Potencial Zeta

Introduction

Zeta potential is a physical property

which is exhibited by any particle in

suspension. It can be used to

optimize the formulations of

suspensions and emulsions.

Knowledge of the zeta potential can

reduce the time needed to produce

trial formulations. It is also an aid in

predicting long-term stability.

Colloid Science

Three of the fundamental states of

matter are solids, liquids and gases. If

one of these states is finely dispersed

in another then we have a ‘colloidal

system’. These materials have special

properties that are of great practical

importance.

There are various examples of

colloidal systems that include

aerosols, emulsions, colloidal

suspensions and association colloids.

In certain circumstances, the

particles in a dispersion may adhere

to one another and form aggregates

of successively increasing size, which

may settle out under the influence of

gravity. An initially formed aggregate

is called a floc and the process of its

formation flocculation. The floc may or

may not sediment or phase separate.

If the aggregate changes to a much

denser form, it is said to undergo

coagulation. An aggregate usually

separates out either by sedimentation

(if it is more dense than the medium)

or by creaming (if it less dense than

the medium). The terms flocculation

and coagulation have often been used

interchangeably. Usually coagulation

is irreversible whereas flocculation

can be reversed by the process of

deflocculation. Figure 1 schematically

represents some of these processes.

Colloidal Stability and

DVLO Theory

The scientists Derjaguin, Verwey,

Landau and Overbeek developed a

theory in the 1940s which dealt with

the stability of colloidal systems.

DVLO theory suggests that the

stability of a particle in solution is

dependent upon its total potential

energy function VT. This theory

recognizes that VT is the balance of