Turn geometry for minimizing band broadening in microfabricated capillary electrophoresis channels

Turns in microfabricated capillary electrophoresis channels generally resul t in degraded separation quality. To circumvent this limitation, channels w ere constructed with different types of turns to determine the design that minimizes turn-induced band broadening In particular, tapered turns were cr eated by narrowing the separation channel width before the start of a turn and widening the channel after the turn is complete. The radius of curvatur e of the turn, the length over which the channel is tapered, and the degree of tapering were explored. The column efficiencies were determined by exam ining the resolution of the 271/281 base pair doublet in the separation of a phi X174 HaeIII DNA sizing ladder. Tapered turns with the smallest radius of curvature (250 mu m), the shortest tapering length between the separati on and turn widths (55 mu m), and the largest tapering ratio (4:1 separatio n channel width to turn channel width) produced the highest resolution sepa rations. These results are discussed by comparison to theoretical predictio ns of the effect of tapers and turns on analyte band dispersion in capillar y electrophoresis.