European Commission, Joint Research Centre, Institute for Reference Materials and Measurements
Abstract
The Community Reference Laboratory for Heavy Metals in Feed and Food (CRL-HM) organised a course on "Uncertainty of Sampling" attended by National Reference Laboratories. After the introductory lecture by Prof. M. Ramsey the first electronic proficiency test on sampling (e-SPT), developed in the frame of the collaboration between the IRMM and the University of Sussex, was carried out. A total of 16 participants reported results. The purpose of the exercise was to monitor the "nitrate contamination in a lettuce field". The same nitrate concentration profile was used throughout the exercise. Participants were guided along the exercise; they collected two compound samples and reported their measurement results. The spreadsheet application accounted for sampling and analytical uncertainties, so that every participant provided four experimental results (two independent analytical measurements per composite sample). The reported results were analysed using the robust ANOVA program (ROBAN). Between participants, within-participant sampling, within-participant analytical and within-participant measurement uncertainties were evaluated. Although the results of a real sampling proficiency test estimate better the uncertainty from sampling,the e-SPT helps to learn how to design better real sampling proficiency tests
