Desenvolvimento de Método para a Determinação de Halogênios e Enxofre em Ovo Integral Desidratado e suas Frações

Abstract

Methods involving microwave-assisted extraction using alkaline solutions, as well as microwave induced combustion (MIC) were applied for sample preparation of whole eggs and its fractions for further Br, Cl, F, I e S determination by ion chromatography (IC), inductively coupled plasma mass spectrometry (ICP-MS) and inductively coupled plasma optical emission spectrometry. Solutions of ammonium hydroxide, tetramethyl ammonium hydroxide and water were evaluated in order to select the best suitable solutions for each studied. Methods based in alkaline extraction were not suitable, taking into account that Br and I concentrations in solutions obtained resulted in extractions incomplete and not homogenous with relative standard deviations (RSDs) up to 71%, as well as high values for Br and I in blanks. Moreover, it was not possible determinate F, Cl and S concentrations by IC after extraction procedures, due the high carbon content present in solution. Using MIC was possible to decompose masses up to 350 mg of whole egg and its fractions. For this, was necessary to use an ammonium nitrate solution as ignition aid, being this added to the polyethylene bag containing the sample. As absorbing solution for Br, Cl, F, I and S NH4OH 50 mmol l-1 was selected. In these conditions, recoveries between 98 and 103% and agreements higher than 94% with reference values of the reference material (RM) NIST 8435 were obtained. Based on this studies it was possible to develop a suitable method for Br, Cl, F, I and S determination in whole eggs powder and its fractions, involving samples decomposition by MIC for further analytes determination by IC, ICP-MS or ICP OES. The proposed method allowed to observe that mainly the Cl and S concentration ranged considerably depending on the fraction and sample analyzed. However, this behavior was not observed for F, since their concentrations were below of the limit of detection (LOD), which was 44.1 mg kg-1 . Agreements between 100 and 103% were obtained for Cl, when compared the values obtained by MIC-IC method with the official method (AOAC).