Jan Migdalski

Conducting polymer-based ion-selective electrodes

Single-piece, conducting polymer-based, potentiometric sensors with enhanced cationic sensitivity were obtained by doping a polypyrrole with metal-complexing, multivalent anions. Sulphosalycilic acid, Tiron, Eriochrome Black T and Kalces have been used as doping ions. Predominant sensitivity for copper was observed for the first two dopants, whereas for the two remaining ones, induced response for magnesium and calcium was found, respectively. Interestingly, in all sensors studied the metal-binding properties of the specific ligands known from polar solvents were retained. Hence, the specific reagents can be deliberately utilized for the construction of conducting polymer-based ion-selective sensors.

Electrochemical deposition and properties of polypyrrole films doped with calcion ligands

The properties of polypyrrole (PPy) film doped with calcion (calcichrome) in the process of electrochemical polymerization from aqueous solutions are presented. The properties of the films were inspected using different electrochemical methods, analysis by energy dispersive X-ray analysis and X-ray diffraction. Since the calcion ligands introduced to the PPy film retain the metal-complexing properties known from the aqueous solutions, it is possible to design calcium-sensitive sensors with an anticipated open-circuit response.

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.

Conducting Polymer-Based Reference Electrodes

In comparison with the conventional reference electrodes (see Chap. 5), application of conducting polymer increases the reference electrodes’ integrity by elimination of water-containing compartments. This allows the electrode miniaturization and eliminates problems resulting from uncompensated transport and undesired leakages from the bridge. The elimination of water compartments from the reference electrodes by use of conducting polymers enables their application at higher temperatures and over a wide pressure range as well as in the measurements in nonaqueous solvents. Numerous attempts were undertaken to apply conducting polymers for the reference electrodes design. They cover the following aspects: (1) adjusting of the electrode response by dispersing molecules enhancing its stability, (2) adjusting ion

Biomimetic Membranes as a Tool to Study Competitive Ion-Exchange Processes on Biologically Active Sites

The change in membrane potential with time is of fundamental importance in cell biology. From the biological point of view we are interested in the mechanism of voltage dependent channel block and related ionic antagonism that happens on the ion-binding sites forming channel necks (Migdalski at al., 2003; Paczosa at al., 2004; Paczosa-Bator at al., 2006). We argue that by applying biomimetic approach, the processes invisible in routine membrane research could be “amplified” and exposed for further scientific exploration. In our case, this argument refers to electrical potential transients and/or local concentration redistributions provoked a competitive calcium/magnesium or potassium/sodium/lithium ions exchange on the biological sites. Voltage-activation of the N-methyl-d-aspartate (NMDA) receptor channel, allowing for calcium ion influx by relieving the block by magnesium ion (Nowak at al., 1984; McBain at al., 1994), or monovalent ion effects such as potassium-sodium/ lithium/TEA(tetraethylammonium) in the case of potassium and sodium channels (Hille, 1992) is used to illustrate the value of biomimetic methodology. From the electrochemical point of view, our strategy means an interest in the timedependent (dynamic) characteristics of a membrane potential resulting from competitive ion-exchange processes. The membranes used in our studies are in electrochemistry known as the electroactive parts of ion-selective sensors sensitive for magnesium, calcium, potassium, sodium and lithium, which are the ions of our interest. To bridge mentioned above biological and electrochemical interests we use biomimetic membranes. The novelty of our approach is in applying conductive polymers (CPs) as with purposely dispersed bioactive sites. This allows observation of a competitive (antagonistic) ion exchange and its coupling with a membrane potential formation process on biologically active sites (BL). The sites in focus of our research, adenosinotriphosphate (ATP), adenosinodiphosphate (ADP), heparin (Hep) and two amino acids – asparagine (Asn) and glutamine (Gln), competitively bind calcium, magnesium, lithium, sodium and potassium ions and thus play an important role in ion-dependent biological membrane processes (Saris

Controlled-Growth Mercury Drop Electrode and Perspectives in Process Monitoring Application

The concept of the dropping mercury electrode (DME) and the technical solution of the device for its realization as proposed by Heyrovsky (1922) have been applied in many laboratories. This kind of working electrode, the so-called Polarographic detector, implies measuring of the current on a mercury drop whose surface is continuously expanding, while the maximum size of the drop is gravity controlled. A particular fraction of the current, the so-called charging current, which is connected with the changing of the drop area or with the changing of the potential of the electrode is independent of the concentration of the depolarizer. The charging current can be concidered as the background signal.