Isotope Effects in High-Performance Liquid Chromatography: First Baseline Separation of Isotopomers on Achiral and Chiral Columns

In this study, the feasibility of very challenging separation of isotopomers by high-performance liquid chromatography in a common setup is successfully demonstrated with the examples of deuterated amphetamine and methamphetamine. Understanding the effect of various factors, such as analyte structure, location of heavy atoms within the structure, separation mode (i.e., surface chemistry of the stationary phase), mobile phase components and their additives, pH of the mobile phase, and separation temperature, that enabled baseline separation of isotopomers with high selectivity is discussed. The results reported here are significant for both the analytical separation of isotopomers and their preparative-scale separation. The understanding and fine-tuning of the mechanisms underpinning isotopomer retention and discrimination enabled the reversal of isotopomer elution order on specific chiral columns. The simultaneous separation of isotopomers and their enantiomers was observed on polysaccharide-based chiral columns. Molecular modeling was used to provide a reasonable explanation of the separation mechanism of the isotopomers.