Supporting Electrolyte Solution Research Articles

Effect of Ionic Surfactants on Kinetics and Mechanism of the Bi(III) Ion Electroreduction in the Mixed Aqueous-Organic Solutions of Supporting Electrolytes.

This work presents the results of a study on the effect of ionic surfactants: cationic hexadecyltriammonium bromide (CTAB) and anionic sodium salt of sulfonic acid (1OSASS) on the Bi(III) electroreduction process in mixed aqueous-organic supporting electrolyte solutions containing methanol. This study showed that the composition of the supporting electrolyte solution, particularly the methanol and surfactant concentrations, significantly affects the mechanism and rate of the Bi(III) ion electroreduction. Analysis of the influence of the indicated factors on the mechanisms and kinetics of metal ion electroreduction can contribute not only to the optimization of industrial electrochemical processes but also to the development of innovative technological solutions, such as advanced electrochemical materials and novel sensors. In these experiments, an innovative electrode made of cyclic renewable liquid silver amalgam (R-AgLAFE) was used as a working electrode, which stands out among classic mercury electrodes (HMDE type) due to the significant reduction in mercury consumption while maintaining similar performance.

Chronoamperometric flow-cell designed to be unaffected by air bubbles

In this paper, we present a new design for a chronoamperometric flow cell in which air bubbles do not interfere with the control of potential between the working and reference electrodes. The flow-through dual-detection cell consists of two independent parts: an upper compartment containing a quiescent supporting electrolyte solution and a channel that operates under hydrodynamically controlled conditions. In this system, the working and counter electrodes can be placed directly in contact with both compartments, whereas the reference electrode can be assembled to be either isolated or in contact with the flowing stream channel. The design ensures that the potential applied to the working electrode (controlled in the upper compartment) is similar to the potential applied in the flowing channel. The performance of the proposed flow cell in generating accurate results, even in the presence of air bubbles, was evaluated through successive air-analyte-air injections. In both series where the analyte was introduced, suitable reproducibility was achieved. The robustness of the design was definitively proven by performing a series of measurements in analytical applications for the determination of hydrogen peroxide in antiseptic samples, yielding very satisfactory results.

NiCu-exchanged hierarchical Y and ZSM5 zeolites for the electrochemical oxidation of glycerol

Two hierarchical Y and ZSM5 zeolites were prepared with a surfactant-mediated desilication method. Both the conventional and hierarchical forms were used to prepare NiCu-zeolites via the ion-exchange method. All samples were characterised using different techniques. For the hierarchical materials, N2 physisorption and TEM analyses confirmed the appearance of mesoporosity. Transition metal-containing zeolites were used as novel electrocatalysts for the glycerol electrochemical oxidation reaction (GEOR) in the form of modified electrodes. Cyclic voltammetry was used to investigate the surface properties of the modified electrodes and their activity toward GEOR at different pH provided by different supporting electrolyte solutions, indicating alkaline conditions as the most promising ones. The hierarchical forms showed a remarkable higher activity compared to the conventional ones, together with appreciable yields towards partially oxidized products of industrial interest. Noteworthy, a stable current higher than 10 mA was generated, which is interesting to produce H2 by coupling GEOR and hydrogen evolution reaction.

Sensitive Determination of Alkali Metals by Liquid Anode Glow Discharge-Atomic Emission Spectrometry (LAGD-AES)

Liquid anode glow discharge-atomic emission spectrometry (LAGD-AES) was employed for the determination of alkali metals in brine and bottled drinking water samples. The results demonstrated that the optimum operating conditions are a discharge voltage of 630 V, a flow rate of 2.0 mL min−1, a supporting electrolyte solution of pH 1.7 HNO3, and a discharge gap of 0.5 mm. Alkaline-earth ions (e.g., Ca2+, Mg2+, and Sr2+) and Cr3+ interfere with the determination of alkali metals. The limits of detection (LODs) for the alkali metals, namely cesium (Cs), potassium (K), lithium (Li), sodium (Na), and rubidium (Rb) are 135, 6.21, 3.15, 7.57, and 31.1 µg L−1, respectively. The relative standard deviations are less than 5%, and the power consumption is approximately 13 W. The obtained results are in good agreement with the certified standard value for Li in the certified reference material and are consistent with the values obtained by ICP-OES and reference standards for K and Na in real samples. The concentrations of the Cs and Rb are considerably below the LAGD-AES detection limit. Consequently, they can be considered negligible. The results of the spiked water analysis are broadly consistent with the spiked values, with recoveries from 82% to 112%. LAGD-AES is an excellent technique for the sensitive determination of alkali metals due to its compact design, no requirement for inert gas, and low energy consumption.

