Wave Anodic Stripping Voltammetry Research Articles

Nanoporous Gold-Modified Screen-Printed Electrodes for the Simultaneous Determination of Pb2+ and Cu2+ in Water.

In this study, nanoporous gold (NPG) was deposited on a screen-printed carbon electrode (SPCE) by the dynamic hydrogen bubble template (DHBT) method to prepare an electrochemical sensor for the simultaneous determination of Pb2+ and Cu2+ by square wave anodic stripping voltammetry (SWASV). The electrodeposition potential and electrodeposition time for NPG/SPCE preparation were investigated thoroughly. Scanning electron microscopy (SEM) and energy-dispersive X-ray diffraction (EDX) analysis confirmed successful fabrication of the NPG-modified electrode. Electrochemical characterization exhibits its superior electron transfer ability compared with bare and nanogold-modified electrodes. After a comprehensive optimization, Pb2+ and Cu2+ were simultaneously determined with linear range of 1-100 μg/L for Pb2+ and 10-100 μg/L for Cu2+, respectively. The limits of detection were determined to be 0.4 μg/L and 5.4 μg/L for Pb2+ and Cu2+, respectively. This method offers a broad linear detection range, a low detection limit, and good reliability for heavy metal determination in drinking water. These results suggest that NPG/SPCE holds great promise in environmental and food applications.

Exploring the synchronized effect of MWCNT/X-manganate (X-Cu, Zn) nanocomposite for the sensitive and selective electrochemical detection of Hg(II) and Pb(II) in water.

The presence of heavy metal ions in the environment is a long-lasting problem that requires the simultaneous detection of Hg(II) and Pb(II) which is both vital and challenging. This present study examines a simplified and effective approach for synthesizing multi-walled carbon nanotube-copper manganese oxide (MWCNT-CuMn2O4) and multi-walled carbon nanotube-zinc manganese oxide (MWCNT-ZnMn2O4) nanocomposites for electrochemical detection of heavy metal ions. The nanocomposites MWCNT-CuMn2O4 and MWCNT-ZnMn2O4 exceptional electrochemical performance was evaluated using Square Wave Anodic Stripping Voltammetry (SWASV). The fabricated MWCNT-ZnMn2O4 demonstrated lower values of Electrochemical Impedance Spectroscopy (EIS) with charge transfer resistance (Rct) of approximately 34.13 Ω. Remarkably, the MWCNT-ZnMn2O4 electrochemical sensor exhibited the widest linear ranges of 0.5-10μM with sensitive detection limits (0.011μM for Hg(II) and 0.014μM for Pb(II)). Interestingly, the MWCNT-ZnMn2O4 sensor showed excellent capability in detecting Hg(II) and Pb(II) in real water samples with a recovery percentage of 94.1% and 91.3%. Overall, the MWCNT-ZnMn2O4 modified GCE showcased superior selectivity, sensitivity, reproducibility, stability, and repeatability.

In situ deposition of bismuth on pre-anodized screen-printed electrode for sensitive determination of Cd2+ in water and rice with a portable device

Electrochemical detection is favorable for the rapid and sensitive determination of heavy metal cadmium. However, the detection sensitivity needs to be further improved, and a portable, low-cost device is needed for on-site detection. Herein, an in-situ bismuth modified pre-anodized screen-printed carbon electrode (SPCE) was developed for Cd2+ determination by square wave anodic stripping voltammetry (SWASV). The in-situ bismuth modification enhances the enrichment of Cd2+, and together with pre-anodization improve the electron transfer rate of electrode, thus enhancing the detection sensitivity. The electrode modification method combines pre-anodization and in-situ bismuth deposition, which is very easy and effective. Furthermore, a self-made PSoC Stat potentiostat coupled with a stirring device was fabricated for portable and low-cost electrochemical detection. After comprehensive optimization, the developed method can reach a testing time of 3 min, a detection limit of 3.55 μg/L, a linear range of 5–100 μg/L, and a recovery rate of 91.7–107.1% in water and rice samples for Cd2+ determination. Therefore, our method holds great promise for the rapid, sensitive and on-site determination of Cd2+ in food samples.

Raw clay material-based modified carbon paste electrodes for sensitive heavy metal detection in drinking water

A new electrode based on carbon paste (CP) modified with natural clay was used for heavy metals detection. The investigation of the raw clay material (X-ray diffraction, infrared spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, thermal analysis and particle size distribution) revealed different morpho-structural properties of the natural material. The electrochemical behaviour of the modified carbon paste electrode and its ability to detect heavy metals (Zn2+, Cd2+, and Cu2+) was studied by different electrochemical techniques like cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and square wave anodic stripping voltammetry (SWASV). Both electrochemical and analytical parameters of the investigated modified electrode recommend them as stable, sensitive and reproducible sensors for individual heavy metals detection.

DFT-based designed surface functionalized carbon black for electrochemical detection of Arsenic and its experimental validation

Carbon-based materials are cost-effective and eco-friendly but have limited sensitivity for detecting heavy metals. Density Functional Theory (DFT) is employed to design materials suitable for sensing, based on their interaction with analytes. Oxidized carbon black embedded with silver nanoparticles (OCB-Ag) is designed and studied via DFT, showing promising conductivity and arsenic interaction. Experimental validation confirmed its efficacy. The OCB-Ag nanocomposite was synthesized via in-situ preparation and used as an electrode material for arsenic detection. Characterization via UV-Visible spectroscopy and X-ray diffraction confirmed successful synthesis. Electrochemical interaction with arsenite was studied using square wave anodic stripping voltammetry. The OCB-Ag platform exhibited a linear current response up to 600 ppm of As3+, with a low limit of detection (0.01 ppm) and good sensitivity (5.9 µA ppm−1). The detection limit of electrode material for As3+ lies within the threshold value set by world health organization for drinking water. The experimental results validated the concept of designing electrochemical sensing platform through DFT, and its potential for detection of As3+.

Green modified electrode for sensitive simultaneous heavy metal ions electrodetection

The detection of heavy metals (HM) is of particular importance in terms of human health and environmental protection. Electrochemical sensors are usually limited by the interference of various cations that coexist in real samples. These shortcomings are usually solved by incorporating various particles into the electrode material, which represents another source of pollution, thus being unsustainable. In this study, it was demonstrated that the new investigated natural clay (nc), used without processing, and immobilized with chitosan (Chi) matrix on the surface of a GCE in order to obtain nc-Chi/GCE modified electrode can detect, separately and simultaneously, four heavy metals (i.e. Zn2+, Cd2+, Pb2+ and Cu2+). The electrochemical behavior of the new eco-friendly modified electrode and its capacity to detect heavy metals has been investigated by electrochemical impedance spectroscopy (EIS) and square wave anodic stripping voltammetry (SWASV). The obtained electroanalytical performances (i.e., a detection limit of 43.1 nM for Zn2+, 19.1 nM for Cd2+, 4.3 nM for Pb2+ and 57.3 nM for Cu2+) corroborated with the reproducibility and stability of the modified electrode successfully recommends it as a suited device for heavy metals ions detection. The nc-Chi/GCE modified electrode was validated by measurements performed in real samples of tap water.

Bipyridine-functionalized covalent-organic-framework-modified screen-printed electrode for ultrasensitive electrochemical determination of arsenic (III)

The high toxicity of the arsenic ion (As3+) and its proliferation as a contaminant make it a significant threat to the environment as well as to human beings. Therefore, recent years have witnessed the development of novel strategies for the ultrasensitive detection of As3+. In this study, we design a covalent organic framework (COF) to modify a screen-printed electrode for the ultrasensitive electrochemical determination of As3+ via square wave anodic stripping voltammetry (SWASV). As a proof of concept, we propose a novel bipyridine-containing COF, namely BPTB, which is a screen-printed electrode modification material with a large Brunauer–Emmett–Teller (BET) surface area, high selectivity, and good anti-interference properties. The extremely selective As3+ receptors are the nitrogen-based sites, and the bipyridine-group skeleton serves as a signal transducer. The COF-modified screen-printed electrode exhibits an ultralow detection limit of 38.09 nmol/L and a wide linear response range of 0.1–80 μmol/L for As3+ determination under optimal conditions. In addition, the electrochemical properties of the COF-modified screen-printed electrode are characterized via cyclic voltammetry and electrochemical impedance spectroscopy. Furthermore, X-ray photoelectron spectroscopy (XPS) analysis confirms the existence of a strong interaction between the bipyridine sites of BPTB and As3+, which influences the stripping current intensity of the modified screen-printed electrode. In summary, this study not only highlights the application potential of COFs for the electrochemical determination of As3+ but also demonstrates a novel, convenient approach for constructing COFs by creatively introducing chelating sites for toxic metals.

A home-made nanoporous gold microsensor for lead(II) detection in seawater with high sensitivity and anti-interference properties.

A nanoporous gold microelectrode (NPG-μE) was fabricated and used for Pb(II) detection in seawater samples via square wave anodic stripping voltammetry (SWASV). The Au microelectrode (Au-μE) was fabricated by embedding a gold microfiber into a Pasteur pipette, and its surface was further modified by an anodization-electrochemical reduction (A-ECR) method, yielding the NPG-μE. The fabricated electrodes were characterized by cyclic voltammetry (CV) and field emission scanning electron microscopy (FE-SEM) for electrochemical and structural morphological investigations. SWASV results show a Pb(II) stripping peak at around -0.05 V vs. Ag/AgCl, sat. KCl, which is unusual for common Pb(II) detection (typically occurring at around -0.40 V) in anodic stripping voltammetry (ASV) analysis. The Pb(II) detection at less negative stripping potential is more beneficial. Hence, it exhibited anti-interference properties with Cd(II), which is attributed to the preferential deposition and stripping of the target analyte on the low-indexed crystal planes of the NPG structure. The calibration plot obtained by SWASV was linear in the concentration range of 0.1-10 μM, and the detection limit was found to be 57 nM (correlation coefficient of 0.9974). The NPG microsensor presented a 15-fold enhanced current response compared to Au-μE, with excellent sensitivity (27.2 μA μM-1 cm-2). The application of the NPG microsensor was examined by detecting Pb(II) in seawater samples, and a satisfactory performance was obtained.

Simultaneous quantification of Hg(II) and Pb(II) by square wave anodic stripping voltammetry using Bi/graphite electrode

In the present work, we report the synthesis and evaluation of a graphite-supported bismuth film working electrode (BiFE) in the simultaneous quantification of Hg(II) and Pb(II) at ppb levels. The BiFE was synthesized in-situ by electrodeposition in 1 M HNO3 as the supporting electrolyte at −0.5 V potential. A design of experiments and a response surface model (RSM) were developed to optimize the parameter of bismuth concentration ([Bi]) and deposition time (tdep) in the synthesis of the BiFE. The electrodeposition conditions of [Bi] = 3 mM and tdep = 10s proved to be the optimal conditions for the highest sensitivity and selectivity of the synthesized working electrode. For the quantification of Hg(II) and Pb(II), the electrochemical technique of square wave anodic stripping voltammetry (SWASV) was used by applying a deposition potential of −1 V in 1 M acetic acid buffer solution. The optimization of the factors analyzed in the design of experiments allowed the simultaneous detection of Hg(II) and Pb(II) at limiting levels of 1 ppb and 10 ppb, respectively. The calibration curves of Hg(II) and Pb(II) present an R2 of 0.988 and 0.982, respectively.

Highly sensitive and highly selective lead ion electrochemical sensor based on zn/cu-btc-nh2 bimetallic MOFs with nano-reticulated reinforcing microstructure

Identifying ultra-trace amounts of divalent lead ions (Pb2+) with high response and selectivity, continues to be a pressing issue in identifying environmental pollutants and preventing health complications. This paper details how the in-situ electrodeposited Zn/Cu-BTC-NH2 metal-organic frameworks (MOFs) boosts Pb2+ concentration for amino adsorption and facilitates ion transfer between Cu element and Pb2+. The modified coating of the glassy carbon electrode (GCE) exhibits a unique nano-reticulated structure loaded with octahedron particles, the nano-reticulated structure ensures the structural strength of the modified electrode layer, while the loaded octahedral particles enhancing electrocatalytic activity. The ultra-trace detection of Pb2+ at concentrations below μg·L−1 is accomplished by using the square wave anodic stripping voltammetry (SWASV) method, the fabricated Zn/Cu-BTC-NH2 modified electrode signifies a detection threshold of 0.021 μg L−1 and a clearly ascending linear interval prior to the rise in Pb2+ concentration to 120 μg L−1. The reported electrochemical method for the precise identification of Pb2+ in water-based solutions offers a practical approach for modifying MOFs materials and detecting heavy metal ions.

Simultaneous quantification of cadmium and lead ions using β-cyclodextrin functionalized poly(amino acid) electrochemical sensor

Heavy metals (HMs) are well-known environmental pollutants that threaten the life forms. The content of HMs in water must be constantly monitored as people are concerned about the ecosystem health, food safety and human health. In this work, a novel green composite consisting of amino acid (AA) and β-cyclodextrin (β-CD) was employed in constructing an electrochemical sensor. The fabricated sensor can be utilized for simultaneous detection of heavy metal ions (HMIs), including cadmium(II) ion (Cd2+) and lead(II) ion (Pb2+), by utilizing the distinctive potential difference between them as the detection signals. Such electrochemical sensor has several merits over the conventional detection approaches due to its portability, flexibility and simplicity. A green approach was used in the preparation of electrode in which β-CD and l-cysteine (Cys) were separately electropolymerized onto the electrode surface without linker in aqueous solution. Electrode fabrication was carried out by layer-by-layer electropolymerization, forming a thin polymeric film with abundant functional groups responsible for anchoring metal ions. Chemical and physical characterizations of modified electrodes were performed to validate the successful synthesis of polymeric film. Under optimal conditions, the developed electrode demonstrated promising simultaneous detection of Cd2+ and Pb2+ in real water samples through square wave anodic stripping voltammetry (SWASV) analysis, with results comparable to conventional methods employing inductively coupled plasma mass spectrometry (ICP-MS). The fabricated sensor revealed sensitivities of 346.26 μAμM-1cm−2 and 250.54 μAμM-1cm−2, and limit of detections (LODs) of 1.13 nM for Cd2+ and 0.53 nM for Pb2+, over the linear ranges of 3.42–700 nM and 1.60–700 nM, respectively. The developed sensor demonstrated a high selectivity, sensitivity, and stability, along with high reproducibility and low LOD over a wide linear range.

Selective Recognition of Lead and Cadmium in Potable Water Using Single Polypyrrole Nanowire Decorated with Cobalt Oxide Nanoparticles Electrode

The fabrication and characterization of a high-performance, robust, and highly sensitive sensor based on a single polypyrrole nanowire (sPpy NW) decorated with cobalt oxide nanoparticles (CoOxNPs) for the selective recognition of lead (Pb2+) and cadmium (Cd2+) in potable water are described in this paper. The electrodeposition technique was used to prepare the sPpyNW/CoOxNPs assembly, and square wave anodic stripping voltammetry (SW-ASV) was used to assess sensor performance. Optimizing sensor performance, such as deposition time, deposition potential, and supporting electrolyte, was used to assess for best sensor performance. The developed sensor exhibited excellent linearity and the linear range for the detection of individual Cd2+ and Pb2+ ions was determined to be 0.00 to 0.11 μM and 0.00 to 0.12 μM, respectively. The detection limits observed for both Pb2+ and Cd2+ sensors are 0.22 μM (R2 = 0.9520) and 0.013 μM (R2 = 0.9723), respectively. The linear range for the detection of Pb2+ and Cd2+ sensors present in the same sample was determined to be 0.00 to 0.09 μM, with a detection limit of 0.026 μM (R2 = 0.8726) and 0.013 μM (R2 = 0.9468) for Pb2+ and Cd2+, respectively. The observed results revealed that the functionalization of CoOxNPs on the surface of a sPpyNW electrode seems to be a very effective way of developing a sensitive, selective, and stable electrochemical sensor for Pb2+ and Cd2+ions.

Sensitive electrochemical detection of As(III) in soil based on CoFe2O4/AuNPs/IL nanocomposite modified electrode: Insight into the sensing mechanism of a dual electrocatalysis system

In this study, a CoFe2O4/AuNPs/IL (ionic liquids) nanocomposite modified glassy carbon electrode (GCE) (CoFe2O4/AuNPs/IL/GCE) was developed as an electrochemical sensor for the sensitive detection of As(III) in soil using square wave anodic stripping voltammetry (SWASV). Taking advantages of the catalytic systems of AuNPs, Fe(II)/Fe(III), and Co(II)/Co(III), along with the excellent adsorption capability of CoFe2O4 and the good conductivity of the IL, the proposed sensor exhibited an enhanced detection performance toward As(III). Additionally, the relevant parameters affecting the stripping peak current of As(III) were optimized, resulting in a detection limit of 0.22 ppb (S/N = 3) and a sensitivity of 0.69 µA ppb-1. Furthermore, the interference of high concentrations of nontarget ions on the peak current of As(III) was evaluated, wherein the current change rate was less than 10 %. Moreover, the developed sensor exhibited good stability and reusability with a relative standard deviation (RSD) of 1.44 % after repeating the measurements five times. The probable mechanism of the enhanced stripping signal based on a dual electrocatalysis system was investigated by X-ray photoelectron spectroscopy (XPS). Finally, the proposed CoFe2O4/AuNPs/IL/GCE sensor was successfully applied to the detection of As(III) in real soil samples, which demonstrated its good practical utility for the accurate detection of As(III) in environmental monitoring.

Highly selective and sensitive Pb2+ detection via sulfur-doped graphitic carbon nitride modified by Bi nanospheres

The present-day human race is facing a series of environmental problems due to sewage discharge, excessive use of chemicals, mineral exploitation and so on, which are closely related to the rapid development of industries. The direct consequence is that the pollution of heavy metal ions is becoming more and more serious. It is very important to develop sensitive and efficient methods for detecting heavy metal ions. In this study, the nanocomposite of sulfur-doped graphitic carbon nitride (SCN) and Bi nanospheres (BiNSs) was prepared by thermal polycondensation reaction to introduce the sulfur into carbon nitride, followed by solvothermal method to realize the decoration of BiNSs. The SCN/BiNSs nanocomposite presents a highly selective and sensitive electrochemical detection capacity for Pb2+, derived from S-Pb strong bonding interaction and Bi-Pb binary alloy formation. The low detection limit of 0.07 μM could be achieved when the current response of Pb2+ was measured in the linear range of 0.1 μM − 4.5 μM by square wave anodic stripping voltammetry. The detection of Pb2+ in actual water specimens led to a recovery rate varied from 88 to 123 %. Further, in the presence of 20-fold interfering ions such as Zn2+, Fe3+, Cd2+, Cu2+, Fe2+ and Ni2+, the SCN/BiNSs-modified electrode still possesses excellent immunity and selectivity. Meanwhile, the remarkable stability, repeatability and reproducibility of the above sensing electrode have also been demonstrated. Our primary results show that the SCN/BiNSs nanocomposite holds great potential for practical application for Pb2+ detection.

ZnO/g-C3N4 photocatalyst activated by low-pressure ultraviolet for restoring the SWASV signals: A fast pretreatment method for electrochemically detecting Cd2+ and Pb2+ in soil extracts

Soil organic matter (SOM) significantly impacts the detection accuracy of Cd2+ and Pb2+ using square wave anodic stripping voltammetry (SWASV) due to the complexation of SOM to heavy metal ions (HMIs), thereby attenuating SWASV signals. This study explored an effective pretreatment method that combined low-pressure ultraviolet (LPUV) photolysis with the ZnO/g-C3N4 photocatalyst, activating the photocatalyst to generate highly oxidative •OH radicals and O2•− radicals, which effectively disrupted this complexation, consequently restoring the electroactivity of HMIs and achieving high-fidelity SWASV signals. The parameters of the LPUV-ZnO/g-C3N4 photocatalytic system were meticulously optimized, including the pH of photolysis, duration of photolysis, g-C3N4 mass fraction, and concentration of the photocatalyst. Furthermore, the ZnO/g-C3N4 photocatalyst was thoroughly characterized, with an in-depth investigation on the synergistic interaction between ZnO and g-C3N4 and the mechanisms contributing to the restoration of SWASV signals. This synergistic interaction effectively separated charge carriers and reduced charge transfer resistance, enabling photogenerated electrons (e−) from the conduction band of g-C3N4 to be quickly transferred to the conduction band of ZnO, preventing the recombination of e− and hole (h+) and generating more radicals to disrupt complexation and restore the SWASV signals. Finally, the analysis of HMIs in real soil extracts using the proposed pretreatment method demonstrated high detection accuracy of 94.9% for Cd2+ and 99.8% for Pb2+, which validated the feasibility and effectiveness of the proposed method in environmental applications.

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.

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.

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.

A highly sensitive electrochemical sensing probe incorporating classical Berthelot's reaction and glassy carbon electrode for measuring ultra-trace levels of ammonia/ NH4+ in water

In quantifying NH3 and/or NH4+ ions, the wavelength-based spectrochemical methods involving formation of colored products of the Berthelot’s or Nessler reactions might be challenging due to auto-self absorbance, spectral overlap, and background scattering noise. Thus, the current study reports a renewable glassy carbon electrode (GCE) sensing probe combined with Berthelot’s reaction (indophenol formation) and adsorptive square - wave-anodic stripping voltammetry (Ads SWSV) at pH = 10 for detection of NH3 and/or NH4+ in water. The redox characteristics and the high surface coverage of the oxidation product of indophenol on the sensing platform suggested its use for NH3 and/or NH4+ detection. The electrochemical sensing probe for NH4+ displayed good linear relationship between 5.56 nM and 55.6 μM of NH4+ with limits of detection (LOD) and quantitation (LOQ) of 4.83 × 10-9 and 1.47 × 10-8 M, and sensing probe sensitivity of 1.27μA/μM−1 cm−2,respectively. The probe was applied for measuring NH3/NH4+in fresh and seawater samples, and the results were validated using standard ion chromatography (IC) and micro spectrophotometry assays. The assembled probe was also tolerably selective against interfering of other contaminants in a comparable potential window. Additionally, the probe has exceptional selectivity, long-term stability, and repeatability, and has good capacity to detect NH3 and/or NH4+ ions with high accuracy (recovery range = 97.14 ± 4.12–102.9 ± 4.7) in environmental water samples. The calculated Student texp and Fexp values (n = 5) were less than the tabulated ttab (2.78) and Ftab (6.39) at 95 % probability (P = 0.05, n = 5). The study offer high reliability towards NH3 and/or NH4+ detection in complex environments.

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.