Plasma amino acids determined by liquid chromatography within 17 minutes

We present an HPLC method for the determination of amino acids in plasma. The method is based on automated precolumn derivatization of amino acids with o-phthalaldehyde, separation of the derivatives by reversed-phase chromatography, and quantification by fluorescence detection. Complete separation was achieved within 12 min. Total analysis time, including derivatization, chromatography, and reequilibration of the column, was 17 min. The assay was linear from 5 to 800 mumol/L for all amino acids. Recovery of amino acids added to plasma samples was 96-106%, except for tryptophan (89%). Within-run precision (CV) was 1.8-6.4%, and between-run precision was 2.1-7.2%. The method can be used for determining primary amino acids in plasma and cerebrospinal fluid. The simple sample preparation and short analysis time make the method particularly suitable for routine analysis of large series of samples.