Development of analytical system for determining oxygen isotope ratios of microgram-sized silicate using laser fluorination method combined with continuous flow system

Abstract

We are developing an analytical system to measure 17O/16O and 18O/16O ratios of microgram-sized silicates. The system consists of vacuum line for extraction and purification of O2 from a sample. The oxygen is extracted by CO2-laser BrF5-flourination and then purified cryogenically. A sub-micromole quantity of oxygen is collected in a cold MS5A trap at liquid N2 temperature. It is then transferred to a cryofocus trap (MS5A PLOT) for concentration under continuous helium flow. The sample gas passes through a GC column containing MS5A PLOT for further purification and separation from any gas other than O2. The purified oxygen is introduced into an ion source of the mass spectrometer through the open split interface. The system is being improved to achieve high precision oxygen isotope analysis.