Carbon electrode cyclic voltammetry analysis

Alemu et al. [35] developed a very sensitive and selective procedure for the determination of niclosamide based on square-wave voltammetry at a glassy carbon electrode. Cyclic voltammetry was used to investigate the electrochemical reduction of niclosamide at a glassy carbon electrode. Niclosamide was first irreversibly reduced from N02 to NHOH at —0.659 V in aqueous buffer solution of pH 8.5. Following optimization of the voltammetric parameters, pH and reproducibility, a linear calibration curve over the range 5 x 10 x to 1 x 10-6 mol/dm3 was achieved, with a detection limit of 2.05 x 10-8 mol/dm3 niclosamide. The results of the analysis suggested that the proposed method has promise for the routine determination of niclosamide in the products examined [35]. 

Finally, a thin chromium deposit was plated in situ on a tungsten substrate, then chronopotentiograms were recorded, the analysis of which showed that Cr(II) species was adsorbed, and that adsorbed and dissolved Cr(II) species participated in the reduction process. No adsorption was demonstrated on a vitreous carbon electrode. Cyclic voltammetry was then used at gold, copper, nickel, vitreous carbon and tungsten electrodes (Figure 19). 

These studies have been mainly carried out using cyclic voltammetry and frequency response analysis as experimental tools. As a typical example. Fig. 9.12 illustrates the voltammogram related to the p-doping process of a polypyrrole film electrode in the LiClQ -propylene carbonate electrolyte, i.e. the reaction already indicated by (9.16). 

Application of adsorptive stripping analysis to the determination of nucleic acids at mercury electrodes has also been reported [195]. Tomschik etal. [196] have studied reduction and oxidation of peptide nucleic acid and DNA at mercury and carbon electrodes. The authors have utilized cyclic and square-wave voltammetries to study reduction and oxidation signals of single-stranded peptide nucleic acid and DNA decamers and pentadecamers. 

The electrochemical behavior of Np ions in basic aqueous solutions has been studied by several different groups. In a recent study, cyclic voltammetry experiments were performed in alkali ([OH ] = 0.9 — 6.5 M) and mixed hydroxo-carbonate solutions to determine the redox potentials of Np(V, VI, VII) complexes [97]. As shown in Fig. 2, in 3.1 M LiOH at a Pt electrode Np(VI) displays electrode processes associated with the Np(VI)/Np(V) and Np(VII)/Np(VI) couples, in addition to a single cathodic peak corresponding to the reduction of Np(V) to Np(IV). This latter process at Ep —400 mV (versus Hg/HgO/1 M NaOH) is chemically irreversible in this medium. Analysis of the voltammetric data revealed an electrochemically reversibleNp(VI)/Np(V)... 

Figure 6.6.5 Application of cyclic voltammetry to in vivo analysis in brain tissue, (a) Carbon paste working electrode, stainless steel auxiliary electrode (18-gauge cannula), Ag/AgCl reference electrode, and other apparatus for voltammetric measurements, (b) Cyclic voltammogram for ascorbic acid oxidation at C-paste electrode positioned in the caudate nucleus of an anesthetized rat. [From P. T. Kissinger, J. B. Hart, and R. N. Adams, Brain Res., 55, 20 (1973), with permission.]...

Various electrochemical methods have been applied for the analysis of nucleic acids, including DPP and DPV, cyclic voltammetry, a.c. voltammetry, and constant current chronopotentiometry, which are particularly useful. Guanine (G) and adenine (A) residues in DNA and RNA molecules are oxidized at carbon electrodes however, their voltammetric peaks are poorly developed, providing insufficient sensitivity in... 

Cyclic Voltammetry was carried out with a BAS 100 W potentiostat coupled with an Ag/AgN03 reference electrode in acetonitrile, platinum or glassy carbon as working and platinum wire as standard electrode. 0.1 M tetraethyl ammonimn perchlorate in dry acetonitrile served as electrolyte with ferrocene as standard. Data analysis was performed with the software BAS 100 W version 2.3. 

Radi [41] used an anodic voltammetric assay method for the analysis of omeprazole and lansoprazole on a carbon paste electrode. The electrochemical oxidations of the drugs have been studied at a carbon paste electrode by cyclic and differential-pulse voltammetry in Britton-Robin-son buffer solutions (0.04 M, pH 6-10). The drug produced a single oxidation step. By differential-pulse voltammetry, a linear response was obtained in Britton-Robinson buffer pH 6 in a concentration range from 2 x 10-7to 5 x 10 5 M for lansoprazole or omeprazole. The detection limits were 1 x 10 8 and 2.5 x 10 8 M for lansoprazole and omeprazole, respectively. The method was applied for the analysis of omeprazole in capsules. The results were comparable to those obtained by spectrophotometry. 

---