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

compositional heterogeneity distributional heterogeneity

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

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

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

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

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)

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

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

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

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

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

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

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

Disc Mill

Ball Mill

Cryogenic Mill

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

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

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

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

Cutting Mill

Centrifugal or Rotor Mill

Cyclone Mill

Knife Chopper

Knife Chopper

Bowl Chopper

Bowl Chopper

Stationary Blender

Immersion Blender