SVIBOR - Project code: 1-07-025

MINISTRY OF SCIENCE AND TECHNOLOGY

Strossmayerov trg 4, HR - 10000 ZAGREB
tel.: +385 1 459 44 44, fax: +385 1 459 44 69
E-mail: ured@znanost.hr

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Project code: 1-07-025


PREPARATION AND APPLICATION SELECTIVE ELECTRODES


Main researcher: RADIĆ, NJEGOMIR (39595)


Assistants
Type of research: basic
Duration from: 01/01/91. to 12/15/95.
Papers on project (total): 16
Papers on project quoted in Current Contents: 12
Institution name: Tehnološki fakultet, Split (11)
Department/Institute: Department of Chemistry Laboratory for Analytical Chemistry
Address: Teslina 10/V
City: 21000 - Split, Croatia
Communication
Phone: 385 (0)21 341 633
Fax: 385 (0)21 341 624
E-mail: NJRADIC@MATEH.TEHST.HR
Summary: The potentiometric determination of mercury(II) and thiourea (TU) in strong acid solution (pH 0 - 1) by using an "all-solid-state" ion-selective electrode with (silver-sulfide 25%, AgI 25% and PTFE 50% m/m) - membrane is described. It was found that, by direct potentiometry at pH 0, mercury(II) can be determined in the presence of up to 1 mmol/L of iron(III). The linear response of the electrode to TU has been discussed through the formation of Ag-TU complex at the exposed surface of the membrane. Two kinetic methods have been proposed by using fluoride ion-selective electrode (FISE). A kinetic-potentiometric method is described for the determination of Fe(III) based on monitoring of the formation of Fe(III)-monofluoride complex in acid solution. A potentiometric method for the determination of N-acetylcysteine (NAC) is based on its reduction action on Fe(III) in acidic fluoride solution, pH 2. The method is described as an equilibrium method and kinetic method. By using Cu(II)-ISE and a (Cu(II), EDTA and La(III)) - filling as internal solution, the FISE with novel reversible contact at the inner surface of the lanthanum fluoride membrane was prepared. The aluminium-fluoride complex formation in water/acetonitrile mixtures has been investigated using FISE. The overall formation constant of the Al(III)-hexafluoride complex was determined. Potentiometric determination of cysteine (Cys) in aqueous solution by using iodide-selective electrode with (Ag2S + AgI) membrane is described. The preparation of CuI + Ag2S and Cu2S(HgI4) + Ag2S membranes hydrophobised by PTFE is described. The pressed membranes have been examined as electrochemical sensors for copper(II) and iodide ions. A multi-purpose solid-state iodide-selective electrode is constructed as a compact tubular sensors. Application of the tubular electrode is exemplified by the determination of cysteine and thiourea.

Keywords: Potentiometric method, kinetic-potentiometric determination, flow-injection analysis, ion-selective electrodes, tubular design, mercury(II), iron(III), copper(II), thiourea, N-acetylcysteine, cysteine.

Research goals: The procedure of the preparation of solid-state ion-selective electrodes with different membranes have been investigated in the laboratory. Our aim was to develop a simple direct potentiometric methods for determination of metal ions (mercury(II), copper(II), iron(III), ...) or nonmetal species (thiourea, cysteine, N-acetylcysteine, ...). Furthermore, our aim was to prepare CuISE with pressed pellet which is contained an sparingly soluble Cu(I) salt instead widely used CuS (or copper(I)-sulfide). The response of the electrode with CuI + silver-sulfide and Cu(I)-tetraiodomercurate(II) + silver-sulfide membrane hydrophobised by PTFE to copper(II) ion and iodide has been studied. The behaviour of CuISEs with these membranes is under further investigation. Combination of the simplicity of the kinetic method with the advantages of fluorid ion-selective electrode (low detection limit, high selectivity) produces an excellent analytical technique for determination of metal ions that form complexes with fluoride. Our aim was to develop two kinetic - potentiometric procedures, for the determination iron(III) and N-acetylcysteine. Since the flow-injection analysis (FIA) is rapidly developing into powerful analytical tool with many merits, our aim is to develop a simple FIA system with flow-through potentiometric sensors. A multi-purpose solid-state electrode with iodide selective membrane will be constructed as a compact tubular sensor. The assembled electrode will be applied as a sensor in FIA system for the determination of thiourea and cysteine.

COOPERATION - INSTITUTIONS


  1. Name of institution: Department of Chemistry, University of Cincinnati
    Type of institution: University/Faculty
    Type of cooperation: Joint publishing of scientific papers
    City: OH 45221 - Cincinnati, USA
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Last update: 10/11/95
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