(Digital Presentation) Development of a Low Cost Pencil Lead Electrode for Simultaneous Detection of Amoxicillin and Uric Acid

Herein, we develop a low-cost pencil graphite (PG) by amine-functionalization and employed for the first time, as an electrochemical transducer for the detection of amoxicillin (AMX). The electrochemical characterization results revealed that amination enhanced 2.17 times surface area than bare PGE. The pH of supporting electrolyte solution significantly influenced the electrochemical response of AMX oxidation. Besides, the experimental data revealed that AMX oxidation is irreversible, and diffusion-controlled process. The cyclic voltammetry (CV) and differential pulse voltammetry (DPV) technique are applied to quantitative determination of AMX. From the constructed calibration plot, a linear range from 2.5 µM to 300 µM with a detection limit (LOD) of 1.1028 µM was obtained for APGE using CV. While a wide linearity of 1µM to 325 µM and a LOD of 0.0113 µM were achieved by using DPV. The electrode was then applied for the simultaneous quantification of AMX and UA. In simultaneous detection the LOD was estimated to 0.964 µM, and 0.8876 µM for AMX and UA, respectively. The sensor substrate was tested in the presence of different potential interfering agent such as fructose, ascorbic acid, valine, sucrose, proline, histidine, glutamic acid, glycine, serine, phenylalanine, aspartic acid, creatinine, arginine, ampicillin, Na+, K+, Ca2+, Cd2+, Cl-, SO4 2-, NO3 -, Zn2+, Ba2+, and Pd2+. Furthermore, how long the modified electrode can alive was checked and a satisfactory reproducibility up to 37 weeks was found. Finally, the sensor substrate was applied for real samples as example in pharmaceutical formulation, in spiked urine, and in cow urine.

Amine-Functionalized Pencil Graphite Electrode for Simultaneous Determination of Dopamine and Uric Acid

In this study, an electrochemical transducer based on an Amine-functionalized cheap and disposable pencil graphite electrode (NPGE) is proposed for the simultaneous monitoring of Dopamine (DA) and Uric Acid (UA) in biological samples such as serum and urine. The prepared NPGE was characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). It was found that the incorporation of amine groups significantly improved catalytic activity than the bare pencil graphite electrode (BPGE). Moreover, the electrode modification parameters and effects of different analytical variables such as sweep rate, pH of the supporting electrolyte solution, and possible interfering ions or molecules in quantification were optimized using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Under optimized conditions, DA and UA oxidation currents showed linear responses over the concentration range of 1.06-160 µM for DA and 30.06-150 µM for UA. The limit of detection (LOD) for DA and UA were estimated to be 0.94 and 1.26 µM, respectively. In addition, the transducer’s sensitivity of 5.47 µA.µM-1cm-2 for DA and 1.70 µA.µM-1cm-2 for UA were calculated. Aiming to reuse the transducer, a regeneration solution is proposed which could successfully remove the adsorbed oxidized products from the surface. Finally, the developed transducer’s performance was compared with the established clinical method. Figure 1

Synthesis of pyrene and pyrrole-appended fluorescent turn-off sensor toward Cr(VI) detection: Chemical oxidative and electrochemical polymerization of carboxamide

A carboxylic amide compound containing pyrrole and pyrene groups, referred to as PP, was synthesized and characterized for its structural, optical, and electrochemical properties. Upon excitation with 320 nm light, PP displayed blue emission at 387 nm, which was found to be quenched due to chelate formation in the presence of Cr(VI). Conducted competition experiments involving chloride salts of Ag+, Al3+, Cd2+, Co2+, Cr3+, Fe3+, Hg2+, K+, Mn2+, Ni2+, Pb2+, Sn2+, and Zn2+ demonstrated the notable selectivity of compoundPP towards Cr(VI)ions. This selectivity was evidenced by a pronounced turn-off fluorescent effect, attributed to a chelation-enhanced quenching (CHEQ) mechanism by the formation of 1:2 chelation between Cr(VI) and the ligand PP. Moreover, addition of EDTA toPP– Cr(VI)chelation recovered the fluorescence offering receptorPPas a reversible sensor. The PP probe demonstrated remarkable selectivity in detection Cr(VI)ions among various metallic ions, displaying a limit of detection (LOD) value of 0.106 µM. Chemical oxidative and electropolymerization methods were employed to synthesize two distinct polymers, namely Poly(PP)-O and Poly(PP)-E, respectively. The electropolymerization of PP was carried out in 0.1 M TBAF6P serving as a supporting electrolyte solution, while oxidative polymerization was conducted in the presence of FeCl3. Mass average molecular weight of the oxidative polymerization product was 5200 Da, as determined by GPC analysis. Thermal characterization was performed via TG-DTA-DTG curves. The electropolymerization product of PP coated on the ITO surface was further characterized by SEM.

Firstly electrochemical investigetions and determination of anticoagulant drug edoxaban at single-use pencil graphite electrode: an eco-friendly and cost effective voltammetric method.

The anticoagulant drug edoxaban has a blood thinning mechanism of action. In this study, a pencil graphite electrode was electrochemically activated at + 1.4V for 60s. in a Britton-Robinson (pH 9.0) supporting electrolyte solution. A simple, fast, and sensitive electrochemical procedure was developed using cyclic voltammetry and square wave voltammetry techniques. It was observed that edoxaban gave a good oxidation signal with cyclic voltammetry technique at a potential of + 0.98V (vs. Ag/AgCl). This procedure showed a linear response in a Britton-Robinson (pH 9.0) media within the concentration range of 0.2-1.8µM and limit of detection (LOD) and the limit of quantification (LOQ) values were determined to be 0.073μM (0.133μgmL-1) and 0.243μM (0.443μgmL-1), respectively. The method developed in this study was successfully applied to drug and urine samples. The developed voltammetric method was highly selective and gave satisfactory recovery results in urine and pharmaceutical samples. The results of the voltammetric method were compared with the spectroscopic method and it was determined that the results were compatible.

A Green Voltammetric Determination of Molnupiravir Using a Disposable Screen-Printed Reduced Graphene Oxide Electrode: Application for Pharmaceutical Dosage and Biological Fluid Forms

A new green-validated and highly sensitive electrochemical method for the determination of molnupiravir (MOV) has been developed using cyclic voltammetry. The proposed analytical platform involves the use of a disposable laboratory-made screen-printed reduced graphene oxide 2.5% modified electrode (rGO-SPCE 2.5%) for the first time to measure MOV with high specificity. The surface morphology of the sensor was investigated by using a scanning electron microscope armed with an energy-dispersive X-ray probe. The fabricated sensor attained improved sensitivity when sodium dodecyl sulfate (SDS) surfactant (3 µM) was added to the supporting electrolyte solution of 0.04 M Britton–Robinson buffer at pH 2. The electrochemical activity of rGO-SPCE was examined in comparison with two different working electrodes in order to demonstrate that it was the most competitive sensor for MOV monitoring. The method was validated using differential pulse voltammetry according to ICH guidelines, resulting in good precision, accuracy, specificity, and robustness over a concentration range of 0.152–18.272 µM, with a detection limit of 0.048 µM. The stability investigation demonstrated that rGO-SPCE 2.5% can provide high-stability behavior towards the analyte throughout a six-week period under refrigeration. The fabricated rGO-SPCE 2.5% was successfully employed for the measurement of MOV in pharmaceutical capsules and human biofluids without the interference of endogenous matrix components as well as the commonly used excipient.

