Electrochemistry Of Acids Research Articles

Comparison of Electrochemical Polishing Treatments between Phosphoric Acid and a Deep Eutectic Solvent for High-Purity Copper

This study investigated and compared the acid-free electropolishing of copper with the state-of-the-art acidic electropolishing process. The acid-free medium used in this study is based on a deep eutectic solvent comprised of 2:1 ethylene glycol and choline chloride. The electrochemical study included voltammetry and chronoamperometry tests during the electropolishing process. The characterization techniques used were atomic force microscopy (AFM) and digital microscopy, and surface morphology comparisons summarized the electropolishing efficiency of phosphoric acid and acid-free deep eutectic solvent treatments for high-purity copper. Electropolishing copper with a deep eutectic solvent resulted in a mirror finish and a post-treatment surface that was 8× smoother than the original metal surface prior to electropolishing treatments with a smoothing efficiency of 91.1 ± 1.5%. This eco-friendly solution produced polished surfaces superior to those surfaces treated with industry standard acid electrochemistry treatments of 1 M H3PO4.

Electrochemical Amino Acid Sensing: A Review on Challenges and Achievements.

The rapid growth of research in electrochemistry in the last decade has resulted in a significant advancement in exploiting electrochemical strategies for assessing biological substances. Among these, amino acids are of utmost interest due to their key role in human health. Indeed, an unbalanced amino acid level is the origin of several metabolic and genetic diseases, which has led to a great need for effective and reliable evaluation methods. This review is an effort to summarize and present both challenges and achievements in electrochemical amino acid sensing from the last decade (from 2010 onwards) to show where limitations and advantages stem from. In this review, we place special emphasis on five well-known electroactive amino acids, namely cysteine, tyrosine, tryptophan, methionine and histidine. The recent research and achievements in this area and significant performance metrics of the proposed electrochemical sensors, including the limit of detection, sensitivity, stability, linear dynamic range(s) and applicability in real sample analysis, are summarized and presented in separate sections. More than 400 recent scientific studies were included in this review to portray a rich set of ideas and exemplify the capabilities of the electrochemical strategies to detect these essential biomolecules at trace and even ultra-trace levels. Finally, we discuss, in the last section, the remaining issues and the opportunities to push the boundaries of our knowledge in amino acid electrochemistry even further.

Optimizing an Electrochemical Protocol for Quantitative Analysis of Ascorbic Acid in Dietary Supplements

AbstractElectroanalytical techniques are versatile and dynamic tools used extensively in research and industrial applications; however, they are not adequately covered in the undergraduate chemistry curriculum. Herein, a fast‐scan cyclic voltammetry (FSCV) protocol is presented as a simple but efficient method of analysis that can be incorporated into analytical chemistry labs to demonstrate the utility and versatility of electrochemical techniques. The simplicity of ascorbic acid's electrochemistry makes it an excellent candidate for evaluating an electroanalytical method. In this work, flow cell‐based FSCV was used to measure the ascorbic acid content in a dietary supplement. The protocol involved optimization of the excitation waveform and scan rate, and external standard calibration analysis. The method was evaluated using spike recovery and a standard addition analysis as a secondary method of validation. The external calibration method exhibited excellent accuracy (relative error=−0.6 %, Recovery=100.5 %), suggesting no significant matrix effect, high precision (RSD=±0.4 %) and sensitivity (m=2224.4 nA mm−1). These observations were comparable to results from the standard addition method as revealed by the statistical analysis. Overall, this work demonstrates the use of a cutting‐edge electroanalytical technique in quality control.

Application of tetrahedral -deoxyribonucleic acid electrochemistry platform coupling aptazymes and hybridized hairpin reactions for the measurement of extracellular adenosine triphosphate in plants

Extracellular ATP (eATP) is an important biological signal transduction molecule. Although a variety of detection methods have been extensively used in ATP sensing and analysis, accurate detection of eATP remains difficult due to its extremely low concentration and spatiotemporal distribution. Here, an eATP measurement strategy based on tetrahedral DNA (T-DNA)-modified electrode sensing platform and hybridization chain reaction (HCR) combined with G-quadruplex/Hemin (G4/Hemin) DNAzyme dual signal amplification is proposed. In this strategy, ATP aptamer and RNA-cleaving DNAzyme were combined to form a split aptazyme. In the presence of ATP, this aptazyme hydrolyzes the cleaving substrate strand with high selectivity, releasing cleaved ssDNA, which are captured by the T-DNA assembled on the electrode surface, triggering an HCR on the electrode surface to form numerous linker sequences of the HCR dsDNA product. When G-quadruplex@AuNPs (G4) spherical nucleic acid enzymes (SNAzymes) with other linkers are used as nanocatalyst tags, they are captured by HCR dsDNA through sticky linkers present on the electrode surface. An amplified electrochemical redox current signal is generated through SNAzyme-mediated catalysis of H2O2, enabling easy detection of picomole amounts of ATP. Using this strategy, eATP levels released by tobacco suspension cells were accurately measured and the distribution and concentration of eATP released on the surface of an Arabidopsis leaf was determined.

Comparison of Electropolishing of Aluminum in a Deep Eutectic Medium and Acidic Electrolyte

Research advances in electropolishing, with respect to the field of metalworking, have afforded significant improvements in the surface roughness and conductivity properties of aluminum polished surfaces in ways that machine polishing and simple chemical polishing cannot. The effects of a deep eutectic medium as an acid-free electrolyte were tested to determine the potential energy thresholds during electropolishing treatments based upon temperature, experiment duration, current, and voltage. Using voltammetry and chronoamperometry tests during electropolishing to supplement representative recordings via atomic force microscopy (AFM), surface morphology comparisons were performed regarding the electropolishing efficiency of phosphoric acid and acid-free ionic liquid treatments for aluminum. This eco-friendly solution produced polished surfaces superior to those surfaces treated with industry standard acid electrochemistry treatments of 1 M phosphoric acid. The roughness average of the as-received sample became 6.11 times smoother, improving from 159 nm to 26 nm when electropolished with the deep eutectic solvent. This result was accompanied by a mass loss of 0.039 g and a 7.2 µm change in step height along the edge of the electropolishing interface, whereas the acid treatment resulted in a slight improvement in surface roughness, becoming 1.63 times smoother with an average post-electropolishing roughness of 97.7 nm, yielding a mass loss of 0.0458 g and a step height of 8.1 µm.

Nanoscale Electropolishing of High-Purity Aluminum with a Deep Eutectic Solvent

Recent advancements in electrochemical polishing have minimized surface roughness and enhanced conductivity properties of high-purity (>99.9% composition) aluminum surfaces in ways that machine polishing and simple chemical polishing cannot compare. Aluminum metals have a high propensity to deliver powerful electric charges with little resistance, thus making them effective for a wide range of electroconductivity experiments. The effects of an acid-free ionic liquid electrolyte solution were tested to determine potential energy thresholds during electropolishing treatments based upon temperature, experiment duration, current, and voltage.High purity aluminum metal specimens were used in electropolishing treatments with an acid-free ionic liquid electrolyte prepared from quaternary ammonium salts as an environmentally friendly alternative to acid-based solutions. An ionic liquid solution was formed from ethylene glycol and choline chloride combined in a 2:1 ratio. Similar ionic liquid solutions have been successfully employed to electropolish metal alloys, but little research has been conducted with this approach to polish rare earth metals like aluminum (1-5). Linear sweep voltammetry and chronoamperometry tests were initially used to determine ideal conditions for electrochemical polishing, while Atomic Force Microscopy revealed nanoscale effectiveness of the ionic liquid relative to an industry standard acid polishing treatment of 1 M Phosphoric Acid. Surface characterization via root mean squared roughness before and after electrochemical polishing treatments in 10x10 µm sample regions were used to estimate polishing efficiency throughout a 15-minute treatment period at 70 deg C and an average voltage of 2V.Results from electropolishing treatments in the ionic liquid electrolyte revealed a significant change in root mean squared roughness from 159.31 nm to 26.649 nm and resulted in an overall mass loss of 0.0394 g. A change of 132.661 nm during the 15-minute treatment resulted in an electropolishing efficiency of 83.272% and a shiny mirror finish 6x smoother than the same aluminum surface prior to treatment.Comparatively, the phosphoric acid electropolishing treatment yielded only a nominal improvement in root mean squared roughness of 97.786 nm, yet resulted in a greater mass loss of 0.0458 g for a lower smoothing efficiency rating of 38.546%. The electropolishing rate via the Phosphoric Acid solution is greater, yet the efficiency is less favorable due to significant pitting at low current densities (Figure 1). Hydrogen contamination was observed to adversely impact the overall root mean squared roughness of all sampled areas, yet this may be remedied via costly degassing treatments at temperatures of greater than 800 deg C to achieve more comparable results to the ionic liquid solution by mitigating some of the pitting and bubbling caused by hydrogen attack. In this study, a green polishing solution was prepared from simple inorganic salts, alkyls, and other organic solvents. This eco-friendly solution produced polished surfaces superior to those surfaces treated with industry standard acid electrochemistry treatments of 1M H3PO4.

