Fig 3. Concentration profiles of NaCl at discrete positions throughout straight-channel preconcentration devices operating at various input flowrates.

The sample solution is 50 mM NaCl, and the draw solution is 500 mM NaCl which should concentrate samples by 10x. Concentrations are predicted by the in-silico model and plotted as curves for each flowrate, and the discreet chloride ion concentration measurements from the Ag/AgCl electrodes are plotted as points. A picture of an actual preconcentration device is depicted below the graph. The location of the screen-printed electrodes are shown below the x-axis. The volume of the feed is based on the channel dimensions: 150 mm x 0.5 mm x 90 μm = 6.75 μL. The volume of the draw is based on the draw reservoir dimensions: 160 mm x 35 mm x 5 mm = 28 mL. The channel volume is just 0.02% that of the draw volume. Therefore, the dilution effects are negligible.