δ13C analysis of bulk organic matter in speleothems using liquid chromatography–isotope ratio mass spectrometry

The determination of δ13C values in speleothems is of considerable importance in palaeoenvironmental research, but has focussed solely on analysis of the carbonate. Here we demonstrate a new method for analysing the δ13C values of organic matter (OM) trapped in speleothems, utilising flow injection liquid chromatography–isotope ratio mass spectrometry (LC–IRMS). Developmental analysis using a homogenised speleothem powder showed that the method is robust, with repeated digests and analyses having an average standard deviation of 0.1‰. Dilution tests with samples of 4–23 μg total organic carbon (TOC) show relatively small linearity effects, with the overall standard deviation across a peak response range of 1700–9000 mV being 0.2‰.