Determinação de elementos traço em carvão por amostragem de sólidos e vaporização eletrotérmica acoplada à espectrometria de massa com plasma indutivamente acoplado

Abstract

In this work, a method using solid sampling electrothermal vaporization inductively coupled plasma mass spectrometry (SS-ETV-ICP-MS) for the determination of As, Sb, Se and Te in mineral coal was developed. The following operational parameters of the ETV-ICP-MS system were evaluated: furnace temperature program, mass of Ir used as modifier, oxygen flow rate (used at the pyrolysis step), carrier and bypass gas flow rates and the possibility of using calibration with aqueous standard solutions. After optimization, the determination of As, Sb, Se and Te in coal was performed. Therefore, the calibration was carried out by using aqueous standard solutions for As, Sb and Te and by using certified reference material (CRM) of coal for Se determination. Coal samples were decomposed by microwave-assisted wet digestion to obtain reference values for As and Sb by ICP-MS and Se by CRC-ICP-MS. In addition, the samples were digested by microwave-induced combustion to obtain reference values for Se and Te by ICP-MS. No statistical difference was observed between the results obtained by SS-ETV-ICP-MS and the values obtained by the reference methods. Additionally, CRMs of coal (NIST 1632b and NIST 1632c) were analyzed by SS-ETV-ICP-MS and the results were in agreement with the certified values. The limits of quantification (LOQ) for As, Sb, Se and Te were 30, 10, 30 and 6 ng g-1, respectively. The determination of As, Sb, Se and Te in coal by SS-ETV-ICP-MS presented some advantages, such as the minimization of the sample preparation step, allowing the achievement of low LOQ and also avoiding the use of large amount of reagents.