Aplicação de métodos quimiométricos na análise direta de constituintes inorgânicos em leite materno por espectrometria de absorção atômica em forno de grafite

Abstract

In this work is described the methodology developments (optimization and validation) for direct quantification of Mn, Cu, Pb and Cr in breast milk without need of previous sample digestion following determination by furnace graphite atomic absorption spectrometry (GF AAS). For the development of methods for analysis of manganese and copper,monoethanolamine and hidroximetilaminometano (TRIS) were evaluated as possible diluents for the breast milk (being that the TRIS presented better accuracy for both metals), whereas for chromium and lead only hidroximetilaminometano was evaluated. The optimization of theparameters of analysis was done through multivariate optimization, which consisted of experiments to choice of modifiers, experiments to preliminary assessment of variables (fractional factorial design 24-1) followed by a methodology surface of response (central composite design). For all the optimizations were evaluated the best atomization and pyrolysis temperatures, the pyrolysis time and the best modifier (permanent or associated with the chemical modifier). The effect of the matrix was assessed in each method through statistical tests F and t Student, and, in some cases, the aqueous calibration was possible. The sensitivity was examined by the characteristic mass and detection limits of detection. Studies on accuracy were made by recoveries of metals in artificially contaminated samples and, where possible, was also used certified reference material. The precision was determined in testsperformed on the same day (intra-assay precision) and on three different days (inter-assay precision). The methods showed good results for precision and accuracy and low limits of detection.At the end of the development of the methods some samples were analyzed.