1. Department of Chemistry and Biochemistry, Faculty of Food Technology and Biotechnology, Pierottijeva 6, 10000 Zagreb, Croatia, Fax: +385‐4836‐082
2. Institute of Inorganic Chemistry and Analytical Chemistry, Johannes Gutenberg University of Mainz, Duesbergweg 10–14, 55128 Mainz, Germany, Fax: +49‐6131‐3927277