1. Department of Analytical Chemistry; Reference Materials, Bundesanstalt für Materialforschung und -prüfung (BAM), Richard-Willstätter-Strasse 11, D-12489 Berlin, Germany
2. Department of Chemistry, Humboldt-Universität zu Berlin, Brook-Taylor-Strasse 2, D-12489 Berlin, Germany
3. LAQV, REQUIMTE, Departamento de Ciências Químicas, Faculdade de Farmácia, Universidade do Porto, Rua de Jorge Viterbo Ferreira, 228, 4050-313 Porto, Portugal
4. Technische Universität Berlin, Straße des 17. Juni 135, D-10623 Berlin, Germany