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 ≈ 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 μm 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.