Biomedical subjects

Agata Michalska

Publications and source records attributed to Agata Michalska.

7 recordsLinked to original sources

PubMed2006

Plastic reference electrodes and plastic potentiometric cells with dispersion cast poly(3,4-ethylenedioxythiophene) and poly(vinyl chloride) based membranes.

A simple procedure of preparing low cost, planar and disposable reference electrodes for potentiometric applications is presented. This method is essentially the same as used for obtaining all-plastic ion-selective electrodes and thus promising for simple fabrication of complete cells. Commercially available aqueous dispersion of poly(3,4-ethylenedioxythiophene) doped by poly(4-styrenesulfonate) ions (PEDOT-PSS, Baytron P) is simply cast on a non-conducting plastic support (transparent foil for laser printers). This layer is covered by a non-selective poly(vinyl chloride) based membrane containing solid AgCl and KCl, added to obtain a stable potential. The conducting polymer layer plays a double role, of electrical contact and ion-to-electron transducer, enhancing the potential stability. The reference electrodes obtained exhibit independence of the kind and concentration of electrolyte applied as well as very low sensitivity to interferences: redox reactants and H+ ions; they are also characterized by both potential stability and low polarisability, sufficient for potentiometric applications. Cells of plastic electrodes (indicator and reference ones) are tested using an arrangement with Pb2+ or Ca2+ selective sensors. Potentiometric characteristic of such cells is satisfactory, well comparable with that using a classical electrode arrangement.

Biosensing Techniques↗

PubMed2006

Laser ablation inductively coupled plasma mass spectrometry assisted insight into ion-selective membranes.

Laser ablation inductively coupled plasma mass spectrometry was used to evaluate ion depth profiles across ion-selective membranes. Advantageously, this approach does not require incorporation of additional components (e.g., chromoionophore) in the membrane composition, as compared to that used in typical potentiometric applications. Moreover, comparison of the distribution of ions in differently pretreated membranes is possible. Concentration profiles of primary and interfering agent (Na+) ions were recorded, for example, of Pb2+-selective poly(vinyl chloride)-based membranes. It was found that the contents and the distribution of Pb(2+) and Na+ ions across the membrane is strongly dependent on the composition of the solutions to which both sides of the membrane are exposed during preconditioning and on the plasticizer included in the membrane formulation. Typical plasticizers, bis(2-ethylhexyl sebacate) (DOS) and the more polar 2-nitrophenyl octyl ether (o-NPOE), were used. It was found that faster ion transport occurs for o-NPOE, and the membrane saturation with Pb2+ ions was achieved within less than 20 h for a 400-microm-thick membrane. In the case of the less polar plasticizer DOS, due to slower rate of ion transport, even after 20 h, the Pb2+ concentration gradients were still visible within the membrane. On the basis of concentration profiles, primary ion diffusion coefficients in both membranes were calculated, and the value obtained for o-NPOE containing membrane was found to be approximately 2 times higher than for its DOS-plasticized counterpart.

Decanoic Acids↗

PubMed2006

Effect of interferents present in the internal solution or in the conducting polymer transducer on the responses of ion-selective electrodes.

The effect of interferents present on the opposite side of the Pb2+-selective membrane has been studied for both internal solution and all-solid-state sensors with a conducting polymer (CP) transducer. For interferents with moderate selectivity coefficients (sodium cations) present in the internal solution or in the CP transducer phase, super-Nernstian responses were obtained. For sensors containing strongly discriminated interferents (lithium ions), however, responses typical of conventional electrodes are observed, despite the low activity of primary ions on the opposite side of the membrane. This effect is attributed to hindered incorporation of interfering ions into the membrane, which also impairs the long term stability of the potential. Because of the relatively small absolute amounts of interferents in the transducer of all-solid-state sensors, their exchange for primary ions occurs quickly. Thus, transformation of the sensor to one with a micromolar detection limit and high potential stability is observed.

