Determination of copper in water and rice samples by flame atomic absorption spectrometry with flow-injection on-line 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 ehelate 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 μg 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 μg l−1 and 2 μg l−1 Cu levels, respectively. Interference from at least 50 μg l−1 Fe(III) was eliminated by adding ascorbic acid. The method has been applied successfully to determine μg l−1 amounts of copper in drinking water and sea water and Ju μg−1 amounts of copper in rice.