Aplicação da amostragem direta-GF AAS para a determinação de elementos traço em metérias-primas para a produção de poliuretanos

Abstract

Polymeric diphenylmethane diisocyanate (PMDI) and diphenylthane dianiline (MDA) are importante raw materials in the manufacture of polyurethanes. These products have wide application in various fields such as medicine, catalysis and electronics. Actually, considerable interest has been given for the presence of metal contaminants in raw materials for the production of polymers, because metals influence the process and modifies the thermal properties of the products. Thus, this paper proposes a procedure for the determination of Cr, Fe, Mg, Mn, Na and Ni using the direct sampling by atomic absorption spectrometry with graphite furnace (DS-GF AAS). Initially, it was obtained pyrolysis and atomization curves for PMDI, MDA samples and reference solutions. It was possible to analytes quantification using calibration using aqueous reference solutions. In addition, it was used a Zeemaneffect background correction system with variable magnetic field for construction curves with higher concentration range, allowing the analysis of samples with higher concentrations. Sample masses between 0.5 and 35 mg were using depending of the analyte concentration. It was obtained good linearity (R> 0.99), relatively good precision (RSD <15%) and detection limit between 0.1 ng g-1 for Fe and 3 ng g-1 for Ni. Samples of PMDI and MDA were decomposed using different digestionprocedures: Wet decomposition in open systems with conventional heating, microwave and microwave-induced combustion for subsequent determination by ICP OES and ICP-MS. The results were compared with those obtained by wet decomposition (microwave heating and combustion initiated by microwave). There was no significant difference (confidence level 95%) for the results obtained for Cr, Fe, Mg, Mn, Na and Ni when compared with wet procedures and DS-GF AAS.