Current Minimum in Differential Pulse Polarography

The application of additive differential pulse voltammetry to the study of the kinetics of a charge transfer process is studied. A simple analytical solution is presented, valid for spherical electrodes of any size and for electrode processes of any reversibility. From this solution, valuable diagnostic criteria for the elucidation of the electrochemical reversibility are established based on the variation of the ADPV signal with the duration of the potential pulses, the electrode radius and the pulse height. Working curves for the determination of the kinetic parameters are also given. The value of the ADPV technique is experimentally demonstrated by studying the kinetics of the reduction of 3-nitrophenolate À and europium 3 + at mercury hemispherical microelectrodes.

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“…These redox couples enable to cover very different electrode kinetics [12][13][14][15][16]. For ADPV experiments, de- Fig.…”

Section: Results and Disccusionmentioning

confidence: 99%

Additive Differential Pulse Voltammetry for the Study of Slow Charge Transfer Processes at Spherical Electrodes

et al. 2010

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“…Otherwise, results are obviously affected by the selenite that always appears as an impurity in such systems. Its direct interaction with the metal ions is most probably not very important at such low concentrations, but its electroactivity which results in modified electrode surface 22 and overlapping of its first reduction peak with uranyl(VI) signal could be of interest.…”

Section: Resultsmentioning

confidence: 99%

Voltammetric Study of Uranyl–Selenium Interactions. Part 2. Uranyl(V) Selenate Complex

2013

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Abstract. Under the influence of recently published papers and some older own results, complex formation in uranyl(VI)-selenium(VI) system was reinvestigated at the ionic strengths of 0.1 and 3.0 mol L -1 . Using electrolyzed selenate solutions (and square-wave voltammetry as a measuring technique) two coordination species at the higher electrolyte concentration (log β 1 = 1.48 ± 0.01, log β 2 = 2.4 ± 0.1) were recognized, in agreement with the literature data based on other experimental methods. For successful interpretation of the voltammetric data, previously unknown weak complex (log β 01 =0.7 ± 0.1) of the reduction product, i.e. uranyl(V) should also be included in the model. At the lower electrolyte concentration (0.1 mol L -1 ), formation of complexes other than UO 2 SeO 4 0 cannot be unambiguously confirmed due to the narrow ligand concentration range.Concerning the number of coordination species and their stability constants, seemingly different results that arise from voltammetry and other (independent) experimental methods reflect the fact that the former, in addition to the complexation of initially present metal ion, "sees" the coordination of its reduction product with the ligand of interest, too. When both processes are taken into account during treatment of voltammetric data, such differences disappear. (doi: 10.5562/cca1952)

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“…The irreversibility of oxidation and reduction processes of SMPC was evidenced by the same direction of forward and backward components of the total current in square wave voltammetry. 34,35 Whereas, anodic and cathodic peaks of SNPC showed irreversible and quasi-reversible electrode processes respectively.…”

Section: Resultsmentioning

confidence: 99%

Synthesis, Spectroscopic Characterization, pH Dependent Electrochemistry and Computational Studies of Piperazinic Compounds

Parveen

Shah

Khan

et al. 2014

J. Electrochem. Soc.

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This work presents the synthesis, redox behavior and spectroscopic characterization of two novel compounds Sodium 4-(3-methoxyphenyl) piperazine-1-carbodithioate and sodium 4-(4-nitrophenyl) piperazine-1-carbodithioate. Pulse voltammetric techniques were utilized to determine the number of electrons involved in the oxidation and/or the reduction step and to ensure the nature of the redox processes. The pH dependent redox mechanistic pathways of the compounds were proposed on the basis of electrochemical and computational results. Different thermodynamic parameters like G # and H # revealed that electrode processes are non-spontaneous and endergonic in nature. Increase in S # values at higher temperature indicated the randomness of the electrode reactions at higher temperatures. Limits of detection and quantification were determined by square wave voltammetry due to its high sensitivity and fast speed. Ionization energy, electron affinity, dipole moment and charge distribution on atoms were computationally determined. Acid-base dissociation constant (pKa) values of the compounds evaluated by voltammetry and electronic spectroscopy were found comparable. Molecular architectures bearing piperazine group have gained the utmost attention due to their vast applications in medical and industrial fields. Piperazines have special importance among nitrogen containing heterocyclic compounds due to their hydrogen bonding ability that make such compounds very specific for the generation of supramolecular structures.1 Piperazine can exhibit chair or boat conformation with chair form being more stable by 17.2 kJ/mol.2 Compounds containing piperazine ring are used as raw materials for the synthesis of epoxy resins, antioxidants, urethane catalysts, insecticides and accelerators for rubber.3 Such compounds possess versatile binding properties and act as potent and selective ligands for different biological activities. The attachment of piperazine to porphrin ring has been reported to enhance the anticancer activity and play the role of sensitizer in photodynamic therapy.4-8 Piperazine derivatives show good activities against chloroquine resistant strain of Plasmodium falciparum in vitro with low toxicity against murine monocyte/macrophage cells.9 Such compounds are also used as chelating agents due to their ability of forming complex with metal ions. Free radicals formation in many bioorganic redox processes may result in oxidation of lipids, proteins, or DNA and thus initiate cancer, cardiovascular, autoimmune, inflammatory and age-related degenerative brain diseases. So, piperazine as reducing agent is gaining mounting attention due to free radicals scavenging ability. 10 Dithio ligands have been documented to play vital roles in numerous biological and non-biological processes.11-13 Dithiocarbamate (DTC) derivatives are used as organic intermediates, vulcanizing agents, rubber additives and fungicides.14 DTC a putative immunomodulator plays pivotal roles in agriculture and enhances immune response in AIDS treatment. 15 Comple...

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Current Minimum in Differential Pulse Polarography

Cited by 17 publications

References 13 publications

Additive Differential Pulse Voltammetry for the Study of Slow Charge Transfer Processes at Spherical Electrodes

Additive Differential Pulse Voltammetry for the Study of Slow Charge Transfer Processes at Spherical Electrodes

Voltammetric Study of Uranyl–Selenium Interactions. Part 2. Uranyl(V) Selenate Complex

Synthesis, Spectroscopic Characterization, pH Dependent Electrochemistry and Computational Studies of Piperazinic Compounds

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