Chemical fractionation of cadmium in natural waters from Paraná river at Corrientes -Argentina

paraná river (spanish río paraná), the second longest river in south america is a very important source of water in argentina. the present paper proposes a technique that combines solid phase extraction (spe) with solid phase spectrophotometry (sps) for cadmium fractionation in natural water. the concentrations of cadmium bound to humic substances and of free metal ions were determined from their sorption-elution from chromatographic support resin (silica c18). cadmium determination is based on solid phase spectrophotometry (sps) with 1-(2-pyridylazo)-2-naphtol (pan) sorbed on anionic resin. it was optimized using response surface methodology (rsm) based on sequential experimental doehlert design. recoveries were obtained for all samples studied. the detection limit (dl) was 1.0 mg l-1 for cd(ii). the precision for 10 replicate determinations at 10 mg l-1 cadmium levels was 3.2% relative standard deviation (rsd).