Zeta potential titration is a

titration Titration (also known as titrimetry and volumetric analysis) is a common laboratory method of quantitative chemical analysis to determine the concentration of an identified analyte (a substance to be analyzed). A reagent, termed the ''titrant'' ...

heterogeneous Homogeneity and heterogeneity are concepts often used in the sciences and statistics relating to the uniformity of a substance or organism. A material or image that is homogeneous is uniform in composition or character (i.e. color, shape, siz ...

systems, for example

colloid A colloid is a mixture in which one substance consisting of microscopically dispersed insoluble particles is suspended throughout another substance. Some definitions specify that the particles must be dispersed in a liquid, while others extend ...

s and

emulsion An emulsion is a mixture of two or more liquids that are normally immiscible (unmixable or unblendable) owing to liquid-liquid phase separation. Emulsions are part of a more general class of two-phase systems of matter called colloids. Althoug ...

s. Solids in such systems have very high

surface area The surface area of a solid object is a measure of the total area that the surface of the object occupies. The mathematical definition of surface area in the presence of curved surfaces is considerably more involved than the definition of arc ...

. This type of titration is used to study the

zeta potential Zeta potential is the electrical potential at the slipping plane. This plane is the interface which separates mobile fluid from fluid that remains attached to the surface. Zeta potential is a scientific term for electrokinetic potential in coll ...

of these

surface A surface, as the term is most generally used, is the outermost or uppermost layer of a physical object or space. It is the portion or region of the object that can first be perceived by an observer using the senses of sight and touch, and is t ...

s under different conditions. Details of zeta potential definition and measuring techniques can be found in the International Standard.International Standard ISO 13099-1, 2012, "Colloidal systems – Methods for Zeta potential determination- Part 1: Electroacoustic and Electrokinetic phenomena"

Iso-electric Point

The iso-electric point is one such property. The iso-electric point is the pH value at which the

is approximately zero. At a pH near the iso-electric point (± 2 pH units), colloids are usually unstable; the particles tend to

coagulate Coagulation, also known as clotting, is the process by which blood changes from a liquid to a gel, forming a blood clot. It potentially results in hemostasis, the cessation of blood loss from a damaged vessel, followed by repair. The mechanism o ...

flocculate Flocculation, in the field of chemistry, is a process by which colloidal particles come out of suspension to sediment under the form of floc or flake, either spontaneously or due to the addition of a clarifying agent. The action differs from pre ...

. Such titrations use acids or bases as titration

reagent In chemistry, a reagent ( ) or analytical reagent is a substance or compound added to a system to cause a chemical reaction, or test if one occurs. The terms ''reactant'' and ''reagent'' are often used interchangeably, but reactant specifies a ...

s. Tables of iso-electric points for different materials are available. The attached figure illustrates results of such titrations for concentrated dispersions of alumina (4% v/v) and

rutile Rutile is an oxide mineral composed of titanium dioxide (TiO2), the most common natural form of TiO2. Rarer Polymorphism (materials science), polymorphs of TiO2 are known, including anatase, akaogiite, and brookite. Rutile has one of the highest ...

(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.

Surfactants and Stabilization

Another purpose of this titration is determination of the optimum dose of

surfactant Surfactants are chemical compounds that decrease the surface tension between two liquids, between a gas and a liquid, or interfacial tension between a liquid and a solid. Surfactants may act as detergents, wetting agents, emulsifiers, foaming ...

for achieving stabilization or

flocculation Flocculation, in the field of chemistry, is a process by which colloidal particles come out of suspension to sediment under the form of floc or flake, either spontaneously or due to the addition of a clarifying agent. The action differs from pr ...

of a heterogeneous system.

Measurement

In a zeta-potential titration, the

Zeta potential Zeta potential is the electrical potential at the slipping plane. This plane is the interface which separates mobile fluid from fluid that remains attached to the surface. Zeta potential is a scientific term for electrokinetic potential in coll ...

is the

indicator Indicator may refer to: Biology * Environmental indicator of environmental health (pressures, conditions and responses) * Ecological indicator of ecosystem health (ecological processes) * Health indicator, which is used to describe the health o ...

. Measurement of the zeta potential can be performed using

microelectrophoresis Microelectrophoresis is a method of studying electrophoresis of various dispersed particles using optical microscopy. This method provides image of moving particles, which is its unique advantage. e.g. observation of RBCs, neutrophiles and bacteria. ...

, or

electrophoretic light scattering Electrophoretic light scattering (also known as laser Doppler electrophoresis and phase analysis light scattering ) is based on dynamic light scattering. The frequency shift or phase (waves), phase shift of an incident laser beam depends on the dis ...

, or

electroacoustic phenomena Electroacoustic phenomena arise when ultrasound propagates through a fluid containing ions. The associated particle motion generates electric signals because ions have electric charge. This coupling between ultrasound and electric field is called el ...

. The last method makes possible to perform titrations in concentrated systems, with no dilution.

Iso-electric Point

Surfactants and Stabilization

Measurement

References

Further reading

Category