1. J. Heyrovský Institute of Physical Chemistry, Academy ofSciences of the Czech Republic, v.v.i., Dolejškova 3, 182 23 Prague 8, Czech Republic
2. Dipartimento di Scienze dell'Ambiente e della Vita, Università del Piemonte Orientale “A. Avogadro”, Viale T. Michel 11, 15121 Alessandria, Italy, Fax: +39‐0131‐360250
3. Faculty of Chemical and Food Technology, Slovak Technical University Bratislava, Radlinského 9, 81237 Bratislava, Slovak Republic