Determination of platinum and rhodium in γ-alumina catalysts by glow discharge atomization atomic absorption spectrophotometry

Abstract

The technique of glow discharge atomization atomic absorption spectrophotometry (GDA-AAS) is used to determine platinum and rhodium concentrations in automotive catalyst materials. The glow discharge atomizer allows these difficult-to-dissolve samples to be atomized directly from the solid state after the alumina-based catalyst is mixed intimately with a conductive host matrix material. A troublesome and time-consuming dissolution step is therefore unnecessary. Optimization of the major analytical parameters (discharge current, discharge pressure, and the percentage of catalyst to be mixed with host material) is presented, along with actual determinations of platinum and rhodium, via calibration curves. Internal standardization is employed to compensate for differences in sputtering efficiency from sample to sample. Relative sensitivity factors (RSF) are also used for quantitation. The technique is shown to provide accurate determinations with relative errors of 2–3% ( C x/ C known × 100%) with either quantitation scheme, providing a relatively rapid and inexpensive alternative to competing methods of analysis.