Desenvolvimento de métodos espectrométricos para a determinação de constituintes inorgânicos em leites e alimentos infantis similares sem prévia decomposição

Abstract

In this work methodologies were proposed to determination of Al, Cr, Mn and Mo by GFAAS and Zn by FAAS in milk and similar samples treated with only solubilization in water and sonication. In the same time, determination by ICP-MS was accomplished with the intention of evaluating the mineral composition of the samples. The multielemental analyses (ICP-MS) revealed the existence of great variations in the compositions of the samples, mainly of infant formula. In the development of methods for determination by GFAAS, the milk and similar samples were treated through a simple and fast method, the solubilization in ultra-pure water and sonication for 10 to 30 minutes, to stabilization of the suspensions. Methods were established from the choice of suitable permanent modifiers and multivariate optimization to obtain the heating program. The permanent modifiers Zr, Rh and Ir were used in the determination of Al, Cr and Mn, respectively, and Eu + Nb for Mo. In optimization step the pyrolysis and atomization temperatures and the pyrolysis time were determined for each method. In the optimized experimental conditions the analytical parameters of merit were assessed as adequate, as characteristic mass, accuracy and precision. Whole milk, skim milk, milk beverage, infant formula, soy-based food and goat milk were analyzed according to the methods proposed and the concentrations obtained varied over a wide range. In the development of methods for determination of Zn by FAAS, the samples were also treated for solubilization in ultra-pure water and sonication for 10 to 30 minutes, for stabilization of the suspensions, and later diluted adequately. The calibration curves revealed absence of matrix effects, which took the proposition of a method fast, simple and with characteristics appropriate analytics. In all the accomplished analyses (GFAAS and FAAS) it was possible to notice that some samples had concentrations above recommended levels of Zn, Cr and Mn and alarming levels of Al.