A method for stable carbon isotope measurement of underivatized individual amino acids by multi-dimensional high-performance liquid chromatography and elemental analyzer/isotope ratio mass spectrometry.

The consistency between the δ13 C values of reference and processed AAs demonstrates that the experimental procedure generates accurate δ13 C values unaffected by fractionation effects and contamination. This method is therefore suitable for δ13 C analysis of biological samples with higher precision than conventional approaches. We propose this new method as a tool to measure δ13 C values of AAs in biological, ecological and biogeochemical studies.