Memory effect in deuterium analysis by continuous flow isotope ratio measurement

The method of deuterium analysis (δD) measurements has previously been shown to suffer from intersample memory effects. In this study the memory effect of δD 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.