Applications of capillary electrophoresis to high-sensitivity analyses of biomolecules*

To increase the detection sensitivity of capillary electrophoresis (CE) and thereby widen its application to biomolecular analyses, we have developed a number of on-line preconcentration strategies, i.e., techniques to increase sample loading without compromising resolution and efficiency. Two such techniques, namely, dynamic pH junction and field-enhanced sample injection (FESI) are covered in this work. Dynamic pH junction is predicated on a sharp reduction in an analyte’s migration velocity following a reversal of its electrophoretic direction from the acidic sample zone to the basic background solution (BGS) zone. FESI, on the other hand, depends on the retardation of analyte velocity as it transits from the low-conductivity sample zone to the high-conductivity milieu of the BGS zone. Their applications to high-sensitivity analyses of peptides and proteins are discussed.