Simultaneous Determination of Kynurenine and Tryptophan in Serum by High Performance Liquid Chromatography

A method was established for the simultaneous determination of kynurenine (Kyn) and tryptophan (Trp) in serum by high performance liquid chromatography-ultraviolet detection (HPLC-UV). It employed a Symmetry Shield RP-C18 column (150 mm x 3. 9 mm i. d., 5 mu m) and a mobile phase of 15 mmol/L sodium acetate-acetic acid solution containing 2. 7% (v/v) acetonitrile (pH 3. 6) at a flow rate of 1. 0 mL/min. The ultraviolet detector was operated at 225 nm. Serum samples were first precipitated with a 5. 0% perchloric acid solution, then centrifuged to remove protein residue and finally analyzed by HPLC. The retention time of Kyn was 3. 5 min, the linear range of the method was from 0. 098 to 49 mu mol/L, and the detection limit was 0. 02 mu mol/L. The recoveries of Kyn were from 90. 82% to 93. 45%, the intraday and inter day variations were 2. 37% and 3. 66%, respectively. The retention time of Trp was 8. 1 min, the linear range of the method was from 4. 9 to 490 mu mol/L, and the detection limit was 0. 20 mu mol/L. The recoveries of Trp were from 95. 51% to 98. 67%, the intraday and interday variations were 1. 50% and 2. 65%, respectively. The method is simple, fast, accurate, and suitable for routine analysis.