EQUATION 1 μ = Δωλ 0Where :μ = the electrophoretic mobilityω = the measured frequency shiftλ = the laser wavelengthn = the refractive index of the mediumθ’ contains the angular light scattering informationAfter the electrophoretic mobility is determined using equation 1, the zetapotential (ζ) is calculated using equation 2.EQUATION 2 μ = 2ζε ƒ(κr)Where:µ = the electrophoretic mobilityζ = the zeta potentialε = the dielectric permittivity of the mediumη o = the viscosityf=(κr) = a function describing the ratio of the particle radius to the double layer Zeta potential is often measured as a function of pH (or other additive property) in order to determine the conditions at which there is zero zeta potential, also known as the isoelectric point (IEP).