Electrochemical characterization of natural gold samples using the voltammetry of immobilized particles

The application of the voltammetry of immobilized particles for characterizing natural gold samples from different geological settings and dating vein deposits is described. This is based on recording characteristic electrochemical oxidation signatures of gold and silver following the attachment of metal sub-microsamples to graphite electrodes. Keywords: Electrochemistry, Gold, Mineralogy, Placer deposits, Vein deposits, Nuggets

Estimation of individual Gibbs energies of cation transfer employing the insertion electrochemistry of solid Prussian blue

Abstract A novel method to determine the Gibbs energy of cation transfer between two miscible solvents is described. This method uses electrochemical data for the reversible cation-assisted solid-state reduction of Prussian blue using ferrocene as internal potential standard. Voltammetric data can be used for a direct measurement of the Gibbs energy of ion transfer from one solvent to another using midpeak potentials in solutions of suitable salts in each one of the solvents separately or mixtures of the solvents. Excess Gibbs energies of solvation in solvent mixtures can also be directly estimated. Gibbs energies of cation transfer of Li+, Na+ and K+ ions from water to MeOH, MeCN and DMSO …

Electrochemistry-based chemotaxonomy in plants using the voltammetry of microparticles methodology

A methodology for characterizing vegetal taxonomic groups using microextraction-assisted voltammetry of microparticles is described. It is based on recording the voltammetric response of microparticulate films of polyphenolic compounds of leaf extracts using different organic solvents. As a result, characteristic voltammetric profiles, tentatively defining an electrochemolomic response, are obtained. Bivariant and multivariant chemometric evaluation of the voltammetric responses of such films allows characterizing vegetal families. Analysis of voltammetric responses for a set of species of the Rosales order suggests that electrochemical data can be correlated with phylogenetic trees.

Electrochemical dating of archaeological gold based on refined peak current determinations and Tafel analysis

Abstract This report proposes a refined method to date archaeological gold samples based on the Tafel analysis of the ascending part of voltammetric curves corresponding to the oxidation of surface flakes of gold in contact with hydrochloric acid aqueous electrolyte. This allows estimating the equilibrium potential of gold oxidation correcting for irreversibility effects. This equilibrium potential can be correlated with the coverage of adsorbed oxygen species and hence the estimated age of the gold samples. A satisfactory potential/time calibration graph was constructed from a set of archaeological samples including two sets of samples from the Mapungubwe Gold Collection, South Africa (120…

Solvent-Independent Electrode Potentials of Solids Undergoing Insertion Electrochemical Reactions: Part III. Experimental Data for Prussian Blue Undergoing Electron Exchange Coupled to Cation Exchange

Prussian blue-modified electrodes immersed in K+-containing solutions can be used to obtain a solvent-independent redox potential system. On the basis of theoretical modeling of diffusion processes occurring under the conditions of voltammetry of immobilized particles, voltammetric and chronoamperometric data can be combined to obtain solvent-independent electrode potentials for the K+-assisted one-electron reduction of Prussian blue to Berlin white. Data for water, MeOH, EtOH, MeCN, DMS, DMF, and NM are provided.

Dating of Archaeological Gold by Means of Solid State Electrochemistry

[EN] In archaeology and history of art, age determination is a fundamental analytical problem. While several techniques for age determination of various materials, like radiocarbon dating, are established, these methods cannot be applied for metals, for which new techniques have to be developed. For the first time a dating method for archaeological gold objects is described which is based on a corrosion clock and electrochemical measurements, using the voltammetry of immobilized particles. Samples are prepared by one touch' with a graphite pencil, only transferring a few nanograms of the archaeological gold. The method has been calibrated with the help of a series of well-documented gold sp…

Electrodes with Immobilized Particles and Droplets: Three-Phase Electrodes

It is a common feature of electrodes with immobilized particles and droplets that three phases are in close contact with each other, i.e., each phase having an interface with the two other phases. This situation exists also in most of the so-called surface-modified or film electrodes, many battery and fuel cell electrodes, electrodes of the second kind, etc. In fact, the majority of surface-modified electrodes consist of arrays of particles that partially cover the electrode surface. It would be far beyond the scope of this book to include all chemical and electrochemical techniques to deposit films on electrodes. Here we shall deal only with electrodes where the particles or droplets have …

The Thermodynamics of Insertion Electrochemical Electrodes—A Team Play of Electrons and Ions across Two Separate Interfaces

Insertion electrochemical electrodes exhibit simultaneous electron and ion transfer, with the two transfers proceeding across different interfaces. Herein the thermodynamics of the overall electrochemical electrode reaction is discussed with respect to the thermodynamics of these two charge-transfer equilibria. This Minireview includes insertion electrochemical systems where the redox centers are in a solid phase and the ions are transferred between that phase and a solution, and also systems where the redox centers are in a liquid phase that is immiscible with another liquid phase and ions are transferred between the two liquid phases. The Minireview is intended to spark similar studies on…

Earlier Developed Techniques

The first electrochemical experiments were performed with solid materials, esp. metals. However, these experiments, conducted in the eighteenth and nineteenth centuries, were directed toward the elucidation of the basic features of the electrical action of chemical substances and the chemical action of electricity. Initially, metals played the major role; only later it became obvious that many chemical compounds possess metallic or semiconducting properties that can be utilized in electrochemical cells. Parallel to the studies of new electrode materials, solid electrolytes were discovered and entire solid galvanic cells could be constructed. In this book, we will entirely neglect pure solid…

Die Thermodynamik von insertionselektrochemischen Elektroden – ein Mannschaftsspiel über zwei separate Grenzflächen

Electroanalytical chemistry for the analysis of solids: Characterization and classification (IUPAC Technical Report)

Solid state electroanalytical chemistry (SSEAC) deals with studies of the processes, materials, and methods specifically aimed to obtain analytical information (quantitative elemental composition, phase composition, structure information, and reactivity) on solid materials by means of electrochemical methods. The electrochemical characterization of solids is not only crucial for electrochemical applications of materials (e.g., in batteries, fuel cells, corrosion protection, electrochemical machining, etc.) but it lends itself also for providing analytical information on the structure and chemical and mineralogical composition of solid materials of all kinds such as metals and alloys, variou…

Electrochemical Age Determinations of Metallic Specimens—Utilization of the Corrosion Clock

Dating needs an age-dependent phenomenon (a "clock"), a procedure for monitoring the advance of time by measuring a physicochemical quantity, and, in the case of archeological artifacts, a sampling procedure that guarantees the representativity and integrity of the dated objects. Metal corrosion in an aerobic atmosphere is a phenomenon whose advance can in principle be used as a clock that depends on the environmental conditions. In spite of the limitation imposed by differences in local conditions of corrosion, a new approach for age determinations has been developed and applied as a feasible tool for age determinations of metallic specimens studied by archeologists and historians. These t…