Comparison of the performance of FI-ICP-MS and FIETV-ICP-MS systems for the determination of trace elements in sea water

The performance of two flow injection systems (FI) for on line separation and preconcentration of Cu, Cd, Pb, Bi, Au, Ag, As(III) and Se(IV) in sea water and determination by inductively coupled plasma mass spectrometry are compared. One system is coupled to the nebulizer of the spectrometer while the other one is coupled to an eletrothermal vaporizer also coupled to the same spectrometer. The matrix separation and analyte pre-concentration are accomplished by retention of the analytes complexed with the ammonium salt of O,Odiethyl dithiophosphate on C18 immobilized on silica in a column coupled directly to the pneumatic nebulizer or to the auto-sampler arm of an electrothermal vaporizer. The eluate is on line diluted with water and introduced directly to the pneumatic nebulizer or vaporized after being automatically injected into the graphite tube, prior to the vaporization of the analytes. The conditions for the complexation-separation and elution were optimized. The accuracy was checked by the analysis of two certified sea waters, CASS-3 and NASS-4, from the National Research Council of Canada. Only As(III) could not be determined in the sea water medium. The recoveries for the non-certified elements were in the range 90-110%. The relative standard deviation are below 10% while the sampling frequencies are in the range 2122h-1, for both systems.