Avaliação de Métodos de Preparo de Amostras para Determinação de Metais em Goma Xantana.

Abstract

Xanthan gum is a natural polysaccharide, synthesized by bacteria of the genus Xanthomonas. Due to its rheological properties such as viscosity and high stability has shown that gum numerous industrial applicability, and thus, consequently replaces many polysaccharides which are traditionally used. For the production of this, are added to the culture medium of bacteria containing metal salts, which directly influence the rheological properties of the gum. In this study, we evaluated three different methods of preparation of samples based on acid decomposition of xanthan gum for later quantification of Na, K, Ca and Mg by spectrometric techniques. The methods evaluated were the acidic decomposition open system (using mixture of HNO3 / HClO4), with the reflux system (using only HNO3) and closed by microwave (using mixture of HNO3 / H2O2). The acid decomposition of the samples using a reflux system was presented as a simple and economical analytical strategy, enabling efficient sample preparation. Thus, the accuracy of the method using the reflux system was evaluated by comparing the results obtained from the methods of digestion, as well as through addition and recovery test, which varied from 90 to 102 %. The detection limits were 0.04, 0.02, 0.02 and 0,001mg g-1 for Na, K, Ca and Mg, respectively.