Evaluating the Sampling Contribution to the Measurement Uncertainty

Abstract

If the objective of the measurement is to estimate the value of the analyte concentration in a sampling target, then the uncertainty associated with the sampling process inevitably contributes to the uncertainty of the measurement result. Heterogeneity, ambiguity in the sampling protocols, loss of analyte and fine particles, or contamination from equipment or previous samples are among the most important factors contributing to uncertainty associated with sampling. The empirical approach by EURACHEM is introduced, the general error sources are quantified as the sampling precision, analytical precision, sampling bias and the analytical bias respectively. The uncertainties associated with sampling precision and analytical precision are evaluated through duplicate methods and analysis of variance. An example is given to demonstrate how to evaluate the uncertainty associated with the sampling and sample preparations.