Rapid method for the determination of amino acids in serum by capillary electrophoresis

A rapid method for the determination of amino acids in serum is presented. The derivatization of amino acids with 2,4-dinitrofluorobenzene was performed in 0.5 M sodium borate (pH 9.5). The complete separation of derivatives of 16 amino acids and an internal standard (d-norleucine) was achieved within 8 min by capillary zone electrophoresis. The running buffer consisted of 30 mM sodium tetraborate (pH 9.8)–isopropanol–30% Brij 35 (825:150:25, v/v). The capillary used had an internal diameter of 75 μm and an effective length of 300 mm. A voltage of 28 kV was applied. Temperature was maintained at 15 °C. Detection was 360 nm. The assay was linear from 10 to 700 μM. The minimal detection limit was 2.5–7.9 μM. The recovery of amino acids added to serum samples was 86.3–107.4%. Within-run precision was 2.8–10.3%, and between-run precision was 3.5–11.6%. The concentrations of amino acids in serum of 32 patients with chronic renal failure were measured. Among them, the levels of serine, isoleucine and valine were significantly lower than those of healthy volunteers (P<0.01), but the concentrations of cystine, tryptophan and phenylane were significantly higher than those of healthy volunteers (P<0.01). The result showed that the method could be used for determining amino acids in clinical practice and scientific research.