Resolution of Overlapped Reduction Signals in Short Hetero-oligonucleotides by Elimination Voltammetry

Strengths and weaknesses of elimination voltammetry with linear scan

Electrochemical methods have undergone many important developments initiated by efforts to increase the sensitivity, selectivity, and stability (S&S&S) and to understand the underlying electrode processes. To meet these goals, there are hardware solutions with applications of new technologies and materials, and software solutions utilizing existing instrumentation. The article presents a viable, easy-to-implement software solution to the main shortcomings of linear sweep voltammetry (low sensitivity, high share of the capacitive component of the current, and the problem of overlapping signals) in the form of elimination voltammetry with a linear scan (EVLS). Based on the different dependences of the individual currents that make up the total voltammetric current (diffusion, charging, kinetics, and various irreversible components) on the scan rate, EVLS can eliminate or preserve particular current components. Increased sensitivity and selectivity can be expected especially in the case of a fully adsorbed electroactive particle subjected to an irreversible electrode process when the elimination of kinetic and capacitive current while preserving the diffusion current provides a theoretically confirmed peak-counter peak signal. EVLS is applicable for testing changes in the polarized electrode/electrolyte interface using EVLS functions eliminating the diffusion component of the current and preserving the kinetic and capacitive currents, which should ensure zero current conduction for a purely diffusion-controlled Nernstian-type reversible process. We point out the strengths, opportunities, and weaknesses of EVLS. Nevertheless, EVLS offers a new tool that contributes to a better understanding of electrochemical processes and their mechanisms.

Nucleobase modification as redox DNA labelling for electrochemical detection

Basic aspects of DNA electrochemistry with a strong focus on the use of modified nucleobases as redox probes for electrochemical bioanalysis are reviewed. Intrinsic electrochemical properties of nucleobases in combination with artificial redox-active nucleobase modifications are frequently applied in this field. Synthetic approaches (both chemical and enzymatic) to base-modified nucleic acids are briefly summarized and their applications in redox labelling are discussed. Finally, analytical applications including DNA hybridization, primer extension, PCR, SNP typing, DNA damage and DNA-protein interaction analysis are presented (critical review, 91 references).

Study of Copper and Purine-Copper Complexes on Modified Carbon Electrodes by Cyclic and Elimination Voltammetry

Using a paraffin impregnated graphite electrode (PIGE) and mercury-modified pyrolytic graphite electrode with basal orientation (Hg-PGEb) copper(II) and Cu(II)-DNA purine base solutions have been studied by cyclic (CV) and linear sweep voltammetry (LSV) in connection with elimination voltammetry with linear scan (EVLS). In chloride and bromide solutions (pH 6), the redox process of Cu(II) proceeded on PIGE with two cathodic and two anodic potentially separated signals. According to the elimination function E4, the first cathodic peak corresponds to the reduction Cu(II) + e^- → Cu(I) with the possibility of fast disproportionation 2Cu(I) → Cu(II)+ Cu(0). The E4 of the second cathodic peak signalized an electrode process controlled by a surface reaction. The electrode system of Cu(II) on Hg-PGEb in borate buffer (pH 9.2) was characterized by one cathodic and one anodic peak. Anodic stripping voltammetry (ASV) on PIGE and cathodic stripping voltammetry (CSV) on Hg-PGEb were carried out at potentials where the reduction of copper ions took place and Cu(I)-purine complexes were formed. By using ASV and CSV in combination with EVLS, the sensitivity of Cu(I)-purine complex detection was enhanced relative to either ASV or CSV alone, resulting in higher peak currents of more than one order of magnitude. The statistical treatment of CE data was used to determine the reproducibility of measurements. Our results show that EVLS in connection with the stripping procedure is useful for both qualitative and quantitative microanalysis of purine derivatives and can also reveal details of studied electrode processes.