Figure 4. A possible relationship exists between particle size and zeta-potential, as shown for the four formulations described in Table 2. Smaller particles, i.e., oil droplets, are obtained at larger zeta-potentials. The measured data taken from Reference 20 is plotted in red and identifies the second point (with the zeta-potential of -42 mV) as an outlier. The blue line represents the overall trend when this point is ignored. This suggests the steric effect of the emulsifier polysorbate-80 is approx. 100 nm, as indicated by the dashed line.