SELM-1: Selenium enriched yeast certified reference material

The following table shows those analytes for which certified values have been established for this selenium enriched yeast reference material (SELM-1).

Certified values are based on unweighted mean results from data generated by three independent sets of measurements in the case of selenomethionine (SeMet ) and methionine (Met) and two independent measurements for total selenium. 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 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) and stability (ustab). It is intended that UCRM encompasses every aspect that reasonably contributes to the uncertainty of the measurand. A coverage factor of 2 was applied.

Table 1: Certified quantity values

Measurand Mass fraction,
mg/kg
Total Selenium 2031 ± 70
Selenomethionine 3190 ± 260
Methionine 5790 ± 100

Intended use

This certified reference material is intended for the calibration of instruments and evaluation of methods for the determination of SeMet, Met, and total selenium in yeast or materials of a similar matrix. The material is not intended for nutritional, medical or diagnostic use. A minimum sample mass of 60 mg is recommended.

Uncertainty

Included in the combined uncertainty estimate (Uc) are uncertainties in the batch characterisation (uchar), uncertainties related to possible between-bottle variation (uhom), uncertainties related to long-term storage and stability (ustab), and uncertainties realted to inconsistency between the various measurement methods (Umethod). Expressed as standard uncertainties, these components are listed in Table 2.

Table 2: Uncertainty components

Substance Uc, mg/kg Uchar, mg/kg Uhom, mg/kg Ustability, mg/kg Umethod, mg/kg
total selenium 35 11 15 - 30
selenomethionine 130 30 20 99 80
methionine 50 20 30 32 10

Date of issue: June 2005
Date of expiry: April 2019
Revised: December 2006, May 2010, December 2006, May 2010, May 2015 (editorial changes, certified values revised for total selenium, methionine and selenomethionine, date of expiry), March 2016 (editorial update)

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