Study of chemical modifiers for direct determination of silver in sea water by ETA-AAS with deuterium background correction

Methods for the direct determination of silver in sea water samples by ETA-AAS using different chemical modifiers were studied. The effect of salinity was studied using synthetic sea water of high (72.8‰) and low (34.2‰) salinity, and the results were compared with aqueous standard solutions. The charring temperatures achieved were 800 and 900 °C for magnesium nitrate and ammonium dihydrogen phosphate respectively, being 1100 °C for palladium nitrate and their mixtures. The best sensitivity obtained in the peak-height measurement mode was achieved by using reduced palladium (limit of detection (LOD) between 0.5 and 1.1 μg l −1 for an injection volume of 20 μ1) with analytical recoveries close to 100% for synthetic and real sea water samples. The use of ammonium dihydrogen phosphate (LOD of 1.3 μg l −1 for an injection volume of 20 μ1) produced good recoveries for low salinity; at high salinity an increase of around 25% was obtained, the method being unsuitable for sea water analysis. Finally, an interference study of the major components of sea water was carried out and applied to the analysis of surface sea water from the Galicia coast.