Proficiency testing in sampling: pilot study on contaminated land

Abstract

Proficiency testing is a well established method for regularly testing the accuracy of particular laboratories. In this study the methodology of proficiency testing has been applied for the first time to sampling, specifically to environmental sampling on contaminated land. Nine different samplers collected soil samples with the objective of estimating the mean concentration of two trace elements at a site. They used sampling protocols of their own choice, analysed their own samples and reported the results to the organizers. Analytical bias was studied separately by distributing a matrix-matched reference material. The experiment demonstrated the feasibility of the proficiency test in sampling. Large differences between the reported results (by a factor of 2.5) illustrate that sampling can be a major source of error in the assessment of contaminated land.