ORMS-5: Elevated Mercury in River Water

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

Table 1: Certified quantity value

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 (UCRM). The results generated by each of these methods were judged to be independent.

The expanded uncertainty in the certified value is equal to UCRM = kuc, where uc is the combined standard uncertainty calculated according to the JCGM Guide and k is the coverage factor. It is intended that UCRM encompasses every source that reasonably contributes to the uncertainty of the measurand. A coverage factor k=2 is used to give an uncertainty interval that contains roughly 95% of the underlying distribution. The value of uc is determined from the combined uncertainties of the methods (uchar) as well as uncertainties associated with homogeneity (uhom).

Intended use

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

Date of issue: September 2011
Date of expiry: September 2021
Revised: March 2016 (editorial update)

Date modified: