Conclusions

In this study, the oxygen yield of silicate was improved using the same TC/EA-IRMS instrument that is widely used for organic matter. Improvements in CO gas generation from silicate minerals can be achieved by (1) using NaF as a fluorine source, (2) using Ni/C, which has a catalytic effect, as a carbon source, and by homogenizing the additive and sample before encapsulation, and (3) increasing the F/O ratio. It was found that a recipe using NaF with an F/O ratio of 6 provided sufficient reactivity and oxygen yield and reduced the measurement time from 60 min to 20–30 min per sample. However, a drawback was also identified in the early cycles of loading the sample bearing NaF. Presumably, excess oxygen released from the residue of the preceding standard samples, resulting in an overestimation of the oxygen yield and inaccurate isotopic composition. Because the TC/EA-IRMS method is highly automated and does not require a specialist apparatus, further refining of this methodology will increase access to isotope measurements. This will further promote isotope studies of oxygen-bearing Earth materials and accelerate the exploration of the biological and geochemical processes between them.