Microchip Electrophoretic Analyses of Cationic Analytes Using Large-Volume Dual Preconcentration by Isotachophoresis and Stacking (LDIS) – Field-Amplified Sample Injection (FASI) in Y-Form Channels

For highly sensitive analyses of cationic analytes in microchip electrophoresis (MCE), large-volume dual preconcentration by isotachophoresis and stacking (LDIS) was combined with field-amplified sample injection (FASI) on Y-shaped channel microchips. To enrich cationic compounds by LDIS-FASI, the microchannel was coated with neutral poly(vinyl alcohol) and cationic poly(allylamine) mixture to obtain weakly and positively-charged surface, generating a reversal electroosmotic flow (EOF). In the conventional LDIS analysis of histamine, the sensitive enhancement factor (SEF) was evaluated to be 142, whereas in LDIS-FASI that was increased to 1572 at the FASI injection time of 90 s.