Rubin Gulaboski - Profile on Academia.edu (original) (raw)

Papers by Rubin Gulaboski

Macedonian Journal of Chemistry and Chemical Engineering, May 19, 2024

Understanding energetics and electron behavior has been pivotal in elucidating numerous fundament... more Understanding energetics and electron behavior has been pivotal in elucidating numerous fundamental phenomena, including electricity, corrosion, respiration, energy generation in biological systems, intermolecular interactions within living organisms, organic synthesis, drug development, enzyme functions, and the design of biosensors, among others. As 2024 records the centennial anniversary of the completion of the first polarograph by Nobel laureate Jaroslav Heyrovský (awarded the Nobel Prize in Chemistry in 1959), it presents an opportune moment to pay tribute to several eminent electrochemists who have made significant contributions to the field of voltammetric techniques. Following our recent acknowledgment of the outstanding women who have made substantial contributions to voltammetry in a prior publication, this article aims to briefly highlight the major achievements of several distinguished male figures in the field (

Macedonian Journal of Chemistry and Chemical Engineering, Dec 23, 2023

Utilizing pulse voltammetric techniques for the electrochemical analysis of lipophilic redox syst... more Utilizing pulse voltammetric techniques for the electrochemical analysis of lipophilic redox systems has proven to be an effective method for studying a diverse range of redox compounds, from simple molecules to intricate proteins. To extract relevant thermodynamic and kinetic data from electrochemical analysis of redox systems exhibiting strong surface activity, there's a crucial need to decipher the underlying electrochemical mechanism in the system being examined. The "split net peak" phenomenon, a defining characteristic observed in all surface-active redox systems featuring fast electron transfer under square-wave voltammetry conditions, has been investigated in this study to establish diagnostic criteria for identifying surface electrochemical mechanisms associated with preceding, subsequent, regenerative, and reactant-inactivating chemical reactions. This understanding can be achieved by tracking the influence of the chemical reaction rate on the split square-wave voltammetric peaks in a particular electrochemical mechanism. The approach reported in the current work enables a very simple and precise differentiation between the elaborated mechanisms frequently encountered in protein-film voltammetry methodologies.

Antonio Doménech-Carbó and Maria Teresa Doménech-Carbó: “Electrochemistry for Cultural Heritage” (Monographs in Electrochemistry, Scholz F, Peter L, eds.)

Journal of Solid State Electrochemistry, Aug 25, 2023

Physical Chemistry Chemical Physics, Feb 7, 2003

halogen substituted acetate anions Z 3Àn CH n COO À (Z ¼ F,Cl,Br,I), and cycloalkyl carboxylate a... more halogen substituted acetate anions Z 3Àn CH n COO À (Z ¼ F,Cl,Br,I), and cycloalkyl carboxylate anions ((CH 2 ) n COO À , n ¼ 3,. . .,7) at the water|nitrobenzene interface. Whereas the data for the small inorganic ions can easily be understood in terms of ion-dipole interactions, the data of the organic ions need consideration of charge delocalisation and its effect on the enthalpy and entropy of solvation.

Biophysical Chemistry, Apr 1, 2011

Protein-film voltammetry is established as an effective tool that provides insight to the redox f... more Protein-film voltammetry is established as an effective tool that provides insight to the redox features of various lipophilic proteins by using a simple methodology. Although the protein-film experimental set up is relatively simple, the redox mechanisms of many proteins are quite complicated, and very often they cannot be resolved without having support from adequate mathematical models. In this work we continue our contribution to modeling relevant redox mechanisms in protein-film voltammetry. We present results from the theoretical simulations of catalytic mechanism at the two-step successive surface redox reaction under conditions of square-wave voltammetry. This mechanism is assigned as a surface EEC′, and it can be presented by the following simplified scheme: A(ads) + ne-⇄ B(ads) + ne-⇄ C(ads) + Substrate → kcat B(ads). Our attention is focused on several phenomena of this complex protein-film mechanism, while we give set of qualitative criteria to distinguish this mechanism from similar ones studied under voltammetric conditions. Moreover, we also provide hints to use methodologies for the determination of thermodynamic and kinetic parameters relevant to the protein-film EEC′ mechanism. The considered protein-film EEC′ mechanism is applicable to all lipophilic redox proteins that undergo electrochemical transformations in more than one successive electron steps. Such examples exist by proteins containing quinone moiety and some polyvalent ions of transition metals as redox active sites.

Electroanalysis, Mar 1, 2002

A new theory of a second order cathodic stripping reaction accompanied by adsorption of the react... more A new theory of a second order cathodic stripping reaction accompanied by adsorption of the reacting ligand is developed under conditions of square-wave voltammetry. In the mathematical model, the following reaction is considered: The relationships between the properties of the voltammetric response and both the kinetic parameters as well as the parameters of the excitement signal were analyzed. Both reversible and quasireversible redox reactions were examined. Criterions for distinguishing the studied mechanism from the other types of cathodic stripping reactions were established. The phenomenon of a quasireversible maximum was studied in details. The theoretical results are qualitatively compared with the SW voltammograms of 6-propyl-2-thiouracil.

Electrochemistry Communications, Oct 1, 2002

When a nitrobenzene (NB) droplet containing iodine is attached to a graphite electrode and immers... more When a nitrobenzene (NB) droplet containing iodine is attached to a graphite electrode and immersed into a chloride containing aqueous (AQ) solution, the electrochemical reduction of iodine is accompanied by a transfer of chloride ions from NB to water. These chloride ions enter the NB phase in a preceding partition between the AQ and the NB phases, supported by formation of I 2 Cl À ions in NB and accompanied by the transfer of stoichiometric amounts of cations. The overall electrode reaction is of CE rev type, where C refers to the preceding chemical step forming I 2 Cl À , and E rev refers to the reversible reduction of iodine at the graphitejNB interface and the simultaneous transfer of chloride from NB to water. If the chloride concentration in NB is insufficient to compensate by leaving the NB the amount of electrochemically produced iodide, a second voltammetric signal occurs at more negative potentials due to the transfer of iodide from NB to water. The kinetics and thermodynamics of the preceding chemical step C, determine the voltammetric behaviour of the system in such way that the ratio of peak currents of the first and second signals depends linearly on the Gibbs energy of transfer of the co-partitioned cations. The method was validated for cations of known Gibbs energies of transfer, and it was applied to cations of amino acids.

Journal of Electroanalytical Chemistry, Sep 1, 2020

Journal of Electroanalytical Chemistry, May 1, 2004

An electrode reaction occurring in a thin-film having a low electrical conductivity was considere... more An electrode reaction occurring in a thin-film having a low electrical conductivity was considered under conditions of squarewave voltammetry (SWV). The ohmic polarization of the system owing to the low conductivity of the film is represented by the complex resistance parameter defined as , where R X is the resistance of the film, S is the electrode surface area, f is the SW frequency and the other symbols have their usual meanings. The influence of the thickness of the film is given by the thickness parameter , where L is the thickness of the layer, and D is the diffusion coefficient. For a thin film (K 6 0:949) the dimensionless net-peak current of a reversible electrode reaction depends parabolically on the resistance parameter, exhibiting a well-developed maximum. A detailed study of this phenomenon revealed that it resembles the charge transfer kinetics effect as well as the property known as a ''quasireversible maximum'' that is typical for an adsorption complicated electrode reaction. The theoretically predicted properties of the SW response are illustrated by experiments with iodine, decamethylferrocene, and azobenzene at the three-phase electrode system. This methodology [Electrochem. Commun. 2 (2000) 112] consists of a single droplet of an organic water immiscible solvent containing an electroactive probe that is attached to the surface of a graphite electrode and immersed in an aqueous electrolyte solution. A good agreement between theory and experiment indicates that the SW voltammetric response of the three-phase electrode system exhibits properties of an electrode reaction occurring under limiting diffusion conditions.

Distinguishing Heterogeneous and Homogeneous CE Mechanisms: Theoretical Insights into Square-Wave Voltammetry

Journal of Physical Chemistry C, Feb 8, 2023

Journal of Physical Chemistry C, Mar 23, 2022

A theoretical analysis of reversible and quasireversible electrode reactions of a dissolved redox... more A theoretical analysis of reversible and quasireversible electrode reactions of a dissolved redox couple under conditions of the novel technique of differential square-wave voltammetry (DSWV) is presented. The technique is recently introduced as a hybrid form between differential pulse voltammetry (DPV) and square-wave voltammetry (SWV) as the two most advanced and competitive pulse-form voltammetric techniques for a purpose of unifying their advantages and further advancing both techniques in terms of analytical performances, mechanistic analysis, and electrode kinetics. The potential modulation of DSWV consists of potential steps and pulses providing a plethora of voltammetric curves, which enable in-depth characterization of the electrode reaction with a minimal set of measurements. Based on numerical simulations, a set of criteria for characterization and differentiation between reversible and quasireversible electrode reactions are established.

Biophysical Chemistry, Sep 1, 2008

Square-wave voltammetry of surface redox reactions is considered as an adequate model for a prote... more Square-wave voltammetry of surface redox reactions is considered as an adequate model for a protein-film voltammetric setup. Here we develop a theoretical approach to analyze the effects of temperature on square-wave voltammograms. The performed simulations address the surface redox reactions featuring slow, modest and fast electron transfer. The theoretical calculations show that the temperature affects the square-wave voltammetric responses in a complex way resulting in a variety of peak shapes. Temperature effects on the phenomena known as "quasireversible maximum" and "split SW peaks" are also analyzed. The simulated results can be used to analyze the redox mechanisms and kinetic parameters of electron transfer reactions in protein-film criovoltammetry and other surface-confined redox systems. Our analysis also shows how "abnormal" features present in some square-wave voltammetric studies can easily be misinterpreted by postulating "multiple species", "stable radicals", or additional processes. Finally we provide a simple algorithm to use the "quasireversible maximum" to determine the activation energy of electron transfer reactions by surface redox systems.

Faraday Discussions, 2005

For the first time the differences in free energies have been experimentally determined for the s... more For the first time the differences in free energies have been experimentally determined for the solvation of two enantiomeric ions in two enantiomeric solvents. Three-phase electrodes consisting of a droplet of a solution of decamethylferrocene in a chiral solvent (Dand L-2-octanol) attached to a graphite electrode and immersed in an aqueous solution containing chiral anions, allow the measurement of these data for the transfer of the enantiomeric ions across the water|chiral solvent interface. In all studied combinations the Gibbs energy to transfer an L-ion from water to the L-solvent was equal to the Gibbs energy of transfer of the D-ion from water to the D-solvent, and the same was found for the transfer of a L-ion from water to the D-solvent and for the D-ion from water to the L-solvent. In all cases, the combinations D-anion/D-solvent and L-anion/L-solvent have smaller standard Gibbs energies than the combinations D-anion/L-solvent and L-anion/ D-solvent. This can be explained by less favourable interactions between an anion and a solvent molecule in the latter cases.

Amino Acids, Mar 1, 2003

tine analytical work is usually involved. For ionic compounds chemical methods can provide inform... more tine analytical work is usually involved. For ionic compounds chemical methods can provide information for the salt as a whole, and the liphopylicity of particular ionic species is accessible only on the base of an extrathermodynamic assumption . In the latter case, electrochemical measurements lend themselves for the determination of the Gibbs energies of transfer because the transfer of ions from one phase to the other is an electrochemical process, and because an electrochemical method will yield these values for a single kind of ions and not for the entire salt. However, the only electrochemical method that was known until very recently was the voltammetry at the interface of two immiscible electrolyte solutions (ITIES) with the help of a fourelectrode potentiostate . In these experiments, the accessible potential range is very limited (300 to 500 mV) that can be extended either by a microelectrode approach or by coupling chemical equilibria on both sides of the interface, however, all these approaches have only a limited practicability. Recently we have introduced a new experimental arrangement to determine the standard Gibbs energies of ion transfer Komorsky-Lovric ´ et al., 2001a,b) that is based on coupling an electron transfer and an ion transfer when three phases, the aqueous solution containing the ions to be transferred, an organic solution of an electroactive compound (e.g. decamethylferrocene dissolved in nitrobenzene), and a solid electrode (e.g. graphite) are in contact. This Summary. The standard Gibbs energies of transfer of anions and cations of amino acids and small peptides across the water nitrobenzene interface were determined with the help of a novel electrochemical technique using three-phase electrodes. This is the first time that reliable data are reported for the anions of amino acids. The main result is that the standard Gibbs energies of transfer of the anion and cation of an amino acid are almost the same.

Journal of Solid State Electrochemistry, Mar 1, 2003

A pseudo-first-order catalytic mechanism in which both reactant and product of a redox reaction a... more A pseudo-first-order catalytic mechanism in which both reactant and product of a redox reaction are strongly immobilized on an electrode surface is theoretically analysed under conditions of square-wave (SWV) and staircase cyclic voltammetry (SCV). A mathematical procedure is developed under diffusionless conditions. The relationships between the properties of the voltammetric response and both the kinetic parameters of the redox reaction and the parameters of the excitation signal are studied. The phenomenon of the quasi-reversible maximum is discussed. A comparative study between SWV and SCV is presented and the limitations and advantages of both techniques, from analytical and kinetic points of view, are discussed. The theoretical predictions are experimentally confirmed by the redox reaction of azobenzene in the presence of hydrogen peroxide as an oxidizing agent.

Springer eBooks, 2015

The use of designations, trademarks, etc. in this publication does not imply, even in the absence... more The use of designations, trademarks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt fi-om the relevant protective laws and regulations and therefore free for general use.

Monatshefte Fur Chemie, Oct 27, 2022

Journal of The Electrochemical Society, 2019

Reactive oxygen species (ROS) exhibit different spatial and temporal distributions as well as con... more Reactive oxygen species (ROS) exhibit different spatial and temporal distributions as well as concentrations in-and outside the cell, thereby functioning as signaling or pathogen-destroying molecules. Especially the ROS H 2 O 2 is important for the patho/physiological status of an organism. Electrochemistry (EM) and electron spin resonance (ESR)-based techniques allow quantification of H 2 O 2 in artificial and living systems, coping a concentration range from low nM up to mM. Working electrodes for EM are optimized by diverse modifications and, additionally, redox mediators are used. Ultramicroelectrodes allow scanning of single cells to spatially resolve and quantify extracellular H 2 O 2 in real-time. With ESR spectroscopy, • O 2 ¯, but not H 2 O 2 , can be directly determined by spin probes in-and outside of cells in suspensions. Monitoring H 2 O 2 requires formation of intermediate radicals, detectable with spin probes. Low μM [H 2 O 2 ] can thus be assessed specifically. Using suitable spin traps, in-vivo ESR and immuno-spin trapping can visualize different radicals at their respective production sites in small animals, organs and tissues. Here, the redox reaction cascades may interfere with cell metabolism. Optimization of all methods established for H 2 O 2 determination would be favorable to finally combine them for mutual validation. Thus, a deeper insight into cellular ROS metabolism can be obtained.

Journal of Solid State Electrochemistry, Jun 5, 2020

The three-phase electrode methodology applied for studying ion transfers across an interface betw... more The three-phase electrode methodology applied for studying ion transfers across an interface between two immiscible liquids is simple and efficient tool to get insight into the activity of many ioniziable drugs and physiologically active substances that can exist in ionic forms. Exactly 20 years ago, the group of electrochemists led by Fritz Scholz, Sebojka Komorsky-Lovric and Milivoj Lovric, invented this set up to get access to the thermodynamics of ion transfers across liquid/liquid interface. Within the last twenty years, the three-phase electrodes have been applied to get access to important phenomena such as: thermodynamics of interfacial chemical reactions, kinetics of ion and electron transfer, interfacial catalysis, recognition of chiral ions, synthesis of nano-particles, and biosensor development are some of the milestones achieved by application of three-phase electrodes. While elaborating briefly major achievements, future perspectives of this simple, but powerful electrochemical tool, have been also envisaged. Scheme: Three phase electrode with TCNQ redox probe.