Sample stacking of cationic and anionic analytes in capillary electrophoresis

The behavior of charged species along concentration boundaries in capillary zone electrophoresis (CZE) that was first described in detail by Everaerts et al. in 1979 assured the possibility of concentrating charged solutes in side the capillary. The concentration effect is based on the sudden change in analyte electrophoretic velocity brought about by the difference in the magnitude of the electric held. Furthermore, this on-line method could be t he needed solution to the problem of low concentration sensitivity in CZE. Sample stacking, which is now its well known name, has then found valuable use in applying CZE in many fields, especially after the in-depth studies p erformed in the early 90s by Chien and Burgi. This article reviews the theo ry and methodological developments of sample stacking developed for charged analytes in CZE and also in electrokinetic chromatography. A table conveyi ng the reported applications especially in the biomedical and environmental fields is given. On top of this, other on-line concentration methods for c harged species, namely, sample self-stacking, acetonitrile stacking, sweepi ng, cation selective exhaustive injection-sweeping, and use of a pH junctio n, are briefly discussed. (C) 2000 Elsevier Science B.V. All rights reserve d.