1. Comminution Equipment and
Selection Techniques
Lawrence Novotny
Midwest AOAC
June 6, 2018

2. compositional heterogeneity
distributional heterogeneity

3. reduction of particle size by
Comminution
reduction of particle size by
crushing
chopping
grinding
blending
etc.
Why comminute?

4. Relationship of Fundamental Sampling Error (FSE) to Particle Size
FSE2 = CH x (diameter )3
mass
CH = compositional heterogeneity
diameter (cubed) of the largest particle
Comminution controls FSE by reducing particle size.
Comminution can also reduce distributional heterogeneity by reducing the range in particle sizes

5. Relationship of Fundamental Sampling Error (FSE) to Particle Size
GOOD Test Portions recommendation:
Comminute the ENTIRE lab sample before doing any selection of subsamples or test portions

6. Considerations for Choosing Comminution Equipment
Test Material Properties
semisolid or solids
liquids or slurries
material hardness of solids
flowability of the material:
fat or oil content
moisture content
sugar content
Cooling, freezing or use of dry ice aids in comminution

7. Considerations for Choosing Comminution Equipment
Particle Size
initial particle size
desired final particle size
desired range of particle sizes
Can do a coarse grind (6 mm) followed by a fine grind (0.75 mm)

8. Considerations for Choosing Comminution Equipment
Capacity
initial mass of samples
use a flow thru device to handle large mass
number of samples

10. avoid loss of any material fines, dust (leaky gaskets) volatiles
Considerations for Choosing Comminution Equipment
Control MRE – mass recovery error
avoid loss of any material
fines, dust (leaky gaskets)
volatiles
stickiness
avoid absorption of analyte

11. all parts that come in contact with sample should be inert
Considerations for Choosing Comminution Equipment
Control CIE contamination introduction error
all parts that come in contact with sample should be inert
hardness of test material vs hardness of grinding surface

12. control of heat generation control of moisture change
Considerations for Choosing Comminution Equipment
Control AIE analyte integrity error
control of heat generation
control of moisture change
avoid chemical reactions
maintain sterility
flow thru device reduces heat
use of dry ice

13. versatile in handling a wide range of materials safety features
Considerations for Choosing Comminution Equipment
Design Considerations
can be easily cleaned
simple to operate
reliable
versatile in handling a wide range of materials
safety features

14. 2 major physical forces of comminution action
Crushing
applies pressure against material to break it into smaller fragments
Cutting
uses knives, blades, or rotors to slice material into small pieces

15. Crushing Equipment Jaw crushers Disc mills (burr mills)
Impact mills (hammer mill)
Ball mills
Planetary mills
Vibrating cup mills or ring & puck mills
Cryogenic mills
Mortar grinders/mortar mills
Cross-beater mills
Tissue grinders
Paddle/peristaltic/bag blenders

16. Disc Mill

17. Ball Mill

18. Cryogenic Mill

19. Cryogenic Mill
Advantages
handle wide variety of materials from high fat to bone
produce a very fine particle size
Disadvantage
limited sample volume

20. final particle size & uniformity is operator dependent
Mortar & Pestle
final particle size & uniformity is operator dependent

21. Hand Tools
mainly used to break up material to make it easier to feed into comminution equipment

22. Cutting Equipment Cutting/shearing mills Choppers Blenders Hand tools
Rotating & stationary blades
Rotating blades & screen/grinding ring
Flow-thru attachments available
Choppers
Knife choppers
Bowl choppers
Blenders
Stationary
Immersion
Hand tools

23. Cutting Mill

24. Centrifugal or Rotor Mill

25. Cyclone Mill

26. Knife Chopper

27. Knife Chopper

28. Bowl Chopper

29. Bowl Chopper

30. Stationary Blender

31. Immersion Blender