Nanofabrication technology enables the application of electrokinetics as a method of performing chemical analyses in electronically-controlled fluidic chips without moving parts. Two important advantages of performing separations in nanoscale fluidic channel systems (in which at least one dimension is a fraction of a micron) are that ions/macromolecules can be separated based on valence, and that separation matrices (gels or entangled polymers) are typically not necessary.

We will describe our on-going efforts to achieve high sensitivity DNA detection and separation in 40-1560 nm deep channels etched in fused silica. One major challenge to improve spectroscopic detection limits in nanochannels is the weak signal due to small detection volumes. Isotachophoresis (ITP) is one preconcentration method of achieving as much as million fold on-chip stacking [1]. We will present preliminary results showing the coupling of ITP with free-solution electrokinetic separation of a 10 to 100 bp DNA ladder. We use electroosmotic flow (EOF) as a counterflow to establish a stationary ITP front. A typical concentration of the leading electrolyte is 600 mM, the trailing electrolyte concentration is 10 mM, and the initial sample concentration is less than 0.1 ƒÝM. This approach has the potential to yield fast separations and high sensitivity detection.

[1] Jung B, Bharadwaj R, Santiago JG, Analytical Chemistry, 2006, 78, 2319-2327