Particle Size Analysis

Fig. 2 - Size distributions for a mixture of 5 and 50 nm particles present in equal numbers.

Particle size significantly affects material properties such as chemical reactivity, bioavailability, dissolution and crystallization rates, stability in suspension, texture of the material, flow ability and handling, packing density and porosity, to name a few. Knowledge of particle size leads to better understanding of products and processes and helps to optimize efficiency of process to reduce costs.

Malvern instruments are currently available at MCL (see Fig.1)

  • Zetasizer Nano ZS
  • Mastersizer 3000
  • Morphologi G3SE

All these instruments have the ability to measure and report particle size distribution of a sample. In addition to particle size, Morphologi, a static microscope-based automated imaging system, provides information on particle shape as well.
Particle size distribution can be represented in different ways with respect to the weighting of individual particles. The weighting mechanism will depend upon the measuring principle/technique being used. The most commonly used are number-weighted, volume-weighted and intensity weighted distributions (See Fig. 2).

The summary of instrument characteristics is presented in the following table:

Instrument

Zetasizer Nano ZS

Mastersizer 3000

Morphologi G3 SE

Technique

Dynamic light scattering

Laser diffraction

Automated imaging

Size distribution by

Intensity

Volume

Number

Size range (diameter)

0.3 nm – 10 μm

10 nm – 3500 μm

0.5 μm – 1000 μm

Type of measurement

  • Bulk technique
  • Weighted towards larger particles
  • Rapid & reproducible
  • Bulk technique
  • Weighted towards larger particles
  • Rapid & reproducible
  • Size & shape of individual particles
  • All particles evenly weighted
  • High resolution & detailed, statistically representative

Specifications

  • Light source: He-Ne 633nm laser
  • Temperature controlled range: 0°C - 90°C +/-0.1
  • 12mm OD square polystyrene cuvette for aqueous solvents and glass cuvette for non-aqueous solvents
  • Blue (LED, 470nm) and Red (He-Ne laser, 632.8nm)
  • Detectors range: 0.015 - 144 degrees
  • Sample dispersion accessories: Hydro MV (~120 mL wet cell), Hydro LV (~600 mL wet cell, AeroS (dry dispersion)
  • Digital camera with sub 3 µm pixel
  • Multiple optical objectives: 2.5x, 5x, 10x, 20x, 50x
  • Dry or wet dispersion accessories: integrated dry powder sample dispersion unit (SDU); 4-slide plate; glass wet cell; 25 mm filter plate

Sample requirements

  • Well dispersed suspension
  • Min sample volume: 12 µL (1 ml for standard sample holders)
  • Sample concentrations from 0.1ppm to 40%w/v, sample dependent
  • Suspension or dry powder
  • Min sample volume depends on material type, suspension concentration and size range
  • Up to 100 mg of powder for dry dispersion; few mg for wet dispersion (sample dependent)
  • Dry powder or well dispersed suspension
  • Dry sample volume from 1 to 20 mm3 for most samples
  • Sample mass up to few mg

Application/Materials

Proteins, biological cells, polymers, micelles, vesicles, carbohydrates, nanoparticles, and gels

Ceramics, metals, biomaterials, soils and sediments, carbon materials, food products

Metal and mineral powders, coal, sand, plant material

Validation of laser diffraction results

 

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Fig. 3 - Data obtained by the Morphologi automated imaging system.