Particle Size Analysis by Sieving Method

Particle Size Analysis by Sieving Method

• Sieving is a simple, inexpensive, rapid, and reproducible method for particle size analysis.
• Sieves are composed of screens and frames. Sieve size is measured in mesh (openings per linear inch) or micrometers.
• To analyze, a set of sieves (at least 5) and a collector are required.
• Particles are placed on the top sieve of a stack.
• The stack is then shaken.
• The weight of the material resting on each sieve is measured.
• This data is used to calculate the percentage of particles within specific size ranges.

Factors Influencing Sieving

• Factors influencing the sieving method include:
  • Sample weight
  • Duration and type of shaking/motion
  • Type of motion during sieving (vibratory, side tap, bottom pat, rotary). Vibratory motion is usually the most efficient.
• Standardized motion is crucial for reproducible results.

Introduction to Powder and Particle Size Distribution

• Powder is a heterogeneous mixture of particles with various shapes and sizes.
• Particle size analysis determines the distribution of particle sizes in a powder bed.
• Particle sizes are usually less than 1000 micrometers.
• Particle size analysis is a process of fractionation, determining the percentage and mean particle size for each fraction.

Importance of Particle Size Analysis

• Particle size analysis is vital for analyzing and understanding material behavior.
• Particle size distribution influences:
  • Processability
  • Disintegration time
  • Dissolution rates
  • Bioavailability
  • Stability of manufactured products.

Particle Size Analysis Techniques

• Several methods can be used to analyze particle size including:
  • Sieving
  • Image analysis
  • Coulter counter method
  • Sedimentation method
  • Laser diffraction method
• The choice of method depends on the material and required information.

Representative Samples in Particle size Analysis:

• A representative sample is needed for accurate analysis.
• The sample should accurately reflect the entire bulk powder.
• The sample selected must be truly representative of the whole material being studied.

Graphical Representation of Data

• The results of particle size analysis can be presented graphically:
  • Distribution curves
  • Histograms
• Graphical representations allow easier visualization of particle size distribution.
• The percentage of oversize (particles larger than specified range) and undersize (smaller than specified range), mean particle size, and distribution curves are determined and shown graphically.