Solid-state electrode with a Cu(I)-based membrane hydrophobised by PTFE for the measurement of Cu2+ and I−

The preparation of CuI + Ag₂S and Cu₂[HgI₄] + Ag₂S membranes hydrophobised by PTFE is described. The pressed membranes mounted in a multi-purpose “all-solid-state” electrode body have been examined as electrochemical sensors for Cu²⁺ and I^? ions. For the electrode with (CuI + Ag₂S + PTFE)-membrane experimental slopes of 29 mV(pCu)^?1 and 62 mV(pI)^?1 were obtained, in good agreement with the theoretical values. For practical measurement in solutions where both Cu²⁺ and I^? can be present, the investigated electrode offers certain advantages in comparison with a commercial Cu-ISE.     

Solid-state electrode with a Cu(I)-based membrane hydrophobised by PTFE for the measurement of Cu2+ and I?

The preparation of CuI + Ag₂S and Cu₂[HgI₄] + Ag₂S membranes hydrophobised by PTFE is described. The pressed membranes mounted in a multi-purpose all-solid-state electrode body have been examined as electrochemical sensors for Cu²⁺ and I^– ions. For the electrode with (CuI + Ag₂S + PTFE)-membrane experimental slopes of 29 mV(pCu)^–1 and 62 mV(pI)^–1 were obtained, in good agreement with the theoretical values. For practical measurement in solutions where both Cu²⁺ and I^– can be present, the investigated electrode offers certain advantages in comparison with a commercial Cu-ISE.     

Accumulation and trace measurement of chloroquine drug at DNA-modified carbon paste electrode

The voltammetric behaviour of chloroquine was investigated at carbon paste and dsDNA-modified carbon paste electrodes in different buffer systems over a wide pH range using cyclic and differential pulse voltammetry. Chloroquine was oxidized in the pH range 2.0-11.0 yielding one irreversible main oxidation peak. A second peak was also observed only in the pH range 5.0-7.0. The modification of the carbon paste surface with dsDNA allowed a preconcentration process to take place for chloroquine such that higher sensitivity was achieved as compared with the bare surface. The response was characterized with respect to solution pH, ionic strength, accumulation time and potential, chloroquine concentration, and other variables. Stripping voltammetric response showed a linear calibration curve in the range 1.0 × 10⁻⁷ to 1.0 × 10⁻⁵ mol l⁻¹ with a detection limit of 3.0 × 10⁻⁸ mol l⁻¹ at the dsDNA-modified electrode. Application of the modified electrode to serum, without sample pretreatment, resulted in good recovery higher than 95% and the higher standard deviation was 3.0%.     

Surface Modification of Porous Silica with Bi-thiophene Tripodal Ligand and Aplication to Adsorption of Toxic Metal Cations

The immobilization of a thiophene-based tripodal ligand, with a donor sulfur, on the surface of an epoxide group containing a silica gel phase for the synthesis of a newly functionalized material based on porous silica-bound bi-thiophene tripodal ligand (SGBT) is described. The modified silica surface was characterized by ¹³C NMR of a solid sample, elemental analysis, and infrared spectra. This new material was also studied and evaluated by determination of the surface area using the BET equation, the adsorption and desorption capability using the isotherm of nitrogen and BJH pore sizes, respectively. The target material exhibits good thermal stability as determined by thermogravimetry curves. The synthesized material was utilized in column and batch methods for adsorption of Hg²⁺, Cd²⁺, Pb²⁺, Cu²⁺, Zn²⁺, K⁺, Na⁺, and Li⁺, and the material exhibits an affinity only towards toxic heavy metals.     

Preconcentration and Voltammetric Study of Nicergoline at a Carbon Paste Electrode

 The electrochemical oxidation of nicergoline is investigated using cyclic and differential pulse voltammetry at a carbon paste electrode. For the determination of nicergoline an adsorptive stripping procedure is proposed. The response is characterized with respect to pH, ionic strength, preconcentration time, accumulation potential, nicergoline concentration, reproducibility and other variables. By differential pulse voltammetry at a carbon paste electrode and pH 8.0, a linear calibration in the range 5×10⁻⁸ M to 1×10⁻⁷ M and a detection limit of 1×10⁻⁸ M are obtained. The preconcentration medium-exchange approach was used for a selective determination of nicergoline in urine. For dilute urine samples a detection limit of 5×10⁻⁸ M is obtained after 3 min of accumulation and medium-exchange. The procedure also is applied for the determination of nicergoline in dosage form. Received August 24, 1998. Revision April 8, 1999.     

