Strategies for in-capillary derivatization of amino acids in capillary electrophoresis using 1,2-naphthoquinone-4-sulfonate as a labeling reagent

This paper examines the potentiality of in-capillary derivatization for imp roving the sensitivity of the spectrophotometric detection of amino acids i n capillary zone electrophoresis. 1,2-Naphthoquinone-4-sulfonate was select ed as the labeling agent of amino acids. The underivatized sample and the r eagent solution se gments are injected by pressure into the capillary prior to applying the running voltage. The corresponding derivatization reaction occurs inside the capillary once the potential is applied, as it induces m ixing of the sample with the reagent. Several introduction modes consisting of tandem or sandwich configuration have been evaluated. These techniques result in a straightforward and automated way of carrying out a derivatizat ion. Furthermore, in-capillary procedures may become much more attractive t han conventional pre-capillary derivatization in terms of sensitivity and r eproducibility. The optimum operation mode found consists of a sandwich sys tem where the sample is injected in between two reagent segments. The metho d was applied to the determination of amino acids in feed samples, Results show a good concordance with those given by a standard amino acid analyzer. (C) 2001 Published by Elsevier Science B.V.