DETERMINATION OF SILVER IN WATERS AND SOIL BY ELECTROTHERMAL ATOMIC-ABSORPTION SPECTROMETRY AFTER COMPLEXATION AND SORPTION ON CARBON

A method for the preconcentration of silver is proposed. Silver is com plexed by the ammonium salt of dithiophosphoric acid O,O-diethyl ester and sorbed on to carbon. After desorption in a small volume of nitric acid solution, silver is determined by electrothermal atomic absorpti on spectrometry. In de-ionized water the yield was about 70%, indicati ng incomplete complexation and/or sorption on the carbon. In purified sea-water (sea-water submitted to solvent extraction to extract silver ), the yield was less, about 40%, probably due to the effect of concom itants in the sea-water. The method was applied to sea and river water s and to a soil reference material. Spiked sea-water samples produced an average recovery of 102%, indicating good accuracy if analytical so lutions in purified sea-water are used for the calibration. The detect ion limit (k = 3) for 200 ml of sea-water is 0.3 ng l-1. After acid di ssolution of the soil sample, ascorbic acid should be added, prior to the complexing agent, to avoid interference of iron(III). Because of t he small final volume, high enrichment factors can be obtained.