Alteration of micromilled carbonate δ18O during Kiel Device analysis.

Isotopic analysis of carbonate material has been greatly facilitated by the development of autosampling devices such as the Kiel III Carbonate Device, allowing rapid automated analysis of small sample sizes. This analysis is facilitated by holding samples and acid at temperatures around 70 °C prior to reaction. In most situations this has no measurable effect on sample powders on practical timeframes, but, when analyzing exceptionally fine-grained material produced by micromilling, the δ(18)O of both aragonite and calcite is altered by -0.1 ‰/day. Laboratories that use this technique should thoroughly test and correct for this phenomenon and avoid storing pre-weighed materials within the Kiel Device or similar drying oven prior to analysis.