A Practical Guide to the Calculation of Uncertainty of Measurement

Abstract

This paper would provide the analyst with an easy to use step-by-step guide to calculate the uncertainty of measurement in implementing a new analytical method. There are two main ways to attain such an achievement. The first is to consider all the possible sources of variability and then to sum up all of them in the final calculation. The second is taking part in a collaborative trial and processing the resulting statistics. Both methods imply different advantages and drawbacks. It is up the analyst to choose the one fits best his requirements. Anyway it is nearly inescapable providing, along with the test result, its own uncertainty. This entire subject is stated by a standard well known to those who practise the profession of a chemical analyst, which is the UNI CEI EN ISO/IEC 17025:2005. This standard has been imposed by the European Community for matters concerning food and environmental surveillance, but it has also become part of the guidelines of several National Associations of Clinical Toxicology. This standard pledges the analyst to use validated analytical methods, issued by one of the national or international Standards Organizations or, at least, by an internationally acknowledged Scientific Society.