Enrichment of cations via bipolar electrode focusing.
We have previously demonstrated up to 5 × 10(5)-fold enrichment of anionic analytes in a microchannel using a technique called bipolar electrode focusing (BEF). Here, we demonstrate that BEF can also be used to enrich a cationic fluorescent tracer. The important point is that chemical modification of the microchannel walls enables reversal of the electroosmotic flow (EOF), enabling cations, instead of anions, to be enriched via an electric field gradient focusing mechanism. Reversal of the EOF has significant consequences on the formation and shape of the region of the buffer solution depleted of charge carriers (depletion zone). Electric field measurements and numerical simulations are used to elucidate the factors influencing the depletion zone. This information is used to understand and control the location and shape of the depletion zone, which in turn influences the stability and concentration of the enriched band.
Department of Chemistry and Biochemistry, The University of Texas at Austin, Austin, Texas 78712-0165, United States.
Eoin
E
Sheridan
Dzmitry
D
Hlushkou
Kyle N
KN
Knust
Ulrich
U
Tallarek
Richard M
RM
Crooks