Quantitative analyses of trace elements in rock samples by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS)

Abstract

For quantitative analyses of trace elements in rock samples by inductively coupled plasma-mass spectrometry (ICP-MS), it is necessary to accommodate instrumental drift and irregularities in detector linearity. Interferences of oxide molecular ions and non-spectral matrix effects are also taken into consideration to establish an appropriate analytical method. Relatively rare trace elements in rock samples, such as rare earth elements, are determined by alternatively analyzing a 10-ppb standard solution and 1000 times diluted rock solutions containing a 10-ppb Indium internal standard. Analytical results for both samples and standards are normalized to the internal standard, which enables minimization of instrumental drift and correction of uncertainty in dilution factors. Using the internal standard, matrix effect is effectively canceled out at the dilutions factor. Determinations of elements present in relatively high concentrations, such as Rb, Sr, Y and Zr, is achieved by increasing dilution to achieve acceptable detector linearity. This further suppresses matrix effects originating from concomitant major elements.