Determinação de impurezas elementares em sulfato de bário por ICP-MS após volatilização empregando combustão iniciada por micro-ondas

• Ano de defesa: 2018
• Autor(a) principal: Carvalho, Gabriel Severo de
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Santa Maria; Brasil; Química; UFSM; Programa de Pós-Graduação em Química; Centro de Ciências Naturais e Exatas
• Palavras-chave em Português: Combustão iniciada por micro-ondas; Produtos farmacêuticos; Impurezas elementares; Preparo de amostra; Sulfato de bário; USP; Barium sulfate; Elemental impurities; Microwave-induced combustion; Sample preparation; CNPQ::CIENCIAS EXATAS E DA TERRA::QUIMICA
• Link de acesso: http://repositorio.ufsm.br/handle/1/18731

In order to volatilize analytes from inorganic samples, additives such as microcrystalline cellulose have been applied. The cellulose is burnt and the heat generated helps to volatilize the analytes of the matrix being, later, recovered by the absorber solution. In the present work, a method was proposed for the volatilization of As, Cd, Hg and Pb in barium sulfate (BaSO4) using microwave-induced combustion (MIC) and subsequent element determination by inductively coupled plasma mass spectrometry (ICP-MS). BaSO4 samples were mixed with microcrystalline cellulose, homogenized and pressed into tablets. The following parameters related to the combustion procedure were evaluated: sample mass (300 to 700 mg), cellulose mass (300 to 900 mg), NH4Cl mass (300 to 600 mg), absorbing solution (3, 5, 7 and 14 mol L -1 of HNO3 and 25, 50 and 100% of inverse aqua regia) and reflux step (5 and 15 min). Reference values were obtained by using acid extraction method assisted by microwave radiation (MAE), using inverse aqua regia as the extractive solution. In addition, three steps of extractions were performed to ensure complete a extraction of the analytes. The most suitable condition for the volatilization method was 300 mg of sample, 600 mg of microcrystalline cellulose and 500 mg of NH4Cl, reflux for 5 min and a mixture of 5.5 mol L -1 of HNO3 with 1.5 mol L -1 HCl. In this condition the extracts presented a colorless appearance and a concentration of Ba at least 250 times lower then those when compared to MAE, thus avoiding problems of calibration of the spectrometer and formation of salt deposits in the cones of ICP-MS equipment. Thus, the main advantage of the proposed method is the separation of the analytes from the matrix, minimizing interferences in the determination step. In addition, when compared to the MAE method, the proposed methodology has the advantage of avoiding the use of concentrated acids for the preparation of BaSO4 samples. The quantification limits for As, Cd, Pb and Hg were 0.012; 0.001; 0.033 and 0.009 μg g -1, respectively (considering 300 mg of BaSO4 sample). Due to the unavailability of BaSO4 certified reference material or similar matrices, analyte addition assays were performed to assess the accuracy (95%).