An investigation of the precision of isotopic abundances determined by secondary ion mass spectrometry

The precision with which the isotopic abundances of palladium and tin can be measured under secondary ion mass spectrometric (SIMS) conditions typically used for organic compound analysis has been determined. The relative abundances of the isotopic peaks, and their associated standard deviations, vary with the number of scans averaged to achieve a spectrum. A representative spectrum is not obtained until more than 40 scans are averaged. In addition, there is a strong correlation between standard deviation and absolute signal intensity. This relationship can allow one to determine the number of scans that need to be averaged to predict true experimental abundances reliably, based on signal intensities.