Trace analysis of D-tyrosine in biological samples by microchip electrophoresis with laser induced fluorescence detection

A rapid and sensitive microchip electrophoresis (MCE) method with laser induced fluorescence (LIF) detection has been developed for the quantification of D-tyrosine (Tyr) in biological samples. The assay was performed using a MCE-LIF system with glass/poly(dimethylsiloxane) (PDMS) hybrid microchip after pre-column derivatization of amino acids with fluorescein isothiocyanate (FITC). Chiral separation of the derivatives was achieved by cyclodextrin-modified micellar electrokinetic chromatography (CD-MEKC) using gamma-CD as chiral selector in the running buffer. D/L-Tyr enantiomer was well separated in less than 140s. The limit of detection (S/N = 3) was 3.3 x 10(-8) M. Using the present method, D-Tyr level in human plasma was found to vary significantly from normal humans to patients suffering from renal failure. (C) 2011 Elsevier B.V. All rights reserved.