DIRECT GRAPHITE-FURNACE ATOMIC-ABSORPTION SPECTROMETRIC DETERMINATION OF METALS IN SEA-WATER - APPLICATION OF PALLADIUM MODIFIERS AND A FRACTAL APPROACH TO THEIR ANALYTICAL SUPPORT

Sea water, like other high-salinity matrices, causes severe interferences in the direct determination of metals by graphite furnace atomic absorption spectrometry (GFAAS), even when Zeeman-effect background correction is applied. A method for eliminating these interferences by the application of mixed modifier system of ammonium oxalate and tetraamminepalladium(II) chloride is presented. In particular these modifiers optimize the direct GFAAS determination of lead and manganese. For cadmium, however, only ammonium oxalate should be used as a modifier. The geometry of the microdistribution of palladium on the palladium-conditioned graphite platform was investigated in order to elucidate possible stabilizing effects of palladium on the analytes which were observed with the different modifiers. Fractal characteristics of the palladium elemental distribution were ascertained by a scanning electron microscope-energy-dispersive x-ray spectrometer image box-counting analysis. The fractal dimension [D(B)(0) = 1,77 +/- 0.04 and 1.81 +/- 0.04] and electron microscopic investigations indicated differences in the structure of palladium deposits on the platform. These variations in the palladium geometry affect the analytes to a certain extent.