Analytical validation on carbon and oxygen isotopic measurement of small carbonate samples by using IsoPrime100 mass spectrometer

Abstract

This paper focused on analytical validation such as the amount needed, time drift, repeatability, memory effect, analytical precision and accuracy on carbon/oxygen isotopic measurement of small carbonate samples (10–80 µg) using an IsoPrime100 mass spectrometer. 10 µg of carbonate samples yielded mass 44-intensity of 2 nA. The minimum amount needed was 10 μg and the repeatability was around 0.1 ‰ (1 s.d.). Through 24-h measurement there was no temporal variation of δ¹³C, but that of δ¹⁸O showed variation with decreasing the amount of CO₂ reference gas, suggesting that δ¹⁸O values need to conduct time drift correction. Inter-sample memory effect was not observed, indicating that IsoPrime100 mass spectrometer with CO₂ purification system is adequately evacuated after each analysis by means of pumping system. Moreover, IAEA-CO-1 and JAMSTEC-WS values calibrated by international reference NBS19 agree within error with the reference values, demonstrating the accuracy of our analytical procedure on carbon/oxygen isotopic measurement of carbonate samples. This paper offers insights into analytical validation procedure when setting up a mass spectrometer on isotopic analyses of small carbonate samples.