1. Institute of Analytical Chemistry, Vienna University of Technology, Getreidemarkt 9/151,1060 Wien, Austria, Institute of Chemical Engineering, Fuel and Environmental Technology, Vienna University of Technology, Getreidemarkt 9/159, 1060 Wien, Austria, and Jobin-Yvon/Dilor GmbH, Neuhofstrasse 9, D-64625 Bensheim, Germany