Presentation is loading. Please wait.

Presentation is loading. Please wait.

WALLIS - Zeta Potential Analyzer

Similar presentations


Presentation on theme: "WALLIS - Zeta Potential Analyzer"— Presentation transcript:

1 WALLIS - Zeta Potential Analyzer
Laser Doppler Electrophoresis (LDE) principle for Zeta potential measurements 2014/04/10

2 Why measuring Zeta potential?
Colloidal solution stability ? Charged particles repel each other Stable systems Flocculations Uncharged particles are free to collide and aggregate Coagulation Sedimentation Electrostatic or charge stabilization : This effect uses more natural interactions between particles through the distribution of charged species (ions) in the solution.

3 Zeta Potential: a phenomenological approach
stable Positive Zeta + 30 mV unstable 0 mV IEP : IsoElectric Point - 30 mV stable Negative Zeta pH If surface has - charge, then Cations are attracted to the NP surface Anions attracted to Cations, builds electric double layer Slipping/shear plane: distance from particle surface where ions move with particle Zeta Potential = potential (mV) at slipping plane

4 Zeta Potential determination
z: Zeta Potential (mV) µe: electrophoretic mobility e: medium permittivity h: medium viscosity a: particle radius k: invert of double layer thickness -1 : Debye length f (k.a) : Henry’s function z = µe f (k.a) h e Calculated Measured Zeta is dependent of the k.a factor value k is dependent of the solvent General cases 1 ≤ f (k.a) ≤ 1.5 99% cases !!!

5 Electrophoresis & Electrophoretic mobility
µe: electrophoresis mobility E: electric field V : voltage applied q : electric charge Fe : electric force Ff : friction force V Applying an Electric field: the particles move with its surrounding layers. Particle velocity directly related to its electrophoretic mobility and E

6 Laser Doppler Electrophoresis (LDE)
Heterodyne optical Interferometer : retrieving doppler low frequency Splitter d = 17° Laser flaser + fdoppler flaser + fmod Photon Counting Module Combiner fdoppler fmod Attenuator Optical Path Modulation fmod Spectrum from FFT fmod ± fD µe = fD llaser E sin d µe: electrophoretic mobility (µmcm/Vs) E : applied electric field fD : Doppler frequency

7 Wallis Measurement Sequence
Heterodyning Signal Measured Computed Double Layer model FFT Zeta Potential z Electrophoretic Mobility µe Doppler shift Huckel ? Smoluchowski ? fD By LDE (Laser Doppler Electrophoresis) f(k.a) Henry function

8 What defines the measurement resolution?
Detected signal fmod Sampling Freq ≥ 2 x fmod (Shannon criteria) Nber of sampling points limited by : buffer size, acquisition duration, calculation time

9 WALLIS : High-Resolution Zeta Potential Analysis
Purely designed and optimized for Charge/zeta potential measurement Complementary tool to VASCO for colloid characterization High resolution analysis down to 0.5 mV

10 Why WALLIS has higher resolution than others?
Correlator (2 in 1 concept Zeta+DLS other supplier) High-speed digital acquisition: Wallis 256 to channels Fmod=256Hz 8192 sampling points Fmod=8 kHz G2(t) Intensité t t FFT Resolution 3-5 mV Resolution < 0.5 mV

11 Sample cell configuration : the dip cell approach
Electro-osmosis effect Capillary 3 mm Vitreous Carbon Electrodes Connector Laser beam Hellma Cell Quartz, Glass or polystyrene polished No electro-osmosis Field proven concept Custom made electrodes Dip cell 10 x 10 mm (WALLIS) No need to focus at any ”stationary plane”

12 Benefits of WALLIS sample cell configuration
Easy to handle Easy filling, no risk of bubbles ! (vs capillary cell/viscosity) Stand alone electrode holder-> easy to replace Vitreous carbon electrodes: extreme chemical resistance (No oxidation); low electrical resistance Easy cleaning of electrodes (rinsing and ultra sound bath tub)->No cross contamination Reusable quartz cell-> no consumable Easy to clean Excellent optical quality Compatible with organic solvent Compatible with standard cell (10x10 mm2) … sample volume ≈750µL

13 ZetaQ software :the brain of WALLIS
Unique and proprietary software User friendly and intuitive GUI SOP and programmable experiments (Time, T°, pH) Experiment storage in data base Many other advanced functionalities

14 Performances example #1
Résolution < 0,5 mV !!! Résolution : 3.7 mV !!! with correlator (other suppliers) with fast acquisition (WALLIS)

15 Performances example #2
IEP characterization of an industrial surfactant WALLIS High resolution allows precise measurement of IEP even with sharp Zeta transition !

16 Further reading! [1] Hunter R, Zeta potential in colloidal science; Academic press, New York, 1981 [2] Reliang Xu; Particle Characterization: light scattering methods; Kluwer Academic Publishers [3] ISO13099B1,Colloidal systems—Methods for zeta potential determination Part 1:Electroacoustic and electrokinetic phenomena [4] V. DELGADO et al.; measurement and interpretation of electrokinetic phenomena; IUPAC Technical Report , Pure Appl. Chem., Vol. 77, No. 10, pp. 1753–1805, 2005

17 Thank you of your attention!
Lab support: Dr. Benoit MAXIT Mail: CORDOUAN TECHNOLOGIES Cité de la photonique 11, Avenue Canteranne 33600 Pessac FRANCE Customer support: Eng. Boris PEDRONO Mail: CORDOUAN TECHNOLOGIES Cité de la photonique 11, Avenue Canteranne 33600 Pessac FRANCE Follow Cordouan Technologies on Twitter!


Download ppt "WALLIS - Zeta Potential Analyzer"

Similar presentations


Ads by Google