The total element concentration does generally not provide adequate information to understand the effects of trace and heavy metals observed in the environment and in living systems. The toxicity, bioavailability, physiological and metabolic processes, and the mobility and fate of elements are, to a large extent dependent on the specific chemical form of an element. Speciation analysis has yet to be developed to its full potential for biochemical, clinical and environmental investigations, and still more work is needed in the near future. Nuclear techniques, particularly the use of radioisotopes, can help in method development, optimization and stability tests of chemical species. It was suspected that the analytical results of many speciation exercises reflect more on the separation scheme than on the original species distribution in a matrix from which the species have been extracted. Validation of speciation analytical procedures is an important prerequisite to estimate the influence of artefacts on the overall analytical result. Due to the toxicological importance it was decided to concentrate this project on the speciation of As+3/As+5, Cr+3/Cr+6 and Se+4/Se+6 in water samples. This pucliation presents the results.--Publisher's description.