Analysis and characterisation of aromatic amino acids, metabolites and peptides by rapid-scanning photodiode array detection in high-performance liquid chromatography.

The role of rapid-scanning UV detectors based on the linear photodiode array has been examined in studies on the chromatography of aromatic amino acids, some metabolites and peptides. Multichannel detectors can generate characteristic qualitative information presented as individual spectra, as three-dimensional spectrochromatograms or as contour maps in the (lambda, t) plane. The use of such contour plots for mapping amino acids and their metabolites, and for peptide mapping Tyr-Gly, Gly-Tyr, Phe-Gly, Tyr-Tyr and Phe-Val, is examined. The application of computer-aided methods for validating peak homogeneity by spectral suppression, second derivative in the time domain and by other methods is discussed with respect to Tyr and its metabolite dopamine, which are not resolved by the system described, and which have closely similar spectral characteristics. The use of colour graphics with the IBM Personal Computer is demonstrated for simplifying the presentation of contour maps of amino acids, metabolites and dipeptides.