DETERMINATION OF IRON AND 10 OTHER TRACE-ELEMENTS IN THE OPEN OCEAN SEAWATER REFERENCE MATERIAL NASS-3 BY INDUCTIVELY COUPLED PLASMA MASS-SPECTROMETRY

Iron and ten other trace elements were determined in the Open Ocean Seawater certified reference material NASS-3 by inductively coupled plasma mass spectrometry (ICP-MS) after separation and concentration on silica-immobilized 8-hydroxyquinoline (I-8-HOQ). Iron and molybdenum were separated from sea-water samples adjusted to pH 3 prior to passage through the column, whereas for the other nine elements preconcentration was performed at pH 8. Determination of iron in the concentrates by isotope dilution, with Fe-56 as the reference isotope and Fe-57 as the spike, required the use of a nitrogen-argon mixed-gas plasma with partial aerosol desolvation. The detection limits of the method, based on a 90-fold preconcentration, range from 0.04 ng dm-3 for U to 6.3 ng dm-3 for zinc.