DETERMINATION OF CADMIUM AND LEAD AT MU-G 1 LEVELS IN AQUEOUS MATRICES BY CHELATION ION CHROMATOGRAPHY/

A method for the simultaneous determination of mug/l or sub-mug/l leve ls of cadmium and lead in sea water by chelation ion chromatography is demonstrated. The method consists in the preconcentration of a sea-wa ter sample containing cadmium and lead on an iminodiacetate chelating resin; alkali and alkaline earth metals are removed from the resin wit h an ammonium acetate buffer, the metals are eluted and separated by c ation-exchange chromatography, followed by postcolumn derivatization w ith 4-(2-pyridylazo)resorcinol and spectrophotometric detection at 520 nm. The concentration and separation steps are automated. The detecti on limit, when concentrating 200 ml of sea water, was found to be 2 ng for cadmium and 6 ng for lead. Relative standard deviations of 4.5% a nd 6.8% for 10 mug/l of cadmium and lead, respectively, were obtained. Transition metals (Fe, Co, Ni, Zn, Cu, Mn) do not interfere in the an alysis. An application of the method to the determination of cadmium a nd lead in sea-water samples collected in the Taranto gulf (Italy) is presented.