Titrations Very Slow and Complicated – Therefore Avoided 2 Methods to Measure - Zeta Potential (ZP) Immobilized Particles at a Plane Teflon® - Surface

Presented by

Dr. Daniel Hagmeyer • Produktmanager Kolloidanalytik • Promovierter Chemiker Das DUO Stabino® / NANO-flex® Inhalt

• Theoretischer Hintergrund zur Partikelladung

• Anwendungsbeispiele

• Was Kunden sagen

• Fragen und Antworten

What are Colloids? clear • Macromolecules in solution – < 1nm – 10 nm

1 nm • Particles dispersed in liquids – < 1 nm – 10 µm

• > 20 nm  turbid turbid > 20 nm 100 nm Colloids How do colloids behave?

• General tendency to agglomerate – dipole - dipole interaction (Van der Waals) – Adhesions forces

• Stability is guaranteed by having a repulsive surface

Stabilization of nanoparticles

. (A) electrostatic stabilization  we can measure . (B) steric stabilization . (C) electrosteric stabilization  we can measure

Any charged surface of an object – macromolecule, particle, wall – has the potential to attract or repulse other charges

Charges, colloid interfaces interact with ALL ions from the surrounding liquid + + ++ + + + + + • Charges stabilize + + + + + ++ + + + + + + + + + • Charges interact with ions + + + + ++ + + + + from the liquid environment + + + ++ • A change in chemical 1 nm + + + + + + + + + + + environment can cause + + + + + + + + + + + + + + + + + + + + + + + + + + + + stability to be better or worse. + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + 100 nm Interaction partners in liquids ❶ Smallest ions (pH & salt) H+, OH- , Na+, Cl-, Ca2+ …

❷ Poly – electrolytes (PE) = charged macromolecules, 100 to 1000 times bigger + NH3 ❸ Particles ALL – that is the difficulty!!!

- ❹ Big surfaces COH (glass with negative ions) Repulsion / Attraction

• Ionic charges on every surface have the POTENTIAL to repulse or attract charges • Depending on the polarity of the interaction partner, there is repulsion or attraction

Required for stability How strong is …?

• Repulsion or attraction depends on the amount of charges per surface area

DLVO-theory

Energy = repulsion energy E R potential

total energy Et attraction energie

EA How to measure the strength of repulsion or attraction?

1. The magnitude of Zeta potential 2. The consumption of calibrated polyelectrolytes for the Total Charge determination

In general, the higher Zeta potential and the consumption of polyelectrolytes  the better is the stability Particle Interface Potential / zeta potential Closer look

Mobile counter ions

Shear plane Creating zeta potential - Closer look

Mobile counter ions

Moving force: Electric field (common) Fluid stream

Shear plane = location of the zeta potential Measurement methods for Zeta Potential

• Electrophoretic mobility – Particles in an electric field µe = vE-1 – zeta potential (ZP, z) calculated ZP ~ µe • streaming zeta potential (SZP) – Liquid moves, particles immobilized (more details later)

• colloid vibration current (cvi) – Movement of the liquid with ultra sound

Difficulties reported • ZP Measurements not repeatable  chemical environment changes • Problems with bubbles • Problems with the optical properties of the sample • Problems with dilution • Titrations very slow and complicated – therefore avoided 2 methods to measure - Zeta Potential (ZP) Immobilized particles at a plane Teflon® - surface

„plane“ surface E  v

Fluid stream  electric field  Streaming zeta potential Electrophoresis zeta (SZP) potential Control the environmental influence by Mix & measure pH-, salt- or Changing the environment of the Polyelectrolyte solutions particles by defined addition of

- SP = k · ZP ZP ~ (measured potential) SP / ZP SP = streaming potential K = system constant + Immobilized ZP = zeta potential particles Why titrations? Many external parameters influence the ZP/stability measured Titration (pH) potential IEP & point of zero charge

pH, additives (polyelectrolytes), Coagulation salt Agglomeration Aggregation Coalescence Role of the Polyelectrolytes (PE) • PE solutions can be manufactured in accurately known charge concentrations – 1N solution carrying 1 mol/L of elementary charges = 9760 C (Coulomb)

• It will coat the surface of particles and change the „zeta“ potential  method to measure the surface charge

PE Titrations are only possible with streaming potential method Calibration of the potential with suspensions and polyelectrolytes

• Zeta Potential (ZP) with a standard suspension of known Zeta potential • Streaming potential (SP) with a standard polyelectrolyte solution of known streaming potential

During a measurement, ZP / SP are displayed simultaneously Multi-parameter titrations  SOPs . Titrations . pH  Isoelectric Point Measurements  Stable pH Areas . Poly Electrolyte (PE)  Coatings with polyelectrolytes  Stability measurements of dispersions  Ionic activity / Charge density RESULT in general: Predicting the status of . Salt colloidal systems  Conductivity (IEP, stable zones, stability) . Size Stabino set-up If the application requires … back titration  Application (pH): 3D Plot of Al2O3 (W630) Application (pH): Titration of Lysozyme polyelectrolyte titration (PE)

Results: Ionic activity charge density [Cg-1] Coating efficiency Application (PE): oil in water emulsion Additive for construction industry 10

0 0 0,5 1 1,5 2 2,5 -10 old

-20 fresh -30

-40

-50

zeta potential / mV / potential zeta -60

-70

-80

-90 volume / mL Predicting stability of filtered beers (PE):

Following the artificial aging method with Stabino

TITZE, J., ILBERG, V., JACOB, F., PARLAR, H., 2008: Einsatzmöglichkeiten der Ladungsttrationsmethode zur Beurteilung der chemisch-physikalischen Bierstabilität, Teil 2. Brauwelt 148, Nr. 23, S. 624-527. Application: Salt titration of Al2O3 with KCl In-situ Size measurement 180° heterodyne back scattering (DLS)

Homodyne Heterodyne Detector Laser

Scattered & reflected light Laser in & reflected laser Scattered light from particles K: colloid D: detector O: imaging optics R: partial reflecting surface

Size & concentration 0.01 – 40 vol% dip-in size measurement – critical coagulation point Application: three modal latex beads mixture Dia / nm Vol % Dia /nm Vol % measured measured theoretical theoretical 83.9 11.7 % 95.6 33.74 % 711 76.8 % 746 63.22 % 3790 11.5 % 4760 3.04 %

711 nm

83.9 nm 3790 nm Application: high resolution and differentiation

200 nm

100 nm Conclusions . Zeta potential and streaming potential in one measurement . Size range for charge: 0.3 nm to 300 µm . Speed: Fast formulation tool . Wide concentration range 0.01 to 40 vol.% . Potential at conductivities  300 mS cm-1 . 3D Particle Charge Mapping . Charge density . NANO-flex® in-situ size (0.3 nm – 6.5 µm)

Customer Feedback… • “The best software we ever have experienced.” • “Easy to learn, easy to use, easy to clean.” • “Precise and Reliable”

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für Ihre Aufmerksamkeit Das DUO Stabino® / NANO-flex®