Particle Size Analysis Key Terms: Get Mastery In 9 mimutes with 21+FAQs

Particle size analysis is a set of laboratory techniques to determine the size range and average size of particles in a sample, such as a powder or liquid. Common methods include sieving, sedimentation, laser diffraction, and microscopy.

1. What is Particle Analysis?

Particle size analysis is the process of determining the size and distribution of particles within a sample, such as a powder, suspension, or emulsion, by measuring the dimensions of individual particles to evaluate their characteristics and behaviour. This analysis plays a vital role in fields such as pharmaceuticals, materials science, and environmental monitoring, where particle size has a direct influence on product performance and process efficiency. Common techniques used include sieving, laser diffraction, and dynamic image analysis.

Key Aspects of Particle Analysis:

1. Particle Size:
   The measurement of the dimensions of individual particles is often expressed as an equivalent spherical diameter (since most particles are irregularly shaped).
2. Particle Size Distribution (PSD):
   The range and proportion of different particle sizes within a sample, typically presented as a percentage finer (passing) versus particle size.
3. Particle Shape and Morphology:
   Describes the form, roundness, or aspect ratio of particles, which affects flowability, packing, and surface area.
4. Particle Count and Concentration:
   The total number of particles present in a given mass, volume, or area.
5. Other Properties (Optional):
   • Surface area
   • Porosity
   • Density
   • Agglomeration behavior

Purpose and Applications of Particle Analysis:

Particle analysis is used in a wide range of industries and scientific fields because particle characteristics strongly influence product performance and process efficiency.

Common Applications:

Why Particle Analysis is Important:

• Determines process efficiency (grinding, filtration, sedimentation).
• Controls product quality and uniformity.
• Ensures compliance with standards (ASTM, ISO, USP).
• Helps in research and material development.
• Impacts the mechanical, chemical, and optical properties of materials.

Common Methods Used for Particle Analysis:

1. Sieve Analysis – mechanical separation for coarse particles (>75 µm).
2. Laser Diffraction – optical scattering for fine particles (0.1–3000 µm).
3. Dynamic Light Scattering (DLS) – for nanoparticles (1 nm–1 µm).
4. Microscopy (Optical or Electron) – direct visualisation and size measurement.
5. Sedimentation Techniques – based on particle settling rate.
6. Coulter Counter (Electrical Sensing Zone) – counts and sizes particles suspended in a conductive fluid.

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2. What is the Basic Principle of Particle Size Analysis?

Principle:

The basic principle of particle size analysis is to determine the size or size distribution of particles by measuring how they interact with physical forces or fields such as light, gravity, or electrical signals.
Different analytical techniques apply different physical principles to obtain size-related data.

Common Underlying Principles Used in Particle Size Analysis:

1. Mechanical Sieving (Separation by Size)

• Principle:
  Particles are separated based on their ability to pass through a series of sieves with progressively smaller openings.
• Applicable Range:
  Typically for particles larger than 75 µm.
• Basis:
  Larger particles are retained on coarser sieves, while finer particles pass through.

2. Light Scattering (Laser Diffraction or Dynamic Light Scattering)

• Principle:
  When a laser beam passes through a dispersed particle sample, the light is scattered at different angles depending on particle size.
  • Large particles scatter light at small angles.
  • Small particles scatter light at large angles.
• Analysis:
  The scattering pattern is mathematically analysed (using Mie or Fraunhofer theory) to determine the size distribution.
• Applicable Range:
  From nanometers to millimetres (depending on the instrument).

3. Sedimentation (Gravitational or Centrifugal)

• Principle:
  Particles suspended in a fluid settle at rates dependent on their size, shape, and density (according to Stokes’ Law).
• Measurement:
  The sedimentation rate or time required to reach a certain depth helps calculate the equivalent particle diameter.

4. Electrical Sensing Zone (Coulter Principle)

• Principle:
  Particles suspended in an electrolyte pass through a small orifice with an electrical current. Each particle displaces its own volume of conducting fluid, momentarily changing the resistance.
  • The magnitude of the resistance change is proportional to the particle’s volume (hence, its size).

5. Microscopy and Image Analysis

• Principle:
  Direct visual observation and measurement of individual particles using an optical or electron microscope.
  Image analysis software can automatically calculate diameter, area, perimeter, and shape parameters.

General Concept Behind All Particle Size Analysis Techniques:

No matter the method used, all particle size analyses share a common goal:

To measure a particle’s characteristic dimension by relating a measurable physical response (light scattering, mass, resistance, or sedimentation rate) to an equivalent particle diameter.

Factors Affecting the Measurement:

1. Particle Shape and Agglomeration
2. Sample Dispersion and Preparation
3. Measurement Medium (air, water, solvent)
4. Instrument Calibration
5. Refractive Index (for optical methods)

Summary:

3. What are three terms associated with particle size?

Three Terms Associated with Particle Size:

1. Mean Particle Size (Average Size):
   The arithmetic or weighted average diameter of particles in a sample.
2. Particle Size Distribution (PSD):
   Describes how the sizes of particles are distributed within a sample, typically represented as a cumulative percentage versus particle size.
3. Equivalent Diameter:
   Since most particles are not perfect spheres, an equivalent diameter is used — the diameter of a sphere that behaves the same way (e.g., in sedimentation or light scattering).

