1. Institute of Food Research, Norwich Laboratory, Norwich Research Park, Colney, Norwich NR2 7UA, United Kingdom, Department of Chemistry, University of Aveiro, Aveiro 3800, Portugal, Department of Chemistry, Birkbeck College, University of London, Gordon House, 29 Gordon Square, London WC1H 0PP, United Kingdom, and Bruker Analytische Messtechnik GMBH, Silberstreifen, D-76287 Rheinstetten, Germany