Determination of trace metals in natural waters at nanogram per liter levesls by electrothermal atomic absorption spectrometry after extraction with sodium diethyldithiocarbamate

The determination of trace metals (Cd, Co, Cu, Fe, Ni and Pb) at concentrations found in fresh and sea waters is described. The metals are extracted as diethyldithiocarbamates from 500-ml samples into carbon tetrachloride, the extracts are evaporated to dryness and the residues are mineralized with 0.1 ml of concentrated nitric acid. This solution is used for graphite-furnace atomic absorption spectrometry after appropriate dilution. The detection limits are 10 pg Cd, 150 pg Co, 125 pg Cu, 100 pg Fe, 250 pg Ni and 100 pg Pb. The extraction/mineralization method is almost free from interferences, e.g., from trace elements at 500-fold and Na, K, Ca and Mg at million-fold amounts. The procedure is successfully applied to the determination of the above metals in deionized water, and river and sea waters.