Particle size analysis

Question 1

Describe optical/light microscopy for particle size analysis

Answer 1

Only technique in which particles are observed
Normally cheap and with rapid methods of preparation
Quality of microscope important
- calibration
Sample
- representiveness of the sample must be assured

Question 2

What are the problems with light microscopy for particle size analysis?

Answer 2

Operator variability
Validation

Question 3

What is the electrical sensing zone?

Answer 3

Measurement of change in electrical resistance across a glass aperture orifice when the sample particles (suspended in an electrically conducting media) are drawn through the orifice
- resistance change proportional to size of particle

Question 4

How is light scattering carried out?

Answer 4

Sample preparation
- suspended in liquid or air (powders)
Need a media in which the particle is insoluble
- may need dispersing agent
Problems with sedimentation rate
- stirring

Question 5

How does Photon Correlation Spectroscopy (PCS) work?

Answer 5

Small particles
- rapid and weak scatter at wide angles
Large particles
- slow and strong scatter