High-resolution δ18O analysis of tooth enamel phosphate by isotope ratio monitoring gas chromatography mass spectrometry and ultraviolet laser fluorination

The viability of oxygen isotope analysis of tooth enamel by UV laser ablation and fluorination has been demonstrated by comparison with the Ag3PO4 extraction method. In-situ analyses by UV laser fluorination using both isotope ratio mass spectrometry and isotope ratio monitoring gas chromatography mass spectrometry (irm-GCMS) microanalysis are comparable to those of the Ag3PO4 method with a mean precision of ±0.4‰ (1σ) for samples with δ18O values ranging from 10.8 to 20.8‰. UV laser ablation provides spatial resolution of 100 μm or less with no laser reaction rim. These data show that irm-GCMS offers a combination of spatial and analytical precision for in-situ sampling of biogenic apatites previously unobtainable by other means.