Comparison of strategies to quantify uncertainty of lead measurements in biological tissue at mg kg^–1 level

Abstract 

The expression of measurement uncertainty in analytical chemistry still presents some difficulties. According to the various guides and standards, several approaches are possible. This paper present two referenced approaches applied to the determination of Pb in a biological tissue at the mg kg^–1 level. Estimations were achieved, either from inter-laboratory precision data, or from the uncertainty propagation equation applied to the measurements of a single laboratory. When comparing final values, for an average concentration of about 2.0 mg kg^–1, expanded uncertainties range from ±0.05 mg kg^–1 up to ±0.31 mg kg^–1, i.e. by a factor of 6. Obviously, both approaches of estimating uncertainty do not cover the same sources of uncertainty and it is interesting to try to understand better these discrepancies in order to try to define realistic guidelines for analysts. Moreover the experimental results of the study are given where a wide number of techniques is applied.