Interlaboratory analytical performance studies; a way to estimate measurement uncertainty

Comparability of data collected within collaborative programmes became the key challenge of analytical chemistry in the 1990s, including monitoring of the marine environment. To obtain relevant and reliable data, the analytical process has to proceed under a well-established Quality Assurance (QA) system with external analytical proficiency tests as an inherent component. A programme called Quality Assurance in Marine Monitoring in Europe (QUASIMEME) was established in 1993 and evolved over the years as the major provider of QA proficiency tests for nutrients, trace metals and chlorinated organic compounds in marine environment studies. The article presents an evaluation of results obtained in QUASIMEME Laboratory Performance Studies by the monitoring laboratory of the Institute of Meteorology and Water Management (Gdynia, Poland) in exercises on nutrient determination in seawater. The measurement uncertainty estimated from routine internal quality control measurements and from results of analytical performance exercises is also presented in the paper.