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 determina tion of trace and ultratrace cadmium, copper and lead in biological an d environmental standard reference materials by graphite furnace atomi c absorption spectrometry (GFAAS). Using ammonium diethyldithiophospha te (DDPA) as complexing agent with citrate as masking agent at pH 2, t he 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 sample s. The two-second eluate containing most of the analyte complexes was collected for the GFAAS measurement. All analytical results obtained w ere in good agreement with the certified values. Enrichment factors of 12, 13 and 13 compared with 20 mu l direct injection of aqueous solut ion 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 e luate injection for peak area measurement. The relative standard devia tion at 0.1 mu g l(-1) cadmium, 1 mu g l(-1) copper or 3 mu g l(-1) le ad was around 2%.