NIMS-1: Natural abundance inorganic mercury isotopic certified reference material

Certified values for isotope amount ratios, isotopic abundances and atomic weight of mercury have been established for this natural abundance inorganic mercury isotopic reference material (NIMS-1). These are listed in the table below.

Certified values are based on the unweighted mean of thirty-seven sets of measurement results generated at NRC. The expanded uncertainty (UCRM) in the certified values is equal to UCRM = kuc, where uc is the combined standard uncertainty calculated according to the JCGM Guide and k is the coverage factor. The value of uc is determined from the combined uncertainties associated with the analytical method (uchar) and with homogeneity (uhom). A coverage factor of two (2) was applied. It is intended that UCRM encompasses the uncertainty of every factor that reasonably contributes to the total uncertainty of the measurand.

Table 1: Certified quantity values

Isotope mass number, A Isotope amount ratio,
Isotope abundance,
196 0.0154(4) 0.001 55(4)
198 1 (exact) 0.100 38(10)
199 1.6873(11) 0.169 38(9)
200 2.3050(24) 0.231 38(6)
201 1.3120(24) 0.131 70(12)
202 2.9629(39) 0.297 43(9)
204 0.6792(12) 0.068 18(6)

Table 2: Certified quantity values

Atomic weight, Ar(Hg)

Intended use

This certified reference material is intended for the calibration of instruments and evaluation of analysis methods for the determination of isotope ratios of mercury.


Guidelines for CRM producers suggest all sources relevant to the user of the material should contribute to the uncertainty of the certified value . Included in the overall uncertainty estimate are uncertainties associated with the batch characterization (uchar) as well as uncertainties related to possible between-bottle variation (uhom).

Potential instabilities due to long-term storage and transport were not considered, as it is believed that the effects of such event would not be isotope specific.

Date of issue: July 2010
Date of expiry: July 2020
Revised: March 2016 (editorial update)

Date modified: