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.