Zeta potential measurement Introduction Zeta potential is the

Zeta potential measurement

Introduction • Zeta potential is the charge that is located at the slipping point of a particle in a medium. • Zeta potential is used mostly in Colloidal chemistry. • If the magnitude of zeta potential is > 30 m. V then it is in stable suspension • p. H has a major effect on the system • Zeta potential can not be calculated directly. • However using Electro kinetic effects zeta potential can be measured

Zeta Potential system(general) • He/Ne laser, goes to a beam splitter which then sends the beam to a fixed mirror and a modulator. • Then the beams head into the sample with an electrode on both ends. • Then a photomultiplier picks up the signal and sends it to a computer.

Electro Kinetic Effects • Electro kinetic potential is caused by the interfacial double layer within a solution. • The double layer has a stern layer and a diffuse layer. • Using an electric field either electrophoresis or electro osmosis will cause the particles to move

Electrophoresis • Under an applied electric field the movement of charged particles in relation to the liquid its suspended in is measured • The velocity of the movement depends on the strength of the field, dielectric constant, viscocity, and zeta potential • Using Henry’s law zeta potential can be measured

Electrophoresis (Cont. ) • Measurement of electrophoretic movement • Laser Doppler Velocimetry(LDV)

Electro Osmosis • Movement of charged particles relative to a stationary charged surface • Similar to electrophoresis an electric field is applied and the charged particles begin to move. • A reverse flow is used to counter the flow of the liquid system when the field is applied

Electro Osmosis (Cont. ) • One problem is that there is only two places where there is truly the electro osmosis effect • M 3 measurment-Using LDV • Slow Field Reversal (SFR) • Fast Field Reversal (FFR)

Zeta Potential uses • Zeta potential can be used as a means to tell how stable a colloid being analyzed is. • Zeta potential is key to understanding dispersion and aggregation processes in water purification, ceramic slip casting and the formation of inks, paints and cosmetics. • Often the only way to charecterize double layer properties

Benefits • A good way to find the characteristics of the double layer in a colloidal mixture. • This also allows you to see how stable the colloid being analyzed is. Limitations • Zeta Potential can not be directly measured. • When finding the Zeta Potential the size of the double layer must be very thin.

Works Cited • Zeta Potential Overview, Brookhaven Instruments, 1, 2009 • Lyklema, J. Fundamentals of Interface and Colloid Science, vol. 2, page. 3. 208, 1995 • The Zeta Potential, Colloidal Dynamics, 4, 1999 • Zeta Potential Introduction, Nicomp 380 ZLS, 101, 2006 • IUPAC Technical Support. Measurement and Interpretation of Electrokinetic Phenomena, vol. 77, pp. 1753 -1805. 2005 • Zeta Potential theory, pp. 16. 1 -16. 12. 2005 • http: //www. silver-colloids. com/Tutorials/Intro/pcs 1. html