University of Sussex
Browse

File(s) not publicly available

Modelling measurement uncertainty as a function of concentration: an example from a contaminated land investigation

journal contribution
posted on 2023-06-08, 06:26 authored by Michae H Ramsey, Jong-Chun Lee
A new method has been developed to model the uncertainty of measured concentrations in test materials as a function of concentration. Previously, the measurement uncertainty which originates mainly from the primary sampling and analysis, has been estimated using robust ANOVA (RANOVA) with duplicated samples and analyses. However, the limitation of this method is that the estimated uncertainty value is only applicable close to the mean value of the sample s concentration, and does not apply to either higher or lower analyte concentration ranges. The new method utilises a linear precision model that describes how the precision of a measurement method changes as a function of concentration. This model can be used to estimate the uncertainty arising from the chemical analysis, and in an analogous way, to that arising from the primary sampling. An investigation of contaminated land in Wolverhampton, UK, is used to demonstrate the technique, using a balanced design of duplicated sampling and analysis. Two linear models of sampling and analytical precision were combined to estimate the total measurement uncertainty for the range of analyte concentrations. Not all the elements showed statistically significant precision changes in this particular sampling and analytical system. This may originate from the rather narrow concentration range and/or insufficient data points for the regression. However, another factor controlling sampling uncertainty may be explained by the particular spatial distribution characteristics of the contaminants across this site. As a result, the refined estimates of uncertainty for each sample provide an improved means for the classification of the extent of contamination. This will give improved reliability in risk assessment and facilitate probabilistic mapping of contaminated sites.

History

Publication status

  • Published

Journal

Analyst

ISSN

0003-2654

Issue

10

Volume

126

Page range

1784-1791

Pages

8.0

Department affiliated with

  • Evolution, Behaviour and Environment Publications

Notes

Lee was Ramsey's graduate student. New approach to uncertainty that quantifies how it increases with concentration, and includes the often dominant contribution from sampling. Has lead to further developments (9 citations; included in European Guidance, Eurachem) in replacing old concept which excluded sampling from estimates of uncertainty on single measurements.

Full text available

  • No

Peer reviewed?

  • Yes

Legacy Posted Date

2012-02-06

Usage metrics

    University of Sussex (Publications)

    Categories

    No categories selected

    Exports

    RefWorks
    BibTeX
    Ref. manager
    Endnote
    DataCite
    NLM
    DC