Determination of tetracycline residue in pork by differential pulse voltammetry using activated glassy carbon electrode

AbstractA simple and environment‐friendly electrochemical method using activated glassy carbon electrodes (aGCE) for monitoring the residues of tetracycline in pork samples was developed. A two‐step pretreatment procedure was established for activating the glassy carbon electrode surface, including mechanical polishing and electrochemical pretreatment. In the supporting electrolyte solution of 0.2 M sodium sulfate (at pH 2.5), the electrochemical response of TC was characterized by two irreversible oxidation peaks at +0.95 V and +1.05 V vs. saturated calomel electrode. The differential pulse voltammetry (DPV) current density response of aGCE for TC exhibited two distinct linear response ranges of 2.0×10‐6÷1.6×10‐5 M and 1.6×10‐5÷8.3×10‐5 M. The limit of detection and the limit of quantitative was 0.23×10‐6 M and 0.77×10‐6 M, respectively. Liquid‐liquid extraction has been applied for the determination of TC residues in pork samples sold in the market of Ho Chi Minh City, Vietnam, with the percentage recoveries of TC varying from 80.1 % to 88.0 % (n = 5). The obtained results of the introduced electrochemical method were in good agreement with the results of high‐performance liquid chromatography‐mass spectrometry (HPLC‐MS/MS).

Gradient elution of hydroxyacetophenones by supercritical fluid chromatography with electrochemical detection.

Linear gradient elution supercritical fluid chromatography with electrochemical detection was developed using hydroxyacetophenones as analytes. Separation was carried out with a diol column (4.6mm id × 250mm length, 5μm) as a stationary phase and a mixture of supercritical carbon dioxide and methanol as a mobile phase, where the ratio of carbon dioxide and methanol was changed from 99:1 (v/v) to 60:40 (v/v). For the electrochemical detection, methanol containing 1.0molL-1 ammonium acetate was used as a supporting electrolyte solution and + 1.2V was applied to the electrochemical cell. We compared the performance of the present method to isocratic elution supercritical fluid chromatography, and the repeatability, linearity, and detection capability all showed better analytical parameters in the gradient elution. As such, we found that gradient elution supercritical fluid chromatography can achieve the faster separation and save resources compared to isocratic elution. Thus, the present method may contribute to the development of green analytical methods.

A new modified carbon paste electrode using N1-hydroxy-N1,N2-diphenylbenzamidine for the square wave anodic stripping voltammetric determination of Pb(II) in environmental samples

This study presents a new method for simple, selective and sensitive electrochemical determination of lead(II) using N1-hydroxy-N1,N2-diphenylbenzamidine (HDPBA) modified carbon paste electrode. HDPBA was easily prepared in the laboratory from common chemicals. Morphological characterizations and spectroscopic analyses of the developed electrode were conducted using various analytical techniques such as electrochemical impedance spectroscopy (EIS), scanning electron microscope (SEM), Fourier transform infrared (FTIR), and ultraviolet-visible (UV–Vis) spectroscopic techniques. The electrochemical determination of Pb(II) was performed using square wave anodic stripping voltammetry (SWASV) and cyclic voltammetry (CV). The effects of several experimental parameters such as modifier composition in the carbon paste, composition and pH of supporting electrolyte solutions, accumulation time, accumulation potential, and other instrumental parameters were studied for the analytical application. Pb(II) was accumulated for 270 s on the surface of the modified electrode using 0.1 M sodium acetate (NaAc) pH 5 at −0.90 V vs Ag/AgCl, followed by electrochemical stripping with SWASV in the same solution after a resting time of 10 s. The linear range was found to be 0.0001–2.5000 μM Pb(II) with a limit of detection of 0.0094 nM which are better than most of the reported method based on 2–4 different modifiers in a single electrode. The proposed method was found to be highly sensitive and selective. In addition, the developed electrode showed good reproducibility (with RSDs of 4.3%), long-term stability, and fast response. The proposed method has been successfully applied to the determination of trace levels of Pb(II) in various environmental samples such as wastewater, vegetable, fish, and cigarette samples.

