Avaliação da decomposição de amostras de cerveja em sistema de refluxo para análise por Técnicas de Espectrometria Atômica.

Abstract

This study describes the development of an analytical method for beer sample mineralization and metal determination by atomic spectrometric techniques. Samples were prepared by nitric acid decomposition with reflux system, and F AAS (Fe, Mg and Zn), F AES (Na) and MIP OES (Ca, Fe, K, Mg, Mn, Na, Ni and Zn) performed the determinations. The best conditions for sample decomposition were obtained through studies with central composite design: 10.0 mL of degassed beer followed by the addition of 5.0 mL of HNO3 and 2.0 mL H2O2 and a heating step in the digester block at 160 °C for 93 min. The limits of quantification of the method were ≤ 0.100 mg L-1 for all analytes investigated, regardless of the analytical technique used, and below the values established for Zn and Ni by the Brazilian Health Surveillance Agency. The recovery test at three different concentration levels showed results around 101% for Fe, Mg, and Zn by F AAS, 99% for Na by F AES and 101% for Ca, K, Mn and Ni by MIP OES. The comparative study of the different techniques showed that by the t-test at 90% level of confidence, there is no significant difference for the analyte determinations in beer samples. Overall the RSD´s were low, ranging on average of 3.2% for all determinations. The sample preparation method proved to be simple, fast, low-cost and reliable for beers analysis by different techniques of atomic spectrometry.