A set of simulated experiments was analysed in order to compare the influence of the titration type and of data treatment methods on the accuracy of metal complexing parameters determination for one-and two-ligand systems. The simulated data corresponded to those obtained by anodic stripping voltammetry and were chosen to represent experiments in linear, logarithmic and decade titration modes. The values of preset complexing parameters for one-and two-ligand systems were chosen to fit into the expected experimental range. Random noise was added to the data prior to the treatment. Five different data treatments were applied: Chau-Buffle, Ružić-van den Berg and Scatchard linearisations, and non-linear fitting and PROSECE optimisations. The investigation has shown that even in the case of a one-ligand system, logarithmic and decade titrations are much better compared to the linear ones. Linearisation methods are in many cases inferior to those using optimisation algorithms. Random noise has a significant influence on the results of linearisation methods as well. For linearisation methods, in the case of a one-ligand system, high correlation has been found for the confidence interval of the calculated parameters and the difference between the preset and the calculated values. This correlation is proposed to be used as an estimation for the results quality in real experiments. PROSECE is by far superior to other methods in most of the cases due to its flexible and powerful mathematical background. It is highly recommended as a tool for data treatment. Construction of "contour-graphs" enables error prediction of the calculated complexing parameters. PROSECE is proposed as an orientation and valorisation tool in real samples analyses.

The physicochemical characterization of uranium(V1) in seawater is described on the basis of species distribution calculations and experiments using polarography and spectrophotometry in artificial seawater at elevated uranium concentrations. Various dissolved uranium(W) species are identified under different conditions of pH and carbonate concentration. Below pH 4, the hydrated uranyl ion is present in the "free" state (forming "labile" complexes). Above pH 4, a stepwise coordination of uranyl by the carbonate ion occurs. The monocarbonate complex is formed in the pH range 4-5, the bicarbonate uranyl complex between 5 and 6. Above pH 8, uranium is present predominately as the tricarbonate and to a smaller extent as a trihydroxide complex. There is satisfactory agreement between our experiments and the theoretically computed distribution of uranium(W) in seawater based on published stability constants.The experiments done at higher concentrations are justified by theoretical distributions showing that there is no great difference in species distribution between the uranium at concentrations of 1O-4 and lo--" mol dm-3.

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