Chromatographic isolation for performing enantiomer-specific radiocarbon analysis (ESRA): first method development for individual L- and D-amino acids

Abstract This contribution presents to our knowledge the first-ever method development with the goal of conducting enantiomer-specific radiocarbon analysis (ESRA) of underivatized L- and D-amino acids. We used a preparative two-dimensional high-performance liquid chromatography (HPLC) approach where we performed the chiral separation of alanine and valine into their L- and D-forms followed by a cleanup step using a mixed-mode reversed-phase cation exchange column. Following this, we utilized an elemental analyzer–accelerator mass spectrometer (EA-AMS) to assess radiocarbon isotope composition of individual enantiomers. This method is intended to be conducted subsequent to previously developed amino acid isolation approaches as the chiral separation of underivatized amino acids requires a single amino acid as input and functions without any derivatization steps. Our results reveal baseline separation of underivatized enantiomers and low blanks, paving the way for future radiocarbon applications.