1. Department of Chemistry, Faculty of Natural Sciences and Informatics, Constantine the Philosopher University in Nitra, 949 01 Nitra, Slovakia
2. Department of Management and Product Quality, Faculty of Chemical Engineering and Commodity Science, Casimir Pulaski University of Radom, 26 600 Radom, Poland
3. Stredná Odborná Škola Chemická, Vlčie Hrdlo 50, 82 107 Bratislava-Ružinov, Slovakia