Special Issue of Electroanalysis Dedicated to the Memory of Professor Emil Paleček

This Special Issue is dedicated to the memory of Professor Emil Paleček, world-recognized biochemist and electrochemist, discoverer of polarographic activity of nucleic acids and founder of nucleic acid electrochemistry as a specific research area. Emil was one of the great persons the presence of whom in our lives constitutes a reassuring aspect and we often cannot imagine that it could change and that they were not there. His sudden decease on October 30, 2018, less than a month after his 88th birthday, was thus shocking for everyone who had the chance to know him and the empty space he left behind will never be filled. Prof. Emil Paleček (Photo by Alois Kozubík) Emil Paleček (EP) was connected for his whole work life with the Institute of Biophysics of the Czech Academy of Sciences in Brno. He ranked among the most recognized Czech scientists and his impact on development of science in the fields of electrochemistry and structure of nucleic acids, proteins and other biomolecules was truly enormous. Owing to EP's interest in a wide spectrum of fields reaching far beyond his own field of study, he was able to establish a laboratory with broad interdisciplinary background. EP stood up for his thoughts and new discoveries despite the deep-rooted dogmas, which could be – in a positive sense – viewed as stubbornness but, as it proved multiple times during his career, his endurance and work commitment enabled him to accomplish his goals. Absolutely deservedly, he was awarded various prizes, for example the Giulio Millazzo Prize from the Bioelectrochemical Society in 2011, the most prestigious Czech award Česká hlava (“Czech Head”) in 2014 or award of the Neuron Benevolent Fund in 2017. As a tribute to Emil, we have organized this Special Issue to collect a selection of papers covering topics to which EP contributed significantly during his long, fruitful scientific life. Most of authors of the contributions knew Emil Paleček personally, some of them used to be his doctoral students, colleagues working for short or longer time in his Brno laboratory or hosted him at their institutions, or just were meeting him frequently at international conferences. As editors of this SI, we would like to express our gratitude to all authors for their great effort to contribute with the results of their research, and all referees for their valuable comments that helped to improve the quality of the manuscripts. While reading the articles, or just leafing through this Special Issue, please, give a remembrance to renowned scientist and great person, Professor Emil Paleček.

Correction to “Electrochemistry of Acids on Platinum. Application to the Reduction of Carbon Dioxide in the Presence of Pyridinium Ion in Water”

Correction to “Electrochemistry of Acids on Platinum. Application to the Reduction of Carbon Dioxide in the Presence of Pyridinium Ion in Water”

Electrochemical analysis of nucleic acids, proteins and polysaccharides in biomedicine

Electrochemical analysis of nucleic acids, proteins and polysaccharides represents an interesting, although not widely spread alternative to current methods based predominantly on optical detection because it offers a relatively inexpensive, fast and instrumentally simple detection of parallel samples on miniaturized chips, ideal for personalized medicine of the 21st century. Nucleic acid electrochemistry enables, for example, detection of specific DNA sequences (for determination of genes or presence of bacteria and viruses, etc.), DNA damage analysis and interaction with other molecules, DNA methylation or detection of microRNAs as potential cancer bio-markers. In the electrochemistry of proteins, great emphasis is put on construction of immunosensors for capturing specific proteins (antigens) using antibodies, suitable for diagnostics. From a bio-physical point of view, intrinsic electrocatalytic signal of proteins sensitive to conformational changes could be useful in discrimination of mutant proteins (e. g. p53), native and aggregated forms (α-synuclein in Parkinsons disease) or for studies of protein interactions with low molecular weight ligands and DNA. Due to an increased interest of scientists in glycoproteins, new electrochemical papers emerged aiming at detection of oligosaccharides and polysaccharides (i.e. glycans, when part of the protein). These assays employ for instance electroactive labels specific for saccharides or lectin bio-sensors using lectins which strongly bind glycans. Electrochemical analysis thus appears as an interesting tool in current genomics, proteomics and glycomics, as well as for cancer diagnostics.

