DESENVOLVIMENTO DE UM MÉTODO DE PREPARO DE AMOSTRAS PARA AVALIAÇÃO DE MATÉRIAS‑PRIMAS DE MATERIAIS ESCOLARES

Abstract

The aim of this study was to evaluate the extraction of elements Ba, Cd, Cr, Hg and Pb in solid samples, using a microwave oven with closed flasks and to understand the physicochemical parameters involved in this process. The conducting of this study was based on directive 2009/48/CE, which specifies the levels of elements in the materials used by children. A total of eight samples were used to evaluate the extraction process. A full factorial design 23 was performed and principal component analysis (PCA) was used to select only critical samples (simultaneously high residual solid content and metal concentrations) for the proposed process, reducing the number of samples tested. A second full factorial design 23 was performed with selected samples (masterbatch, polymer and kaolin) and the following variables investigated: addition of H2O2, addition of analytes, and HNO3 volume. The responses observed for this factorial design were recoveries of the analytes (Ba, Cd, Cr, Hg, and Pb) and a desirability function was used in order to combine all responses. The conclusions were that it is not possible to digest some samples with different physicochemical characteristics (masterbatch and polymer, for example) in the same batch and that the proposed system can be used to perform sample screening.

Keywords

• microwave
• chemometrics
• factorial design
• school supplies
• extraction