Coupling electrokinetic with a cork-based permeable reactive barrier to prevent groundwater pollution: A case study on hexavalent chromium-contaminated soil

This work proposes an eco-efficient treatment technology for the remediation of a kaolinite-based clay soil artificially contaminated with hexavalent chromium (50 mg Cr(VI) kg–1 soil), combining electrokinetics (EK) with permeable reactive barriers (PRB) composed of cork granules, the major by-product of cork stoppers production. This 100% natural and sustainable material can act as (i) an electron donor in the Cr(VI) reduction into trivalent chromium [Cr(III)], the less toxic state, and as (ii) a binder for the reduced Cr(III) on its pre-oxidized surface. The EK and Cr(VI) reduction efficiencies were assessed over 15 days as a function of the: (i) supporting electrolyte solution (demineralized water – DW, tap water, citric acid – CA, and sodium chloride – NaCl); and (ii) cork-PRB inclusion and position (near the anodic compartment, using direct current, or in the soil middle section, applying reversal polarity). Results showed that DW was the best supporting electrolyte solution, removing about 33% of total chromium (CrT) from the soil towards the anode, mainly under the Cr(VI) form, even though CA and NaCl presented higher electrical conductivity. Besides, nearly 67% Cr(VI) was reduced into less mobile Cr(III) only by soil-borne electron donor constituents, especially iron (> 6 g kg–1), which impaired the overall Cr migration due to the Cr(III) precipitation/adsorption over/onto the soil. Such reaction was boosted by CA and NaCl electrolytes, which increased H+ ions availability, reaching reduction efficiencies higher than 98%. When the cork-PRB was incorporated into the DW-driven EK process near the anode, the best position owing to the low pH, the Cr(VI) reduction and CrT removal efficiencies improved to about 97% and 42%, respectively. Furthermore, virtually no Cr(VI) migrated to the anolyte/catholyte, and less than 2% Cr(III) was found in the anodic chamber, being c.a. 40% of CrT retained in the cork-PRB as Cr(III) and c.a. 3%/55% of Cr(VI)/Cr(III) into the soil. Notwithstanding, the EK-PRB process can render polluted soil somewhat less dangerous and prevent the spreading of contamination to natural aquifers.

(Invited, Digital Presentation) La-Sr-Co Oxide Catalysts for Oxygen Evolution Reaction in Anion Exchange Membrane Water Electrolyzers: The Role of Electrode Fabrication on Performance and Durability

The low temperature water electrolysis technology is essential to allow the production of “green” hydrogen at an affordable cost. Recently, successful development and commercialization of anion exchange membranes (AEMs) with improved performance and durability has accelerated progress in low-temperature water electrolyzers (LTWEs) with AEM acting as a solid polymer electrolyte.1 Although still at an R&D stage, AEM-LTWEs are attracting a lot of interest as a promising alternative to liquid-alkaline and proton exchange membrane (PEM) devices thanks to the promise of operating with pure water feed and using inexpensive platinum group metal-free (PGM-free) electrocatalysts.2 Among different catalysts for oxygen evolution reaction (OER), La-Co perovskite oxides have been extensively investigated in liquid alkaline electrolytes, showing promising OER activity and stability.3–6 A series of La-Sr-Co oxides were recently developed by a joint research effort of Los Alamos National Laboratory and Pajarito Powder LLC, showing promising performance in an AEM-LTWE.7 In this work, we investigated the application of a LaxSr1-xCoO3-δ oxide at the AEM-LTWE anode.As first step, we prepared and tested a series of membrane electrode assemblies (MEA) using different commercial AEMs and ionomers, as well as standard commercial PGM catalysts (PtRu/C on the cathode and IrO2 on the anode). This first set of experiments served to establish a performance baseline and to validate the MEA fabrication method and testing procedure.For testing the LaxSr1-xCoO3-δ PGM-free OER catalyst, we fabricated a series of three electrodes using the same procedure but varying the ink formulation. We demonstrated how the anode catalyst ink composition is improving the AEM-LTWE performance and durability when using a PGM-free catalyst. In particular, we investigated the electrolyzer operation with pure water and with 0.1 M KOH and 1% K2CO3 aqueous electrolyte solutions feed. The electrolyzer performance was much less sensitive to the electrode composition when operated with a supporting electrolyte than when operated on pure water. In the latter case, achieving an optimum interface between the AEM, ionomer, and catalyst particles is essential to ensure good OH- ionic conductivity within the electrode. On the other hand, when a supporting electrolyte solution is used, the abundance of OH- ions within the electrode volume enables a faster ionic OH- transport, making the electrolyzer operation less sensitive to electrode optimization parameters. References H. A. Miller et al., Sustain. Energy Fuels, 4, 2114–2133 (2020).G. A. Lindquist et al., ACS Appl. Mater. Interfaces (2021).C. E. Beall, E. Fabbri, and T. J. Schmidt, ACS Catal., 11, 3094–3114 (2021).J. Suntivich, K. J. May, H. A. Gasteiger, J. B. Goodenough, and Y. Shao-horn, Science (80-. )., 334, 2010–2012 (2011) http://www.sciencemag.org/cgi/doi/10.1126/science.1212858.J. Suntivich et al., Nat. Chem., 3, 546–550 (2011) http://www.nature.com/doifinder/10.1038/nchem.1069.J. Kim, X. Chen, P. C. Shih, and H. Yang, ACS Sustain. Chem. Eng., 5, 10910–10917 (2017).H. T. Chung, 2020 DOE Annu. Merit Rev. - Proj. ID p185 (2020).

