[1] Univ Surrey, Sch Biol Sci, Ctr Clin Sci & Measurement, Supra Reg Assay Serv Trace Element Lab, Guildford GU2 5XH, Surrey, England
[2] Lord Rank Ctr, High Wycombe HP12 3QR, Bucks, England
[3] Glasgow Royal Infirm Univ NSH Trust, Dept Clin Biochem, Trace Element Unit, Glasgow G4 0SF, Lanark, Scotland
[4] Min Agr Fisheries & Food, Food Sci Lab, CSL, Norwich NR4 7UQ, Norfolk, England
[5] Hlth & Safety Execut, Hlth & Safety Lab, Sheffield S3 7HQ, S Yorkshire, England