1. Department of Beverage Analysis, Bavarian Health and Food Safety Authority, Luitpold Strasse 1, D97082 Würzburg, Germany
2. Isolab GmbH, D-85301 Schweitenkirchen, Germany
3. Bavarian Health and Food Safety Authority, D-85762 Oberschleissheim, Bavaria
4. Hydroisotop GmbH, D-85301 Schweitenkirchen, Germany