GSS-1 is a river sediment sample. A 0.5 g in a 50 ml PTFE beaker was dissolved with alternate treatment of 5 ml of conc. nitric acid and conc. hydrofluoric acid on a hot plate (2508C). The organic matter was destroyed with 10 ml of conc. perchloric acid. This process was repeated twice. Then the contents of the beaker were heated to near dryness and were transferred to a 100 ml measuring flask with small portions of 0.1% nitric acid and the volume was made up with 0.1% nitric acid. Similarly, a blank was also prepared. As GSS-1 contains a large concentration of aluminum (14.18% Al2O3) which may hydrolyze at pH 5 (optimum pH) causing high backpressure in the manifold lines, NaF (1.0 g/100 ml of sample) was added to the sample solution to mask the aluminum. The amount of copper and cadmium was determined, using the same sequence of preconcentration for 30 s, from the calibrations prepared by the addition of same amount of NaF to the standard solutions as in the sample. As pH is very critical for cadmium preconcentration, in order to maintain the pH at 5-6, the phen solution was prepared in 0.1 mol l ÿ1 buffer solution (Na2HPO4NaH2PO4, pH 5) containing 2% ethanol