Colloidal Dispersions: General Characteristics, Size & Shapes of Colloidal Particles, Optical, Kinetic & Electrical Properties.

Electrophoresis:

Colloidal particle carries net electrical charges due to the adsorption of ions from the surrounding medium or dissociation of a functional group on the particle surface. Motion in charged colloidal particles in an electric field is electrophoresis. Charged particles migrate toward the electrode of the opposite charge. The principle of electrophoresis is used to determine the sign and magnitude of the zeta potential. This phenomenon is used for various applications like particle separation based on their charge and size analysis.

An electrophoresis cell is used for the electrophoresis. It consists of two electrodes. A colloidal dispersion is placed into the electrophoresis cell. The electric potential is applied across the electrodes. Colloidal particles migrate towards oppositely charged electrodes. Colloidal particles moving toward the anode carry a negative charge. Colloidal particles moving towards carry a positive charge. This helps to decide the sign of zeta potential in colloidal dispersion. The rate of migration of charged particles depends upon the magnitude of charges on the colloidal particles.

The velocity of migration of colloidal particles in cm/sec is directly proportional to the potential gradient across particles in volts.

· Donnan Membrane Equilibrium: It occurs in dispersion and solution containing colloidal particles and electrolytes separated by the semi-permeable membrane. Colloidal particles are electrically charged that create a charged environment in the colloidal dispersion. Additionally, electrolytes are present in the solution. If both liquid preparations are separated by the semi-permeable membrane, it starts to establish Donnan equilibrium. It involves the distribution of ions on either side of the membrane to maintain equilibrium. Donnan equilibrium helps to understand into distribution across cell membranes and dialysis processes. This principle is used to enhance the absorption of drugs like sodium salicylates, potassium benzylpenicillin, etc.                       alokpdf.copm