New Approach Synthesis of S, N Co‐Doped Graphenes for High‐Performance Supercapacitors

AbstractIn this study, S, N co‐doped graphene‐based electrodes were synthesized by a one‐step, environmentally friendly and low−Cost method known as Yucel's method in the solutions consisting of different concentration ratios of sulfuric and nitric acids and different cycles in the certain potential range for the first time in the literature. The prepared S, N co‐doped graphene‐based electrodes were characterized by spectroscopic, microscopic and electrochemical methods. In electrochemical characterization, cyclic voltammetry and electrochemical impedance spectroscopy were used. The supercapacitor performances were examined by cyclic charge‐discharge tests of the electrodes in the specified supporting electrolyte solution. Areal capacitance values varied from 71.48 mF.cm−2 to 893.2 mF.cm−2 at a current density of 10 mA cm−2 in the prepared electrodes.

Supercritical fluid chromatography with post-column addition of supporting electrolyte solution for electrochemical determination of tocopherol and tocotrienol isomers.

A supercritical fluid chromatography with electrochemical detection system was developed for the simultaneous determination of tocopherol and tocotrienol isomers. The supercritical fluid chromatography with electrochemical detection system was connected with an additional pump to create a flow path to add a supporting electrolyte solution. The supporting electrolyte solution was mixed with a mobile phase in a post-column fashion, enabling the independent control of the separation and detection. After optimization of the measurement conditions, vitamin E isomers and an internal standard substance (2,2,5,7,8-pentamethyl-6-hydroxychroman) were separated within 30min using a mixture of supercritical carbon dioxide and methanol (99:1, v/v) as a mobile phase and a cyanopropyl column (4.6mm inner diameter × 250mm length, 5 μm). For the electrochemical detection, methanol containing 1.0mol/L ammonium acetate was used as a supporting electrolyte solution, and the applied potential was set at +0.8 V. This analytical method showed good linearity (5-100 μg/mL) and repeatability (less than 2.5% relative standard deviation, n=6) and was applicable to the determination of tocopherol and tocotrienol isomers in nutrition supplements.

A Review on the Application of Voltammetry in the Determination of Various Substances in Fruit Juices

Voltammetry is preferred amongst other detection techniques for vitamins and antioxidants because of its selectivity, sensitivity, ease of access, and inexpensive instrumentation. This study aims to assess and evaluate existing studies revolving around the voltammetric determination of vitamins and antioxidants of fruit juices, seeing as they are a rich source of vitamins and antioxidants, to find commonalities and trends over the years. Literature studies found differential pulse voltammetry (DPV) and square wave voltammetry (SWV) to be the most utilized determination method for vitamins and antioxidants, respectively. Electrode performance was also compared between bare and modified electrodes by comparing the limit of detection and recovery rate of each sample. Bare electrodes are found to be suitable for the detection of vitamins by having a high level of detection (LOD) values, but modified electrodes seemed to display enhanced performance when compared to the bare electrode. The optimal pH value of the supporting electrolyte in vitamins is 5.0 ≤ pH ≤ 7.0, while it was found that the optimal pH value for antioxidants was 2.0 ≤ pH ≤ 6.0. Voltammetric determination is highly dependent on the combination of the method, the material used in making the electrode, and the pH of the supporting electrolyte solution.

