DETERMINATION OF PICOMOLAR CONCENTRATIONS OF TITANIUM, GALLIUM AND INDIUM IN SEA-WATER BY INDUCTIVELY-COUPLED PLASMA-MASS SPECTROMETRY FOLLOWING AN 8-HYDROXYQUINOLINE CHELATING RESIN PRECONCENTRATION

Picomolar concentrations of dissolved titanium, gallium and indium in sea water are measured using in inductively coupled plasma mass spectrometry (ICP-MS) after concentration and separation from the major ions in sea water via an 8-hydroxyquinoline chelating ion exchange resin (TSK-8HQ). Detection limits of 5-10 pM (0.2-0.4 part per trillion, ppt), 0.5 pM (0.02 ppt) and 0.1 pM (0.01 ppt) were found for Ti, Ga and In, respectively, after a 400-fold (Ti) or 3000-fold (Ga and In) concentration. The detection was blank limited for Ti, due primarily to background interferences from the HNO3 matrix, and sensitivity limited for Ga and In. Open ocean sea water concentrations for these elements are in the range of 6-300 pM for Ti, 2-60 pM for Ga, and 0.1-2.0 pM for In. Sampling and analytical precision of 7-10% was generally found for concentrations greater than twice the detection limit.