Tech Team · Kintek Solution

Particle size determination is a critical aspect of material characterization, particularly in industries like pharmaceuticals, construction, and food processing. The four primary methods for determining particle size are sieve analysis, direct image analysis, static light scattering (SLS or laser diffraction), and dynamic light scattering (DLS). Each method has its unique principles, applications, and limitations, making them suitable for different types of materials and particle size ranges. Sieve analysis is the most traditional and widely used method, while the others leverage advanced technologies for more precise measurements.

Key Points Explained:

1. Sieve Analysis

   • Principle: Sieve analysis involves passing a sample through a series of sieves with progressively smaller mesh sizes to separate particles based on their size. The weight of particles retained on each sieve is measured to determine the particle size distribution.
   • Applications: This method is ideal for dry, solid particles and is commonly used in industries like construction (e.g., sand, gravel) and food processing (e.g., flour, grains).
   • Advantages:
     • Simple and cost-effective.
     • No specialized equipment is required beyond sieves and a balance.
     • Suitable for a wide range of particle sizes (125 mm to 20 μm).
   • Limitations:
     • Limited to dry, free-flowing materials.
     • Less accurate for very fine particles or cohesive materials.
     • Time-consuming for large sample volumes.

2. Direct Image Analysis

   • Principle: Direct image analysis uses microscopy or imaging techniques to capture and analyze individual particle images. Static image analysis involves analyzing still images, while dynamic image analysis captures particles in motion.
   • Applications: This method is suitable for particles that can be visualized under a microscope, such as powders, granules, or fibers. It is widely used in pharmaceuticals and materials science.
   • Advantages:
     • Provides detailed information about particle shape and morphology in addition to size.
     • High resolution and accuracy for small particles.
     • Can analyze both dry and wet samples.
   • Limitations:
     • Requires specialized imaging equipment and software.
     • Limited by the resolution of the imaging system.
     • Time-consuming for large sample sizes.

3. Static Light Scattering (SLS) / Laser Diffraction (LD)

   • Principle: Static light scattering measures the angular distribution of light scattered by particles when illuminated by a laser beam. The scattering pattern is analyzed to determine particle size distribution.
   • Applications: This method is widely used for analyzing powders, suspensions, and emulsions in industries like pharmaceuticals, paints, and cosmetics.
   • Advantages:
     • Fast and highly accurate for a wide range of particle sizes (nanometers to millimeters).
     • Suitable for both dry and wet samples.
     • Provides a complete particle size distribution curve.
   • Limitations:
     • Requires expensive equipment and expertise.
     • Assumes spherical particle shapes, which may not be accurate for irregularly shaped particles.
     • Sensitive to sample preparation and dispersion quality.

4. Dynamic Light Scattering (DLS)

   • Principle: Dynamic light scattering measures the fluctuations in the intensity of scattered light caused by the Brownian motion of particles in a suspension. The rate of these fluctuations is used to calculate particle size.
   • Applications: DLS is primarily used for analyzing nanoparticles and colloidal suspensions in fields like biotechnology, nanotechnology, and pharmaceuticals.
   • Advantages:
     • Highly sensitive to small particles (nanometer range).
     • Requires minimal sample preparation.
     • Provides real-time measurements.
   • Limitations:
     • Limited to very small particles (typically < 1 μm).
     • Requires a stable suspension with minimal aggregation.
     • Less accurate for polydisperse samples (samples with a wide range of particle sizes).

Conclusion:

The choice of particle size determination method depends on the material properties, particle size range, and specific application requirements. Sieve analysis is the most traditional and cost-effective method for larger particles, while direct image analysis provides detailed morphological information. Static light scattering is versatile and widely used for a broad range of particle sizes, and dynamic light scattering is ideal for nanoparticles and colloidal systems. Understanding the strengths and limitations of each method ensures accurate and reliable particle size analysis.

Summary Table:

Method	Principle	Applications	Advantages	Limitations
Sieve Analysis	Separates particles by size using sieves and measures weight distribution.	Construction, food processing (e.g., sand, flour).	Simple, cost-effective, wide size range (125 mm to 20 μm).	Limited to dry, free-flowing materials; less accurate for fine particles.
Direct Image Analysis	Uses microscopy to capture and analyze particle images.	Pharmaceuticals, materials science (e.g., powders, fibers).	Detailed shape/morphology info; high resolution for small particles.	Requires specialized equipment; time-consuming for large samples.
Static Light Scattering	Measures light scattering patterns to determine size distribution.	Pharmaceuticals, paints, cosmetics (e.g., powders, emulsions).	Fast, accurate for wide size range (nanometers to millimeters).	Expensive; assumes spherical shapes; sensitive to sample preparation.
Dynamic Light Scattering	Measures light fluctuations from Brownian motion to calculate particle size.	Biotechnology, nanotechnology (e.g., nanoparticles, colloids).	Highly sensitive for small particles; minimal sample prep; real-time results.	Limited to <1 μm particles; requires stable suspensions; less accurate for polydisperse samples.

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