Determination of Blood Plasma Aminothiols Using Derivatization-enhanced Capillary Transient Isotachophoresis

Abstract

A sensitive capillary electrophoresis method was developed for the determination of aminothiol (cysteine, homocysteine, and glutathione) total levels in human blood plasma. Analytes were derivatized with Ellman’s reagent (5,5′-dithiobis(2-nitrobenzoic acid)) after reduction with dithiothreitol. Liquid–liquid extraction was applied to purify the samples and concentrate the analytes. Total analysis time was 7.5 min using a silica capillary (50 μm i.d.; effective separation length 23.5 cm). Electrophoretic separation was performed using 50 mM citric acid with 20 mM triethanolamine (pH 3) containing 2% Ficoll 400. Detection limit was 0.8 μM for glutathione and 0.3 μM for both cysteine and homocysteine. Accuracy was 94 – 107%, repeatability and reproducibility were ca. 2.7 – 3.5 and 2.5 – 6.5%, respectively.