Measurement Quality in Analysis—Guidelines and Software Tools ^†

Abstract

Measurement quality is about fulfilling analytical requirements, which should be based on the intended use of the results. Within the European Union, environmental requirements can be set in a directive based on the maximum allowable concentration of a substance in air, soil or water, e.g., an Environmental Quality Standard (EQS) or an Emission Limit Value (EVS); and the requirements on measurement quality, e.g., the limit of quantification (LOQ), within-laboratory reproducibility (s_Rw) or measurement uncertainty (MU). This presentation is about publicly available guidelines that can help the analytical chemist working in the laboratory by implementing a specific method to (1) set up internal quality control over the whole concentration range based on the requirements through the use of target control limits, (2) perform ongoing internal quality control based on only two rules, (3) plan method validation, and (4) estimate the MU based on quality control and validation data. Normally for instrumental methods, the MU is estimated as a relative uncertainty at higher concentrations and as an absolute uncertainty at lower concentrations close to the LOQ. For quality control and MU estimation, free open source software will be presented.