Evaluation of uncertainty sources associated with toxic trace element concentrations in rice

Today’s and tomorrow’s globalized world requires the acceptance of each other’s capabilities, competence and metrological traceability of measurements to the International System of Units and thus mutual acceptance of quantitative results. Therefore, mutually and publicly recognized standards and certificates are needed at national and international levels. An important step to attain this ambitious goal is to intensify regional metrological collaboration. The exercises of interlaboratorial comparisons are important as part of a system to guaranty the quality of analysis. To estimate the sources of uncertainty associated with the determination of toxic trace element concentrations in rice and to perform an interlaboratorial comparison, a sample containing cadmium, copper, lead and zinc was distributed to four Brazilian laboratories. The laboratories used atomic emission spectroscopy, graphite furnace atomic absorption spectroscopy and flame atomic absorption spectroscopy. The evaluation of the results provided by the laboratories was made by statistical and graphical methods comparing the results of each laboratory to the certified value.