1. Ghent University, Faculty of Sciences, Department of Organic and Macromolecular Chemistry, Organic and Biomimetic Chemistry Research Group, Krijgslaan 281 (S4), 9000 Ghent, Belgium
2. BAM Federal Institute for Materials Research and Testing, Department of Analytical Chemistry; Reference Materials, Richard-Willstätter-Str. 11, D-12489 Berlin, Germany