1. Department of Analytical Chemistry; Reference Materials; BAM Federal Institute for Materials Research and Testing; Richard-Willstätter-Str. 11 12489 Berlin Germany
2. Department of Materials and the Environment; BAM Federal Institute for Materials Research and Testing; 12205 Berlin
3. Institute of Biomaterial Science and Berlin-Brandenburg Centre for Regenerative Therapies; Helmholtz-Zentrum Geesthacht; 14513 Teltow Germany
4. Berlin-BrandenburgSchool for Regenerative Therapies; Charité Universitätsmedizin; 13353 Berlin Germany