Flame atomic absorption spectrometric determination of iron, nickel, cobalt and molybdenum in petroleum industry catalysts after microwave oven digestion

Abstract

A method has been developed for the determination of iron, nickel, cobalt and molybdenum in different types of heterogeneous catalysts employed in the petroleum industry. The procedure is based on the previous acid digestion of the samples with nitric and phosphoric acids, in closed Teflon vessels, into a microwave oven. This treatment provides a total recovery of iron, nickel, cobalt and molybdenum without complete destruction of the matrix. To avoid the filtration of the residual solids, a slurry of the sample is aspirated directly into an air-acetylene flame and the elements are determined by atomic absorption spectrometry using acid solutions as standards. The results were compared with those found after a conventional wet digestion of the sample and recoveries of 99.6–105% were found for all the elements in the different samples analysed.