Reference Material Production and Support

Summary

Reference materials (RMs), including NIST Standard Reference Materials (SRMs) are used for quality assurance, traceability of measurements and instrument and method validation. The Cryogenic Reference Material Production Facility at the Hollings Marine Laboratory houses specialized equipment required to generate fresh-frozen RMs, as well as multiple innovative tools used for processing unique materials. The distinctive ISO Class 5 and 7 clean room settings helps eliminate external sources of contamination, an important consideration when generating large batches of homogenous materials. To date, the facility staff have assisted in the development and production of more than 30 different reference materials, including dietary supplements and food products, wood products, sediment and coal dust as well as many marine species (mussels, kelp, aquacultured seafood and wild-caught seafood).

Description

Bulk Cryogenic Production

Large-batch cryogenic reference materials are produced using a Palla VM-KT Vibrating Cryomill. The mill is pre-cooled to cryogenic temperatures using liquid nitrogen. Frozen material is fed through the inlet funnel to a vibrating chamber containing 26 titanium rods. The rods pulverize the material into a fine powder. The fresh-frozen product is then extruded from the chamber through the outlet below.

Steps in processing RM 8256, Wild-caught Coho Salmon.  Left:  salmon fillets prior to freezing; middle:  processing frozen fillets; right:  cryogenic processing 

Credit: NIST

Particle Size Analysis

The particle size distribution of the resultant material is evaluated using laser-diffraction.  These data help assess homogeneity based on size and are used as a process control indicator to determine if additional milling is required.  Laser diffraction particle size analysis (PSA) is also used to assign informational values to existing RMs that require particle size data.

Production of SRM 1565 Mycotoxins in Corn.  Left:  cryogenic processing; middle:  researcher logging data; right:  ground samples

Credit: Alex Holt, NIST Staff

Small-Batch Production

Smaller batches of RM can be homogenized either cryogenically or at room temperature using polytetrafluoroethylene (PTFE) disk mills. Material is added to the disk mill in small pieces and loaded into a shaker. High force oscillations pulverize the material into a fine powder.

Grinding botanical samples for production of RGTM 10190 [Pesticide Residues in Spinach Leaves, Left:  disk mill containing botanical sample; middle:  disk mill apparatus for agitating disk mill, and right:  ground botanical sample.

Credit: NIST

Custom and Rapid-Response Materials

Staff are also developing and implementing protocols for generating custom RMs. Using techniques such as blending of multiple materials or amending matrices with endogenous analytes, in-house RMs can be generated when natural sources of material cannot be procured. These techniques can also be used to develop ‘rapid-response’ RMs to aid the measurement community in the event standardization of a specific measurement is immediately required and there is no time to collect and process large amounts of naturally- sourced material.

Antibiotics in Fish Tissue (test material).  Left:  Disk mill with powdered sample, middle:  apparatus for agitating disk mill, and right:  disk mill with sample, after removal of the grinding cylinder.

Credit: NIST

Production Contributions

• SRM 2974a: Organics in Freeze-Dried Mussel Tissue (Mytilus edulis)
• SRM 1974c/d: Organics in Mussel Tissue (Mytilus edulis)
• SRM 3279: Chromium Dietary Supplement
• SRM 2790: Inorganic Constituents in Hardwood Biomass Material
• SRM 2791: Inorganic Constituents in Softwood Biomass Material
• SRM 3233: Fortified Breakfast Cereal
• SRM 1936: Great Lakes Sediment Organics and Trace Elements
• SRM 1548b: Typical Diet
• RM 8301: Boron Isotopes in Marine Carbonate
• RM 1565: Mycotoxins in Corn
• RM 8256: Wild-caught Coho Salmon
• RM 8257: Aquacultured Coho Salmon
• RM 8258: Wild-caught Shrimp
• RM 8259: Aquacultured Shrimp
• SRM 2983: Inorganics in Geoduck Clam tissue*
• SRM 2783a: Air Particulate on Filter Media*
• RM 8694: Per- and Polyfluoroalkyl Substances in Bovine Tissue (Dairy Cow)*
• RM 8695: Per- and Polyfluoroalkyl Substances in Bovine Tissue (Beef Bull)*
• RM 8696: Per- and Polyfluoroalkyl Substances in Porcine Tissue*
• SRM 3223: Inorganic Constituents in Cigarette Tobacco Filler*
• SRM 1947a: Great Lakes Fish Tissue*
• RM 8462: Liver Suite (Omics Measurements Suitability)*
• RM 8048: Human Fecal Material*

PSA Contributions

• SRM 2684c: Bituminous Coal (Nominal Mass Fraction 3 % Sulfur)
• SRM 2448: Mercury in Brominated Activated Carbon
• SRM 2682c: Subbituminous Coal (Nominal Mass Fraction 0.5 % Sulfur)
• SRM 1635a: Trace Elements in Coal (Subbitumimous)
• SRM 1632e: Trace Elements in Coal (Bituminous)
• SRM 2683c: Bituminous Coal (Nominal Mass Fraction 2 % Sulfur)
• SRM 2445: Mercury in Iodized Activated Carbon
• SRM 2710a: Montana I Soil Highly Elevated Trace Element Concentrations
• SRM 1649b: Urban Dust
• SRM 2706: New Jersey Soil, Organics and Trace Elements
• SRM 2709a: San Joaquin Soil Baseline Trace Element Concentrations
• SRM 2711a: Montana II Soil Moderately Elevated Trace Element Concentrations
• SRM 2718a: Green Petroleum Coke
• SRM 2963a: Bituminous Coal (Nominal Mass Fraction 0.5 % Sulfur)*

*Candidate materials in progress