Accurate assessment of labeling measurements Amino acids Metabolic flux analysis Fluxomic Flaxseed A B S T R A C T In context of fluxomic studies, 13 C labeling analysis of amino acids are very important for solving the carbon flow calculation, because they are synthesized in various biosynthesis pathways and cellular compartments in plant cells. Traditionally, 13 C labeling analysis are performed using low resolution mass spectrometry detector by GC-MS. We compared a method using capillary electrophoresis-high resolution mass spectrometry without deri-vatization and with better accuracy assessment of labeling measurements comparing to classical GC-MS. Our method allowed us to show that valine, leucine, alanine are not synthesized from the same pyruvate pool during the period of reserves accumulation in flax seeds.