4. What Are D10, D50, and D90 in Particle Size?

• D10 (Effective Size):
  The particle diameter below which 10% of the sample’s mass (or volume) exists.
  → It represents the finer end of the distribution.
• D50 (Median Particle Size):
  The particle diameter at which 50% of the particles (by volume or mass) are smaller and 50% are larger.
  → Indicates the central tendency of the particle size distribution.
• D90:
  The particle diameter below which 90% of the particles exist.
  → Represents the coarser portion of the sample.

5. How to Calculate D10, D50, D90 in Excel?

1. Prepare data:
   • Column A: Particle Size (µm)
   • Column B: % Passing or % Finer (cumulative)
2. Use Interpolation:
   • Find where the cumulative % passes 10%, 50%, and 90%. Use linear interpolation between the two nearest points.
   Formula:

1. Example (for D50): =D1 + ((50 - P1)/(P2 - P1)) * (D2 - D1)

6. How Can You Measure Particle Size?

The following Common measurement methods are used to Measure Particle Size:

• Sieve Analysis: for coarse particles (>75 µm)
• Laser Diffraction: for fine powders and suspensions
• Dynamic Light Scattering (DLS): for nanoparticles (1 nm–1 µm)
• Sedimentation Method: based on settling velocity in a fluid
• Optical Microscopy: visual measurement using image analysis
• Electron Microscopy (SEM/TEM): for nanoscale imaging

7. Purpose of Particle Size Distribution Test (Fine and Coarse Aggregate)

• To assess the gradation and uniformity of aggregates.
• To ensure aggregates meet specification limits for concrete or asphalt.
• To predict workability, strength, void content, and durability.
• To detect segregation or contamination in materials.

8. What are the different techniques used for Particle Analysis?

Techniques Used for Particle Analysis

1. Sieve Analysis
2. Sedimentation
3. Coulter Counter (Electrical Sensing Zone)
4. Laser Diffraction
5. Dynamic Light Scattering (DLS)
6. Image Analysis (Optical or Electron Microscopy)
7. X-ray or Neutron Scattering

9. What is The Particle Size Distribution and Its Representation?

The Particle Size Distribution and Its Representation

The Particle Size Distribution (PSD) shows how particle sizes are spread across a sample.
It can be represented as:

• Frequency Distribution: % retained in each size range.
• Cumulative Distribution: % passing (or finer) vs. particle size.
• Graphical Representation: typically plotted on semi-log graph paper.

10. What is the difference between Number and Volume Distributions?

Example: A few large particles can dominate a volume distribution, but not a number distribution.

11. What are the Advantages of Particle Size Analysis?

• Predicts material behaviour (flowability, packing, reactivity)
• Ensures process control and quality assurance
• Helps optimise grinding/milling operations
• Aids in formulation design (pharma, cement, paint, etc.)

12. What are the Limitations of Particle Size Analysis?

• Assumes particles are spherical (not always true)
• May require dilution or dispersion, affecting results
• Different methods can give different averages
• Limited accuracy for broad or multimodal distributions

11. How to Calculate Average Particle Size from Sieve Analysis?

Use the mean particle size method:

12. What Is a Particle Size Analysis Graph?

A graphical representation of particle size data showing either:

• Cumulative % passing vs. particle size, or
• % retained vs. particle size

It helps visualise distribution, uniformity, and gradation.

13. How to Interpret the Particle Size Analysis Graph

• Steep curve: Uniform particle sizes (poorly graded)
• Flat curve: Wide range of sizes (well graded)
• Shifts in curve: Indicate a change in fineness or coarseness
• Inflexion points: Suggest multiple modes (bimodal distribution)

14. How to Generate a Particle Size Distribution Curve

1. Perform sieve or instrument analysis.
2. Compute % retained and cumulative % passing.
3. Plot % passing (Y-axis) vs. particle size (X-axis, log scale).

15. What Information Does a PSD Curve Provide?

• Range of particle sizes
• Uniformity and gradation
• Dominant particle size (median)
• Proportion of fine vs. coarse material
• Comparative data between samples

16. What Common Mistakes Are Made When Generating a Particle Size Distribution Curve?

Common Mistakes When Generating a PSD Curve:

• Not using a logarithmic scale for particle size
• Incorrect cumulative percentage calculation
• Ignoring mass balance errors
• Mislabeling axes or data units
• Failing to account for outliers or agglomeration

17. What are common problems, and what do they mean?

18. What is the Importance of Particle Size Distribution?

• Determines performance in concrete, paints, pharmaceuticals, etc.
• Influences porosity, strength, reactivity, and stability.
• Critical for quality control and specification compliance.

19. What is the best way to measure particle size with a simple optical microscope?

Best Way to Measure Particle Size with a Simple Optical Microscope

• Use a calibrated eyepiece graticule or digital image software.
• Capture images under known magnification.
• Measure several particles and calculate the average diameter.
• Suitable for particles >1 µm in size.

21. What is the simplest method for determining the number of particles in a given volume (mL)?

Simplest Method for Determining the Number of Particles in a Given Volume (mL)

• Direct Microscopic Counting:
  • Use a counting chamber (hemocytometer) or microscope slide grid.
  • Count the number of particles in a known grid volume.
  • Calculate the number per mL using:
  • Particles/mL} = (N x D)/V
    
    Where:
    ( N ) = particles counted,
    ( D ) = dilution factor,
    ( V ) = volume observed.

Expert Tips:
Particle size analysis provides essential data on material characteristics, helping control product quality and process efficiency. Different techniques and representations reveal complementary information about the size, distribution, and behaviour of particles.

Further reading:

• Particle Size Analysis