All-Solid-State Reference Electrode with Heterogeneous Membrane.

Novel reference electrodes with a solid contact coated by a heterogeneous polymer membrane are described. The electrodes are obtained using Ag nanoparticles, AgBr, KBr suspended in tetrahydrofuran solution of PVC and DOS and deposited on Ag substrate, or another substrate covered with Ag, by drop casting. After a short period of soaking in a KBr solution, stable and reproducible formal potentials of -157 ± 2 mV (vs Ag/AgCl/3 M KCl) were observed, and the solid-contact reference electrodes were ready to use. It is shown that the described reference electrodes are relatively insensitive to the changes in the sample matrix, the concentrations of ions, the pH and the redox potential. These electrodes can also be fabricated in miniaturized form, and thus used to produce miniaturized multielectrode probes.

Galvanic cell without liquid junction for potentiometric determination of copper.

This paper describes potentiometric measurements in an integrated galvanic cell with both indicator and reference electrodes. Both electrodes are conducting polymer-based. The copper-sensitive indicator electrode is made by using poly(3,4-ethylenedioxythiophene) (PEDOT) doped with 2-(o-arsenophenylazo)-1,8-dihydroxynaphthalene-3,6-disulphonic sodium salt (Arsenazo-I) as the electroactive substance in the film, while the reference electrode is based on PEDOT doped by 2-morpholineoethanesulfonic acid (MES). It is shown that the galvanic cell can be used for determination of copper both in non-aqueous media (where all PVC-based membranes failed) and in the presence of chloride ions, which disturb the signal of conventional copper ion-selective electrodes with solid-state membranes. It is further shown that the titration of copper ions can be successfully monitored using the described electrochemical cell.

Conducting polymers in modelling transient potential of biological membranes.

The possibility of using conducting polymer (CP) films doped with biological ligands as artificial biological membranes to study potential formation mechanisms is presented. Calcium and magnesium ion-binding anionic sites--asparagine, glutamine, adenosinotriphosphate and heparin are incorporated into the poly(pyrrole) film during electrochemical polymerization. This approach allows the competitive calcium-magnesium ion-exchange to be inspected by open circuit measurements. After a close-to-Nernstian sensitivity of the CP membranes was induced by soaking in alkaline solutions of calcium or magnesium, dynamic experiments were performed by a change in the bulk concentration of magnesium or calcium ions. A characteristic transitory potential response, though distinctively different for the calcium and magnesium ions, was observed and explained using the diffusion layer model (DML).

Junction-less reference electrode for potentiometric measurements obtained by buffering pH in a conducting polymer matrix.

A reference electrode for potentiometric measurements based on conducting polymers (CP) doped with pH buffering ligands is described. Both the CPs and doping ligands are selected and adjusted in such a way that possible ionic and redox sensitivity is hampered, while the pH buffering property of the CP film is exposed. In this way, the electric potential drop at the conducting polymer|solution interface is stabilized and close to constant over a certain pH range. The electrode behaves as a pseudo-reference electrode in amphiprotic solvents or their mixtures, e.g. water-alcohol mixtures. For the first time titration of sulfates with lead(ii) in water-methanol solution using two "plastic" electrodes, CP-based Pb(2+)-sensitive indicator and CP-based reference electrode, is shown. Because the electrode is junction-less it may easily be miniaturized and maintained and thus may serve in frontier applications of sensors.

[Incidence of Graves disease in children in some regions of south-eastern Poland]. / Zapadalnosc dzieci na chorobe Gravesa-Basedowa w wybranych regionach Polski poludniowo-wschodniej.

The aim of the studies was the assessment of Graves disease (G-D) incidence in children aged 0-15 years who inhabited the Krakowskie (K), Nowosadeckie (N) and Rzeszowskie (Rz) provinces in the years 1989-1996. The incidence of G-D was evaluated depending on the age, sex and place of residence (urban vs. rural area). The analyses for particular years were carried out separately for each province and for three provinces combined. The mean incidence coefficient (I.C.) for three provinces in the years 1989-1996 was 1.83. The highest incidence of G-D was noted in the group of 10-15 year old patients (I.C.=3.81). In the youngest children the disease was sporadic (I.C.=0.12). A significantly higher incidence rate was observed in girls, in whom the I.C. value was the highest in the oldest age group, amounting to 6.92. In boys the incidence of G-D was 8 times lower and the I.C. value in the 10-15 year group was 0.79. It was also demonstrated that the incidence of Graves disease in the entire group showed no significant differences in urban and rural areas. The incidence of Graves disease in subsequent years of the analyzed period was diversified. The linear regression analysis demonstrated a growing tendency in the years 1989-1996. In the period under investigation, the highest incidence was noted in the Rz region, where the standardize incident coefficient was 2.4. In the K and N provinces the incidence was lower and both cases amounted to 1.6 after standardization. The incidence of Graves disease showed a seasonal variation, associated with a significantly more frequent diagnosis established in autumn months.