Treatment of wastewater from adhesive-producing industries by electrocoagulation and electrochemical oxidation

Adhesive wastewater from adhesive-producing industries is a kind of refractory organic wastewater containing high chemical oxygen demand (COD) and ammonia nitrogen. In this study, the electrocoagulation and electrochemical technology were in series attempted to treat adhesive wastewater from adhesive-producing industries. The effects of operating parameters such as current density and initial pH were investigated to determine the optimum electrocoagulation parameters. The removals of COD and ammonia nitrogen achieved 81.62%, and 50.92%, respectively, under the optimum electrocoagulation conditions (current density of 5 mA/cm2, pH 3, 2 g/L Na2SO4 supporting electrolyte solution, 60 min of electrocoagulation). The effluent of electrocoagulation was subsequently treated by electrochemical oxidation. The effects of operating parameters, such as current density, initial pH, and supporting electrolyte, on the degradation of COD and ammonia nitrogen were investigated. The COD and ammonia nitrogen removal ratios were both as high as nearly 100% after electrolysis of 120 min (current density of 35 mA/cm2, pH 8.4, 2 g/L NaCl supporting electrolyte solution). The results of excitation-emission-matrix (EEM) revealed the changes of different dissolved organic matter after electrocoagulation and electrochemical oxidation treatment. The experimental results proved that the electrocoagulation combined with electrochemical oxidation methods are the potential technologies for treatment of adhesive wastewater.

A modified TCAD simulation model for a-InGaZnO based ISFETs on GaAs substrate for pH sensing applications

In this paper, an ISFET model is established and its accuracy is verified. The model can overcome the limitation of TCAD of not supporting electrolyte solution simulation. The source and drain of the model structure are doped with different types of impurities. The influence of GaAs as a substrate on the device sensitivity is also studied. Amorphous indium gallium zinc oxide (a-IGZO) material is used as a semiconductor layer to obtain a new type of ISFET with a higher detection sensitivity to the pH value. Furthermore, the addition of SiC material to the new ISFET further improves the device sensitivity. The influence of different oxide layers on the model when GaAs is used as a substrate is also studied. The results show that the new ISFET can not only break through the Nernst limit of the device sensitivity (59 mV pH−1), but also increase the sensitivity by nearly 12 times.

Electrochemical Detection of Mercaptans in Wine Using Gold Nanoparticle-Modified Carbon Electrodes

The organoleptic virtues of wine can be damaged by the presence of compounds produced during fermentation or aging, such as mercaptans. This work presents an environmentally friendly electrochemical sensor for the easy detection of mercaptans in wine samples, using glassy carbon and screen-printed carbon electrodes. The modification of the carbon working electrodes with gold nanoparticles increased the sensitivity and selectivity of the procedures, considering the strong covalent bond that forms readily between sulfur and gold atoms. Ethanethiol reduction has been shown to depend both on pH and on adsorption time since the electrode is immersed in the solution until the voltammogram is recorded. The highest current has been recorded in a supporting electrolyte solution at pH 4.2 with an adsorption time of 10 min in the case of gold nanoparticle modified glassy carbon electrodes and pH 3 and 90 s for gold nanoparticle screen-printed carbon electrodes. The developed procedures reach a reproducibility of 7.9% (n = 7), based on the slopes associated with different calibration curves registered in the concentration range from 7.7 to 36.6 μg l−1 when using gold nanoparticle modified glassy carbon electrodes and 7.2% (n = 5) in the case of gold nanoparticle modified screen-printed carbon electrodes (concentration range, from 1.6 to 10.9 μg l−1). The sensors have successfully been applied to the detection of ethanethiol, representing mercaptans, in white and red wines.