ABSTRACT
Ultraviolet-visible (UV-Vis) detection in liquid chromatography (LC) is often hampered by the poor spectral properties of the analytes at the applied analytical wavelengths. Modern UV-Vis LC detectors present the possibility of variable-wavelength detection, usually in the range of 190–600 nm, thus offering the potential to optimize selectivity as well as the sensitivity of detection. The most widely used method for the derivatization of carboxylic acids is the formation of esters using UV-Vis absorbing alcohols or halides as labels. Derivatization reactions to improve the UV-Vis detectability in LC can be performed pre- and postchromatographically. An original combination of pre- and postchromatographic techniques is developed by LePage and Rocha. Separation of the amino acids is achieved by IP chromatography using dodecyl sulfonate as the ion-pairing agent and octyl-modified silica as the stationary phase. The simultaneous analysis of analytes with different functional groups may be a necessity in some cases, e.g., profiling of amino acids in peptides and proteins.
