Estratégias no preparo de amostras para determinação de Br e Cl em polímeros oriundos de equipamentos elétricos e eletrônicos.

Abstract

Sample preparation methods involving microwave-induced combustion (MIC) or pyrohydrolysis were evaluated for sample decomposition of Waste Electrical and Eletronic Equipment (WEEE) for further determination of bromine and chlorine by ion chromatografy (IC) as well as of bromine by potenciometry with ion selective eletrode (ISE). For MIC parameters were evaluated as the sample mass as well as the most suitable absorption solution to retain and stabilize the analytes, whereas in the pyrohydrolysis were evaluated the sample mass, the absorbing solution, the flow of air and water, temperature and using aid for the decomposition of the sample. Method based on pyrohydrolysis was not suitable for sample decomposition for further determinations of Br and Cl by IC and ISE, because the decomposition was incomplete. However, through the MIC was possible to decompose 400 mg of sample using (NH4)2CO3 25 mmol l-1 as absorbing solution. In these conditions, the agreement with certified values for the certified reference material ERM-EC680k was better than 94% for both elements by IC. Method based on decomposition by MIC and determination of Br and Cl by IC present some advantages as the multielemental capacity and lower values for relative standard deviations (RSDs) and limits of detection (LODs) (6,9 µg g-1 for Br e 60,4 µg g-1 for Cl), when compared with the method involving the determination of Br by ISE (118 µg g-1 ). However, the ISE presents advantage related to low cost associated with the acquisition and maintenance, and it could be considered an alternative for the determination of Br in polymers from WEEE. Thus, using MIC associated with IC and ISE was possible to observe that the concentration of Br and Cl varied significantly in polymers from different types of WEEE, the which reinforces the need of to control the concentration of Br and Cl these residues.