Detection limits and goodness-of-fit measures for the two-component model of chemical analytical error
Machelle D. Wilson a, David M. Rocke b, Blythe Durbin b, Henry D. Kahn C
a
Savannah River Ecology Laboratory, The University of Georgia, P.O. Drawer
E, Aiken. SC 29802, USA
b University of California. Davis, CA. USA
C United States Environmental Protection Agency, USA
Received 8 July 2003; received in revised form 12 December 2003; accepted
19 December 2003
Abstract
The utility of analytical chemistry measurements in most applications is dependent on an assessment of measurement error. This paper demonstrates the use of a two-component error model in setting limits of detection and related concepts and introduces two goodness-of-fit statistics for assessing the appropriateness of the model for the data at hand. The model is applicable to analytical methods in which high concentrations are measured with approximately constant relative standard deviation. At low levels, the relative standard deviation cannot stay constant, since this implies vanishingly small absolute standard deviation. The two-component model has approximately constant standard deviation near zero concentration, and approximately constant relative standard deviation at high concentrations, a pattern that is frequently observed in practice. Here we discuss several important applications of the model to environmental monitoring and also introduce two goodness-of-fit statistics, to ascertain whether the data exhibit the error structure assumed by the model, as well as to look for problems with experimental design.
Keywords:
Chemical analytical error; Limits of detection; Two-component error model;
Goodness-of-fit
SREL Reprint #2726
Wilson, M. D., D. M. Rocke, B. Durbin and H. D. Kahn. 2004. Detection limits and goodness-of-fit measures for the two-component model of chemical analytical error. Analytica Chimica Acta 509:197-208.
