Desenvolvimento de métodos de preparo de amostra para a determinação de Br e I em mel por ICP-MS

Abstract

Methods involving alkaline dissolution with heating in a water bath, or assisted by microwave and ultraviolet radiation, as well as microwave induced combustion (MIC) were applied for sample preparation of honey for further determination of bromine and iodine by inductively coupled plasma mass spectrometry (ICP-MS). Different types and concentrations of solutions were evaluated in order to select a suitable solution for each procedure studied. Methods based in alkaline dissolution were not suitable taking into account that the concentrations of the analytes in the sample were below of the limits of detection (LODs) obtained (LOD ≥ 700 µg kg-1 for Br e LOD ≥ 326 µg kg-1 for I). However, through the MIC was possible to decompose up to 1000 mg of sample using microcrystalline cellulose as an auxiliary of combustion. In this context, microcrystalline cellulose contributes for the combustion reaction occurs of a more controlled way, avoiding the projection of the sample, ensuring the complete decomposition of the sample. As absorbing solution for Br and I was used NH4OH 50 mmol l-1 . In these conditions recoveries for Br and I between 98 and 104% were obtained and the agreement with informed values for the RM NIST 8435 was better than 98% for both elements. Furthermore, using MIC was obtained lower values for blanks and better LODs for both analytes (Br: 34 µg kg-1 ; I: 6 µg kg-1 ) when compared with other methods evaluated. Therefore, MIC was suitable for honey digestion for subsequent determination of Br and I by ICP-MS. In addition, using this method was possible to observe that concentrations of Br varied significantly when honeys of different botanical and/or geographical origins were analyzed. However, the same behavior was not observed for I, where the concentrations were below of the LOD.