The Determination of Arsenic in Reforming Catalysts by Hydride Generation Atomic Absorption Spectrometry

摘要

The determination of arsenic in reforming catalysts by hydride generation atomic absorption spectrometry (IIG-AAS) was investigated. Platinum and platinum-rhenium catalysts based on alumina were digested with hydrochloric acid in Teflon vessels of a closed microwave system. The mixture of potassium iodide and ascorbic acid was added to the solutions to ensure that the analytc was in trivalent form before hydride generation. The influence of several metals on the arsenic signal at concentrations up to10 times higher than expected in catalysts was evaluated and a significant interference was found only for platinum; However, in the case of highly polluted catalysts, an additional decrease of the signal is caused by the simultaneous presence of otherelements. The Standard Addition and Successive Dilution (SASD) method was successfully applied for calibration purposes. The accuracy of the proposed procedure was confirmed by the determination of arsenic in certified reference material CFA-FFA-1 fly ash. The RSD of the analytical procedure was found to be below 10% and the detection limit was calculated to be 0.2 mu g/g. The procedure is fast and takes less than two hours. As a result of our investigation, the arsenic, being the main factor influencing the quality of the reforming catalysts, was determined in the range from below 0.2 mu g/g (non-contaminated catalysts) up to 10.4 mu g/g (highly-contaminated catalysts).