PRECONCENTRATION OF TRACE-ELEMENTS BY SORPTION

In the determination of trace elements in complex matrices, enrichment and separation of the analytes is of special importance. A wide variety of methods have been proposed for preconcentration according to the nature of the samples, the types and concentrations of the analytes, and the methods to be used for measurement. Among them, the preconcentration techniques based on sorption seem to be convenient, rapid and capable of attaining a high concentration factor. Various efforts have been made to improve selectivity, rate and capacity of sorption, specially for heavy metals in natural waters. The use of silica gel as a support for loading or chemically immobilizing with complexing agents is a particular example. In this paper, the preparation and characterization of complex-forming absorbents for the sorption of heavy metals will be critically reviewed, laying stress on the utilization of silica gel as a supporting material.