Oxygen isotope composition (ratios 17O/16O and 18O/16O on the molecule O2) of silicates and oxides can be measured in our laboratory by fluorination (F2, BrF5) in classical nickel bombs or fluorination coupled to laser ablation. The typical sample size is respectively 10 mg and 2 mg, and the analysis by mass spectrometry (MAT 253, Delta Plus XP or Delta V) provides precisions of about ±0.07 and ±0.02 ‰ (2 SD) respectively for δ18O and ∆17O.
The ratio 18O/16O in water samples is routinely measured using a technique based on CO2 equilibration with water, and He continuous flow mass spectrometry (via either GasBench or AP2003). The analysis is performed on water samples of ~1 mL, and gives a precision better than ± 0.2 ‰ on the δ18O value.
The isotope ratio 18O/16O of carbonates is analyzed, together with C isotopes (see "Analysis of carbon isotope composition) on sample powders of ~2 mg (for pure carbonates). The technique is based on sample acidification using H3PO4 allowing CO2 gas extraction. Then, the CO2 is analyzed by He continuous flow mass spcetrometry (AP2003) with a precision of ± 0.1 ‰ (2 SD).
For further information, please contact Nelly Assayag, Carine Chaduteau, Pierre Agriner et Pierre Cartigny.