COLLOID ZETA POTENTIAL Kausar Ahmad httpstaffiiumedumyakausar akausariiumedumy Physical Pharmacy 2 1 CONTENTS Physical Pharmacy 2 2 ELECTROKINETIC PHENOMENA Physical Pharmacy 2 3 ELECTRICAL POTENTIALS ID: 772996
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COLLOID:ZETA POTENTIAL Kausar Ahmadhttp://staff.iium.edu.my/akausarakausar@iium.edu.my Physical Pharmacy 2 1
CONTENTSPhysical Pharmacy 2 2
ELECTROKINETIC PHENOMENA Physical Pharmacy 23
ELECTRICAL POTENTIALSPhysical Pharmacy 2 4
ZETA POTENTIALPhysical Pharmacy 2 5 The shear plane separates the thin layer of liquid bound to the particle surface (elastic behavior) from the rest of the continuous phase ( normal viscous behavior)
DETERMINATION OF ZETA POTENTIALMeasure electrophoretic mobility the electrophoretic mobility is the ratio of the velocity of particles to the field strength = v/E v - Particle velocityE - strength of electrical field Physical Pharmacy 2 6
TRADITIONAL MEASUREMENT OF ELECTROPHORETIC MOBILITY Physical Pharmacy 27
CALCULATION OF ZETA POTENTIALSMOLUCHOWSKI EQUATION From Marian Smoluchowski: m=ez /h m electrophoretic mobility, e electric permittivity of the liquid, is the viscosity applicable for thin double layer when the zeta potential is not too high large colloidal particles and high ionic strengths Physical Pharmacy 2 8
CALCULATION OF ZETA POTENTIAL HUCKEL EQUATION IF size of particle is small compared to EDL (or thick EDL)Use Huckel equation: m=ez /1.5h Physical Pharmacy 2 9 Thickness of EDL, 1/ κ
LASER DOPPLER VELOCIMETRYPhysical Pharmacy 2 10 Using Fourier Transform, the correlator produces a frequency spectrum from which the mobility distribution and hence zeta potential are calculated. Young’s interference fringes formed at stationary level
FLUCTUATION IN INTENSITY OF SCATTERED LIGHTPhysical Pharmacy 2 11 From: http ://www.silver-colloids.com/Tutorials/Intro/pcs23.html
ADVANTAGES OF LASER TECHNIQUEPhysical Pharmacy 2 12
EXAMPLES OF APPLICATION Physical Pharmacy 213
ISOELECTRIC POINT (IEP) Physical Pharmacy 214 If pH<4 or pH>8 there is sufficient charge to confer stability If 4<pH<8 dispersion may be unstable. Most unstable at around pH 6 (IEP) From: http://www.silver-colloids.com/Tutorials/Intro/pcs18.html
ZETA POTENTIAL OF CHLORAMPHENICOL AND GLASS PARTICLES IN BENZETHONIUM (+) CHLORIDE SOLUTION (ADSORBING CATION) Physical Pharmacy 215 Charge reversal concentration From: Florence & Attwood
REFERENCES RJ Hunter, Zeta Potential in Colloid Science, Academic Press (1988)RJ Hunter, Foundations of Colloid Science Volume 2, Clarendon Press Oxford (1989)ID Morrison & S Ross, Colloidal Dispersions, Wiley- Interscience, New York (2002) http://zeta-potential.sourceforge.net/ http://www.silver-colloids.com/Tutorials/Intro/pcs1.html http://www.luminet.net/~wenonah/riddick/chap22.htm Physical Pharmacy 2 16