Particle Size Analysis of Nanoparticles: Methods and Accuracy Compared

Image Credit: www.cordouan-tech.com

Nanoparticles are integral to cutting-edge applications in pharmaceuticals, materials science, cosmetics, and chemical manufacturing. Their size and size distribution influence product performance, stability, and functionality.

Measuring nanoparticle size accurately is essential but choosing the right technique depends on the particle type, concentration, and application requirements. In this article, we compare common nanoparticle size analysis methods, their advantages and limitations, and how modern Dynamic Light Scattering (DLS) analyzers from Cordouan Technologies deliver reliable results.

Why Accurate Nanoparticle Size Measurement Matters

Particle size impacts:

• Drug delivery efficiency in pharmaceuticals and biopharma
• Optical properties in coatings and electronics
• Stability in emulsions and colloids
• Process control in nanomaterial manufacturing

Accurate size analysis ensures consistency, optimizes product performance, and meets regulatory requirements.

Common Methods for Nanoparticle Size Analysis

1. Dynamic Light Scattering (DLS)

How it works: DLS measures the Brownian motion of nanoparticles suspended in liquid by analyzing fluctuations in scattered light intensity. Using the Stokes-Einstein equation, this motion is converted into hydrodynamic diameter and size distribution information in seconds.

Measurement Range: Typically 0.3 nm to 10 μm (instrument-dependent)

Advantages:

• Non-destructive
• Rapid measurements
• High sensitivity for nanoscale particles
• Minimal sample preparation

Limitations:

• Best suited for spherical particles
• Limited ability to resolve multimodal size distributions without advanced analysis
• Requires stable suspensions

Accuracy:
Modern DLS systems, such as Cordouan Technologies’ Amerigo and Vasco Kin, deliver sub‑nanometer resolution and reliable repeatability, with error margins as low as ±1–2%.

Best For: Routine quality control, stability studies, formulation development, and process monitoring where speed and reproducibility are essential.

2. Nanoparticle Tracking Analysis (NTA)

How it works:
NTA visualizes and tracks individual particles using laser illumination and video microscopy. Software algorithms track particle movement frame-by-frame to calculate size based on Brownian motion, providing both size distribution and particle concentration.

Measurement Range: Typically 10 nm to 1000 nm

Advantages:

• Resolves multimodal size distributions
• Provides particle concentration data
• Works well for polydisperse samples

Limitations:

• Slower analysis compared to DLS
• Requires significant sample preparation
• Less suited for very small particles (<10 nm)

Accuracy:
NTA accuracy depends on sample clarity and preparation, with typical error ranges of ±5–10%.

Best For: Research applications requiring particle concentration, aggregation studies, and samples with mixed populations.

3. Electron Microscopy (TEM/SEM)

How it works: Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM) offer direct imaging of nanoparticles at high resolution by using electron beams to visualize particle morphology.

Resolution: Down to sub-nanometer and atomic scale

Advantages:

• Provides detailed particle morphology
• High resolution down to atomic scale

Limitations:

• Labor-intensive and time-consuming
• Requires sample preparation that can alter particles
• Not suitable for routine size distribution analysis

Accuracy:
Highly accurate for imaging, but statistical size analysis requires large datasets and extensive preparation.

Best For: Research and development, morphology studies, quality verification, and when visual confirmation of particle shape is required.

4. Atomic Force Microscopy (AFM)

How it works:
AFM scans a particle surface with a fine cantilever probe to map three-dimensional topology and measure size at the nanometer scale.

Resolution: Sub-nanometer vertical, 1-5 nm lateral

Advantages:

• High-resolution surface analysis
• Useful for shape and morphology studies

Limitations:

• Slow and labor-intensive
• Small sample area analyzed
• Requires flat surfaces

Accuracy:
AFM provides nanometer-scale accuracy, but results can vary with sample preparation.

Comparing Accuracy of Nanoparticle Size Analysis Methods

When to Use Multiple Methods

For comprehensive particle characterization, combining methods often provides the most complete picture:

• DLS + TEM/SEM: DLS for fast size distribution, TEM/SEM to verify morphology and confirm DLS results
• DLS + NTA: Compare hydrodynamic size (DLS) with direct particle tracking (NTA) for validation
• DLS + Zeta Potential: Understand both size and surface charge for stability predictions

Dynamic Light Scattering Remains the Most Practical Choice

For many applications, Dynamic Light Scattering (DLS) strikes the best balance of speed, accuracy, and ease of use. Its ability to provide real-time size distribution without extensive preparation makes it ideal for research and process monitoring.

Cordouan Technologies’ DLS analyzers bring industry-leading accuracy to nanoparticle measurement:

• Amerigo — an all-in-one instrument for size, zeta potential, and molecular weight.
• Vasco Kin — enables in situ real-time particle size analysis for dynamic processes.
• Vasco — high-resolution DLS for opaque or concentrated samples.

Bringing Precision Particle Size Analysis to Your Lab

At Barnett Technical Services, we are proud to be an authorized distributor of Cordouan Technologies. We support researchers and process engineers in selecting, installing, and optimizing nanoparticle characterization systems to meet their exact needs.

Ensure your nanoparticle measurements are accurate and reliable – every time.
Contact Barnett Technical Services to learn more or schedule a demonstration.

FAQ

Which method is most accurate for nanoparticle size analysis?

Accuracy depends on your application. For individual particle precision, TEM offers ±0.5-2 nm accuracy. For statistical size distribution of particle populations, DLS provides ±1-2% accuracy with superior speed and reproducibility. DLS is most accurate for spherical particles in suspension, while TEM is best for morphology verification.

What is Dynamic Light Scattering (DLS) used for?

DLS is used to measure the hydrodynamic size and size distribution of nanoparticles, colloids, proteins, and polymers suspended in liquids. Common applications include drug formulation development, quality control, stability studies, protein aggregation monitoring, and process optimization in pharmaceuticals, cosmetics, materials science, and food industries.

Can DLS measure non-spherical particles?

Yes, but DLS reports the hydrodynamic diameter—the diameter of a sphere that diffuses at the same rate as your particle. For highly asymmetric particles (rods, platelets), DLS provides an equivalent spherical size that’s useful for comparative analysis, but complementary techniques like TEM or AFM may be needed for detailed morphology.

What sample volume is required for DLS analysis?

Modern DLS instruments like the Cordouan Amerigo require as little as 50-100 μL for standard measurements, making them ideal for precious samples. Standard cuvettes typically use 1-3 mL for optimal results.

How do I choose between DLS and NTA?

Choose DLS for: fast routine analysis, quality control, monodisperse or simple samples, high repeatability, and when concentration data isn’t critical.

Choose NTA for: research requiring particle concentration, highly polydisperse samples with multiple populations, aggregation studies, and when visual confirmation of particles is valuable.

For most industrial and QC applications, DLS is the preferred choice due to speed, accuracy, and ease of use.

What is the difference between Z-average and number distribution?

• Z-average (intensity-weighted): Most common DLS output, emphasizes larger particles due to their stronger light scattering. Most reproducible and suitable for QC.
• Number distribution: Converts intensity data to show particle count, better represents small particles but more susceptible to noise and artifacts.

For regulatory and quality control purposes, Z-average is typically reported.