Desenvolvimento de métodos de preparo de amostras de margarina e chocolate para a posterior determinação de elementos com potencial tóxico por ICP-MS

Abstract

In this study were developed sample preparation methods for margarine and chocolate, for subsequent determination of potential toxic elements by ICP-MS. Firstly, methods based on conventional heating, microwave-assisted heating (MWAD), microwave and UV-assisted heating (MW-UV), and microwave-assisted heating in a single reaction chamber (SRC) using acid solutions were evaluated for margarine decomposition. In these methods, the use of higher sample mass and diluted acid solution was evaluated. Thus, the MW-UV method using 4 mol l-1 HNO3 was selected for decomposition of 0.5 g of margarine, in view of the use of diluted solution and the lower residual carbon content obtained in the digests. This method was also optimized for chocolate samples, being possible to decompose up to 0.6 g of sample, using 4 mol l-1 HNO3. By ICP-MS analysis was possible to determine several elements in margarine and chocolate samples. For chocolate, a relation between the higher concentrations of some elements and the cocoa content was observed. The accuracy was evaluated by decomposition of a certified reference material (CRM BCR 414) in same conditions of the sample, and no significant differences were observed between the certified concentrations and the obtained values for all analytes. Moreover, a spike test was performed and recoveries between 93 and 105% were obtained for analytes in both samples. The relative standard deviation was always lower than 7%.