Similarly, for the examination of the oxidation resistance of the samples, the secondary clusters of interest are oxides. To determine which primary ion would provide the highest yield for the secondary clusters of interest, a Principal Component Analysis (PCA) was applied on a series of acquisitions made on the Ru-Pt-Pd-Ir alloy analyzed with 4 different primary ions (Bi1 + , Bi3 + , Bi3 ++ and Bi5 + ).