[1] Sandwell Gen Hosp, Black Country Pathol Serv, Trace Elements Lab, West Midlands B71 4HJ, England
[2] Thames Water Util Ltd Lab, 9 Manor Farm Rd, Reading RG2 0JH, England
[3] LGC, Queens Rd, Teddington TW11 0LY, Middx, England
[4] Palacky Univ Olomouc, Fac Sci, Dept Analyt Chem, 17 Listopadu 12, Olomouc 77146, Czech Republic
[5] Univ Massachusetts Amherst, Dept Chem, 710 North Pleasant St, Amherst, MA 01003 USA