Highly Sensitive Electrophoretic Analyses Based on On-line Sample Preconcentration Techniques

Microchip electrophoresis (MCE) have attracted considerable attention as high-performance electro-driven separation methods and applied to various research fields. To improve concentration sensitivity in MCE, we have developed and modified online sample preconcentration techniques for a sample solution introduced into a whole separation channel. By employing such enrichment approaches, we investigated the development of highly-sensitive electrophoretic microchips that eliminate the need for complex voltage-programs in the sample injection processes. In the present focusing review, the contents can be categorized as follows: (1) application of large volume sample stacking with an electroosmotic flow (EOF) pump (LVSEP) to MCE, (2) development of a novel channel modification method for controlling EOF, (3) sensitivity enhancements by combining LVSEP with field-amplified sample injection (FASI), (4) sensitivity enhancements by coupling LVSEP with transient isotachophoresis (tITP), and (5) sensitivity enhancements by integrating large-volume dual preconcentration by isotachophoresis and stacking (LDIS) with FASI.