A reliable LC-MS/MS method for the quantification of natural amino acids in human plasma and its application in...

A simple and fast LC-MS/MS method was developed and validated for simultaneous quantification of 20 L-amino acids (AAs) in human plasma. Chromatographic separation was achieved on an Agilent AdvanceBio Hilic column within 15 min via gradient elution with an aqueous solution containing 5 mM ammonium formate, 5 mM ammonium acetate and 0.1 % formic acid and an organic mobile phase containing 0.1 % formic acid, 5 mM ammonium formate and 5 mM ammonium acetate acetonitrile-water (90:10, v/v) at the flow rate of 0.25 mL/min. Individual AAs and internal standard were analyzed by multiple reaction monitoring (MRM) in positive ion mode under optimized conditions. Method validation consisted of linearity, sensitivity, accuracy and precision, recovery, matrix effect, and stability, and the results demonstrated this LC-MS/MS method as a specific, accurate, and reliable assay. The method was thus utilized to compare the dynamics of individual plasma AAs between healthy females and patients with ovarian tumors. Our results revealed that, in cancer group, plasma 3-Methyl-L-Histidine, L-Proline, L-Phenylalanine and L-Lysine concentrations were significantly increased in patients with malignant ovarian tumors while L-Leucine and L-Isoleucine levels were sharply decreased. These findings support the utilities of this LC-MS/MS method and the promise of specific AAs as possible biomarkers for ovarian cancer.