Application of electroosmotically-driven solution displacement for on-chip probing and characterization of protein adsorption

Source: Appl. Phys. Lett. 97, 043704 (2010); doi:10.1063/1.3459688

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The reported formula is (in  mV)=6.75–29.75pC for 6.5<pH<7. With pC1.48 for the 20 mM buffer, the estimated is −37.3 mV.

10. The actual current changes are not strictly linear in time, which is attributed to the O((1−₂/₁)²) terms neglected in Eq. (2). We also use the unsimplified equation to determine the zeta potential. The result merely has a few percent of difference compared to that using Eq. (2) because of this small nonlinear effect.
    
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14. In principle, both and can be determined solely by the kinetic study, as they can be obtained by plotting k against C if sufficient data of k are available in a wide range of C. At high C(>10  ppm), however, an accurate kinetic study would hardly be attainable, since the adsorption rate would become so fast that the system would have already reached an equilibrium by the time we measure the zeta potential. In other words, because the surface concentration now changes very rapidly, it is impossible in practice to rinse the channel and to load the solutions in time while still keeping the surface not changed significantly prior to the zeta-potential measurement. At the other extreme, too low C such as 1 ppm will not give enough data showing discernable zeta potential changes (<3  mV) for determining k.