Isotopic analyses strontium ratio measurement

Mass spectrometers usually measure two or more isotopes at one time and calculate their ratio. Standards are measured at the same time in order to confirm the precision of the instrument and allow corrections to be made if needed. The results of the analysis provide the ratio measurements along with several other kinds of information. Table 4.2 shows some typical results from a mass spectrometer, in this case a Ust of calculated strontium isotope ratios on human tooth enamel measured on TIMS. The first column in the table gives the sequential lab number for each individual sample. The site is the place from where the sample comes. The corrected Sr/ Sr is the isotope ratio for strontium in the sample, corrected on the... 

Despite the potential to track the spatial movement of marine shell beads, archaeometric attempts at sourcing have been minimal. We are aware of only three other groups that have taken this approach including a neutron activation analysis (NAA) of Busycon sp. shells and artifacts in the American Southeast (/), the use of strontium isotopes as a measure of geologic age of fossil shells in Southwest Europe (2), and the use of oxygen isotope ratios to source Sporufylus sp. beads in Central Europe (5). 

We tested this data acquisition method by first ablating bracketing concentration standard glasses that had been determined from previous measurements. All the samples in this analysis had total strontium elemental concentrations between 95 and 350 parts per million strontium. We then collected 150-300 one second ion count packets for MSr, Sr, 87 Sr and 88Sr, plus the instantaneous ratio of each isotope to Sr (Figure 3). 

---