Produção e avaliação de materiais de referência para nutrientes e contaminantes inorgânicos em amostras agronômicas

Abstract

The intensive search for the reliability of results increases the role of reference materials, mainly in analytical chemistry, because they provide metrological references to ensure traceability of measurements and are still central to the validation of analytical methods. The increasing demand for new reference materials is gradual in all areas of knowledge, but the agricultural and food sectors are among the neediest. In Brazil, this requirement is met only by the import of the material at high costs, being frequently the lack of adequate material to the needs of the country. In this context, this work aimed at the production of reference material for inorganic nutrients and contaminants present in a phosphate rock, the raw material used to manufacture fertilizers. The material was produced by following the next steps, internationally established by ISO GUIDES 30 to 35: preparation and ackaging material, assessment of uniformity, stability test in short and long periods and in prior characterization that was the assembly of the collaborative trial, with the distribution of the prepared material to laboratories that were willing to collaborate with the project.Sample preparation studies also have been conducted, aimed at speed and reduced use of reagents. The evaluation of the estimated minimum mass, homogeneity, and stability of the material was performed using inductively coupled plasma optical emission spectrometry (ICP OES) as determination technique. Phosphorus determination was evaluated by laser-induced breakdown spectroscopy (LIBS).Analysis of single-factor variance (ANOVA) was applied to results and the homogeneity and stability of the material presented averages within the 95% confidence interval. The obtained resultsalong the prepare and with collaborative trialallowed the chemical characterization and the determinationof the uncertainties related to each stage of the preparation of the material, and final preparation of the chart control with results of the reference materialwith the expanded uncertainty for each of the analytes under study.Part of the work was developed by the National Research Council Canada (NRCC) in Ottawa in Canada.The applicability of the microwave-induced combustion for sample preparation of previously prepared national reference materials, bovine liver (RM-Agro E3001a) and forage (RM E1001a-Agro) was evaluated for the determination of As, Cd, Cu, and Pb by inductively coupled plasma mass spectrometry (ICP-MS), and the recults coulb be applied in other organic and inorganic materials.