Levels of Uncertainty

All chemical analysis is ultimately an approximation to the ‘right’ value, this applies as much to the laboratory as it does to on-site testing. Each laboratory will probably have differing techniques of analysis and extraction. Consequently they will conclude with differing values for similar samples, despite the differing techniques being certified.

In the vast majority of cases the greatest discrepancy between samples is down to actually taking the sample in the field. QROS has in place a standard operating procedure for sampling which can be seen here which will help to minimise this. However many sites have an extremely heterogeneous profile and it will often be that case that two sample taken from the same area of ground will have widely disparate contamination levels.

Extraction processes will also have a substantial effect on the final results with contaminants being easier to extract in differing solutes and at different temperature and pressures. Mindful that QROS will be conducting analysis in the field our extraction techniques are designed to be as efficient as possible whilst using acceptably safe reagents.

There are studies being conducted to give more insight into the acceptability of on-site measurement by estimation and optimisation of uncertainty one of which can be found opposite.

Estimating and Optimising Analytical and Sampling Uncertainty in Environmental Investigations: Application and Evaluation

10.1111/j.1751-908X.2007.00854.x

Authors: Boon, Katy A.; Taylor, Paul D.; Ramsey, Michael H.

Source: Geostandards and Geoanalytical Research, Volume 31, Number 3, September 2007 , pp. 237-249(13)

Publisher: Blackwell Publishing.

Evaluating uncertainty in routine analysis

doi:10.1016/S0165-9936(99)00151-X

Authors: Alicia Maroto, Ricard Boqué, Jordi Riu and F. Xavier Rius

Source: TrAC Trends in Analytical Chemistry,
Volume 18, Issue 9-10, September 1999 , pp. 577-584

Publisher: Reed Elsevier.