1. Institute of Nutritional and Food Sciences, Chair of Bioanalytics, University of Bonn, Endenicher Allee 11-13, D-53115 Bonn, Germany
2. ELFI Analytik GbR, Massenhausener Straße 18a, D-85375 Neufahrn, Germany
3. Institute of Agricultural Engineering, University of Bonn, Nußallee 5, D-53115 Bonn, Germany