Keywords:High precision, stable isotopic analysis, carbon and oxygen isotope, carbonate, development
The stable carbon and oxygen isotopic compositions (δ13C and δ18O) of calcium carbonate, especially biogenic calcite, are used for environmental analysis (e.g. reconstruction of paleo-seawater temperature). The measurement of δ13C and δ18O of calcium carbonate is performed based on the comparison between the δ13C and δ18O of international standard calcite. Through the analysis, the isotopic values of samples should be determined precisely in order to compare and discuss with the analytical results reported in previous studies. In this study, we have developed a sample preparation system for IRMS (isotope ratio mass spectrometer) for high precision and high sensitive analysis. As a result, analytical results of NBS-19 (international standard calcite) using the developed system with dual-inlet IsoPrime100 (IRMS) showed δ13C= +1.95 +/-0.026‰ and δ18O= -2.20 +/-0.056‰ in long-term external analytical precision (n=36). Moreover, we found that short-term external precision (within a day) for this system have achieved around +/-0.01‰. By using the developed system with continuous-flow IsoPrime100 (IRMS), we can determine δ13C and δ18O of calcite and seawater (as low as 0.1 microgram of CaCO3; 1 nmol of CO2) with standard deviations of +/-0.1 ‰.