AMET-1: Certified Reference Material of L-methionine

The following tables show those constituents for which certified and information values have been established for this L-methionine pure substance certified reference material (CRM).

The value represents the purity of L-methionine and is based on results from data generated at NRC using quantitative proton nuclear magnetic resonance spectroscopy (1H‑qNMR). 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 [1] and k is the coverage factor. A coverage factor of two (2) was applied for L-methionine. It is intended that UCRM accounts for every aspect that reasonably contributes to the uncertainty of the certified value.

Table 1: Certified value for AMET-1

Substance Molecular formula Mass Fraction,
L-methionine (a) C5H11NO2S 0.9989 ± 0.0034

Table 2: Information value for AMET-1

Substance Molecular formula Mass Fraction,
water (b) H2O 9.9×10–5


The coding refers to the instrumental method of analyte determination.

  • a - Quantitative proton nuclear magnetic resonance spectroscopy (1H-qNMR)
  • b - Karl Fischer titration

Intended use

This reference material is primarily intended for use in the calibration of procedures and the development of methods for the determination of L-methionine. A minimum sample mass of 15 mg is recommended.


It is recommended that the material be stored in a controlled cold temperature environment such as a refrigerator between 2 to 8 °C. After use the bottle should be tightly closed and stored properly.


Included in the combined uncertainty estimate (uc) are uncertainties in the batch characterization (uchar), uncertainties related to possible between-bottle variation (uhom), uncertainties related to stability (ustability) and uncertainties related to variability between different qNMR signals (umethod). Expressed as standard uncertainties, these components are listed in Table 3.

Table 3: Uncertainty components for AMET-1

Substance Uc,k=2,
L-methionine 0.0034 0.0017 0.0017 0.0000 0.0000 0.0002

Date of issue: February 2017
Date of expiry: February 2022
Revised: December 2017 (homogeneity and uncertainty sections, uhom in table 3 and editorial updates)

Date modified: