Conventional Electrochemical Methods Research Articles

Anodic oxidation of wireless niobium electrode in bipolar electrochemistry

The anodic oxidation of a wireless niobium substrate serving as a bipolar electrode (BPE) in a direct or alternating current electric field was investigated in detail via spectrophotometry, electrochemical measurement, glow discharge–optical emission spectroscopy, and direct microscopic observation. Niobium oxide was a suitable material for the experiment because it is amorphous and can be evaluated through conventional electrochemical methods. It also has a clear interference color, enabling easy optical evaluation. The effect of the BPE configuration (e.g., vertical and horizontal alignments) in the cell on the anodic oxidation area was also investigated visually using the interference color. Transmission electron microscopy observation was also performed for an accurate measurement of the thickness of the anodic film formed on the niobium BPE. Although the basic film formation behavior and film composition were consistent with those in conventional anodization, even in wireless operation, the effective voltage directly contributing to film formation was found to be lower than the applied voltage (30%–70% of the applied voltage), depending on the electrolysis conditions.

Directing the photogenerated charge flow in a photocathodic metal protection system with single‐domain ferroelectric PbTiO3 nanoplates

AbstractPhotocathodic protection (PCP) is arguably an ideal alternative technology to the conventional electrochemical cathodic protection methods for corrosion mitigation of metallic infrastructure due to its eco‐friendliness and low‐energy‐consumption, but the construction of highly‐efficient PCP systems still remains challenging, caused primarily by the lack of driving force to guide the charge flow through the whole PCP photoanodes. Here, we tackle this key issue by equipping the PCP photoanode with ferroelectric single‐domain PbTiO3 nanoplates, which can form a directional “macroscopic electric field” throughout the entire photoanode controllable by external polarization. The properly poled PCP photoanode allows the photogenerated electrons and holes to migrate in opposite directions, that is, electrons to the protected metal and holes to the photoanode/electrolyte interface, leading to largely suppressed charge annihilation and consequently a considerable boost in the overall solar energy conversion efficiency of the PCP system. The as‐fabricated photoanode can not only supply sufficient photocurrent to 304 stainless steel to initiate cathodic protection, but also shift the metal potential to the corrosion‐free range. Our findings provide a viable design strategy for future high‐performance PCP systems based on ferroelectric nanomaterials with enhanced charge flow manipulation.

Electrocatalytic Effects of Au Nanoclusters in Its Electrochemiluminescence Enhanced by Coreactant Tertiary Amines

AbstractAtomically precise metal nanoclusters are increasingly exploited in electrocatalysis such as water electrolysis and CO2 reduction. The catalytic effects are generally evaluated by conventional electrochemical methods or end‐product analysis. Herein, near infrared electrochemiluminescence (ECL) of the nanoclusters is introduced as a new signaling mechanism to complement classical voltammetric analysis for elucidating essential electrocatalytic parameters. Coreactant ECL from an aqueous soluble Au22 nanocluster (NCs) enhanced by a common pH buffer materials 4‐(2‐hydroxyethyl)‐1‐piperazineethanesulfonic acid (HEPES) and by a piperazine drug hydroxyzine (HDZ) is studied under oxidative reduction pathways. Foot of the wave analysis on voltametric features and the kinetics profiles in potential‐step experiments are studied in different nanocluster and coreactant concentrations. Benchmark parameters such as rate constants are determined under EC (Electron‐transfer‐Chemical‐reaction) mechanism as feasibility validations. Because the luminescence properties of AuNCs are sensitive to the surface ligands or adsorbents, ECL is proposed as a new signal readout for operando studies providing insights for governing reaction mechanism and kinetics during catalytic reactions. Retrospectively, mechanistic understanding of the complex multi‐step reactions during ECL generation can provide guidance for the evaluation and optimization of ECL property for better quantitative applications.

Tuning the carboxyl content of carbon quantum dots by an electrochemical exfoliation method to enhance Fenton-like reactions for contaminants removal in a wide pH range

The complexation of CQDs with Fe(III) through -COO-Fe bond in the CQDs-Fe(III)/H2O2 system can accelerate the Fe(III)/Fe(II) cycle and broaden the pH range for application. However, the yield and carboxyl content of CQDs prepared by conventional electrochemical exfoliation were limited, which hampered the application of CQDs and the enhancement of CQDs Fenton-like process. Hence, in this study, carboxyl-rich and high-yield CQDs were successfully prepared by electrochemical exfoliation of graphite rods in hydrogen peroxide (H2O2) solution. The results suggested that the yield and carboxyl content of the optimal CQDs (CQD@5) were 1.49 and 2.01 times those of CQDs prepared by the conventional electrochemical exfoliation method (CQD@0), respectively. Subsequently, the CQDs were applied in CQDs-Fe(III)/H2O2 systems for phenol degradation. Due to 1.73 times the carboxyl of CQD@ 5 complexing with Fe(III) than that of CQD@ 0, the kinetic constant and removal of the CQD@ 5-Fe(III)/H2O2 system for phenol degradation were 2.36 and 1.44 times those of the CQD@ 0-Fe(III)/H2O2 system at pH= 6, respectively. Under the same condition, Fe(III)/H2O2 and Fe(II)/H2O2 showed negligible degradation performance. Furthermore, the removals of phenol in the CQD@ 5-Fe(III)/H2O2 system were 1.08–7.77 times those of the CQD@ 0-Fe(III)/H2O2 system at pH= 4–8, respectively. Finally, the effect of Fe(III), CQDs, and H2O2 dosages on the phenol degradation, reusability, and universality of CQD@ 5-Fe(III)/H2O2 were investigated individually. In summary, this work provides a new method for tuning the CQDs yield and carboxyl content, which enhances pollutant degradation in CQDs-Fe(III)/H2O2 systems at a wide pH range.

Fluorescence-Recovered Wearable Hydrogel Patch for In Vitro Detection of Glucose Based on Rare-Earth Nanoparticles.

The physiological state of the human body can be indicated by analyzing the composition of sweat. In this research, a fluorescence-recovered wearable hydrogel patch has been designed and realized which can noninvasively monitor the glucose concentration in human sweat. Rare-earth nanoparticles (RENPs) of NaGdF4 doped with different elements (Yb, Er, and Ce) are synthesized and optimized for better luminescence in the near-infrared second (NIR-II) and visible region. In addition, RENPs are coated with CoOOH of which the absorbance has an extensive peak in the visible and NIR regions. The concentration of H2O2 in the environment can be detected by the fluorescence recovery degree of CoOOH-modified RENPs based on the fluorescence resonance energy transfer effect. For in vivo detection, the physiological state of oxidative stress at tumor sites can be visualized through its fluorescence in NIR-II with low background noise and high penetration depth. For the in vitro detection, CoOOH-modified RENP and glucose oxidase (GOx) were doped into a polyacrylamide hydrogel, and a patch that can emit green upconversion fluorescence under a 980 nm laser was prepared. Compared with the conventional electrochemical detection method, the fluorescence we presented has higher sensitivity and linear detection region to detect the glucose. This improved anti-interference sweat patch that can work in the dark environment was obtained, and the physiological state of the human body is conveniently monitored, which provides a new facile and convenient method to monitor the sweat status.

Monitoring Electrochemical Signals from Sacrificial Coatings for Pipeline Materials with Membrane-Based Sensors

Monitoring internal corrosion within pipelines is essential to the safe management of gas transportation infrastructures. Membrane-based electrochemical sensors are a promising new method of monitoring corrosion risk, as they can operate in humidified gas environments which were previously inaccessible to conventional electrochemical monitoring methods. In parallel, new sacrificial coatings and coating application methods are being explored to extend the lifetime of existing pipeline structures and minimize repair costs. Herein, we extend the use of membrane-based electrochemical sensors to examine the response of electrodes with sacrificial coatings for a series of fluids with varying extents of corrosivity applicable to natural gas pipelines. Multiple sensors with X65 steel working electrodes were coated then exposed to humidified gases with differing relative humidities (RH) (5 , 50 , and 95 %) and condensed phases with differing salt content (deionized water and 0.1 mol kg-1 NaCl solution). Three electrochemical techniques (potentiometry, impedance spectroscopy and potentiodynamic scans) were used to monitor the corrosive environment and probe the extent of coating coverage. For the conditions studied, impedance values were extremely sensitive to changes in water content through changes in the membrane resistance (from ~1 kΩ in deionize water to ~10 MΩ with 5 % RH). Polarization resistances (Rp) consistently decreased with increasing corrosivity (~10 kΩ in deionized water to 1 MΩ with 5 % RH). Of the methods used, open circuit potential (OCP) values were the most sensitive to the presence of a sacrificial coating. Fully coated samples typically had OCP values 0.2 V lower than uncoated and partially coated samples in humidified environments, suggesting this sensing method made provide a means to monitor coating lifetime.

On-chip electrocatalytic microdevices.

On-chip electrocatalytic microdevices (OCEMs) are an emerging electrochemical platform specialized for investigating nanocatalysts at the microscopic level. The OCEM platform allows high-precision electrochemical measurements at the individual nanomaterial level and, more importantly, offers unique perspectives inaccessible with conventional electrochemical methods. This protocol describes the critical concepts, experimental standardization, operational principles and data analysis of OCEMs. Specifically, standard protocols for the measurement of the electrocatalytic hydrogen evolution reaction of individual 2D nanosheets are introduced with data validation, interpretation and benchmarking. A series of factors (e.g., the exposed area of material, the choice of passivation layer and current leakage) that could have effects on the accuracy and reliability of measurement are discussed. In addition, as an example of the high adaptability of OCEMs, the protocol for in situ electrical transport measurement is detailed. We believe that this protocol will promote the general adoption of the OCEM platform and inspire further development in the near future. This protocol requires essential knowledge in chemical synthesis, device fabrication and electrochemistry.

The development of a gas-feeding CO2 fuel cell using direct hydrazine oxidation reaction

Electrochemical carbon dioxide (CO2) reduction has attracted attention for converting CO2 into value-added products at room temperature. Conventional electrochemical CO2 reduction methods require external energy because of the high overpotential of the oxygen evolution reaction (OER). To overcome the limitation of the OER, we propose a gaseous CO2 reduction system that uses an aqueous hydrazine (N2H4) oxidation reaction. In this study, the N2H4-CO2 fuel cell is proposed for the simultaneous generation of electricity with CO2 conversion. During the operation of the aqueous N2H4/gas-feeding CO2 fuel cell, a power density of 20.31 mW/cm2 was obtained and 49.20 % of CO2 was converted to CO at the Ag cathode. We also evaluated the correlation between the flow rate of the anolyte and the hydrophobicity of the Ag cathode in terms of cell performance.

Optimized geometric structure of Zn-BTC/POAP and Fe-BTC/POAP systems as electroactive materials in pseudocapacitors

In this work, Fe(II)-based metal organic framework (MOF), Zn-based MOF and hybrid poly orthoaminophenol/MOF composite were synthesized via a chemical method. Synthesized composite films have been characterized by conventional electrochemical methods and computational approach. The computational results show that both Zn-BTC and Fe-BTC interact well with 3POAP. Meanwhile, the adsorption energy of 3POAP on Fe-BTC is 2.03 eV higher than that of Zn-BTC. Therefore, it can be mentioned that the high adsorption energy of conductive polymer POAP on Fe-BTC compared to Zn-BTC has led to its better performance as the electrode of supercapacitors and these findings confirm the electrochemical results. It was found that in Zn-BTC/3POAP and Fe-BTC/3POAP systems the charge is transferred from the 3POAP to the MOFs. The results showed that the charge transfer from 3POAP to Fe-BTC is more than Zn-BTC which is a confirmation of the higher adsorption of 3POAP on Fe-BTC. The 3D periodic structure of Fe-BTC is generated by binuclear Fe(II) paddlewheel building units (PBUs) connected via the 1,3,5-benzenetricarboxylate organic ligands. Also, the adsorption energy of 3POAP on Fe2(PhCOO)4 and Zn2(PhCOO)4 was calculated using supermolecular approach. These results are compatible with the adsorption energy obtained from the periodic calculations, so that the adsorption of Fe structure was more than that of Zn. The Fe2(PhCOO)4…3POAP structure has the lowest band gap energy, so it can be concluded that the better adsorption of 3POAP on Fe-BTC not only results in higher adsorption energy, but also better electrical conductivity than the Zn-BTC. Computational results are in agreement with electrochemical results.

Corrosion Performance of Ti6Al7Nb Alloy in Simulated Body Fluid for Implant Application Characterized Using Macro- and Microelectrochemical Techniques

In this paper, the applicability of Ti6Al7Nb as a more biocompatible alternative for bone and dental implants than Ti6Al4V and pure titanium in terms of corrosion resistance and electrochemical inertness is investigated. The chemical inertness and corrosion resistance of the Ti6Al7Nb biomaterial were characterized by a multi-scale electrochemical approach during immersion in simulated physiological environments at 37 °C comparing its behavior to that of c.p. Ti, Ti6Al4V, and stainless steel. The establishment of a passive regime for Ti6Al7Nb results from the formation of a thin layer of metal oxide on the surface of the material which prevents the action of aggressive species in the physiological medium from direct reaction with the bulk of the alloy. Conventional electrochemical methods such as potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) provide quantified information on the surface film resistance and its stability domain that encompasses the potential range experienced in the human body; unfortunately, these methods only provide an average estimate of the exposed surface because they lack spatial resolution. Although local physiological environments of the human body are usually simulated using different artificial physiological solutions, and changes in the electrochemical response of a metallic material are observed in each case, similar corrosion resistances have been obtained for Ti6Al7Nb in Hank’s and Ringer’s solutions after one week of immersion (with a corrosion resistance of the order of MΩ cm2). Additionally, scanning electrochemical microscopy (SECM) provides in situ chemical images of reactive metal and passive dielectric surfaces to assess localized corrosion phenomena. In this way, it was observed that Ti6Al7Nb exhibits a high corrosion resistance consistent with a fairly stable passive regime that prevents the electron transfer reactions necessary to sustain the metal dissolution of the bulk biomaterial. Our results support the proposition of this alloy as an efficient alternative to Ti6Al4V for biomaterial applications.

Operando small‐angle x‐ray scattering for battery research

AbstractWith the rapid growth of secondary batteries used in various industries, methods for analyzing battery elements such as electrodes and electrolytes have also improved. In addition, as the utility of nano‐scaled electrode materials have attracted greater attention, it has become increasingly clear that conventional electrochemical analytic methods have limitations. Consequently, electron microscopy and even synchrotron x‐ray radiation techniques have been adopted and are now widely used. Among several advanced analytical techniques, synchrotron radiation‐based operando small‐angle x‐ray scattering (SAXS) enables real‐time analysis of changes in the ordering of nanostructures and in the electron densities of electrodes and solid electrolytes during electrochemical reactions. In this review, the principle and applications of operando SAXS are briefly introduced, to help in understanding the complex nanostructural behaviors of battery components used in secondary batteries, and furthermore, it is hoped to contribute to innovative materials design.

Preparation and mechanism analysis of nano-Mg(OH)2 by electroconversion of MgCl2

The preparation and application of porous laminated nanomaterials have been widely concerned because of their large surface area, abundant active sites, and enhanced mass transmission and diffusion. This study used a simple and economical method to synthesize metal hydroxide by the cationic membrane electroconversion synthesis method (CMESM). However, CMESM is not a typical metal electrodeposition process, it is a pseudoelectrolysis process, there is no gain or loss of metal electrons, but metal deposits will be generated. Therefore, its mechanism cannot be studied by conventional electrochemical methods. Thus, we change the research ideas, take the cheap and easy-to-obtain MgCl2·6H2O as raw material, use the chemical precipitation method and the cation membrane permeation method as comparative experiments, study the effect of different current densities on the product, and discuss the mechanism of CMESM. The results show that the Mg(OH)2 nanosheets are electric field induced and assembled into a three-dimensional porous layered petal structure with a large specific surface area and aperture. The metal hydroxides with low cost and high purity can be prepared by cationic membrane electrolytic synthesis.

Preparation of Polycarbazole Nanofibers Using an Electric Field and the Investigation of Its Electrical Conductivity

In conventional chemical and electrochemical oxidation methods, it is very difficult to control the active centers, and the average prepared polymers are short and wide. The use of an electric field creates the most stable intermediate form of active centers, as well as permitting a longer half-life. Therefore, this increases the physical resistance and electrical conductivity of the polymer. In this paper, polycarbazole nanofibers were prepared using an electric field, reporting on its influences on the polymerization of carbazole. Therefore, its electrical conductivity and some physical properties were investigated. We observed the nanofibers’ shape, increasing electrical conductivity, thermal resistance and a higher molecular weight with the synthesized polycarbazole under an electric field compared to the polymer synthesized in the same conditions in the absence of an electric field. First, we chemically synthesized polycarbazole at different times. Additionally, to find the optimizing conditions, we changed certain parameters, such as the ratio of the obtained molar of initiator to monomer, the oxidant, initiator and solvent, separately, and compared the obtained results. Then, we repeated this reaction in the best conditions and under different electric fields in constant time, allowing us to characterize the shape, mass and conductivity. Next, the polymerization was carried out at the best electric field in different times. Finally, the best time and amount of electric field for polymerization were determined. The electrical conductivity of polycarbazoles was studied with the four-probe method. The conductivity of the films oxidized using FeCl3 (dry) and protonated with p-toluenesulfonic acid (PTSA) at 3 h was higher than 8.9 × 10−4 S/cm under a 12 KV/m electric field. Additionally, the results showed an enhanced thermal resistance to ageing.

Incorporating quartz crystal microbalance with chronoamperometry to enhance manganese detection stability in drinking water

Mn was previously considered a mere esthetic issue in drinking water; however, excessive Mn exposure has been linked to negative effects on children's neurological development. Current conventional laboratory techniques are constrained in their ability to provide real-time measurement of Mn release events, due to expensive bench-sized instrumentation and lengthy turn-around times. Herein, we developed and investigated the working principle and application of a portable and rapid electrochemical method to detect Mn2+ in drinking water. The method employs quartz crystal microbalance (QCM) integrated with chronoamperometry (CA) to measure charge transfer and weight change during Mn2+ oxidation. The deposition of MnO2 is characterized by electrochemical methods, SEM, EDS and QCM. The CA-QCM calibration curves were determined in Milli-Q water and a real drinking water sample with a detection limit of 12.9 µM in drinking water sample. Additionally, an effective cleaning procedure was developed to regenerate the sensor after use. The CA-QCM technique demonstrated higher reproducibility and interference resistance than other conventional electrochemical methods in the presence of common drinking water components, as well as an excellent recovery rate (101.7%) in a real drinking water sample.

Advancing Electrochemical Screening of Neurotransmitters Using a Customizable Machine Learning-Based Multimodal System

High throughput and automated optical readout systems are already an industry standard in life sciences for screening several reactions at once. However, such high throughput systems are in an inceptive stage for studying electrochemical interactions. This limitation, for example, slows down the process of establishing property-performance relation of novel materials for biochemical sensing. Herein, building on our prior work, we fabricate a low-cost customizable platform to screen response of acetic acid-treated laser induced graphene to identify and quantify four biogenic amine neurotransmitters in artificial saliva, namely dopamine, serotonin, epinephrine, and norepinephrine, which due to similar molecular structures are difficult to differentiate using conventional electrochemical methods. Our analytical platform analyzes multiple sensors at once and processes the data using machine learning to rapidly screen the material–molecule interactions by combining several electrochemical spectral components (fingerprints). Combining multiple spectral features, both within one electrochemical module and across different modules, significantly improves the sensor performance and allows identification of the biomolecules using the same material system. The proposed automated electroanalytical system can be used to screen material–molecule interactions as well as high throughput point-of-care testing for rapid, multiplexed, and low-cost molecular detection.

Sensitive and selective impedimetric determination of TNT using RSM-CCD optimization

Detection of trace amounts of 2,4,6-Trinitrotoluene as a widely used explosive in the military and industrial sectors is of vital importance due to security and environmental concerns. The sensitive and selective measurement characteristics of the compound still is considered a challenge for analytical chemists. Unlike conventional optical and electrochemical methods, the electrochemical impedance spectroscopy technique (EIS), has a very high sensitivity, but it faces a significant challenge in that it requires complex and expensive steps to modify the electrode surface with selective agents. We reported the design and construction of an inexpensive, simple, sensitive, and selective impedimetric electrochemical TNT sensor based on the formation of a Meisenheimer complex between magnetic multiwalled carbon nanotubes modified with aminopropyl triethoxysilane (MMWCNTs @ APTES) and TNT. The formation of the mentioned charge transfer complex at the electrode-solution interface blocks the electrode surface and disrupts the charge transfer in [(Fe (CN) 6)] 3−/4- redox probe system. Charge transfer resistance changes (ΔRCT) were used as an analytical response that corresponded to TNT concentration. To investigate the influence of effective parameters on the electrode response, such as pH, contact time, and modifier percentage, the response surface methodology based on central composite design (RSM-CCD) was used. The calibration curve was achieved in the range of 1–500 nM with a detection limit of 0.15 nM under optimal conditions, which included pH of 8.29, contact time of 479 s, and modifier percentage of 12.38% (w/w). The selectivity of the constructed electrode towards several nitroaromatic species was investigated, and no significant interference was found. Finally, the proposed sensor was able to successfully measure TNT in various water samples with satisfactory recovery percentages.

Passive layer investigation on tin and tin solder alloys

AbstractThe present work investigates the passive film formation and properties on tin and tin solder alloys in weakly acidic nitrate solution by using conventional electrochemical methods as well as electrochemical impedance spectroscopy and Mott–Schottky analysis. It is observed that the influence of the main alloying elements, antimony and copper, positively influences the formation and properties of native oxide films on the respective alloys. If the oxide film is anodically formed, the process can be interpreted as a high‐field mechanism. In this case, antimony, as well as copper, increases the electron conductivity of the anodic formed layers analogous to the transparent conducting oxide layers (e.g., ATO layers).

MD and DFT computational simulations of Caffeoylquinic derivatives as a bio-corrosion inhibitor from quince extract with experimental investigation of corrosion protection on mild steel in 1M H2SO4

The inhibition performance of Quince Extract (Q.E.) at concentrations of 0–1200 ppm on the low carbon steel corrosion in the corrosive media of sulfuric acid (H2SO4) was evaluated by using conventional electrochemical methods (potentiodynamic polarization and impedance spectroscopy). Based on the results, Q.E. displays a mixed-type behavior as an inhibitor. The inhibition efficiency of Q.E. increased with its concentration in the acid solution .The highest performance was observed at the maximum tested concentration (1200 ppm). Using polarization and EIS results, the highest inhibition efficiency of Q.E. was estimated to be 94.5% and 90.7%, respectively. Structural units and functional groups of Q.E. were detected by Fourier transform infrared spectroscopy. This spectroscopy confirmed that the extract contains nitrogen atoms, oxygen atoms, and aromatic rings that are known to have corrosion inhibition effects. The morphology of the specimen's surface after exposure to H2SO4 with and without Q.E. was examined by SEM and AFM techniques. This examination showed substantially lower surface degradation in the low-carbon steel specimens exposed to the acid in the presence of Q.E. The Langmuir isotherm approach was utilized to explain the adsorption of Q.E. onto the low-carbon steel surface. The Gibbs free energy calculated based on this approach (-21.05 kJ-mol−1) confirmed that the Q.E. adsorption onto the steel surface is supposed to involve more physisorption. In addition to the results of molecular simulation and computational chemistry, such as molecular dynamics simulation (MD), density functional theory (DFT), and Monte Carlo for all Caffeoylquinic acid derivatives confirmed that amino acid of quince extracts in an acidic medium (1 M sulfuric acid) adsorbed on compact and energetic iron surfaces mainly surfaces with miller index (110), which are inclined to corrosion and electrochemical reactions, takes place spontaneously.

Quantitative Estimation of COD Values from an Array of Metal Nanoparticle Modified Electrodes and Artificial Neural Networks

Water quality monitoring has become critical in modern societies in multiple areas and at different stages. In this regard, chemical oxygen demand (COD) has become a key index in water testing, as it readily allows the determination of its overall quality and the presence of organic contaminants. However, conventional COD determination presents several drawbacks in view of the use of toxic reagents and possible interferences. The electrochemical determination of COD can be an alternative with many advantages, especially if using an array of sensors. Herein, the use of an electronic tongue (ET) for the estimation of COD was explored. The proposed ET was formed by an array of five voltammetric electrodes modified with different metal nanoparticles. An artificial neural network (ANN) model was built based on the responses of the array towards glucose and glycine as standards. This model was then used with real and spiked water samples, and the results compared to the electrochemical calibration and the commercial COD colorimetric methods. While the COD values of the real samples were low and outside the range of the ANN model, a satisfactory prediction for the spiked samples was achieved, showing a good agreement with the reference colorimetric method, that was better than the performance of the conventional electrochemical calibration method.

Thionine-mediated electrocatalytic reduction for electrochemical detection of EDTA-Fe(III) in soy sauce.

Electrocatalytic reactions based on electron transfer mediators provide a simple and effective route for the development of convenient and sensitive electrochemical assays. Here, we report a novel electrocatalytic assay for detection of EDTA-Fe(III), which is widely used as a supplement in iron-fortified foods to reduce prevalence of iron deficiency. Unlike conventional electrochemical methods to detect Fe(III) ion, signaling mechanism of our electrocatalytic assay relies on the previously unexplored thionine-mediated electrochemical reduction of EDTA-Fe(III). This electrocatalytic detection method is sensitive for EDTA-Fe(III) detection in the linear concentration range from 10 to 750μM with a detection limit of 2.5μM. It is also specific enough and applicable to detection of EDTA-Fe(III) in real soy sauce samples with satisfactory recovery. The one-step electrocatalytic reduction for signal generation enables the direct and sensitive electrochemical detection of EDTA-Fe(III). We believe that this electrocatalytic assay can serve as a general platform for quantification of EDTA-Fe(III) in many EDTA-Fe(III)-fortified foods. And because thionine is increasingly used as a signal reporter in electrochemical DNA/aptamer sensors, the engineered electrocatalytic reaction of thionine-mediated electrochemical reduction of EDTA-Fe(III) will also provide a simple signal amplification means for the development of highly sensitive electrochemical biosensors.