Tandem Preconcentration of Cobalt by On-line Ion Exchange and Gas Phase Chelates Generated by Merging-zones Flow Injection Analysis With Electrothermal Atomic Absorption Spectrometric Determination

An automated combined method of on-line preconcentration of Co on Amberlite IR-120 resin was developed followed by the generation of volatile cobalt chelates (diethyldithiocarbamate and acetylacetonate) which are then vaporized with a thermospray device to obtain a second preconcentration stage with decomposition of the gas phase generated on the surface of a pre-heated graphite platform with subsequent determination by ETAAS. The use of a by-pass valve between the thermospray device and the graphite chamber makes it possible to overcome the classical problems caused by condensation of the eluates. The sensitivity (0.0044 A s) achieved by the proposed tandem preconcentration–ETAAS method is 0.8 and 1.1 ng l–1 with a detection limit (3σ) of 2 and 3 ng l–1 for cobalt diethyldithiocarbamate and cobalt acetylacetonate, respectively. The method was evaluated against unpolluted certified reference natural waters and satisfactory results were obtained.