Pressurized gradient capillary electrochromatographic separation of eighteen amino acid derivatives

A pressurized gradient capillary electrochromatography (pCEC) instrument wa s developed to separate 18 amino acid derivatives. A reversed-phase C-18 co lumn (3 mu m, 130 mmX75 mu m I.D.) and an acetate buffer (50 mmol/l NaAc, p H 6.4) with an ion-pair reagent (1% N,N-dimethylformamide) were used to sep arate derivatized amino acids from a standard solution (2 mu g/ml), and the wavelength of the UV-Vis detector was 360 nm. The pressure on the capillar y column was kept at approx. 70 Pa and 3 kV positive voltage was added on t he outlet end of column. The effect of voltage on the eluting order of amin o acids and the resolution of separation were studied, and it was found tha t when the voltage was higher than 3 kV, the adsorption of amino acids in t he porous C-18 column occurred. The effect of salt concentration, injection volume, and column length on the separation of amino acids was determined. The amino acid sample was separated by pCEC, and RSDs of the migration tim es of each amino acid were all less than 2.5%. (C) 2000 Elsevier Science BN . All rights reserved.