TORT-3: Lobster Hepatopancreas 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 (U_CRM) in the certified value is equal to U = ku_c where u_c is the combined standard uncertainty calculated according to the JCGM Guide ^{Footnote 1} and k is the coverage factor. It is intended that U_CRM accounts for every aspect that reasonably contributes to the uncertainty of the measurement. A coverage factor of 2 was applied for all elements. The table below lists certified values for TORT-3 expressed on a dry mass basis.

Table 1: Certified Quantity Values for TORT-3

Element	Mass fraction, (mg/kg)
Arsenic (d,i)	59.5 ± 3.8
Cadmium (i,p)	42.3 ± 1.8
Chromium (i,p)	1.95 ± 0.24
Cobalt (d)	(1.06)*
Copper (d,i,p)	497 ± 22
Iron (d,i)	179 ± 8
Lead (d,p)	0.225 ± 0.018
Manganese (d,p)	15.6 ± 1.0
Mercury (p)	0.292 ± 0.022
Molybdenum (d,p)	3.44 ± 0.12
Nickel (d,p)	5.30 ± 0.24
Selenium (d,p)	10.9 ± 1.0
Strontium (i,p)	36.5 ± 1.6
Tin (d,p)	(0.029)*
Vanadium (d,p)	9.1 ± 0.4
Zinc (i,p)	136 ± 6
Arsenobetaine (as As)(o,t)	54.9 ± 2.5
Methylmercury (as Hg)(q,s)	0.137 ± 0.012

* an information value is listed due to insufficient information to accurately assess uncertainties.

Coding

The coding refers only to the instrumental method of analyte determination.

• d - inductively coupled plasma mass spectrometry
• i - inductively coupled plasma atomic emission spectrometry
• o - isotope dilution liquid chromatography orbitrap mass spectrometry
• p - isotope dilution inductively coupled plasma mass spectrometry
• q - gas chromatography inductively coupled plasma mass spectrometry
• s - gas chromatography mass spectrometry
• t - liquid chromatography inductively coupled plasma mass spectrometry

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 0.200 g sub-sample from the bottle.

Instructions for drying

Determination of dry mass should be performed on a separate sample to avoid contamination. TORT-3 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 material

This reference material was prepared from edible grade lobster tomalley. The material was homogenized, spray dried, defatted with hexane and vacuum dried. The resulting powder was bottled at NRC.

After bottling the material was sterilized by subjecting it to a minimum dose of 25 kGy gamma irradiation at the Canadian Irradiation Centre, Laval, Québec.

TORT-3 is lot #3 in the series of lobster hepatopancreas CRM's for trace metals.

Stability

The predecessor CRM, TORT-2, has been periodically analyzed for more than ten years and found to be both physically and chemically stable over this time interval. We expect similar results for TORT-3. Uncertainty components for long and short term stability were considered negligible and are thus not included in the uncertainty budget.

The methymercury content of TORT-3 is continually monitored by NRC. Studies indicate the methylmercury content in similar materials has been stable for more than ten years. This is not expected to change, provided the material is stored as noted above.

Homogeneity

The material was tested for homogeneity at NRC. Results from sub-samples (0.200 g) from thirty bottles were evaluated using ANOVA and included in the calculation of the certified values.

Uncertainty

Included in the overall uncertainty estimate (u_c) are uncertainties in the batch characterization (u_char) and uncertainties related to possible between-bottle variation (u_hom). Expressed as standard uncertainties these components are listed in Table 2.

Table 2: Uncertainty components for TORT-3

Element	uc, mg/kg	uchar,	uhom,
As	1.9	1.7	0.8
Cd	0.9	0.5	0.8
Cr	0.12	0.06	0.10
Cu	11	9	6
Fe	4	4	3
Pb	0.009	0.004	0.009
Mn	0.5	0.5	0.2
Hg	0.011	0.005	0.010
Mo	0.06	0.04	0.05
Ni	0.12	0.10	0.06
Se	0.5	0.4	0.3
Sr	0.8	0.6	0.5
V	0.2	0.2	0.2
Zn	3	2	2
MeHg(Hg)	0.006	0.004	0.005
AsBet(As)	1.23	0.96	0.77

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.

Acknowledgements

The following staff members of the Measurement Science and Standards portfolio at the NRC contributed to the production and certification of TORT-3: I. Pihillagawa Gedara, P. Maxwell, J. Meija, Z. Mester, S. Willie and L. Yang.

The cooperation of the following in the preparation and analysis of this material is gratefully acknowledged:

Doug Singer and Tom Gill, Canadian Institute of Fisheries Technology, Dalhousie University, Halifax, NS.

Udaya Wanasundara, POS Biosciences, Saskatoon, SK.

Date of issue: April 2013
Date of expiry: April 2023

Approved by:

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
Email: CRM-MRCInorganic-Inorganiques@nrc-cnrc.gc.ca