SECM approach curves to the nanopore membrane for Arixtra in 0.10, 0.03, and 0.01 M PBS (solid lines). Probe scan rate, 0.23 μm/s. The circles represent approach curves simulated with the corresponding k values in Table 2. The dashed and dotted lines were simulated for freely permeable (kd = 1.1 × 10−2 cm/s from eq 2 with l = 16 nm) and impermeable membranes, respectively. All simulated curves were obtained using (a, h/a, rg/a) = (1.8 μm, 0.81, 1.2).