Biosorption of platinum and palladium for their separation/preconcentration prior to graphite furnace atomic absorption spectrometric determination

Inexpensive baker's yeast Saccharomyces cerevisiae and green algae Chlorella vulgaris, either free or immobilized on silica gel have been shown to selectively accumulate platinum and palladium from water samples in acidic medium (pH 1.6-1.8). Optimization of conditions of metals biosorption (sample pH, algae and yeast masses, adsorption time, temperature) was performed in batch mode. The procedure of matrix separation based on biosorption of platinum and palladium on algae C. vulgaris covalently immobilized on silica gel in flow mode was developed. The use of algae in flow procedure offers several advantages compared with its use in the batch mode. The procedure shows better reproducibility (<2%), improved efficiency of platinum retention on the column (93.3 +/- 1.6%), is less laborious and less time consuming. The best recovery of biosorbed metals from column (87.7 +/- 3.3% for platinum and 96.8 +/- 1.1 for palladium) was obtained with solution of 0.3 mol l(-1) thiourea in 1 mol l(-1) hydrochloric acid. The influence of thiourea on analytical signals of examined metals during GFAAS determination is discussed. The procedure has been applied for separation of noble metals from tap and waste water samples spiked with platinum and palladium. (C) 2003 Elsevier Science B.V. All rights reserved.