1. National Physical Laboratory, Hampton Road, Teddington TW11 0LW, U.K.
2. Department of Chemistry, Umeå University, 901 87 Umeå, Sweden
3. LAQV, REQUIMTE, Department of Chemical Sciences, Faculty of Pharmacy, University of Porto, R. Jorge Viterbo Ferreira 228, 4050-313 Porto, Portugal
4. Department of Biotechnology and Nanomedicine, SINTEF Industry, 7465 Trondheim, Norway