Determination of Vanadium, Rhodium and Platinum in Automotive Catalytic Converters Using Inductively Coupled Plasma Mass Spectrometry With Spark Ablation

Abstract

A high voltage unidirectional spark source was used as a sampling tool for ICP-MS analysis of automotive catalytic converters. Electrical conductivity of the samples, required for spark experiments, was provided by mixing samples with powdered graphite. Spark discharge parameters, such as peak current and repetition rate, which influence spark sampling efficiency, were studied and optimized. Prior work involving liquid nebulization ICP-MS analysis of series of lladium-only wavelength dispersive X-ray fluorescence secondary standards’ was compromised owing to spectral interferences arising primarily from polyatomic oxide species. Additional separation techniques were required in order to separate analyte from matrix elements in cases where interferences could not be resolved. Spark ablation, with its dry plasma, was shown to result in a significant reduction in the formation of polyatomic species and simplification of the analytical procedure. Analytical results achieved by ICP-MS with liquid nebulization and with solid sampling are compared. Limitations of the spark ablation technique owing to high voltage rf interference on the ICP-MS instrument and spark discharge wander around the sample surface are discussed.