Strontium Isotope Ratios in Bone Samples by HR-ICPMS

After the achievement of the primary aim of the performed work, the development of an analytical setup for fast, precise and accurate measurement of strontium isotope ratios using HR-ICPMS (high-resolution inductively coupled plasma mass spectrometry), the method was applied to a statistical number of ancient human skeletal remains from 3 different localities in Austria for the reconstruction of migration processes. For the separation of Rb and Sr, an online matrix separation method using HPLC coupled to an ICP-MS was developed. The method was compared to batch based matrix separation. We could develop a novel off-line method for the accurate determination of Sr isotope ratios in fractions of dissolved samples of human skeletal remains. The main advantage of the latter method is the high sample throughput in combination with a simple operation procedure. Furthermore, we could for the first time distinguish between biogenic and diagenetic Sr by using fractionated dissolution. The results using ICP-MS were underlined by IR spectroscopy. The possibility of analyzing tooth samples using chemical and mechanical separation techniques led to the conclusion that both methods are not adequate for reliable determination of enamel Sr or dentine Sr, respectively. Thus, we measured for the first time samples using laser ablation in combination with ICP-MS and obtained very good results. As an important objective of our research so far, we could clarify that processes in the soil did not significantly alter the isotope ratios but effective decontamination is a prerequisite when using wet chemical digestion methods. Moreover, we could underline the hypothesis that water is the main source of Sr in human diet (drinking water as well via the food chain). Since Sr sources in water are determined by secondary geogenic or anthropogenic impact, Sr isotopic composition always represents a snapshot of the environmental conditions during the lifespan of the individual. Within a study of a Latenic site in Pottenbrunn / Lower Austria we could clearly distinguish between two different groups, which is underlined by archaeological evidence. Human migration was a possible explanation since the chemical analysis of another site nearby in Franzhausen / Lower Austria led to comparable isotope ratios as found for one group. Within the latter study, effective Sr/Rb separation turned finally out to be a prerequisite for the accurate determination of Sr isotope ratios. Within a preliminary study in co-operation with the University of Norfolk, USA, first results on Sr isotope ratio measurements using LA-ICP-SFMS on human teeth and bone material revealed good results. Moreover, we revealed that calcite inclusions ("Brushit") in Haversian systems of cortical bone material contain a significantly higher amount of Rb leading to false results. The results led to a new FWF project. The results of this project have been published in 6 reviewed publications and were presented in 26 contributions to conferences and meetings.