Desenvolvimento de métodos analíticos para determinação de As, Cd, Ni e Pb em batata e em mandioca produzidas em regiões mineiras empregando espectrometria de absorção atômica em forno de grafite

Abstract

In this dissertation methods to determine arsenic, lead, nickel and cadmium in food are described, more precisely in potato and manioc, grown in the Minas Gerais state territory in Brazil, which is also known as "Quadrilátero Ferrífero" (an area in the state where mining for ore and other metals is a current major economic activity). In the methods proposed there was no need of previous digestion, using the Graphite furnace atomic absorption spectrometry technique. A slurry was prepared with the food samples and was automatically injected into GF AAS. The parameters of analysis were optimized through the multivariate method, which consisted of an experiment of selection of variables (complete factorial planning), followed by a surface response method (Central Composite Design - CCD). For all methods the optimal temperature of pyrolisis and atomization were evaluated as well as the use of permanent modifiers. The effect of the matrix was verified in each method through statistical Student's t-test and in most cases, the aqueous calibration became viable. The sensitivity was analysed through characteristic mass (mo) and quantification limits (LOQ). Accuracy studies were carried out by recovering metals in fortified samples in several levels of concentrations of each metal and, for cadmium and arsenic methods, certified reference material (CRM) was also utilized. The precision was determined in tests carried out on the same day (precision intra-assay) and on different days (precision inter-assay). The methodologies presented parameters compatible to the employed technique, compared to data available in the specific literature. Some samples of manioc and potato, analysed with the proposed methods, presented values of concentration that point towards problems in some cropping areas, in accordance with previous work and research that have already been done