Post-column derivatization for fluorescence and chemiluminescence detection in capillary electrophoresis

Instrumental developments and applications of post-column derivatization fo r fluorescence and chemiluminescence detection in capillary electrophoresis (CE) are reviewed. Various systems to merge the reagent solution with the separation medium have been developed, including coaxial capillary reactors , gap reactors and free solution or end-column systems. For all reactor typ es the geometry of the system, as well as the method to propel the reaction mixture (by pressure or by voltage) appeared to be critical to preserve th e separation efficiency. Plate numbers of over 100 000 could be realised wi th different reactors. The strict requirements on the rate of post-column d erivatization reactions to be applied in CE limit the number of different r eagents that have been used. For fluorescence detection, with laser or lamp s as the excitation source, so far mainly o-phthalaldehyde and its naphthal ene analogue have been used as reagent. Derivatization systems that are bas ed on complexation reactions also showed good promise for application in CE . Detection limits could be obtained that were comparable to those obtained after pre-column derivatization. Various reagents for chemiluminescence de tection (e.g. the luminol and peroxyoxalate systems) have been studied. The often complicated chemistry involved made application of these reagents in CE even more difficult. Results obtained so far, in terms of sensitivity, have not been up to expectation, with detection limits usually in the order of mu mol l(-1). (C) 1998 Elsevier Science B.V. All rights reserved.