A Novel LC-MS/MS Method for Direct Analysis of Underivatized Amino Acids in Human Plasma

Amino acids are critical molecules for biological function as they serve as building blocks of peptides/proteins and intermediates of various metabolic pathways (e.g., urea cycle and citric acid cycle). Amino acids profiling in plasma is an important tool for the diagnosis of metabolic disorders, especially for inborn errors of metabolism. A fast-and-accurate, large-panel amino acids analysis is critical not only for disorder identification but also for continued monitoring and assessment of nutritional status of patients and treatment plans. Traditionally, amino acids were analyzed by either post-column or precolumn derivatization methodologies. The major shortcomings of these approaches are long chromatographic cycling time (post-column derivatization) and poor chromatographic separation (precolumn derivatization) for comprehensive amino acid quantification in plasma. The relative lack of applications for direct analysis of underivatized amino acids by LC-MS/MS is due to limited chromatographic retention and insufficient detection sensitivity.