ORMS-5: Elevated Mercury in River Water

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ORMS-5 is a river water spiked with inorganic mercury. The material is packaged in 50 ml glass ampoules stabilized with 0.5% v/v BrCl.

Table 1: Certified quantity value for ORMS-5

Element	pg/g
Hg	26.2 ± 1.3

The certified value was derived gravimetrically and corroborated with two methods of analysis: cold vapour isotope dilution inductively coupled plasma mass spectrometry (ID-ICP-MS) and flow injection cold vapour atomic absorption spectrometry (CV-AAS). The certified value is the unweighted mean of the results ± the expanded (k=2) uncertainty (U_CRM). The results generated by each of these methods were judged to be independent.

The expanded uncertainty in the certified value is equal to U_CRM = ku_c, where u_c is the combined standard uncertainty calculated according to the JCGM Guide ^Footnote1 and k is the coverage factor. It is intended that U_CRM encompasses the uncertainty of every factor that reasonably contributes to the total uncertainty of the measurand ^{Footnote2 Footnote3}. A coverage factor k=2 is used to give an uncertainty interval that contains roughly 95% of the underlying distribution. The value of u_c is determined from the combined uncertainties of the methods (u_char) as well as uncertainties associated with homogeneity (u_hom).

Intended use

This CRM is intended for the calibration of instruments and evaluation of methods for the determination of mercury.

Preparation

This sample of river water was collected from the Ottawa River near Ottawa, Ontario. An appropriate volume of concentrated BrCl, prepared according to reference 4 ^Footnote4, was added in addition to a spike of inorganic Hg. The water was aliquoted into 50 ml precleaned glass ampoules and flame sealed. The ampoules were gamma irradiated to a minimum dose of 25 kGy at the Canadian Irradiation Centre, Laval, Quebec.

Storage

It is recommended that the material be stored at room temperature and the vials opened immediately prior to use.

Stability

Studies of similar waters indicate that the material is stable with respect to the total Hg mass fraction for more than ten years.

Opening the vials

PLEASE USE APPROPRIATE CAUTION WHEN OPENING THE VIALS AS SHARP GLASS EDGES MAY CAUSE INJURY.

A piece of tubing has been provided to provide protection when snapping open the prescored vial. When opening an ampoule, place the plastic tubing over the stem, grasp the tubing in one hand and the body in the other, placing thumbs tip-to-tip near the constriction. Using thumb tips as a hinge, bend the stem and the body to break the ampoule open. It is preferable to sample directly from the vial as contamination may occur if the liquid comes in contact with freshly exposed surfaces of the vial.

Expiration of certification

The certified value is considered valid until September 2021 within the measurement uncertainty specified, provided the CRM is handled and stored in accordance with the instructions.

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 ORMS-5: P. Grinberg, S. Willie and L. Yang.

Date of issue: September 2011
Date of expiry: September 2021

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.inms@nrc-cnrc.gc.ca