measurements of this pair of micronutrients was demonstrated towards personalized nutrition by providing real-time monitoring of the dose-response relationship. Our findings indicate that the new sweat nutrition sensing device holds considerable promise for guiding dietary interventions and enhancing personalized nutrition.

Electropolymerization of poly(phenol red) on laser-induced graphene electrode enhanced adsorption of zinc for electrochemical detection

We present a highly sensitive and selective electrode of laser-induced graphene modified with poly(phenol red) (P(PhR)@LIG) for measuring zinc nutrition in rice grains using square wave anodic stripping voltammetry (SWASV). The physicochemical properties of P(PhR)@LIG were investigated with scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), Fourier infrared spectroscopy (FT-IR) and Raman spectroscopy. The modified electrode demonstrated an amplified anodic stripping response of Zn2+ due to the electropolymerization of P(PhR), which enhanced analyte adsorption during the accumulation step of SWASV. Under optimized parameters, the developed sensor provided a linear range from 30 to 3000 μg L−1 with a detection limit of 14.5 μg L−1. The proposed electrode demonstrated good reproducibility and good anti-interference properties. The sensor detected zinc nutrition in rice grain samples with good accuracy and the results were consistent with the standard ICP-OES method.

Efficient Electrochemical Lead Detection by a Histidine-Grafted Metal-Organic Framework MOF-808 Electrode Material.

As the excessive presence of heavy metals in the environment significantly affects human health, it becomes necessary to develop efficient, selective, and sensitive methods for their detection. In this study, a novel electrochemical sensor for the detection of Pb2+ ions is described. The proposed sensor is based on a glassy carbon electrode (GCE) modified by a thin film of histidine-grafted metal-organic framework (MOF-808-His). The MOF-808 was obtained solvothermally, and then postsynthetically modified by substituting the coordinated acetate with histidinate. By electrochemistry, the MOF-808-His-modified GCE demonstrated high charge selectivity, while electrochemical impedance spectroscopy (EIS) and kinetic studies gave a lower charge transfer resistance (4196 Ω) and a better standard heterogeneous electron transfer rate constant (1.80 × 10-5 cm s-1) on MOF-808-modified GCE. These results indicated a swift and direct electron transfer rate from [Fe(CN)6]3-/4- to the electrode surface. Using square wave anodic stripping voltammetry (SWASV), the rapid and highly sensitive determination of Pb2+ was achieved on MOF-808-His-modified GCE. By optimizing the accumulation-detection parameters including pH of the detection medium, deposition time and potential, and concentration, a remarkable limit of detection (LoD, based on a signal-to-noise ratio of 3) of (1.12 × 10-10 ± 0.10 × 10-10) mol L-1 was obtained, with a sensitivity of (9.6 ± 0.1) μA L μmol-1. After interference and stability studies, the MOF-808-His-modified GCE was applied to the detection of Pb2+ in a tap water sample with a concentration of 10 μmol L-1 Pb2+.

Modified 3D Graphene for Sensing and Electrochemical Capacitor Applications.

Less defective, nitrogen-doped 3-dimensional graphene (N3DG) and defect-rich, nitrogen-doped 3-dimensional graphene (N3DG-D) were made by the thermal CVD (Chemical Vapor Deposition) process via varying the carbon precursors and synthesis temperature. These modified 3D graphene materials were compared with pristine 3-dimensional graphene (P3DG), which has fewer defects and no nitrogen in its structure. The different types of graphene obtained were characterized for morphological, structural, and compositional assessment through Scanning Electron Microscopy (SEM), Raman Spectroscopy, and X-ray Photoelectron Spectroscopy (XPS) techniques. Electrodes were fabricated, and electrochemical characterizations were conducted to evaluate the suitability of the three types of graphene for heavy metal sensing (lead) and Electric Double-Layer Capacitor (EDLC) applications. Initially, the various electrodes were treated with a mixture of 2.5 mM Ruhex (Ru (NH3)6Cl3 and 25 mM KCl to confirm that all the electrodes underwent a reversible and diffusion-controlled electrochemical process. Defect-rich graphene (N3DG-D) revealed the highest current density, followed by pristine (P3DG) and less-defect graphene (N3DG). Further, the three types of graphene were subjected to a sensing test by square wave anodic stripping voltammetry (SWASV) for lead detection. The obtained preliminary results showed that the N3DG material provided a great lead-sensing capability, detecting as little as 1 µM of lead in a water solution. The suitability of the electrodes to be employed in an Electric Double-Layer Capacitor (EDLC) was also comparatively assessed. Electrochemical characterization using 1 M sodium sulfate electrolyte was conducted through cyclic voltammetry and galvanostatic charge-discharge studies. The voltammogram and the galvanostatic charge-discharge (GCD) curves of the three types of graphene confirmed their suitability to be used as EDLC. The N3DG electrode proved superior with a gravimetric capacitance of 6.1 mF/g, followed by P3DG and N3DG, exhibiting 1.74 mF/g and 0.32 mF/g, respectively, at a current density of 2 A/g.

A novel electrochemical sensing method based on an amino-functionalized MXene for the rapid and selective detection of Hg2.

Mercury is a highly toxic element that is widely present in all types of environmental media and can accumulate in living organisms. Prolonged exposure to high levels of mercury can lead to brain damage and death, so the detection of mercury is of great importance. In this study, a cost-effective and easy-to-operate electrochemical sensing method was successfully developed based on an amino-functionalized titanium-based MXene (NH2-Ti3C2Tx) for the rapid and selective detection of Hg2+ that could have a coordination effect with the -NH2 group of NH2-Ti3C2Tx to promote the efficient accumulation of Hg2+. In this strategy, the NH2-Ti3C2Tx was first modified on glassy carbon electrodes (GCE) to fabricate the electrochemical sensor. Benefiting from the excellent electrical conductivity, abundant active sites, and strong adsorption capacity performance of the NH2-Ti3C2Tx, the NH2-Ti3C2Tx modified GCE (NH2-Ti3C2Tx/GCE) exhibited satisfactory selectivity and enhanced square wave anodic stripping voltammetry (SWASV) measurement for the rapid detection of trace amounts of Hg2+ in aqueous solutions. The electrochemical sensor was found to be capable of detecting Hg2+ with a low detection limit of 8.27 nmol L-1 and a linear range of 0.5 μmol L-1 to 50 μmol L-1. The response time of the electrochemical sensing method was 308 s. In addition, the electrochemical sensing method has good selectivity, repeatability and stability, and multiple heavy metal ions have no effect on its detection, with repeatability and stability RSDs of 1.68% and 1.43%, respectively. Furthermore, the analysis of practical water samples demonstrated that the developed method was highly practical for the actual determination of Hg2+ with recoveries in the range of 99.22-101.90%.

Increasing Sensitivity and Selectivity for Heavy Metal Sensing through Microfluidic Electrochemical Sensor

Introduction Cadmium usually exists in nature as a compound and under normal environmental conditions, its small content will not affect human health. Nevertheless, with human society's development, heavy metal ions pollution has become substantially serious, and they have serious biological toxicity. Hence, it is important to develop simple, rapid, sensitive, and portable devices for Cd2+ sensing [1].In the present work, we show how paper based microfluidic sensors improve sensitivity and limit of detection (LOD) in comparison to classical screen-printed carbon-based electrode (SPCE). Furthermore, the presented microfluidic electrochemical carbon-based sensor (μCS) do not employ critical metals and rely on graphite foil that is modified by N-doped carbon nanoonions (N-CNOs) N-CNOs. Experimental For the synthesis of N-doped CNOs the Kuznetsov method was employed [2]. The alignment of the component for μCS device is sketched below. After providing the analyte solution through the sponge the electrochemical detection is carried out through accumulation of the metal at the working electrode for varying times and cathodic potentials. The final detection is carried out through square wave anodic stripping voltammetry (SWASV) of the accumulated metal. Results and discussion To realize a sensitive measurement, some experimental conditions including the optimal amount of the employed N-doped CNOs and Nafion in the nanocomposite, deposition time and potential, and the effect of pH of supporting electrolyte were studied. By increasing the deposition time ranging from 0 to 5 min, the SPCE/N-CNOs signal was increased and after that, it remains roughly constant because the WE surface is being saturated and also the amount of analyte in the droplet was reduced due to the presence of a stagnant flow. However, for μCS/N-CNOs by increasing the accumulation time ranging from 0 to 10 min the signal was increased which shows that the electrode surface is still far from being saturated (because of the live flow). A linear concentration range from 1.0 to 100.0 μg L- 1 was achieved using SWASV. Also, the LOD and sensitivity are calculated to be 0.5 μg L- 1 and 1.02 μA µM-1 cm-2, respectively. Additionally, the method was successfully employed for measurements of Cd2+ in different real samples, which demonstrated the excellent applicability of the device for the adsorption and detection of heavy metal ions. Conclusion The μCS/N-CNOs offers several core advantages over SPCE/N-CNOs in terms of cost, simplicity, analysis time, and sensitivity. These unique advantages are due to the combined microfluidic configuration, 3D electrode layout, and a unique modifier. We believe our findings would have significant implications in developing other portable, fast, and cost-effective electrochemical detection platforms, such as clinical diagnosis and security inspection.

Microelectrode Set Made of Carbon Nanotubes for the Detection of Biomolecules and Neurotransmitters

Electrode miniaturization is an alternative path for the development of sensitive electrochemical sensors. The low charging current, enhanced mass transport and their suitability to be employed in resistive mediums has made microelectrodes attractive for detection of biomolecules. Carbon nanotubes (CNTs) are unique nanomaterials with high electrical conductivity and mechanical strength. They are known for their chemical stability and the ability to assemble them into nano and microelectrodes makes them an appealing alternative electrode material compared to metals. This talk will report the fabrication of an electrochemical-set that has CNT microelectrode assemblies as working, reference, and counter electrode components and have been tested for the detection of heavy metals (Pb2+), neurotransmitters (dopamine), and other biomolecules (nicotinamide adenine dinucleotide (NADH), furosemide). Limits of detection of 0.5 nM for dopamine, 18 nM for NADH, 2 nM for Furosemide, and 0.4 ppt for Pb2+ have been achieved. Different voltammetric techniques were employed during the study: cyclic voltammetry (CV), square wave voltammetry (SWV), amperometry, and square wave anodic stripping voltammetry (SWASV). The robustness of the electrodes and the simplicity of its fabrication have been demonstrated. Furthermore, a simple method for the fabrication nanoelectrode arrays that can be employed as working electrodes will be presented. The background and key components that are considered important to achieve this performance will be reported.

Development of smartphone-controlled and machine-learning-powered integrated equipment for automated detection of bioavailable heavy metals in soils

Rapid and accurate on-site detection of crop-absorbable cadmium (Cd) and lead (Pb) in soils is important for food security and human health. The automated soil sample pretreatment method, including the ultrasonic extraction of weakly acid-soluble heavy metals, suction-filtration, and UV photolysis, was proposed to achieve the high-efficiency preparation from soil sample to extract solution. Bismuth-film-modified glass carbon electrode combined with the homemade potentiostat was fabricated to implement the square-wave anodic stripping voltammetry (SWASV) measurements of soil extracts. The peak-information-acquisition algorithm was designed to automatically obtain peak heights and widths of Zn2+, Cd2+, Pb2+, Bi3+, and Cu2+ stripping currents, and then which were used as input variables for establishing machine-learning models to enhance the detection accuracy of SWASV to Cd2+ and Pb2+ under the coexistence of multiple heavy metal ions. Eventually, the smartphone-controlled integrated-automated detection equipment was developed and successfully applied to the automatic pretreatment of soil samples and the determination of weakly acid-soluble Cd2+ and Pb2+ in real soil samples. The detection speed was 75 min/sample, and the detection results were close to the standard method (BCR-ICP-MS). This equipment can provide powerful technical support for on-site rapid and accurate determination of crop-absorbable heavy metals in soils.

Development of Microfluidic Paper-Based Analytical Devices (µPADs) for Determination of Cd2+, Pb2+, and Cu2+ Ions in Mineral Water

Microfluidic paper-based analytical devices (µPADs) have been successfully developed using dual detection: electrochemical and colorimetric systems. The µPADs have the potential to be used as Pb(II), Cd(II), and Cu(II) sensors to test the quality of water. The fabrication process uses hot embossing and screen-printing methods. The working electrode in the electrochemical zone was enhanced by the bismuth metal deposition process, while in the colorimetric zone, the gold nanoparticles modified with thioctic acid and dansylhydrazine (TA-Au-DNS) were used as a colorimetric sensor to detect Cu. The basic material of µPADs was characterized using a Fourier-transform infrared (FTIR) and a contact angle meter (CAM). In the electrochemical zone, the signals of square wave anodic stripping voltammetry (SWASV) resulted in good detection of Pb(II) and Cd(II) (from 0 to 100 ppb) with a limit of detection of 1.588 and 1.42 ppb, respectively. In the colorimetric zone, the performance of TA-Au-DNS for detecting Cu metal was obtained from readings through the red-green-blue (RGB) sensor as a miniature of µPADs reader. The LOD, LOQ, and average Vx0 (linearity values) in the detection of Cu(II) (from 58 to 100 ppb) are 8.51 ppb, 28.36 ppb, and 0.41%, respectively.

Ultrasensitive Electroanalytical Detection of Pb2+ and H2O2 Using Bi and Fe-Based Nanoparticles Embedded into Porous Carbon Xerogel-The Influence of Nanocomposite Pyrolysis Temperatures.

Multifunctional materials based on carbon xerogel (CX) with embedded bismuth (Bi) and iron (Fe) nanoparticles are tested for ultrasensitive amperometric detection of lead cation (Pb2+) and hydrogen peroxide (H2O2). The prepared CXBiFe-T nanocomposites were annealed at different pyrolysis temperatures (T, between 600 and 1050 °C) and characterized by X-ray diffraction (XRD), Raman spectroscopy, N2 adsorption, dynamic light scattering (DLS), and electron microscopies (SEM/EDX and TEM). Electrochemical impedance spectroscopy (EIS) and square wave anodic stripping voltammetry (SWV) performed at glassy carbon (GC) electrodes modified with chitosan (Chi)-CXBiFe-T evidenced that GC/Chi-CXBiFe-1050 electrodes exhibit excellent analytical behavior for Pb2+ and H2O2 amperometric detection: high sensitivity for Pb2+ (9.2·105 µA/µM) and outstanding limits of detection (97 fM, signal-to-noise ratio 3) for Pb2+, and remarkable for H2O2 (2.51 µM). The notable improvements were found to be favored by the increase in pyrolysis temperature. Multi-scale parameters such as (i) graphitization, densification of carbon support, and oxide nanoparticle reduction and purification were considered key aspects in the correlation between material properties and electrochemical response, followed by other effects such as (ii) average nanoparticle and Voronoi domain dimensions and (iii) average CXBiFe-T aggregate dimension.

(111) Facet-enhancing performance of pure octahedral Cu2O nanocrystal for the electrochemical detection of malachite green

ABSTRACT Malachite Green (MG) is a widely used triphenyl alkyl dye, which can cause serious water pollution. Therefore, it is necessary to monitor the MG residue in the environment. In this paper, octahedral cuprous oxide (o-Cu2O) nanoparticle has been synthesised for the modification of glassy carbon electrode (GCE), aiming to determine trace MG by square wave anodic stripping voltammetry (SWASV). Since the exposed (111) crystal facet of o-Cu2O contains abundant unsaturated active ‘copper’ atoms, it can not only enrich MG to the surface of GCE through strong coordination, but also amplify MG response signal due to its excellent electrocatalytic activity. Finally, the electrochemical detection of trace MG can be realized by only using the synthesised o-Cu2O as the electrode modification material. Mechanism studies reveal that the adsorption of MG onto o-Cu2O/GCE surface is controlled by an irreversible ‘two-electron/single-proton’ transfer process. Under optimal conditions, the peak current of MG shows a good linear relationship with its concentration in the range of 0.04 μmol/L − 10 μmol/L and 10 μmol/L − 100 μmol/L, and the limit of detection is 4.57 nmol/L (S/N = 3). This novel electrochemical sensor can be applied for the determination of MG residues in real aquatic products and water resources. In conclusion, this work has successfully developed a simple, economical and environmentally friendly MG analysis method, which can be realized by modifying the electrode with only one single highly active material, providing new possibilities for the efficient detection of similar poisons by electrochemical methods in a more convenient way.

Sensitive sensing of Hg(II) based on lattice B and surface F co-doped CeO2: Synergies of catalysis and adsorption brought by doping site engineering

Transition metal oxides are widely used in the detection of heavy metal ions (HMIs), and the co-doping strategy that introducing a variety of different dopant atoms to modify them can obtain a better detection performance. However, there is very little research on the co-doped transition metal oxides by non-metallic elements for electrochemical detection. Herein, boron (B) and fluorine (F) co-doped CeO2 nanomaterial (BFC) is constructed to serve as the electrochemically sensitive interface for the detection of Hg(II). B and F affect the sensitivity of CeO2 to HMIs when they were introduced at different doping sites. Through a variety of characterization, it is proved that B is successfully doped into the lattice and F is doped on the surface of the material. Through the improvement of the catalytic properties and adsorption capacity of CeO2 by different doping sites, this B and F co-doped CeO2 exhibits excellent square wave anodic stripping voltammetry (SWASV) current responses to Hg(II). Both the high sensitivity of 906.99 μA μM−1 cm−2 and the low limit of detection (LOD) of 0.006 μM are satisfactory. Besides, this BFC glassy carbon electrode (GCE) also has good anti-interference property, which has been successfully used in the detection of Hg(II) in actual water. This discovery provides a useful strategy for designing a variety of non-metallic co-doped transition metal oxides to construct trace heavy metal ion-sensitive interfaces.

Fabrication of novel electrochemical sensor based on NiO-nanoparticles for copper detection in drinking water

Nickel oxide film (NiO-nanoparticles) was successfully deposed onto the carbon graphite electrode (GrE) and used as an electrochemical sensor for the detection of trace levels of copper Cu(II) by using square wave anodic stripping voltammetry (SWASV). This cost-effective and simple sensor was developed through a two-step process. In the initial step, the electrochemical deposition of metallic nickel onto the carbon graphite electrode occurs in a 0.1 M boric acid and nickel salt solution. Subsequently, in the second step, the deposited metal undergoes anodic oxidation in a 0.1 M NaOH solution. To characterize and verify the modification process of the electrode, several electrochemical and physico-chemical techniques were employed such as OCP, EIS, SEM, XRD and XPS. In an acid medium, the modified electrode exhibited a significant improvement in electrocatalytic activity for the oxidation of Cu(II) compared to bare GrE. The effect of several parameters on the sensor response were also examined. Under optimal conditions, the sensor exhibited a linear response to Cu(II) concentrations ranging from 0.0 to 1.5 × 10−7 M with a detection limit of 3.83 × 10−9 M, quantification limit of 1.37 × 10−8 M and a high sensitivity of 226.13 μA.M−1.cm−2. Furthermore, the sensor showed a good repeatability (RSD = 1.47 %), a good stability (retain 99.5 % after 40 measurements) and a minimal interference from ionic species was observed on the SWASV signals of Cu(II). The as-prepared sensor was then applied to determine the Cu(II) in two different brands of local source water, and the results were very satisfactory by showing a recovery values between 97.5 and 103.6 %. In summary, our study presents an innovative and cost-effective electrochemical sensor utilizing a modified carbon graphite electrode for sensitive and accurate detection of copper at trace levels.

Hydrogels of PANI doped with Fe3O4 and GO for highly stable sensor for sensitive and selective determination of heavy metal ions

Heavy metal ion (HMI) pollution is threat to human health and environment. Here, a sensor for the electrochemical detection (ECD) of Pb+2 along with simultaneous detection of Cd+2, Cu+2 and Hg+2 utilizing the synergic effect of dopants like graphene-oxide (GO) and iron oxide (Fe3O4) into hydrogels of polyaniline (H-PANI/Fe-GO) displays an excellent square wave anodic stripping voltammetry (SWASV) performance towards Pb+2, with an impressive limit of detection (LOD) of 5.15 nM. The oxidative peaks were observed for simultaneous detection at −0.7306, −0.4899, −0.0092 and 0.3417 V vs. Ag/AgCl for Cd+2, Pb+2, Cu+2 and Hg+2 with good sensitivity, reproducibility and stability. Additionally, H-PANI/Fe-GO sensor is effectively employed to detect Pb+2 in real water samples.

Simultaneous electrochemical determination of cadmium(II), lead(II), and mercury(II) ions in water and food samples using N1‐hydroxy‐N1,N2‐diphenylbenzamidine and multi‐walled carbon nanotubes modified carbon paste electrode

AbstractA novel modified carbon paste electrode has been developed using a laboratory synthesized metal chelating ligand (L), N1‐hydroxy‐N1,N2‐diphenylbenzamidine (HDPBA) and multi‐walled carbon nanotubes (MWCNTs) composite (L‐MWCNTs/CPE). The developed modified electrode was applied for selective and sensitive simultaneous electrochemical determination of cadmium(II), lead(II), and mercury(II) using square wave anodic stripping voltammetry (SWASV). The accumulation of metal ions on the electrode surface was performed in 0.1 M acetate buffer solution (ABS, pH 5.0) by applying a potential of–1.10 V versus Ag/AgCl for 210 s, followed by stripping in the positive potential scan of the SWASV after a rest time of 10 s. Under the optimum experimental conditions, the linear dynamic ranges were found to be 2×10−4–2, 1×10−4–2 and 2×10−3–2 μM of cadmium(II), lead(II), and mercury(II), respectively, with the detection limits (LODs) of 2.5×10−2, 7.8×10−3 and 4.6×10−1 nM for cadmium(II), lead(II), and mercury(II), respectively. The proposed electrode exhibited high sensitivity for the determination of these metal ions with excellent reproducibility and stability. The influence of several ions on the simultaneous determination of Cd(II), Pb(II), and Hg(II) was studied, and the prepared electrode was found to be highly selective for the detection of the three metal ions. The developed electrode was effectively applied to the determination of the three metal ions in water, vegetable and tobacco samples, and the obtained results were similar to those measured with graphite furnace atomic absorption spectrometry (GFAAS).