Abstract
This handbook is written for environmental testing laboratories in the Nordic countries, in order to give support to the implementation of the concept of measurement uncertainty for their routine measurements.
The aim is to provide a practical, understandable and common way of measurement uncertainty calculations, mainly based on already existing quality control and validation data, according to the European accreditation guideline /12/, the Eurolab Technical Report No. 1 /3/ and the ISO/DTS 21748 Guide /8/. Nordtest has supported this project economically in order to promote and enhance harmonisation between laboratories on the Nordic market.
Practical examples, taken directly from the everyday world of environmental laboratories, are presented and explained. However, the approach is very general and should be applicable to most testing laboratories in the chemical field.
The handbook covers all steps in the analytical chain from the arrival of the sample in the laboratory until the data has been reported. It is important to notice that vital parts of the total measurement uncertainty are not included, e.g. sampling, sample transportation and possible gross errors during data storage/retrieval.
The recommendations in this document are primarily for guidance. It is recognised that while the recommendations presented do form a valid approach to the evaluation of measurement uncertainty for many purposes, other suitable approaches may also be adopted – see references in Section 9. Especially the EURACHEM/CITAC-Guide /2/ is useful in cases where sufficient previous data is not available, and therefore the mathematical analytical approach according to GUM /1/ with all different steps is to be used.
Basic knowledge in the use of quality control and statistics is required. In order to make it possible for the reader to follow the calculations, some raw data is given in appendices.
The Finnish Environment Institute (SYKE) has published
MUkit – Measurement Uncertainty software kit, which can be downloaded free of charge from ENVICAL – SYKE website
www.environment.fi/syke/envical
