Rapid Determination of Underivatized Arginine, Ornithine, Citrulline and Symmetric/Asymmetric Dimethylarginine in Human Plasma by LC–MS

A rapid and specific liquid chromatography-mass spectrometry method was developed for the simultaneous determination of underivatized arginine, ornithine, citrulline, symmetric and asymmetric dimethylarginine in human plasma. The plasma samples were extracted with acetonitrile after addition of isotopic internal standards and then chromatographed on an Atlantis dC18 column (4.6 × 100 mm, 3.0 μm). The mobile phase was composed of 0.03% trifluoroacetic acid in water and the flow rate was 0.6 mL min−1. Selected ion monitoring detection was performed on a single-quadrupole mass spectrometer using positive electrospray ionization. The method was well validated and then successfully applied to a clinical study in healthy subjects.