A simple method was developed for the pre-concentration of Co(II) based on the adsorption of its (E)-N1-((1-thiophen- 2- yl) ethylidene) benzene-1,2-diamine complex on a neutral alumina column. The influence of acidity, eluting agents, stability of the column, sample volume and interfering ions was investigated in details. The adsorbed complex could be eluted using environmentally benign polyethylene glycol (PEG 400) and the concentration of Co(II) was determined by visible spectrophotometry at a wavelength maximum of 636 nm. A detection limit of 6 µg/l could be achieved and the developed procedure was successfully applied for the determination of Co(II) in spiked water samples. The pre-concentration factor attainable for quantitative recovery (>96%) of Co(II) was 100 for a 1000 ml sample volume.
Key words: Co(II), pre-concentration, alumina column, polyethylene glycol, (E)-N1-((1-thiophen-2-yl) ethylidene) benzene-1,2-diamines.
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