On-line preconcentration using an amberlite XAD-16 resin and determinationof cadmium by flow-injection-inductively coupled plasma atomic emission spectrometry

An on-line cadmium preconcentration and determination system implemented wi th inductively coupled plasma atomic emission spectrometry (ICP-AES) associ ated to flow injection (FI) method was studied. For the retention of cadmiu m, 2-(5-broma-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) and Amberlite XAD-16 were used, at pH 9.5. The cadmium was removed from the micro-column in countercurrent with nitric acid. An enrichment factor of 60 was obtaine d with respect to ICP-AES using pneumatic nebulization, for the preconcentr ation of 50 ml of sample solution. The detection limit value for the precon centration of 50 ml of aqueous solution of Cd was 0.04 mug l(-1). The preci sion for 10 replicate determinations at the 5 mug l(-1) Cd levels was 2.0% relative standard deviation (RSD), calculated with the peak heights obtaine d. The calibration graph using the preconcentration system for cadmium was linear with a correlation coefficient of 0.9995 at levels near the detectio n limits up to at least 100 mug l(-1). The method was successfully applied to the determination of cadmium in drinking water samples.