New methods for preconcentration and determination of heavy metals in natural water

Numerous instrumental methods are used to determine heavy metals in natural water, mainly with preconcentration, since the sensitivity of direct analysis is often insufficient. A number of such methods have been developed in the authors' laboratory. Highly selective solvent extraction separation of heavy metals (Ag, Cu, Hg) has been achieved by using macrocyclic extractants. The separated elements are determined by means of atomic absorption spectrometry and spectrophotometry. Heterochain polymer sorbents (polymeric thioether and tertiary amine) have been used to concentrate Se, Te, Hg, As, Cd, Pb and other heavy metals. Atomic absorption spectrometry and X—ray fluorescence analysis have been used to determine the elements in the concentrate. The methods are characterized by a high sensitivity and accuracy. Thin layer chromatography in combination with precontration of a group of metals by solvent extraction has been used for the analysis of surface waters. Chelates, mainly diethyldithiocarbamates, are extracted and separated in a thin layer. Visual or densitometric determination is possible. In a similar way tritium—labelled chelates have been used for radiometric determination of Pb, Cd and Hg. Several methods are based on using ion chromatography. Highly sensitive techniques have been proposed to determine As, Se, Te, Cr, Mo, W and V, as well as Cd, Cu, Mn, Ni and Pb; preconcentration is necessary only in some individual cases.