Determinação de Na, K, Ca e Mg em amostra de requeijão por técnicas de espectrometria atômica após digestão ácida com sistema de refluxo e solubilização em TMAH

Abstract

In this work there were evaluated two sample preparation procedures for subsequent determination of Na, K, Ca and Mg in brazilian cream cheese (locally know as “requeijão”) samples by atomic spectrometry techniques. The first procedure was realized by acidic decomposition (HNO3/H2SO4) in a reflux system, and the second used the alkaline solubilization with tetramethylammonium hydroxide (TMAH). The procedures were optimized using central composite design (CCD) to assess the significance of the variables and thus establish the best working conditions. The optimized conditions was for the first procedure was 875 mg of sample, 3 mL of H2SO4, 325 °C on the digester block and 180 min of decomposition time. For the second procedure was 300 mg of sample mass and 100 μL of TMAH. The accuracy was verified by recovery tests and the results were between 80 and 104 % for both procedures. A comparison with a reference procedure was also performed and applying the Tukey test at 95 % confidence level, and no significant differences have been observed. The MP AES was used for comparison of the analyte results. The results showed the simplicity and efficiency of procedures in the preparation of brazilian cream cheese samples , presenting as viable alternatives for the control of Na and for the determination of elements K , Ca and Mg .