DETERMINATION OF COPPER IN WATER AND RICE SAMPLES BY FLAME ATOMIC-ABSORPTION SPECTROMETRY WITH FLOW-INJECTION ONLINE ADSORPTION PRECONCENTRATION USING A KNOTTED REACTOR

A flow-injection on-line adsorption preconcentration flame atomic absorption spectrometric system for the determination of copper was developed. The copper diethyldithiocarbarmate chelate was adsorbed on the walls of a PTFE knotted reactor. The sorbed species was eluted by isobutyl methyl ketone at a flow-rate of 4.1 ml min(-1). Air segmentation between sample and eluent was employed to avoid mixing of the neighbouring phases under fast elution rates. An enhancement factor of 120 and a detection limit of 0.2 mu g l(-1) Cu were achieved for a 60 s loading period (sample throughput 46 h(-1)). The relative standard deviations were 1.7% and 3.6% at the 20 mu g l(-1) and 2 mu g l(-1) Cu levels, respectively. Interference from at least 50 mu g l(-1) Fe(III) was eliminated by adding ascorbic acid. The method has been applied successfully to determine mu g l(-1) amounts of copper in drinking water and sea water and mu g g(-1) amounts of copper in rice.