Extração em fase sólida utilizando minicolunas contendo fibras de sisal impregnadas com tiazolilazo-resorcinol e ácido n-diácetico 3-aminometilalizarina-n, para a determinação de cádmio e cobre em amostras de água mineral e folhas de tabaco empregando espectrometria de absorção atômica com chama

Abstract

In this study, one system using solid phase extraction minicolumns with sisal impregnated N-diacetic acid-N Aminometilalizarina 3, and 4 - (2-thiazolylazo)-resorcinol (TAR) are proposed as strategies for preconcentration and determination of metals in leaf tobacco and mineral water. The method adopted a system employing off-line preconcentration atomic absorption spectrometry in flames. The variables were optimized buffer concentration, pH, sample flow rate and flow eluted. Factorial design was used for evaluation of individual factors and their interactions. In the analysis of the studied system, the buffer concentration and pH were significant factors. After optimization of the system, the critical points were: pH 4.75, buffer concentration of 0.005 mol L-1. This system allowed the determination of copper content with a limit of detection (LOD) of 0.018 μg L-1 and a limit of quantification (LOQ) of 0.061 μg L-1, precision expressed as relative standard deviation (RSD) of 4, 6 and 5.0% using a concentration of 10 μ and 2.0 μg L-1, respectively. The determination of cadmium in mineral water, we used two-level factorial design in order to investigate which variables are statistically significant. The results showed that the buffer concentration and pH were factors that significantly affect the system. For the optimization of the significant variables was used factorial design of three levels as response surface methodology, but the result indicated saddle point. Optimum conditions were established using visual inspection. From the contour plot analysis of the experimental conditions were established: pH 7.0 buffer concentration 0.009 mol L-1 used for the elution HCl 2.0 mol L-1. The determination of cadmium was possible with a detection limit of 0.05 μg L-1 and a limit of quantification of 0.17 μg L-1 accuracy, expressed as relative standard deviation (RSD) of 2.9 and 3.4% cadmium concentration of 10.0 and 20.0 μg L-1, respectively.