1. Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Roma, Italy
2. Trace Elements Laboratory, Black Country Pathology Services, Sandwell General Hospital, West Bromwich, West Midlands, B71 4HJ, UK
3. Reading Scientific Services Ltd, The Reading Science Centre Whiteknights Campus, Pepper Lane, Reading, Berkshire, RG6 6LA, UK
4. LGC, Queens Road, Teddington, Middlesex, TW11 0LY, UK
5. Department of Biochemistry, Manchester University NHS Foundation Trust, Oxford Rd, Manchester, M13 9WL, UK
6. Guildford, Surrey, UK
7. Department of Chemistry, University of Massachusetts Amherst, 710 North Pleasant Street, Amherst, MA 01003, USA