Determination of chromium, copper and lead in river water by graphite-furnace atomic absorption spectrometry after coprecipitation with terbium hydroxide.

Coprecipitation with terbium hydroxide quantitatively recovered trace amounts of chromium(III), copper(II) and lead(II) at pH 8.4 - 10.8, 8.0 - 11.5 and 8.7 - 11.5, respectively. The precipitate was dissolved in 0.85 mol dm(-3) nitric acid, and the analytes were determined by graphite-furnace atomic absorption spectrometry (GF-AAS). The presence of terbium (up to 7 g dm(-3)) did not interfere with the determination. The detection limits were 0.3 microg dm(-3) for chromium, 0.4 microg dm(-3) for copper and 0.5 microg dm(-3) for lead, when the analytes in 200 cm3 of the sample solution were concentrated into 10 cm3. The ions added to river or seawater were quantitatively recovered. Chromium and copper in a contaminated river water were successfully determined.