Preconcentration by coprecipitation of chromium in natural waters with Pd/8-quinolinol/tannic acid complex and its direct determination by solid-sampling atomic absorption spectrometry

A sensitive and accurate method for the determination of chromium at the ultra-trace levels has been investigated and applied to river water and seawater. Chromium was pre-concentrated by coprecipitation with a combination of 8-quinolinol, palladium as a carrier element and tannic acid as an auxiliary complexing agent, and the coprecipitates obtained were directly measured by graphite furnace atomic absorption spectrometry (GFAAS) using the solid Sampling technique. The coprecipitation conditions for chromium with Pd/8-quinolinol/tannic acid complex, such as the effects of the pH, amounts of palladium and tannic acid, were examined in detail. It was found that chromium is coprecipitated quantitatively with Pd/8-quinolinol/tannic acid complex in the pH range of 5.1-5.3. The detection limit for chromium, which was defined as the concentration calculated from three times of the standard deviation of the procedural blanks, is 20 ng/l for 300 ml portions of water samples in the proposed method. (C) 1999 Elsevier Science B.V. All rights reserved.