[1] Univ Surrey, Sch Biomed & Life Sci, Ctr Clin Sci & Measurement, Suprareg Assay Serv Trace Element Lab, Surrey GU2 7XH, England
[2] Lord Rank Ctr, RHM Technol, High Wycombe HP12 3QR, Bucks, England
[3] Univ Plymouth, Dept Environm Sci, Plymouth PL4 8AA, Devon, England
[4] Glasgow Royal Infirm Univ NHS Trust, Dept Clin Biochem, Trace Element Unit, Glasgow G4 0SF, Lanark, Scotland
[5] Hlth & Safety Execut, Hlth & Safety Lab, Sheffield S3 7HQ, S Yorkshire, England