SLRS-5: River water reference material for trace metals

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The following table lists the elements for which certified values have been established along with their expanded uncertainty (U_CRM = ku_c, where u_c is the combined standard uncertainty calculated according to the JCGM Guide ^{Footnote 1} and k=2 is the coverage factor). It is intended that U_CRM encompasses every aspect that reasonably contributes to the uncertainty of the certified mass fraction ^{Footnote 2}.

Certified values are based on the results of determinations by at least two independent methods of analysis. Information values (identified with an "*") are listed for elements which could not be certified because of insufficient information for accurate assessment of the associated uncertainties. The density of SLRS-5 is 1.0007 g/mL.

Table 1: Certified quantity values for SLRS-5

Element	Mass Fraction, (μg/kg)
Aluminum (c,g,j)†	49.5 ± 5.0
Antimony* (d)	0.3
Arsenic (c,h)	0.413 ± 0.039
Barium (d,j)	14.0 ± 0.5
Beryllium* (c)	0.005
Cadmium (d,e,n)	0.0060 ± 0.0014
Chromium (d,e)	0.208 ± 0.023
Cobalt* (c)	0.05
Copper (d,g,j)	17.4 ± 1.3
Iron (d,g,i)	91.2 ± 5.8
Lead (d,e,n)	0.081 ± 0.006
Manganese (c,g,i)	4.33 ± 0.18
Molybdenum (d)	0.27 ± 0.04
Nickel (d,e)	0.476 ± 0.064
Strontium (d,i)	53.6 ± 1.3
Uranium (d)	0.093 ± 0.006
Vanadium (c,n)	0.317 ± 0.033
Zinc (d,g,i)	0.845 ± 0.095

Table 2: Certified Quantity Values for Major Elements in SLRS-5

Element	Mass Fraction, (μg/g)
Calcium (f,i)	0.845 ± 0.095
Magnesium (c,f,i)	2.54 ± 0.16
Potassium (f,i)	0.839 ± 0.036
Sodium (f,i)	5.38 ± 0.10

Coding

• c - Direct determination by inductively coupled plasma mass spectrometry (ICPMS)
• d - Direct determination by isotope dilution ICPMS
• e - Concentration by evaporation; determination by graphite furnace atomic absorption spectrometry (GFAAS)
• f - Direct determination by flame atomic absorption spectrometry (FAAS)
• g - Direct determination by GFAAS
• h - Hydride generation; determination by GFAAS
• i - Direct determination by inductively coupled plasma emission spectrometry (ICPAES)
• j - Concentration by evaporation; determination by ICPAES
• n - Matrix separation; determination by ICPMS

Intended use

This certified reference material is primarily intended for use in the calibration of procedures and the development of methods used for the analysis of water for trace metals.

Storage and sampling

It is recommended that the material be stored in a cool, clean location. The bottles should be opened only in a clean area with precautions taken against contamination during sampling.

Preparation of SLRS-5

Untreated river water was collected at the City of Ottawa's Britannia Water Purification Plant. The water was peristaltically pumped through 0.45 μm porosity acrylic copolymer filters and immediately acidified with ultrapure nitric acid to pH 1.6 during transfer to polypropylene carboys. The water was later refiltered through 0.2 μm porosity acrylic copolymer filters into a polyethylene tank in a clean room at NRC. It was subsequently blended and bottled in precleaned polyethylene containers. The bottled water was gamma irradiated to a minimum dose of 25 kGy at the Canadian Irradiation Centre, Laval, Québec, to inhibit any bacterial action.

Stability

Studies of similar waters indicate that the material is stable with respect to total trace metal concentrations for at least ten years.

Expiry

The certified values for SLRS-5 are considered valid until May 2019, provided the CRM is handled and stored in accordance with instructions herein.

Certified value

The analytical work was done within NRC. Randomly selected bottles were chosen for the analytical determinations. Results from different bottles showed no significant differences, nor was there any correlation between values obtained and bottle sequence.

Certified values were calculated using a procedure that conforms to the ISO framework of combining measurement uncertainties. Individual method uncertainties were calculated and combined with a type B bias uncertainty to derive the final values ^{Footnote 2}. Based on NRC's experience with similar materials, uncertainty components for homogeneity, and long and short term stability were considered negligible and are thus not included in the uncertainty budget.

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 SLRS-5: V. Boyko, C. Brophy, V. Clancy, S. Willie and L. Yang.

The cooperation of the following is gratefullyacknowledged:  Erin Gorman and Ian Douglas, P. Eng. City of Ottawa, Drinking Water Services, Ottawa, ON Canada.

Date of issue: May 2009
Date of expiry: May 2019
Revised February 2012, Mo and U updated

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