What Is Zeta Potential?
The electric double layer consists of two main parts: the Stern layer and the diffuse layer. The Stern layer is a tightly bound layer of counter-ions, while the diffuse layer is a more mobile cloud of weakly bound ions. The slipping plane lies between these layers, typically just into the diffuse layer. It reflects where ions outside that plane move freely with the liquid, while those inside remain bound to the solid surface. The zeta potential reflects the net surface charge under flow or motion of the liquid medium.
Since the zeta potential depends on how surface groups ionize and how counter-ions arrange themselves, it is highly sensitive to pH and ionic strength. It can be a strong indicator of colloidal stability, ion-surface interaction behavior, or the functionality of solid materials. For particles in liquid dispersion, zeta potential can be determined by electrophoretic light scattering, and for macroscopic solids, by streaming potential measurements.
Other details:
- Works with powders, colloids, and solids.
- Measurements are completed in minutes for fast results.
- Reliable zeta potential determination under real-world conditions.
Versatility
Versatility
Ability to measure various types of solid surfaces or colloidal suspensions.
Efficient Measurement
Efficient Measurement
Rapid, straightforward, and non-destructive data collection.
Performance Insights
Performance Insights
Provides valuable information on long-term colloidal stability or coating performance.
Why Use Zeta Potential?
- Important for characterizing a material’s surface and its surface charge under real-world conditions to optimize performance.
- Measures important parameters for determining colloidal stability and aggregation behavior.
- Provides insight into surface functionalization and interaction with dissolved species.
- Can be performed quickly for liquid dispersions or a variety of solid materials, often in a non-destructive manner.
Zeta Potential and Surface Charge
Rapid measurement of the zeta potential and isoelectric point for a wide variety of solid materials and colloids.
Particle Size and Dispersion
Parallel dynamic light scattering for colloidal particle size analysis.
Automation and Compatibility
Automated pH titration and wide electrolyte compatibility.
Covalent’s Capabilities Offer Zeta Potential Determination for Colloids and Solid Surfaces
Working Principle
For liquid, colloidal dispersions, Electrophoretic light scattering (ELS) is used to measure the zeta potential of the particles. An electric field is applied, and the particle movement in response to this applied field is analyzed as particles will move at speeds proportional to their surface charge which causes a measurable doppler shift in the incident laser light. This electrophoretic mobility is used in the Henry equation with additional known parameters of the sample to calculate the zeta potential.
For macroscopic solid surfaces, the streaming potential method is used. This involves flowing an electrolyte solution at various pressures over a geometrically defined area of the sample surface. During this flow, ions from the EDL are sheared off, resulting in a buildup of charge downstream which comprises the streaming current. These parameters along with properties of the electrolyte and geometric factors are used in the Helmholtz-Smoluchowski equations to calculate the zeta potential of the solid surface.
Equipment Used for Zeta Potential:
Anton Paar SurPASS 3
For solid, granular, and powder samples:
- Streaming Potential Voltage: ± 2000 mV.
- Streaming Current: ± 2 mA.
- Cell Resistance: 5 Ω to 20 MΩ.
- Conductivity: 0.1 to 2×10^5 mS/m.
- pH Scan Range: 1 to 14.
- Temperature Range: 5 °C to 40 °C.
Anton Paar Litesizer 500
For liquids / colloidal dispersions:
- Zeta Potential Range: ± 1000 mV.
- Particle Size Range: 3.8 nm to 100 μm.
- pH range: 2 to 12.
- Temperature Range: 0 °C to 90 °C.
- Minimum Sample Volume: 50 μL.
- Sensitivity: 0.1 mg/mL.
- Max Concentration: 70 % w/v (sample-dependent).
- Accuracy: +/- 10 %.
- Repeatability: +/- 3 %.
- Maximum Sample Conductivity: 200 mS/cm.
Key Differentiators
Directly measures particle surface charge to predict stability, dispersion behavior, and performance characteristics.
Strengths
- Rapid and straightforward data collection.
- Insights for long-term dispersion.
