Analysis of underivatized amino acids by capillary electrophoresis using constant potential amperometric detection

A mixture of native (underivatized) amino acids is separated by capillary electrophoresis under alkaline conditions (pH approximately 12) and amperometrically detected with a copper-disk microelectrode. A simple design facilitates capillary-electrode alignment without the need for micropositioning equipment. The limits of detection for the amino acids are in the low microM concentration range, and the signal response is linear over 2-3 orders of magnitude. This procedure is applied to analyze the amino acid hydrolysis products from cytochrome c.