Preparation of an ion-selective electrode by chemical treatment of copper wire for the measurement of copper(II) and iodide by batch and flow-injection potentiometry

The preparation of an ion-selective electrode by chemical treatment of copper wire and its application for the measurements of copper (II) and iodide ions is described. The proposed reaction mechanism at the sensing surface, which explains the response of the electrode to Cu²⁺ and iodide ions, is discussed. The prepared electrode was suitable for direct potentiometric measurements of iodide and copper (II) in batch experiments down to concentrations of 1 × 10^–5 mol L^–1. A tubular electrode, prepared in the same way, may be used as a potentiometric sensor in a flow-injection analysis for Cu (II) and/or iodide determinations. Received: 4 December 1998 / Revised: 31 March 1999 / Accepted: 6 April 1999     

Provenance studies of obsidian artifacts: Trace elements analysis and data reduction

Iron and trace elements, such as rare-earth elements, scandium, rubidium, cesium, tantalum, thorium and uranium were determined by instrumental neutron activation analysis in geological samples of obsidian rocks from the Mediterranean Area and in obsidian artifacts found in some prehistorical human settlements in Italy. REE patterns and discriminant analysis allow a firm identification of the source material of artifacts, thus confirming and implementing fission track data of the same artifacts and rocks on the origin of the obsidian rock used to mould the artifacts.     

Potentiometric response of a commercial (Ag2S+PbS)-membrane selective electrode to Hg(II) in aqueous solution

Summary The preparation and performance of an Hg(II)-ISE are described. The analytical behaviour of this electrode, made by chemical treatment of a commercial silver sulphide type Pb(II)-ISE, is discussed in terms of potentialvs. concentration curves, potentialvs. pH curves, and selectivity. The response to fixed c_Hg(II) as the pH is increased in the alkaline region corresponds to decrease in the free Hg²⁺concentration down to pHg 17. The estimated limit of detection of total Hg(II) concentration is 10^–5 M.

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Potentiometrisches Verhalten einer handelsüblichen (Ag₂S+PbS)-Membran-Elektrode gegenüber Hg(tt) in wäßriger Lösung

Zusammenfassung Herstellung und Wirkungsweise einer gegen Hg(II) ionenselektiven Elektrode wurde beschrieben. Das analytische Verhalten dieser Elektrode, die sich durch chemische Behandlung einer handelsüblichen Silbersulfidelektrode, die für Pb(II)-Ionen selektiv ist, herstellen läßt, wurde an Hand von Potential-Konzentrationskurven, Potential-pH-Kurven und ihrer Selektivität diskutiert. Das Verhalten gegenüber fixemc _Hg(ii)bei Anstieg des pH ins alkalische Gebiet korrespondiert mit der Abnahme der Konzentration an freien Hg²⁺-ionen bis herab zu pHg 17. Die Nachweisgrenze liegt schätzungsweise bei einer totalen Hg(II)-Konzentration von 10^–5 M.

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Presented at the Fifth European Conference on Analytical Chemistry (EUROANALYSIS-V), Cracow, Poland, 26–31 August, 1984.     

Determination of Esomeprazole on an Electropolymerized L‐arginine and β‐cyclodextrin Modified Screen Printed Carbon Electrode

The formation of an inclusion complex of the proton‐pump inhibitor (PPI) drug esomeprazole (ESO) with ß‐cyclodextrin (ß‐CD) has been investigated and proven by cyclic voltammetry (CV). The formation constant of the complex was determined. Thereafter, an electropolymerized β‐CD and L‐arginine (L‐arg) modified screen printed carbon electrode (P‐β‐CD‐L‐arg/SPCE) was developed for the determination of ESO using differential pulse adsorptive stripping voltammetry (DPAdSV). A significant enhancement of the peak current was observed when applying an accumulation step due to the effect of adsorption. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) further indicated that the polymer of β‐CD and L‐arg efficiently improved the electron transfer kinetic between analyte and electrode surface. Under the optimized conditions, the oxidation peak current was linearly proportional to the concentration of the drug in the range of 1.0×10^?8 to 1.0×10^?5 M. The DPAdSV method was successfully used to determine the concentrations of the drug in spiked human serum samples.