Zeta potential titration is atitration ofheterogeneous systems, for examplecolloids andemulsions. Solids in such systems have very highsurface area. This type of titration is used to study thezeta potential of thesesurfaces under different conditions. Details of zeta potential definition and measuring techniques can be found in the International Standard.[1]
Theiso-electric point is one such property. The iso-electric point is the pH value at which thezeta potential is approximately zero. At a pH near the iso-electric point (± 2 pH units), colloids are usually unstable; the particles tend tocoagulate orflocculate. Such titrations use acids or bases as titrationreagents. Tables of iso-electric points for different materials are available.[2] The attached figure illustrates results of such titrations for concentrated dispersions ofalumina (4% v/v) andrutile (7% v/v). It is seen that iso-electric point of alumina is around pH 9.3, whereas for rutile it is around pH 4. Alumina is unstable in the pH range from 7 to 11. Rutile is unstable in the pH range from 2 to 6.
Another purpose of this titration is determination of the optimum dose ofsurfactant for achievingstabilization orflocculation of a heterogeneous system.
In a zeta-potential titration, theZeta potential is theindicator. Measurement of thezeta potential can be performed usingmicroelectrophoresis, orelectrophoretic light scattering, orelectroacoustic phenomena. The last method makes possible to perform titrations in concentrated systems, with no dilution.