Determinação de cádmio, cobre e chumbo em catalisadores por espectrometria de absorção atômica com forno de grafite e amostragem direta de sólidos

Abstract

Trace impurities of Cd, Cu and Pb were determined in alumina-based catalysts using direct solid sampling graphite furnace atomic absorption spectrometry (DSS-GF AAS). The analyzed catalysts are widely used in petrochemical industry. Major elements were determined by inductively coupled plasma optical emission spectrometry (ICP OES) for matrix characterization. The following analytical parameters were evaluated: pyrolysis and atomization temperatures, feasibility of calibration with aqueous solutions, the use of palladium as chemical modifier, influence of sample mass introduced into the atomizer. Test samples between 0.05 and 30 mg were used and palladium was considered unnecessary for all elements. The obtained results were compared to those obtained by ICP OES, inductively coupled plasma mass spectrometry (ICP-MS) and by graphite furnace atomic absorption spectrometry (GF AAS). By using DSS-GF AAS the relative standard deviation was less than 10%, good agreement with results by ICP-MS and GF AAS, while characteristic masses were 1.3, 8.9 and 22 pg, for Cd, Cu and Pb, respectively. Calibration by means of aqueous solutions showed good linearity along the calibration range, being the correlation coefficient typically better than R2 = 0.997. Limits of detection (3σ, n =10) for Cd, Cu and Pb using the DSS-GF AAS proposed procedure were 0.2, 22, and 1.2 ng g-1, respectively.