Conditions for Electrophoresis

If the suspension is too stable, the repulsive forces between the particles will not be overcome by the electric field, and deposition will not occur. According to some models for electrophoretic deposition the suspension should be unstable in the vicinity of the electrode Local Instability could be caused by the formation of ions from electrolysis or discharge of the particles these ions then cause flocculation close to the electrode surface. 

The rate of deposition of material can be determined theoretically from Hamaker s equation  

While A, C and E are externally controlled variables, p is determined by the properties of the suspension. In simplified double-layer theory the interface is treated as a capacitance and p is given by the Smoluchowski 

The physical significance of the zeta potential is discussed in the following section. The suspension could be characterised by particle charge density, which can in principle be determined from the electrophoretic mobility, but which requires certain assumptions regarding the particle size and shape distribution and conductivity effects. The zeta potential is the most commonly used parameter for characterising a suspension, and can be determined from measurements of particle velocity or mobility in an applied field using commercially available electrophoresis cells. In practice electrophoretic mobilities are not easy to measure accurately, and since the Smoluchowski equation is based on a model of doubtful validity, the view sometimes expressed that zeta potentials are difficult to measure and impossible to interpret has a ring of truth but is probably unduly pessimistic. The Smoluchowski relation is valid provided that the double 

---

Optimum conditions for electrophoresis The voltage of 150 V is applied for 30 minutes initially to obtain maximum sample entry, and increased gradually until it reaches 3500 V. The optimum time for application depends on the following factors (a) type of sample, (b) amount of protein in the sample, (c) length of the IPG strips, (d) pH gradient. 

---