Use of Chemometric Tools for HG-AAS Instrumental Optimization in the Determination of Se in Nuts Grown in Brazil

摘要

The determination of total selenium (Se) is described in nuts such as bacuri (Platonia insignis Mart.), baru (Dipteryx alata Vog.), bocaiuva (Acrocomia aculeata (Jacq.) Lodd), and cashew (Anacardium occidentale L.) (other than the well-known Brazilian nut) using hydride generation coupled to a flame atomic absorption spectrometer (HG-AAS). The best experimental conditions to generate the volatile hydride (H2Se) were established by multivariate statistical analysis. The conditions of the pre-reduction step to generate the Se hydride were optimized using the Pareto diagram and Doehlert design. Best results were achieved when 0.6 mol L-1 HCl, 1.0% (m/v) NaBH4 in 0.5% (m/v) NaOH, and a 00-cm reaction coil were used. For Se determination by HG-AAS, analytical curves were built in the 0.50 - 25.0 mu g L-1 range resulting in a linear coefficient correlation better than 0.9970. The accuracy of the sample preparation procedure and HG-AAS determination were evaluated by addition and recovery tests, and the recoveries were found in the 90.3-95.8% range with a relative standard deviation (%RSD) of <4.7%. Using the proposed methodology, the limit of detection obtained was 0.1315 mu g L-1 with a %RSD up to 1.9%. The Se concentrations in the samples were in the 0.515 +/- 0.017-0.657 +/- 0.029 mu g g(-1) Se range. The multivariate analysis applied to the experimental results showed to be a useful tool because it allows reducing the number of experiments (from 60 to 8) with satisfactory accuracy.