Desenvolvimento de método analítico para determinação de selênio em castanhas do cerrado por espectrometria de absorção atômica com geração de hidreto

Abstract

Nuts, almonds and walnuts are food sources that contain high levels of monounsaturated and polyunsaturated fats and are also rich in nutrients, such as selenium [1]. In this sense, this work describes the development of an analytical method for the determination of selenium (Se) in bacuri (Platonia insignis), baru (Dipteryx alata), bocaiuva (Acrocomia aculeata) and cashew (Anacardium occidentale, L.) nuts using hydride generation atomic absorption spectrometry (HG AAS). The best experimental conditions to generate the volatile hydride of selenium (H2Se) were established by multivariate statistical analysis. According to Pareto’s diagram, NaBH4 and HCl were those variables that presented significant influence on the system. According to these results, both parameters were systematically evaluated using Doehlert matrix, and according to the analysis of variance (ANOVA), the value of Fcalculated (6.737) was smaller than the value of Fvalue (18.51), at 95% confidence level, and p value obtained for the lack of fit was 0.121886. The highest absorbance signals to determine Se were obtained with 0.6 mol L-1 HCl, 1.0% (w/v) NaBH4 using a reaction coil of 100 cm. Using a flow rate of 1.0 mL for solution of HCl and for NaBH4 and 8.0 mL to the standard and samples solutions, analytical curves in the range of 0.50 – 25.0 μg L-1 were obtained with linear correlation coefficients better than 0.9970, with detection limits of 0.1315 ug L-1 and relative standard deviation (% RSD) less than 1.9%. The precision and accuracy of the sample preparation procedure and method determination were evaluated by addition and recovery test, and found values ranged from 90.3 to 95.5% with RSD <4.9%. The Se content in the samples showed concentrations in the 0.107±0.005 – 0.374±0.006 ug g-1 range. The multivariate analysis applied to the experimental results showed to be a useful tool because allows reducing the number of experiments with sensitivity, correlation coefficient and relative standard deviations satisfactory to determine Se in Brazilian nuts.