Journal Article↗

PubMed2005

Optimizing the analytical performance and construction of ion-selective electrodes with conducting polymer-based ion-to-electron transducers.

All-solid-state ion-selective electrodes that use a conducting polymer as the ion-to-electron transducer have emerged as one of the most promising classes of all-solid-state potentiometric sensors in recent years. This is largely because it has many analytical advantages, including high response stability, which is unique in the field of internal-solution-free ion-selective electrodes. This paper reviews the considerable progress that has been made in this area of sensing in recent years, in terms of detection limits, selectivity coefficients and novel construction methods.

Journal Article↗

PubMed2005

All-solid-state reference electrodes based on conducting polymers.

A novel construction of solution free (pseudo)reference electrodes, compatible with all-solid-state potentiometric indicator electrodes, has been proposed. These electrodes use conducting polymers (CP): polypyrrole (PPy) or poly(3,4-ethylenedioxythiophene) (PEDOT). Two different arrangements have been tested: solely based on CP and those where the CP phase is covered with a poly(vinyl chloride) based outer membrane of tailored composition. The former arrangement was designed to suppress or compensate cation- and anion-exchange, using mobile perchlorate ions and poly(4-styrenesulfonate) or dodecylbenzenesulfonate anions as immobilized dopants. The following systems were used: (i) polypyrrole layers doped simultaneously by two kinds of anions, both mobile and immobilized in the polymer layer; (ii) bilayers of polypyrrole with anion exchanging inner layer and cation-exchanging outer layer; (iii) polypyrrole doped by surfactant dodecylbenzenesulfonate ions, which inhibit ion exchange on the polymer/solution interface. For the above systems, recorded potentials have been found to be practically independent of electrolyte concentration. The best results, profound stability of potentials, have been obtained for poly(3,4-ethylenedioxythiophene) or polypyrrole doped by poly(4-styrenesulfonate) anions covered by a poly(vinyl chloride) based membrane, containing both anion- and cation-exchangers as well as solid potassium chloride and silver chloride with metallic silver. Differently to the cases (i)-(iii) these electrodes are much less sensitive to the influence of redox and pH interferences. This arrangement has been also characterized using electrochemical impedance spectroscopy and chronopotentiometry.

Chromatography, Ion Exchange↗

PubMed2004

Factors affecting the potentiometric response of all-solid-state solvent polymeric membrane calcium-selective electrode for low-level measurements.

An all-solid-state calcium-selective electrode was constructed with poly(pyrrole) solid-contact doped with calcium complexing ligand Tiron. The potentiometric response of this sensor can have a linear range down to 10(-)(9) M with a slope close to Nernstian and detection limit equal to 10(-)(9.6). The effects of pH and the activity of the interfering ion in the conditioning solution on the potentiometric behavior of the constructed sensors were examined. Potential stability, reproducibility, and impedance studies were performed. The selectivity of the constructed electrode is better than that of the conventional calcium-selective electrode with internal filling solution of 10(-)(2) M CaCl(2) and comparable to that of the best liquid-contact electrodes.

Calcium↗

PubMed2003

All-solid-state calcium solvent polymeric membrane electrode for low-level concentration measurements.

An all-solid-state calcium-selective electrode with a plastic membrane phase containing a calcium ionophore ETH-1001 placed on poly(3-methylthiophene) ion-to-electron transducting layer functionalized to bind calcium cations has been constructed. The obtained potentiometric sensors were characterized with a calibration line of slope close to Nernstian within the activity from 10(-5) to 0.1 M. For Ca2+ activity lower than 10(-5) M, super-Nernstian behavior was observed. The super-Nernstian response that is observed for electrodes with an internal solution strongly binding primary ions was in this case attributed to incorporation of calcium ions in the modified solid-contact phase. With this arrangement, the evaluation of selectivity coefficients much closer to those that depend on the properties of the ion-selective membrane itself was possible.

Journal Article↗