Determination of iron and ten 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 56Fe as the reference isotope and 57Fe 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.