- Non-destructive.
- High sensitivity.
Limitations
- No capability for layered detection.
- Requires exact dimensions and capillary channel cross-section for solid samples.
- Zeta potential is only present when a material contacts a liquid.
Unsure Whether Zeta Potential Is Right for You?
Find out whether zeta potential analysis is the best choice for your colloidal stability, aggregation, or surface-charge questions, with guidance tailored to your material and medium.
Sample Information
Zeta potential distribution of carbon-black dispersed in toluene (left) and surface zeta potential of SiN wafers after cleaning by hydrofluoric acid, displayed as a function of pH (right).
What we accept:
Various simple geometries of solid samples are compatible. Please contact us to inquire if your sample is measurable. Irregular sample geometries are not well-suited for this measurement. Solid samples need a minimum particle size (powders) of 25 μm. Available sample cells are cylindrical, adjustable-gap, and clamping. Liquid dispersed samples require a volume of 2 mL, a maximum sample concentration of 70 % w/v, and a particle size range of 3.8 nm to 100 μm.
Use Cases
Pharmaceuticals & Medicine
Zeta potential helps characterize colloidal drug formulations and predict particle interactions for stability and efficacy.
Cosmetics & Personal Care
Used to evaluate emulsions, creams, and suspensions to ensure long-term dispersion and product consistency.
Paints and Coatings
Assesses particle interactions and stability in pigments and coatings for uniform application and performance, as well as hydrophobicity and other properties of coated solid surfaces.
Water Treatment
Monitors suspended particles and predicts flocculation or aggregation for optimized treatment processes.
Food & Beverages
Analyzes colloidal suspensions to improve the texture, stability, and shelf life of liquid and semi-solid products.
Advanced Materials
Used to assess the surface functionality, stability, uniformity, and as a proxy to composition for precursor materials in refractory, battery, and semiconductor materials.
Complementary Techniques
- Dynamic Light Scattering (DLS): Measures particle size and distribution by analyzing Brownian motion. ELS evaluates particle kinetics in response to an oscillating electric field. The field induces electrophoretic movement, yielding a slight frequency shift in the scattering laser beam.
- Ellipsometry: Measures changes in the polarization state of light reflected from a sample. Resulting optical models can provide insight into sample composition and a correlation between electrochemical properties found through zeta potential measurement and structural properties.
- Scanning Electron Microscopy (SEM): Provides high-resolution images of sample morphology. It also visually confirms particle aggregation or dispersion, explaining specific zeta values.
- X-ray Photoelectron Microscopy (XPS): Measures elemental composition and surface chemistry of the top ~10 nm of samples. Results from XPS can confirm abnormalities of measured zeta potential values related to surface functionality. XPS can reveal the presence of certain charged functional groups within the surface layers of samples that influence zeta potential analysis values.
Dynamic Light Scattering (DLS)
Quantifies particle size and uniformity in minutes. Explore
Scanning Electron Microscopy (SEM)
Images surface topography and composition with electrons. Explore
X-ray Photoelectron Spectroscopy (XPS)
Measures surface elemental composition and chemical states. Explore
Why Choose Covalent for Your Zeta Potential Needs?
Frequently Asked Questions
Identifying the right test can be complex, but it doesn’t have to be complicated.
Here are some questions we are frequently asked.
How is zeta potential measured?
Zeta potential can be measured in two ways. For particles in liquid dispersions, particle movement in an electric field is tracked using laser Doppler or phase analysis light scattering. For solid surfaces, electrolyte flows over the material, generating charge displacement that is measured using streaming potential or streaming current techniques.
What factors influence zeta potential measurements?
Zeta potential is influenced by factors such as pH, ionic strength, and surface functional groups. Controlling these conditions is essential for accurate measurement.
What is the difference between electrophoretic and streaming potential methods?
Electrophoretic light scattering (ELS) measures the mobility of dispersed particles in a liquid under an electric field. Streaming potential measures the charge generated when a liquid flows across a solid surface, making it ideal for membranes, wafers, fibers, and powders.
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