Abstract

For the evaluation of different analytical methods the best achievable final uncertainty can be used as the criterion. Evaluation of an analytical method on this basis includes the magnitude and also the robustness of the uncertainty budget. This evaluation was applied to laboratory-scale migration experiments on soil columns. These experiments were performed in order to estimate soil transport parameters of heavy metal pollutants (cadmium). In these studies a tracer (stable ¹¹¹Cd isotope), having nearly the same physico-chemical properties as the pollutant of concern, was added on top of a contaminated soil and the column effluents were fractionally collected at the bottom. This paper presents three different calculation models, derived from the isotope dilution equation, for the simultaneous determination of the concentration tracer cadmium, [Cd_t], and indigenous cadmium, [Cd_n], in soil column effluents with ICP-MS. The methods differ in the method of calculation but are, in principal, based on the same measurements. The uncertainty budgets of the different methods were used in the evaluation. In addition to the magnitude of the total uncertainty, the boundary conditions of some parameters were investigated in detail. The influence of the following parameters on the uncertainty budget was studied: the concentration level of cadmium, the isobaric interference of tin and the molar fraction of indigenous cadmium.