Statistical comparison of two metrological techniques for the estimation of the measurement uncertainty of an analytical methodology implemented in the laboratory of natural waters of the CIRA - UNAN-Managua

Abstract

In the different testing methodologies implemented in laboratories at the international level, there is some doubt about the validity of the reported results, therefore, as a requirement is mandatory for all laboratories that intend to be accredited according to ISO 17025, to have a reliable theoretical and technical basis to “estimate” such doubt called measurement uncertainty. In this sense, the CIRA-UNAN-Managua Natural Waters laboratory developed a metrological comparison, using as a starting point a validated test method and two techniques for estimating uncertainty (GUM method and Kragten method) both techniques consist of the clear definition of measuring and understanding of the measurement procedure. Metrological comparison consisted of taking the GUM method by establishing which magnitudes influence measurement, defining a mathematical model that relates input magnitudes to measuring, determines sensitivity coefficients, and finally estimates uncertainty using the law of spread of uncertainties. On the other hand, Kragten used a numerical method of differentiation that allows visualizing the components of greater influence so that only requires knowledge of how to obtain the final result.