SELECTIVE FLOW-INJECTION SORBENT EXTRACTION FOR DETERMINATION OF CADMIUM, COPPER AND LEAD IN BIOLOGICAL AND ENVIRONMENTAL-SAMPLES BY GRAPHITE-FURNACE ATOMIC-ABSORPTION SPECTROMETRY

A flow injection sorbent extraction system was developed for determination of trace and ultratrace cadmium, copper and lead in biological and environmental standard reference materials by graphite furnace atomic absorption spectrometry (GFAAS). Using ammonium diethyldithiophosphate (DDPA) as complexing agent with citrate as masking agent at pH 2, the analytes were selectively preconcentrated with effective removal of the matrixes including the salt matrix in saline water and the other high-content heavy metals in digested biological and geological samples. The two-second eluate containing most of the analyte complexes was collected for the GFAAS measurement. All analytical results obtained were in good agreement with the certified values. Enrichment factors of 12, 13 and 13 compared with 20 mu l direct injection of aqueous solution and detection limits (3 sigma) of 0.003, 0.05 and 0.04 mu g l(-1) for cadmium, copper and lead respectively, could be obtained with 20-s sample loading at 8.7 ml min(-1) for sorbent extraction and 20 mu l eluate injection for peak area measurement. The relative standard deviation at 0.1 mu g l(-1) cadmium, 1 mu g l(-1) copper or 3 mu g l(-1) lead was around 2%.