Critical Comparison of Preconcentration Methods for Trace Ion Determination by Energy and Wavelength Dispersive X-Ray Spectrometry

In recent years, considerable progress has been made in the field of metal ion preconcentration from environmental water samples. The methods most widely used include ion-exchange, precipitation (and coprecipitation), adsorption and chelation with immobilized and non-immobilized reagents. As the mechanisms underlying the various methods are different. it is expected that these methods perform differently with respect to the enrichment factor. sensitivity and recovery of trace metal ions. In this investigation, the preconcentration of 10 cations. Ag, As, Co, Cr, Cu, Fe, Hg, Mn, Pb and Zn was studied. The methods of preconcentration include (1) cation-exchange resin-loaded filter paper. (2) precipitation with sodium diethyldithiocarbamate, (3) precipitation with ammoniumpyrrolidinedithiocarbamate. (4) chelation with oxine with subsequent adsorption on activated carbon and (5) chelation with diethyldithiocarbamate immobilized on controlled pore glass. Among the factors compared are the detection limits, sensitivity, precision. linearity and dependence of the recovery on the concentration of metal ions.