Optimization of a free separation of 30 free amino acids and peptides by capillary zone electrophoresis with indirect absorbance detection: a potential for quantification in physiological fluids

This report describes a rapid, single-run procedure, based on the optimization of capillary electrophoresis (CE) and indirect absorbance detection capabilities, which was developed for the separation and quantification of 30 underivatized physiological amino acids and peptides, usually present in biological fluids. p-Aminosalicylic acid buffered with sodium carbonate at pH 10.2±0.1 was used as the running electrolyte. Electrophoresis, carried out in a capillary (87 cm×75 μm) at 15 kV potential (normal polarity), separated the examined compounds within 30 min. Limits of detection ranged from 1.93 to 20.08 μmol/l (median 6.71 μmol/l). The method was linear within the 50–200 μmol/l concentration range (r ranged from 0.684 to 0.989, median r=0.934). Within run migration times precision was good (median C.V.=0.7%). Less favorable within run peak area precision (median C.V.=6.6%) was obtained. The analytical procedure presented was successfully tested for separation and quantification of amino acids in physiological fluids, such as plasma or supernatant of macrophage cultures. Sample preparations require only a protein precipitation and dilution step.