DETERMINATION OF TRACE-ELEMENTS IN SEA-WATER BY INDUCTIVELY-COUPLED PLASMA-MASS SPECTROMETRY AFTER PRECONCENTRATION BY FORMATION OF WATER-SOLUBLE COMPLEXES AND THEIR ADSORPTION ON C-18-BONDED SILICA-GEL

A simple and reliable preconcentration method was developed for the de termination of seven trace metals (Mn, Fe, Wi, Cu, Zn, Cd and Pb) in s ea-water by ICP-MS, The method is based on the formation of water-solu ble complexes in an aqueous sample followed by adsorption of the compl exes onto a C-18-bonded silica gel column. The chelating reagent used was romo-2-pyridylazo)-5-(N-propyl-N-sulfopropylamino) phenol (5-Br-PA PS). By passage of 100 mi of sea-water sample, after addition of 5-Br- PAPS and adjustment of the pH to 8.3, quantitative adsorption of the m etal complexes onto the column took place while the major matrix ions in sea-water passed through the column, A similar but separate sample work-up at pH 4.5 provided acceptably low blank values for Fe, The met als were subsequently eluted with 4.0 mi of 1.0 M HNO3. All seven elem ents were determined with an all-argon plasma, whereas ultratrace leve ls of Fe were determined with a nitrogen-argon mixed-gas plasma to red uce the isobaric interference by (ArO)-Ar-40-O-16 On Fe-56. The detect ion limits of the method, based on a 25-fold preconcentration, range f rom 0.08 ng l(-1) for Cd to 16 ng l(-1) for Fe, The precision and accu racy of the method were demonstrated by analyzing coastal and open-oce an sea-water certified reference materials.