CACB-1: Calcium carbonate certified reference material for lead and cadmium

The following table shows those elements for which certified values have been established for this calcium carbonate reference material (CACB-1).

Certified values are based on unweighted mean results from data generated by two independent methods. The expanded uncertainty (UCRM) in the certified value is equal to U = 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 of the various analytical methods (uchar) as well as uncertainties associated with homogeneity (uhom).

It is intended that UCRM encompasses every aspect that reasonably contributes to the uncertainty of the measurement. A coverage factor of k=2 was applied for all elements.

Table 1: Certified quantity value

Element Mass fraction, ng/g
Cd 7.6 ± 1.1
Pb 243 ± 14

Intended use

CACB-1 is intended for the calibration of instruments and evaluation of methods for the determination of Pb and Cd in calcium carbonate or materials of a similar matrix.


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 in the characterization (uchar), uncertainties related to possible between-bottle variation (uhom) as well as instability derived from effects relating to long-term storage and transport (ustab). Results from the uncertainty components used to calculate the certified values are shown in Table 2.

Table 2: Uncertainty Components

Element Uncertainty, ng/g
uchar / (ng/g) uhom / (ng/g) uc / (ng/g) uCRM (k=2)
Cd 0.50 0.12 0.53 1.1
Pb 7.1 1.0 7.2 14

Table 3: Information values for trace metals

Element Mass fraction, ng/g
Mean s
Ba 3.45 0.02
Sr 225 1
Ni 4.33 0.03
Cu 0.35 0.01
Zn 4.88 0.10
Mo 0.40 0.01

Date of issue: August 2005
Date of expiry: April 2020
Revised: January 2015 (expiry date extended, layout and editorial changes), March 2016 (editorial update)

Date modified: