PNNL

Abstract

We report on the application of high-resolution multi-step resonance ionization mass spectrometry (RIMS) to the trace determination of the rare earth element gadolinium. Utilizing three-step resonant excitation into an autoionizing level, we attain both isobaric and isotopic selectivity of >107. An overall detection efficiency of -10-7 and an isotope specific detection limit of 1.5x109 atoms have been demonstrated. When targeting the major isotope 158Gd, this corresponds to a total Gd detection limit of 1.6 pg. Additionally, linear response has been demonstrated over a dynamic range of six orders of magnitude. The method has been used to determine the GD-content in various normal and tumor tissue samples, taken from a laboratory mouse shortly after injection of Gd-DTPA, which is used as a contrast agent for magnetic resonance imaging (MRI). The RIMS results show Gd concentrations that vary by more than two orders of magnitude depending on the tissue type. This is variability is similar to that observed in MRI scans that depict Gd-DTPA content in the mouse prior to dissection, and illustrates the potential for quantitative trace analysis in microsamples of biomedical materials.