Pulse Cathodic Stripping Voltammetry Research Articles

Voltammetric determination of copper with proton pump inhibitor drug omeprazole

The electrochemical behavior of copper(II)-omeprazole complex was studied by differential pulse and cyclic voltammetry at a hanging mercury drop electrode. A well-defined voltammetric peak was obtained at −0.6 V (vs. Ag/AgCl sat’d KCl) in phosphate buffer (pH 7). The experimental results show that the reduction of the copper(II)-omeprazole complex is irreversible. The stoichiometry and stability constant of the Cu(II)-omeprazole complex were evaluated using differential pulse cathodic adsorptive stripping voltammetry and found to be 1 : 2 and 1.39 × 1011 M−1. The limits of detection and quantitation were found to be 3 × 10−9 and 1 × 10−8 M, respectively. The proposed procedure was successfully applied for the determination of trace level of copper in bottled natural drinking water samples.

A new voltammetric method for the simultaneous monitoring of heavy metals in sea water, sediments, algae and clams: application to the Goro Bay ecosystem.

Arsenic(III), selenium(IV), copper(II), lead(II), cadmium(II), zinc(II) have been determined in sea water, sediments, algae and clams by differential pulse cathodic (DPCSV) and anodic (DPASV) stripping voltammetry. The voltammetric measurements are carried out using a conventional three-electrode cell and the ammonia-ammonium chloride buffer pH 9.2 as supporting electrolyte. The analytical procedure has been verified by the analysis of the standard reference materials (Estuarine Sediment BCR- CRM 277, Ulva Lactuca BCR-CRM 279 and Mussel Tissue BCR-CRM 278). The precision and the accuracy are less than 5%. This procedure is utilized for the monitoring of heavy metals in the Po river mouth area (Italy).

Assay of terfenadine in pharmaceutical formulation and human plasma by adsorptive stripping voltammetry.

The controlled adsorptive accumulation of Zn(II)-terfenadine complex (1:1) onto a hanging mercury drop electrode (HMDE) provides the basis for determination of the antihistamine drug terfenadine by differential pulse cathodic adsorptive stripping voltammetry. The adsorbed Zn(II)-terfenadine complex (1:1) at the HMDE developed a stripping voltammetry peak at more negative potential than that of the free Zn(II) ions. The peak current was used for the determination of terfenadine in pharmaceutical formulation and human plasma in 0.1 mol l(-1) sodium perchlorate solution under the optimized conditions (E(acc), -0.5 V; t(acc) 360 s; scan rate, 5 mV s(-1) and pulse height 100 mV). The developed peak current (i(p)) showed a linear dependence with terfenadine concentration within the range of 6 x 10(-8) - 9 x 10(-7) mol l(-1). The recoveries were found 98.97-99.35%, 99.72-99.02% and 100.58-101.08% with the R.S.D. 0.16-0.27%, 0.25-0.82% and 0.44-1.14% in authentic form, pharmaceutical formulations and human plasma, respectively. The detection limits were 0.4505 and 0.6115 ng ml(-1) terfenadine in pharmaceutical formulations and human plasma, respectively.

Discrete Complexed Ligand and Catalytic Nickel Peaks in the Differential Pulse Polarography and Cathodic Stripping Voltammetry of Mordant Red 74

Cathodic stripping voltammograms of Mordant Red 74 obtained in the presence of nickel ion exhibit both a discrete complexed ligand peak and a catalytic nickel peak. The complexed ligand peak is discrete from the free ligand peak and the catalytic nickel peak is discrete from the diffusion-controlled free nickel peak. It would be possible, using a slight excess of Mordant Red 74, to determine nickel using the complexed ligand peak, and it is possible to determine Mordant Red 74 in the presence of a relatively large excess of nickel using the catalytic nickel peak. This latter method has much greater sensitivity than can be obtained with the direct use of the Mordant Red 74 peak in the absence of nickel. The attainment of improved detection limits for the determination of Mordant Red 74, using the catalytic nickel peak, however, is restricted by the need, at very low concentrations of Mordant Red 74, to reduce the concentration of nickel used in order to resolve the catalytic and free nickel peaks: the decrease in nickel concentration near the electrode surface reduces the catalytic activity.

Reaction of the purine and pyrimidine derivatives with the electrode mercury

Summary The electrochemical behaviour of 30 purine and pyrimidine derivatives and of a further 12 derivatives containing sulphur or halogens was studied. It was demonstrated that most of these substances react with the electrode mercury and form sparingly soluble compounds; this phenomenon can be exploited for the determination of purine and pyrimidine derivatives at low concentrations. The relation between the structural formulae of the substances and their ability to yield anodic polarographic currents conditioned by formation of sparingly soluble compounds with mercury was found. The behaviour of adenine and 8-oxyadenine was studied in greater detail by means of differential (DPP) and normal pulse polarography (NPP), d.c. polarography and cathodic stripping voltammetry (CSV). Both substances can be determined with the aid of CSV at concentrations of the order of magnitude of 10−9 M, while DPP may be used at concentrations three to four orders of magnitude higher. Interactions of some purine and pyrimidine derivatives with Hg(II) ions in homogeneous aqueous solutions were investigated. On the one hand, a correlation was found between the ability of these substances to react with mercury in solution and form precipitates, and, on the other hand, to yield anodic polarographic currents.

Determination of Arsenic and Selenium in Foods By Electroanalytical Techniques

Arsenic and selsnium are determined in foods be differential pulse polarography and cathodic stripping voltammetry. The sample is digested with nitric acid and magnesium nitrate and then dissolved in dilute hydrochloric acid. An aliquot is removed, the arsenic is chemically reduced to the trivalent state, and interferences are removed by ion exchange before polarography. Selenium is determined in a second aliquot by cathodic stripping voltammetry. Recoveries for both elements in several foods were from 90 to 110%. The relative standard deviations for arsenic at 5 ppm and selenium at 0.48 ppm were 5.8 and 7.3%, respectively.