It is now widely recognised that the evaluation of the uncertainty associated with a result is an essential part of any quantitative analysis. Without knowledge of the measurement uncertainty the statement of an analytical result cannot be considered complete. The ‘Guide to the Expression of Uncertainty in Measurement’ published by the International Organisation for Standardisation (ISO) establishes general rules for evaluating and expressing uncertainty for a wide range of measurements. The ISO guide has subsequently been interpreted for analytical chemistry by EURACHEM. The EURACHEM Guide sets out procedures for the evaluation of uncertainty in analytical chemistry. The main stages in the process are identified as specification; identify uncertainty sources; quantify uncertainty components; and calculate total uncertainty.
This guide focuses on identifying uncertainty sources and quantifying uncertainty components, and in particular gives guidance on how uncertainty estimates can be obtained from method validation experiments. It does not offer definitive guidance on the requirements for method validation, instead it recognises that key studies routinely undertaken for validation purposes, namely precision studies, trueness studies and ruggedness tests, can if properly planned and executed, also provide much of the data required to produce an estimate of measurement uncertainty.