Participation and performance of the analytical geochemistry and isotope geology laboratories on the international proficiency test geopt™

Abstract

The determination of bigger, smaller elements and traces in geological materials is routinely performed at the IG's Analytical Geochemistry and Isotope Geology Laboratories, using X-ray fluorescence (FRX) and mass spectrometry with coupled plasma source by induction (ICP-MS) techniques, respectively. The results are widely used by the community in the research works and consequent publications. In order to assess the quality of analytical results obtained, in a biannual basis, the laboratory voluntarily participates in the international proficiency test GeoPT™. GeoPT™ is a well-established proficiency test and widely used by research, commercial and univesity laboratories, involved in geological material analysis. Each GeoPT™ test round involves a homogeneous sample distribution to participating laboratories. The laboratories must submit the sample received to their analytical routine. The frequent participation on the international proficiency teste enables the critical assessment on the analytical results obtained by the Geochemistry and Isotope Geology Laboratories. The test organizers perform a statistic assessment of the results received and a Z score is calculated; for each information submitted by the participating laboratories, a Z score in the ±2 range is considered as satisfactory. The results obtained show the laboratory's participation and performance on the GeoPT™ proficiency test in the period from July 2010 to July 2014. In summary, 377 results were sent, from which 90% presented satisfactory values (-2<Z<2 score). Only 4.5% obtained unsatisfactory results (Z>3 ou Z<-3 score) and 5.5% of the results presented 2<Z<3 and ---3<Z<-2 score.