Tadeusz Krawczyński vel Krawczyk

INHIBITIVE DETERMINATION OF MERCURY AND OTHER METAL IONS BY POTENTIOMETRIC UREA BIOSENSOR

The biosensor with urease entrapped in PVC layer at the surface of pH-sensitive iridium oxide electrode was applied for testing of mercury and other metal ions inhibition on enzymatic reaction. The calculation of inhibition effect was based on the measurement of initial rate of decrease of biosensor potential (proportional to the initial rate of enzymatic reaction) after addition of substrate after inhibition step. Some differences of inhibition extent were observed for various mercury forms (Hg(NO3)2, HgCl2, PhHgCl and Hg2(NO3)2) as well as for other heavy metal ions investigated as potential interferents. Because the method was not specific, it was applied for the determination of total inhibition effect caused by heavy metal ions in water samples. In the case of most cations tested the total recovery of enzyme activity was possible using Tris buffer solution with EDTA and thioacetamide after less than 10 min regeneration time.

Electrochemical biosensors based on enzymes immobilized in electropolymerized films

A review based on 135 references concerns the design and properties of electrochemical biosensors for 13 different substrates of enzymatic reactions. In the sensors discussed the enzymes are immobilized within or on the top of electropolymerized films, mostly of conducting polymers. Amperometric detection is most often used for internal electrochemical sensing.

Effect of addition of main ion to carrier solution in potentiometric flow-injection measurements with solid state ion-selective electrodes

SummaryFlow-injection measurements were performed using chloride, fluoride, iodide and copper(II)-selective electrodes. A pronounced effect of addition of main ion to the carrier solution was observed for the fluoride- and iodide-selective electrode. Super-Nernstian slope observed for the fluoride- and copper(II)-selective electrode in the absence of the sensed ion in the carrier solution decreased to Nernstian values in the presence of the measured ion in the carrier solution. This phenomenon is explained by different response times at different concentrations of the sensed ion.

Effect of some chelating ligands on the potential response of the chalcocite copper ion-selective electrode

Abstract The effects of diethylenetriamine, triethylenetetramine, tetraethylenepentamine, aminoacetic acid, iminodiacetic acid, nitrilotriacetic acid, ethylenediaminediaminetetraacetic acid, diethylenetriaminepentaacetic acid and triethylenetetraminehexaacetic acid on the behaviour of the synthetic chalcocite (copper(I) sulphide) copper-selective electrode are described. The effects of those ligands on the electrode response at different pH values is explained on the assumption that copper(I) ions contribute to the potential indicated. Copper(I) ions originate from the membrane phase and participate in exchange and redox reactions. The effects of oxygen and temperature are reported. The electrode response can be predicted on the basis of copper(II) equilibria in solution, only if the conditions are such that there is no interference from copper(I) ions.

Lactate solid-state biosensor with multilayer of electrodeposited polymers for flow-injection clinical analysis

In the lactate biosensor, electrodeposited poly(o-phenylenediamine) serves as a convenient matrix for the immobilization of lactate oxidase, but does not provide sufficient discrimination from several interfering species present in physiological fluids. Their effect, however, can be eliminated by additional modification of the working Pt electrode with a bilayer of electrodeposited polypyrrole/polyphenol. Despite continued decrease in biosensor sensitivity, the newly developed three-layer solid-state biosensor was successfully applied in flow-injection determination of lactate in both undiluted and diluted human blood serum samples over a 10 day period. For the lactate concentration range 0.2-5.0 mM in several series of measurements the correlation coefficient values for comparison with photometric determination using a DuPont dimension clinical analyzer were between 0.96 and 0.99. The reproducibility measured for 1:10 diluted serum was 0.6%. The detection limit was estimated as 2 microM.

Determination of copper in water by means of chalcocite copper ion-selective electrode

The possibility of determination of copper in natural waters was tested by direct potentiometry with chalcocite copper sensitive ion selective electrode. This can be carried out for the copper concentration down to 6 μg l−1 when the standard additions procedure is used. The electrode characteristics was investigated and as a medium was proposed a TFB solution containing Tris, potassium fluoride and potassium nitrate. However at the extreme low concentrations of copper the water samples after addition of TFB should be heated to boiling. In these conditions the accuracy of determination for the average of five measurements is not worse than 25%, and precision is of the order of 20%.

Simple antilog converter for conventional and flow-injection measurements with ion-selective electrodes

Abstract The antilog converter for potentiometric measurements produces an output voltage which is linearly dependent on the concentration of the sensed species over two orders of magnitude. Signals obtained in measurements with chloride, fluoride, potassium and copper ion-selective electrodes range from 1.0 to 10.0 V. The converter is successfully applied for flow-injection potentiometry within one concentration decade but its sensitivity depends on the dispersion in the flow system.

Enhancement of selectivity of electrochemical detectors by kinetic discrimination in flow‐injection systems

Appropriate design of flow-injection (FI) manifold and selection of suitable detectors may provide additional changes in the selectivity of the FI response compared to conventional nonflow measurements. As an example of such systems, based on data from the literature and our own experimental data, the potentiometric detection with different ion-selective electrodes and two different amperometric systems are discussed. Selectivity changes in flow-injection analysis (FIA) systems for ion-selective membrane electrodes depend on relative response to interferences observed in batch measurements. Simultaneous detection of pesticides is shown as an example of an amperometric FIA system with a bilayer lipid membrane working electrode. Simultaneous detection of lactate and ascorbate is shown in an FIA system with amperometric biosensing detection.

Behaviour of a chalcocite copper ion-selective electrode in solutions of iron(III) ions

The effect of iron(III) ions on the potential of the chalcocite electrode was investigated. Linear graphs were obtained for pFe(III) = 2-4, and were suitable for analytical purposes. The effect of ligands complexing iron(III) was studied, and the potential shown to be due to the concentration of free iron(III) ions only. The pH effect is mainly connected with solution reactions. A mechanism of potential response, based on a redox reaction, has been postulated, but the response does not depend on the redox potential in the bulk of the solution.

Flow-injection analysis of inorganic pollutants in gaseous phase with piezoelectric detection Part 1. Verification of principal experimental parameters affecting the detector response

Abstract Piezoelectric quartz crystal detectors with several coating materials sensitive to sulphur dioxide and ammonia are used as model sensors for the optimization of a flow-injection measuring system with a gaseous carrier. As factors affecting the quality of detector response, the amount of coating material and its distribution on the quartz oscillator surface, the composition, flow rate and purity of the gaseous carrier, the design of the flow-through detector, the temperature and the injection volume are considered. The experimental data obtained illustrate the significance of careful optimization of these parameters for the detectability, stability and reproducibility of flow-injection analysis in the gaseous phase with piezoelectric detection.