Determination of Main Aminothiols in Blood Plasma Using Capillary Electrophoresis With UV Detection

A new approach of total major aminothiols determination (cysteine, homocystine, cysteinylglycine, and glutathione) in human plasma by capillary electrophoresis (CE) is presented. It is based on the analytes reduction by tris (2-carboxyethyl) phosphine and derivatization with N-ethylmaleimide, with subsequent ultrafiltration of the sample. Separation was performed using 0.1-M phosphate Na рН 2.48 with 1% Ficoll-400 and 10% methanol. The in-capillary concentration of the analytes was achieved with a pH gradient created via the preinjection of triethanolamine. The absorbance signal was detected at 200 nm. The total analysis time was 16 min (using a silica capillary [50 μm i.d.; total length 42 cm] at a 20-kV voltage). The limits of detection varied from 1.3 μM (glutathione) to 5.4 μM (cysteine). Within-run and between-run precision (CV) was < 7%; reduction of analytes ranging from 91% to 106%, were obtained. The approach was validated on control samples of children's blood plasma. The simplicity of the method and the availability of reagents make the presented approach most suitable for use on standard CE systems.