NISTCharleston

CHEMICAL SCIENCES DIVISION: Cryogenic Reference Material Production Facility

Chemical Sciences Division 

PSA utilized for multiple purposes

CRYOHOMOGENIZATION

The NIST Cryogenic Reference Material Production Facility at the Hollings Marine Laboratory produces raw material for developing Standard Reference

Materials (SRMs®) and control materials (CMs) used in the measurement of analytes of interest. This facility consists of ISO Class 7 clean room space and the

specialized equipment required for producing fresh-frozen cryohomogenized materials.

Continuously develop and 

provide the world-class 

measurement science 

expertise and capabilities 

needed to support 

economically critical U.S. 

enterprises in biology, 

chemistry, and materials 

science, and to underpin 

related global standards.

Broaden access to and 

impact of NIST reference 

products and standards to 

accelerate innovation, 

support the creation of 

new industries, and 

enhance global commerce 

and trade.

Actively engage with 

customers, partners, 

stakeholders, and 

collaborators to expand 

our scientific reach and 

heighten our customer 

focus.

Develop the leadership 

depth, breadth of 

technical capabilities and 

staff talents, and 

administrative expertise 

and processes needed to 

excel in our mission.

Cryohomogenized SRMs are produced using

the Palla VM-KT Vibrating Cryomill (Cryomill)

creating a fresh, frozen powder sample.

1.) Before using the Cryomill samples must be

cut or crushed (if already frozen) into small

fragments (< 2.5 cm) in order to fit properly

into the Cryomill feeder.

The Cryomill is cooled using liquid nitrogen

(LN2). The motor begins vibrating and

rotating 26 titanium rods located within the

drum chamber.

2.) The pre-frozen sample fragments are

introduced into the feeder at the top of the

Cryomill.

3.) The sample travels through the

vibrating chamber where the titanium rods

are located.

4.) Cryohomogenized powder sample falls from a

distribution tube at the bottom of the Cryomill.

The sample is caught in a container and quickly

placed in an LN2 vapor-phase freezer (-150° C).

The cryohomogenized powder is then passed

through the Cryomill following the steps above 2

to 3 more times to ensure homogeneity.

After homogenization is complete, the sample is

bottled and ready for value assignment and

certification.

PARTICLE SIZE ANALYSIS OF SRMs®/CMs

Laser-diffraction particle size analysis (PSA) using wet dispersion can measure the

equivalent spherical diameter in an average volume distribution.

Particles are recirculated via wet dispersant.

Lasers produce scatter as particles pass

through beams. Light scattering and optical

properties of the material are used to

determine the equivalent spherical diameter.

 During production to determine diminishing returns of milling or if material is 

sufficiently milled past a pre-determined threshold.

 Determine fraction that is below the respiratory hazard threshold ( < 10 μm) 

 Size characterization of a material to determine homogeneity of size across batches 

 Whether material is too large/small for critical environments or instrumentation.

Example 1. SRM 1565 Mycotoxins in Corn

PSA used to track progress in cryomilling

operations

SRM Mycotoxin Corn Round 1 SRM Mycotoxin Corn Round 2

Round 1 Round 2

Example 2. SRM 2682c Subbituminous Coal

Particle size characterization reported as an 

Information Value on the Certificate of Analysis

36% < 10 μm in diameter

1)

2)

3)

4)