Derivatization Reactions in Capillary Electrophoresis of Amino Acids

Abstract

The article deals with derivatization reactions employed in capillary electrophoresis (CE) of amino acids (AA). Currently preferred reactions are classified into seven groups according to their reaction mechanisms and schemes. Many of them were originally developed for liquid chromatography of AA and their implementation in CE usually requirer minor modifications of the working conditions depending on specificities of the process. So far, more than fifty derivatization reactions of AA have been reported in the literature in the context of CE. This apparently reflects not only different reactivities of AA with different derivatization agents but also different envisaged applications of CE. Therefore, in some instances, requirements for high reaction rates determine the choice (e.g., post-column derivatizations of AA, in-vivo monitoring of AA in microdialysates from biological processes). On the other hand, a need for the detection of amol-zmol amounts of AA may be often better met by the reactions characterized by lower reaction rates. Some of the derivatization agents provide very selective detections of a specific class of AA, e.g., detection of sulfanyl amino acids based on their reactions with 2,2´-dinitro-5,5´-disulfonyldibenzoic acid. So far, only a limited number of the derivatization reactions is applicable in the AA sequenations of peptides and proteins by CE. Here, phenyl isothiocyanate, 7-(N,N-dimethylsulfamoyl)-2,1,3-benzoxadiazol-4-yl isothiocyanate and 1-fluoro-2,4-dinitrobenzene appear to have a prominent position.