1. Faculty of Chemistry, Instrumental Analytical Chemistry, University of Duisburg-Essen, Universitätsstraße 5, 45141 Essen, Germany
2. Centre for Water and Environmental Research (ZWU), Universitätsstraße 5, 45141 Essen, Germany
3. IWW Water Centre, Moritzstraße 26, 45476 Mülheim an der Ruhr, Germany