RESUMO
The new electrolytic dissolution in batch of aluminum alloys samples as grains or turns and the determination of Fe, Cu, Mn, Mg, Cr, Ni, Zn, Pb and Ti by ICP OES was investigated. In on-line electrodissolution procedures described in the literature, samples were restricted to be in the form of solid blocks or plates with one polished flat face. Here, the sample was loaded in the barrel of a modified disposable syringe (the anodic semi-cell) and pressed with a modified plunger fitted with a platinum disk to establish electrical contact with the analyte. This arrangement was introduced in a beaker containing the electrolyte (1 mol L(-1) HNO(3)) and a platinum wire as the cathode. The resulting solution from electrodissolution (0.6A) was used for the ICP OES determinations. The influence of the aluminum concentration increase on the determination of the elements was evaluated. Electrodissolution of certified reference materials and commercial samples revealed relative errors lower than 10% for the elements Fe, Cu, Mg, Ni, Cr, Zn and Ti (when their content is above 0.1%). Higher inaccuracies (>10%) were observed for Mn and for Fe in B.C.S. 268/1 reference material certified. The proposed method presented a relative standard deviations (R.S.D.) lower or circa 10% to all of the elements (except Pb). In comparison with traditional acid dissolution, the proposed electrodissolution method is relatively fast (about 30 min), it is clean (there is no projection of solution) and simple (heating and fumes exhaust system were not necessary).
RESUMO
O presente trabalho descreve um método para determinaçäo de arsênio e selênio em café solúvel por espectrometria de emissäo atômica com plasma acoplado a geraçäo de hidretos, com o objetivo de atender aos limites estabelecidos pela legislaçäo brasileira de alimentos. Digestöes das amostras foram realizadas com ácido nítrico e peróxido de hidrogênio em sistema de microondas focalizadas. O excesso de ácido nítrico foi eliminado através de aquecimento lento e o selênio (VI) foi reduzido a selênio (IV) através de tratamento com ácido clorídrico 6 mol/L e aquecimento a 90§C em sistema de refluxo. A influência da acidez na sensibilidade foi investigada, sendo o meio mais estável a concentraçäo de ácido clorídrico de 6mol/L. Os limites de determinaçäo foram de 2.0ug/L para o As e 1.0ug/L para o Se. Os resultados das amostras enriquecidas demonstram a precisäo e exatidäo do método proposto
Assuntos
Arsênio , Café/química , Produção de Alimentos , Tecnologia de Alimentos , Selênio , Análise Espectral , Ácido ClorídricoRESUMO
The objective of this report was the evaluation and establisment of an appropriate digestion procedure for soluble coffee, in order to determine, by ICP-AES(inductively coupled plasma atomic emission spectrometry), the following elements:Mg, Al, P, S, Ca, Mn, Fe, Na, K, Cr, Ni, Cu, Zn, As, Se, Cd, Sb, Pb and Hg. Six differents digestion procedures have been evaluated and classificated in three groups: (I) focused microwave system, (II) conventional wet digestion and (III) pressure digestion system by teflon bombs. Quick and safe digestion of the samples, with decreasing of the reactives, have been obtained by one of the procedures using focused microwaves system