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. Author manuscript; available in PMC: 2012 Feb 1.
Published in final edited form as: Sens Actuators A Phys. 2011 Feb 1;165(2):310–315. doi: 10.1016/j.sna.2010.10.002

Figure 3.

Figure 3

Simultaneous visualizations of a) Alexa Fluor 594 and b) Fluorescein about our porous glass frit. As described in Section 2, we project the emissions of each dye onto separate quadrants of the CCD chip. The silica frit is located between the dashed lines, the anode surface is at 0 mm, and the cathode is 3 cm out of the field of view to the right. The background electrolyte is 0.1 mM borate buffer, and 25 μA current is applied at 10 s. The front sourced by and propagating from the anode is bright in the (pH-insensitive) Alexa Fluor images, but dark in the pH-sensitive Fluorescein images. This suggests the anode sources a propagating enrichment front of low pH. The anode front propagates at constant velocity and with a sharp front interface until it intersects and interacts with the CP depletion zone from the frit (past about 75 s).