Electrochemistry of Acids on Platinum. Application to the Reduction of Carbon Dioxide in the Presence of Pyridinium Ion in Water

A detailed cyclic voltammetric investigation of the reduction of moderately weak acids on platinum reveals that they are reduced in two steps: one involving the hydrated protons initially present at equilibrium and the second the reduction of the acid through its prior conversion into hydrated protons. The reduction of pyridinium ions (protonated pyridine) follows this reaction scheme as does any other acid of similar pK (e.g., acetic acid). Rather than being catalytically reduced, CO2 plays a similar role through its prior conversion to carbonic acid. No trace of methanol or formate could be detected upon preparative-scale electrolysis of CO2 on the same electrode in the presence of pyridinium ions.

Early stage of nucleic acid electrochemistry. Detection of DNA damage in X-ray-irradiated rats

First papers on electroactivity of DNA and RNA were published more then 50 years ago. For about 8 years oscillographic polarography at controlled a.c. (OP, proposed by J. Heyrovský already in 1941) was the method of choice for DNA analysis. Since approximately 1954 Robert Kalvoda developed OP for wide application in various fields. It is shown that already before 1960 it was possible to detect damage to DNA in X-ray-irradiated rats by means of OP. DNA samples from irradiated animals produced significantly larger OP anodic guanine signal indicating changes in the DNA structure. At present, radiation-induced strand breaks and damage to bases in DNA can be electrochemically detected at high sensitivity.

Mercury Electrodes in Nucleic Acid Electrochemistry: Sensitive Analytical Tools and Probes of DNA Structure. A Review

This review is devoted to applications of mercury electrodes in the electrochemical analysis of nucleic acids and in studies of DNA structure and interactions. At the mercury electrodes, nucleic acids yield faradaic signals due to redox processes involving adenine, cytosine and guanine residues, and tensammetric signals due to adsorption/desorption of polynucleotide chains at the electrode surface. Some of these signals are highly sensitive to DNA structure, providing information about conformation changes of the DNA double helix, formation of DNA strand breaks as well as covalent or non-covalent DNA interactions with small molecules (including genotoxic agents, drugs, etc.). Measurements at mercury electrodes allow for determination of small quantities of unmodified or electrochemically labeled nucleic acids. DNA-modified mercury electrodes have been used as biodetectors for DNA damaging agents or as detection electrodes in DNA hybridization assays. Mercury film and solid amalgam electrodes possess similar features in the nucleic acid analysis to mercury drop electrodes. On the contrary, intrinsic (label-free) DNA electrochemical responses at other (non-mercury) solid electrodes cannot provide information about small changes of the DNA structure. A review with 188 references.

Electronically conductive anion exchange polymers based on polypyrrole: Preparation, characterization, electrostatic binding of ferrocyanide and electrocatalysis of ascorbic acid oxidation

Electronically conductive anion exchange polymers have been prepared by the electrochemical polymerization of protonated and quatemized 3-(pyrrol-1-ylmethyl)pyridine. The quaternized polymer has been characterized by elemental analysis, gravimetry, cyclic voltanunetry, scanning electron microscopy and conductivity measurements. Its structure, conductivity and electrochemistry are similar to those of other N-substituted polypyrroles. However, the high concentration of permanent cationic sites (5-6 M) improve its electrochemical properties, increase its permeability and make it superior to polypyrrole for the binding of anionic electrocatalysts and the preconcentration of ardonic analytes. Voltammetric studies of ferrocyanide and ascorbic acid electrochemistry at poly-[1-methyl-3-(pyrrol-1-ylmethyl)pyridinium] coated electrodes are used to illustrate these points. Ferrocyanide is rapidly ion-exchanged into the polymer with a partition coefficient of 3.2 ×10 4 (vs. 0.01 M NaClO 4) to a saturation concentration of 1.4 M. Ascorbic acid can be preconcentrated in the polymer at pH 7 and its oxidation is catalysed both by the polymer itself and by bound ferrocyanide.