The Handbook for Environmental Laboratories has
now been launched - NT TR 537 as version four.
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 harmonisationbetweenlaboratories 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.
Major updates in the 2017 version are as follows:
- Uncertainty over the measurement range – a separate section on estimating measurement uncertainty over the measurement range, in either absolute units or relative units, has been added, this being one of the major difficulties of applying this approach.
- Estimating standard deviation from duplicates – a pooled standard deviation is used instead of a factor applied to the mean range.
- Use of control chart limits for the within-lab reproducibility component u(Rw) is pointed out more clearly
- Harmonisation with ISO 11352 Water quality — Estimation of measurement uncertainty based on validation and quality control data. The terminology has been harmonised with the ISO standard which applies this approach to measurement uncertainty.
Software for measurement uncertainty calculation according to Nordtest TR 537:
The Finnish Environment Institute (SYKE) has published MUkit - measurement uncertainty software, which can be downloaded for free of charge from ENVICAL-SYKE website: www.environment.fi/syke/envical