Separation of 13 C and 15 N-Isotopologues of Amino Acids with a Primary Amine without Mass Resolution by means of O-Phthalaldehyde Derivatization and Collision Induced Dissociation.

Computational and experimental advances of recent years have culminated in establishing C-13-Metabolic Flux Analysis (C-13-MFA) as a routine methodology to unravel the fluxome. As the acronym suggests, C-13-MFA has relied on the relative abundance of C-13-isotopes in metabolites for flux inference, most commonly measured by mass spectrometry. In this manuscript we expand the scope of labeling measurements to the case of simultaneous C-13- and N-13-labeling of amino acids. Analytically, the separation of isotopologues of this metabolite class can only be achieved at resolving power beyond 65,000. In this manuscript we harvest an overlooked property of the collision induced dissociation of amino acid adducts to discern C-13- and N-15 isotopologues of amino acids with a primary amine without separating them in the m/z domain.