DORM-4: Fish protein certified reference material for trace metals

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The following table shows those elements for which certified values have been established for this reference material. Certified values are based on results from data generated at NRC. The expanded uncertainty (UCRM) in the certified value is equal to U = kuc where uc is the combined standard uncertainty calculated according to the JCGM Guide Footnote1 and k is the coverage factor. It is intended that UCRM encompasses every aspect that reasonably contributes to the uncertainty of the measurement Footnote2. A coverage factor of 2 was applied for all elements. The table below lists certified values for DORM-4 expressed on a dry mass basis.

Table 1: Certified quantity values for DORM-4
Element Mass fraction, (mg/kg)
Arsenic (d) 6.80 ± 0.64
Cadmium (p) 0.306 ± 0.015
Copper (p) 15.9 ± 0.9
Chromium (p) 1.87 ± 0.16
Iron (p) 341 ± 27
Lead (p) 0.416 ± 0.053
Mercury (p) 0.410 ± 0.055
Nickel (p) 1.36 ± 0.22
Tin (p) 0.056 ± 0.010
Selenium (p) 3.56 ± 0.34
Zinc (p) 52.2 ± 3.2
Methylmercury (as Hg) (q,s) 0.354 ± 0.031

Coding

The coding refers only to the instrumental method used for quantitation.

  • d - Inductively coupled plasma mass spectrometry
  • p - Isotope dilution inductively coupled plasma mass spectrometry
  • q - Isotope dilution gas chromatography inductively coupled plasma mass spectrometry
  • s - Isotope dilution gas chromatography mass spectrometry

All measurements contributing to this certificate were conducted by Chemical Metrology personnel at NRC in Ottawa.

Intended use

This reference material is primarily intended for use in the calibration of procedures and the development of methods for the determination of trace metals in marine fauna and materials of similar matrix.

Storage and sampling

This material should be stored in a cool and dark location. Prior to use, the bottle should be rotated and shaken to ensure the contents are well mixed. The bottle should be tightly closed thereafter. Certified values are based on a minimum 0.250 g sub-sample from the bottle.

Instructions for drying

Determination of dry mass should be performed on a separate sample to avoid contamination. DORM-4 can be dried to constant mass by:  (1) drying at reduced pressure (e.g., 50 mm Hg) at room temperature in a vacuum desiccator over magnesium perchlorate for 24 hours; (2) vacuum drying (about 0.5 mm Hg) at room temperature for 24 hours.

Preparation of DORM-4

This reference material was prepared from a fish protein homogenate. A uniform material was produced using an enzyme hydrolysis procedure subsequent to removal of the bones and the majority of the oil. The protein hydrolysate was spray dried, sieved to pass a 297 μm screen, blended and bottled. After bottling the material was sterilized by subjecting it to a minimum dose of 25 kGy gamma irradiation at the Canadian Irradiation Centre, Laval, Quebec.

Stability

The predecessor CRM, DORM-3, has been periodically analyzed for more than nine years and found to be both physically and chemically stable over this time interval. We expect similar results for DORM-4. Uncertainty components for long and short term stability were considered negligible and are thus not included in the uncertainty budget.

Homogeneity

The material was tested for homogeneity at NRC using ICP-MS. Results from sub-samples (0.250 g) from thirty bottles were evaluated using ANOVA and included in the calculation of the certified values.

Metrological traceability

Results presented in this certificate are traceable to the SI through gravimetrically prepared standards of established purity and international measurement intercomparisons. As such, they serve as suitable reference materials for laboratory quality assurance programs, as outlined in ISO/IEC 17025. This CRM is registered at the Bureau International des Poids et Mesures (BIPM) in Appendix C of the Comité International des Poids et Mesures database listing Calibration and Measurement Capabilities accepted by signatories to the Mutual Recognition Arrangement of the Metre Convention.

Accreditation

The Chemical Metrology laboratory is compliant to ISO 17025 and ISO Guide 34, with approval by The Inter-American Metrology System (SIM). The certificate of approval is available upon request.

Updates

Users should ensure that the certificate they have is current. The NRC web site will contain any new information.

References

Footnote 1

Evaluation of measurement data – Guide to the expression of uncertainty in measurement JCGM 100:2008.

Return to footnote 1 referrer

Footnote 2

J. Pauwels, A. van der Veen, A. Lamberty, H. Schimmel, Evaluation of uncertainty of reference materials. Accred Qual Assur (2000) 5:95-99.

Return to footnote 2 referrer

Acknowledgements

The following staff members of the Measurement Science and Standards portfolio at the NRC contributed to the production and certification of DORM-4: C. Brophy, V. Clancy, J. Lam, R. Sturgeon, L. Yang and S. Willie.

Date of issue: June 2012
Date of expiry: June 2022

Approved by:

Signature image of Dr. Zoltan Mester, Ph. D.

Zoltan Mester, Ph. D.
Group Leader, Chemical Metrology
Measurement Science and Standards

Comments, information and inquiries should be addressed to:

National Research Council of Canada
Measurement Science and Standards
1200 Montreal Road
Building M-12
Ottawa, Ontario K1A 0R6

Telephone: 613-993-2359
Fax: 613-993-2451
EmailCRM-MRCInorganic-Inorganiques@nrc-cnrc.gc.ca