Memory effect in deuterium analysis by continuous flow isotope ratio measurement

International Journal of Mass Spectrometry, 254 (1-2), 44-52, 2006

J. Olsen and J. Heinemeier
Aarhus Univ, Dept Phys & Astron, Aarhus, DK-8000 C Denmark.
I. Seierstad, B. Vinther and S. Johnsen
Ice and Climate, The Niels Bohr Institute, Juliane Maries Vej 30, DK-2100 Copenhagen, Denmark

The method of deuterium analysis (delta D) measurements has previously been shown to suffer from intersample memory effects. In this study the memory effect of delta D continuous flow isotope ratio mass spectrometry (CF-IRMS) employing the chromium reduction technique is investigated with the goal of optimising the system configuration. By optimising the system configuration, the magnitude of the memory effect has been reduced from 6% to 1-2%. It is shown that the memory effect displays a long range behaviour which can be described by a sum of two exponential decay functions, indicating two main sources with different time constants. Furthermore, a correction algorithm which takes into account the observed long range nature of the memory effect is developed and tested against waters of known isotopic composition.