CAC/GL 54-2004 Guidelines on Measurement Uncertainty
Introduction
It is important and required by ISO/IEC 17025:1999 that analysts are aware of the uncertainty associated with each analytical result and estimates that uncertainty. The measurement uncertainty may be derived by a number of procedures. Food analysis laboratories are required, for Codex purposes, to be in control, usecollaboratively tested or validated methods when available, and verify their application before taking them into routine use. Such laboratories therefore have available to them a range of analytical data which can be used to estimate their measurement uncertainty.
These guidelines only apply to quantitative analysis.
Most quantitative analytical results take the form of “a ± 2u or a ± U” where “a” is the best estimate of the true value of the concentration of the measurand (the analytical result) and “u” is the standard uncertainty and “U“ (equal to 2u) is the expanded uncertainty. The range “a ± 2u” represents a 95% level of confidence where the true value would be found. The value of “U“ or “2u” is the value which is normally used and reported by analysts and is hereafter referred to as “measurement uncertainty” and may be estimated in a number of different ways.
