Detection of native amino acids and peptides utilizing sinusoidal voltammetry

Native amino acids and peptides were detected at a copper microelectrode us ing sinusoidal voltammetry (SV). Traditionally, these molecules can only be measured after derivatization with either a fluorescent or electroactive t ag. In this:work, an electrocatalytic oxidation reaction at copper is used to detect underivatized peptides and amino acids; The:oxidation reaction is somewhat independent of peptide structure (i.e., it is not limited to the detection of aromatic amino acids) and is therefore able to produce nanomol ar detection limits for all amino acids and peptides tested. A scanning tec hnique, sinusoidal voltammetry, is used to provide the sensitivity of const ant-potential techniques but also provide selectivity gained through utiliz ation of the frequency domain. The frequency spectrum due to the oxidation of each molecule has a unique "fingerprint" response resulting from the kin etics of oxidation at the electrode surface. Through examination of the fre quency spectra, even structurally similar molecules can be easily distingui shed from one another. mow injection analysis is used to demonstrate the se nsitive and selective detection of a variety of amino acids and peptides.:T his technique can also be easily coupled to a separation step, i.e., high-p erformance liquid chromatography or capillary electrophoresis without elect rode fouling fi-om the adsorption of the analytes.