Stable carbon and oxygen isotopic determination of sub‐microgram quantities of CaCO3 to analyze individual foraminiferal shells

Abstract
We have developed an analytical system to determine stable isotopic compositions (δ13C and δ18O) of sub-microgram quantities of CaCO3 for the purpose of analyzing individual foraminiferal shells, using continuous-flow isotope ratio mass spectrometry (CF-IRMS). The system consists of a micro-volume CaCO3 decomposition tube, stainless steel CO2 purification vacuum line with a quantity-regulating unit, helium-purged CO2 purification line, gas chromatograph, and a CF-IRMS system. By using this system, we can determine stable carbon and oxygen isotopic compositions as low as 0.2 μg of CaCO3, with standard deviations of ±0.10‰ for δ13C and ±0.18‰ for δ18O within a 4-h reaction time and 30-min analysis period. Copyright © 2004 John Wiley & Sons, Ltd.