We next evaluated the distribution of two anionic fluorescent tracers (BODIPY 2-and dyelinked albumin (Texas Red BSA)) in these solutions under conditions appropriate for electrokinetic enrichment. First, the channel was filled with the BGE, and then a constant flow rate of 100 nL min -1 was established by a syringe pump connected to the inlet reservoir. Next, a voltage bias of V + = 6.0 V was applied between a driving electrode in the microchannel inlet and outlet and a wire lead connected to the Au microband. Finally, a series of fluorescence micrographs was obtained to monitor the distribution of the tracers. Figures and are fluorescence micrographs obtained following 10 min of enrichment of these tracers in the Tris buffer. These species accumulated upstream of the microband, indicating that an IDZ and electric field gradient have formed. Since each tracer is focused at an axial location at which its electrophoretic and convective velocities are equal, but opposite, BODIPY 2-, which has a higher electrophoretic mobility, forms an enriched plug further upstream than does the dye-linked albumin (Figure ), the mobility of which is minorly impacted by Texas Red, a zwitterion. Focusing of these species by fICP was not observed in KNO3 or phosphate buffer solutions. A key point is that BODIPY 2-has an electrophoretic mobility (2.11 × 10 !" cm 2 /V•s) that is similar to that of nucleic acids (2 -3 × 10 !" cm 2 /V•s, depending on ionic strength), and therefore, the degree to which it is enriched and the location at which it focuses approximate the performance of our device for nucleic acid preconcentration and separation from other sample components (e.g., albumin). Such a separation has been reported previously by Ouyang et al. who utilized pressure modulation at the device inlet to push dye-linked albumin past the locally enhanced electric field. Similarly, a balance favoring convection led to the narrow width of the enriched plug of BSA shown in Figure and the significant red fluorescence downstream of the electrode (~50% that of upstream intensity).