Analyses

Ion probes allow three types of analyses:

  • Point analysis : a stationary or rastering primary beam is used to know the composition in a point with a spot size between 5-20µm
  • Imaging : an image of either elemental or isotopic variations in composition with a spatial resolution of roughly 1µm
  • Depth profiling: the progressive erosion of the sample surface using a scan of a small surface (raster) allows monitoring of the variations of composition as a function of depth

We currently focus on point analysis for isotopic ratios measurements.

The measurements accuracy allowed by the IMS 1280 HR can be as low as conventional bulk technique (e.g. 2SD for oxygen isotopes is 0.2-0.3‰).

Accurate isotopic analysis requires matching of the chemical matrix composition (to a few % weight) and the unknown sample, as well as a match of the structure. Chemical variations due to solid solutions, present in many glasses and crystals, requires a series of standards wich cover the range in composition to be analyzed (with respect to major elements).

SwissSIMS precisions for regular (~10-15µm) spot size

  • δ18O: ± 0.3‰ 2SD
  • δ13C: ~ ± 1‰ 2SD
  • δ30Si: ± 0.3‰ 2SD
  • δ56Fe: ± 0.3‰ 2SD
  • δ37Cl: ± 0.4‰ 2SD for [Cl] > 100 ppm
  • δ7Li: ± 1‰ 2SD or better for [Li] > 20 ppm
  • δ11B: ± 1‰ 2SD or better for [B] > 20 ppm
  • Cl, F, H2O: F-H2O: 0.3 – 0.6% s.e., Cl: 1% s.e. (F-OH-rich minerals)
  • Trace elements: ~ ± 10 %