Abstract
Using a paraffin impregnated graphite electrode (PIGE) and mercury-modifiedpyrolytic graphite electrode with basal orientation (Hg-PGEb) copper(II) and Cu(II)-DNApurine base solutions have been studied by cyclic (CV) and linear sweep voltammetry(LSV) in connection with elimination voltammetry with linear scan (EVLS). In chlorideand bromide solutions (pH 6), the redox process of Cu(II) proceeded on PIGE with twocathodic and two anodic potentially separated signals. According to the eliminationfunction E4, the first cathodic peak corresponds to the reduction Cu(II) e⁻ → Cu(I) withthe possibility of fast disproportionation 2Cu(I) → Cu(II) Cu(0). The E4 of the secondcathodic peak signalized an electrode process controlled by a surface reaction. Theelectrode system of Cu(II) on Hg-PGEb in borate buffer (pH 9.2) was characterized by onecathodic and one anodic peak. Anodic stripping voltammetry (ASV) on PIGE and cathodicstripping voltammetry (CSV) on Hg-PGEb were carried out at potentials where thereduction of copper ions took place and Cu(I)-purine complexes were formed. By usingASV and CSV in combination with EVLS, the sensitivity of Cu(I)-purine complexdetection was enhanced relative to either ASV or CSV alone, resulting in higher peakcurrents of more than one order of magnitude. The statistical treatment of CE data wasused to determine the reproducibility of measurements. Our results show that EVLS inconnection with the stripping procedure is useful for both qualitative and quantitativemicroanalysis of purine derivatives and can also reveal details of studied electrodeprocesses.
Highlights
Nucleic acid bases and some of their derivatives can be detected by stripping analysis with mercury electrodes
The pH dependence showed that alkaline solutions did not encourage the formation of cyclic voltammetry (CV) signals
Our study of redox systems of Cu(II) on two modified graphite electrodes (PIGE and Hg-pyrolytic graphite electrode with basal orientation (PGEb)) in the presence or absence of purines contributes to the family of papers that deals with microdetection of purine bases and/or bases released from oligonucleotide chains by means of acid hydrolysis [3,7,2628,50-52,54,55]
Summary
Nucleic acid bases and some of their derivatives can be detected by stripping analysis with mercury electrodes. Voltammetric ultra-trace determination of some nucleic bases in the presence of Cu(II) using a mercury electrode or solid amalgam electrodes has been described [2,3,4,5,6]. Determination is based on the formation of purine-copper complex at the electrode surface and subsequent stripping resulting in a voltammetric signal suitable for analytical purposes [3,7,8]. As mercury and amalgam electrodes are avoided for both industrial and scientific purposes in many countries around the world, new types of working electrodes for analysis of nucleic acids and their components are needed. Electrochemical characteristics of PIGE electrodes are comparable with other carbon electrodes; their advantages include easy of preparation and very low negative potential limits [18]
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