Original Paper

Analytical and Bioanalytical Chemistry

, Volume 385, Issue 1, pp 168-180

Certification of a new selenized yeast reference material (SELM-1) for methionine, selenomethinone and total selenium content and its use in an intercomparison exercise for quantifying these analytes

  • Zoltán MesterAffiliated withInstitute for National Measurement Standards, National Research Council of Canada Email author 
  • , Scott WillieAffiliated withInstitute for National Measurement Standards, National Research Council of Canada
  • , Lu YangAffiliated withInstitute for National Measurement Standards, National Research Council of Canada
  • , Ralph SturgeonAffiliated withInstitute for National Measurement Standards, National Research Council of Canada
  • , Joseph A. CarusoAffiliated withUniversity of Cincinnati, Department of Chemistry
  • , María Luisa FernándezAffiliated withDepartment of Physical and Analytical Chemistry, University of Oviedo
  • , Peter FodorAffiliated withDepartment of Applied Chemistry, Corvinus University of Budapest
  • , Robert J. GoldschmidtAffiliated withFood Composition Laboratory, BHNRC, ARS, USDA
  • , Heidi Goenaga-InfanteAffiliated withLaboratory of the Government Chemist
    • , Ryszard LobinskiAffiliated withGroup of Bio-Inorganic Analytical Chemistry, CNRS UMR 5034Department of Chemistry, Warsaw University of Technology
    • , Paulette MaxwellAffiliated withInstitute for National Measurement Standards, National Research Council of Canada
    • , Shona McSheehyAffiliated withInstitute for National Measurement Standards, National Research Council of Canada
    • , Aleksandra PolatajkoAffiliated withGroup of Bio-Inorganic Analytical Chemistry, CNRS UMR 5034Department of Chemistry, Warsaw University of Technology
    • , Baki B. M. SadiAffiliated withUniversity of Cincinnati, Department of Chemistry
    • , Alfredo Sanz-MedelAffiliated withDepartment of Physical and Analytical Chemistry, University of Oviedo
    • , Christine ScriverAffiliated withInstitute for National Measurement Standards, National Research Council of Canada
    • , Joanna SzpunarAffiliated withGroup of Bio-Inorganic Analytical Chemistry, CNRS UMR 5034
    • , Raimund WahlenAffiliated withLaboratory of the Government Chemist
    • , Wayne WolfAffiliated withFood Composition Laboratory, BHNRC, ARS, USDA

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Abstract

A new selenized yeast reference material (SELM-1) produced by the Institute for National Measurement Standards, National Research Council of Canada (INMS, NRC) certified for total selenium (2,059±64 mg kg−1), methionine (Met, 5,758±277 mg kg−1) and selenomethionine (SeMet, 3,431±157 mg kg−1) content is described. The ±value represents an expanded uncertainty with a coverage factor of 2. SeMet and Met amount contents were established following a methanesulfonic acid digestion of the yeast using GC-MS and LC-MS quantitation. Isotope dilution (ID) calibration was used for both compounds, using 13C-labelled SeMet and Met. Total Se was determined after complete microwave acid digestion based on ID ICP-MS using a 82Se spike or ICP-OES spectrometry using external calibration. An international intercomparison exercise was piloted by NRC to assess the state-of-the-art of measurement of selenomethione in SELM-1. Determination of total Se and methionine was also attempted. Seven laboratories submitted results (2 National Metrology Institutes (NMIs) and 5 university/government laboratories). For SeMet, ten independent mean values were generated. Various acid digestion and enzymatic procedures followed by LC ICP-MS, LC AFS or GC-MS quantitation were used. Four values were based on species-specific ID calibration, one on non-species-specific ID with the remainder using standard addition (SA) or external calibration (EC). For total selenium, laboratories employed various acid digestion procedures followed by ICP-MS, AFS or GC-MS quantitation. Four laboratories employed ID calibration, the remaining used SA or EC. A total of seven independent results were submitted. Results for methionine were reported by only three laboratories, all of which used various acid digestion protocols combined with determination by GC-MS and LC UV. The majority of participants submitted values within the certified range for SeMet and total Se, whereas the intercomparison was judged unsuccessful for Met because only two external laboratories provided values, both of which were outside the certified range.

Keywords

Selenomethionine Yeast Reference material Speciation Intercomparison