DETERMINATION OF CADMIUM, COPPER AND LEAD IN ENVIRONMENTAL-SAMPLES - AN EVALUATION OF FLOW-INJECTION ONLINE SORBENT EXTRACTION FOR FLAME ATOMIC-ABSORPTION SPECTROMETRY

A flow injection on-line sorbent extraction system was studied in conj unction with flame atomic absorption spectrometry to determine cadmium , copper and lead in digest solutions of solid environmental samples u sing octadecyl functional groups (C18) bonded silica gel as sorbent wi th diethylammonium-N,N-diethyldithiocarbamate (DDDC) or ammonium dieth yldithiophosphate (DDPA) as complexing agent and methanol as eluent. U sing DDDC as complexing agent, citric acid was used as masking agent f or iron and manganese. The complexing agent DDPA selectively extracts cadmium, copper and lead at pH values 1 to 3. Using DDPA as complexing agent with citric acid at pH 1.0, the results of the analysis of five environmental standard reference materials, including coal fly ash (C RM 038), calcareous loam soil (CRM 141), lake sediment (CRM 280), rive r sediment (CRM 320) and estuarine sediment (CRM 277) after digestion were in good agreement with the certified values except cadmium in the river sediment with a very high iron content. With a 20-s sample load ing at 8.7 ml min-1 detection limits (3sigma) were 0.8, 1.4 and 10.0 m ug l-1 respectively for cadmium, copper and lead.