Flow injection on-line preconcentration and flame atomic absorption spectrometric determination of iron, cobalt, nickel, manganese and zinc in sea-water

A rapid and sensitive flow injection analysis-atomic absorption spectrometric procedure is described for the determination of iron, cobalt, nickel, manganese and zinc based upon on-line preconcentration on a microcolumn packed with C-18 material. These metals were complexed with 5,7-dichlorooxine from weakly acidic or neutral solutions in the flow system and adsorbed on the column. The preconcentrated elements were eluted with acidified methanol (pH greater than or equal to 2) and injected directly into the nebulizer for atomization in an air-acetylene flame for measurement. The retention efficiency was better than 98%, resulting in sensitivity enhancement factors of 60, 80, 80, 80 and 60 for a 1 min preconcentration time for iron, cobalt, nickel, manganese and zinc, respectively. The respective detection limits were 4.0, 1.0, 1.0, 0.5 and 0.5 ppb, respectively. The throughput of samples was 30 h(-1), with a loading time of 1 min. The method was applied to sea-water samples.