title: 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.
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.
authors.affiliation: Institute for National Measurement Standards, National Research Council of Canada, Ottawa, ON K1A 0R6, Canada. Zoltan.mester@nrc.ca
authors.forename: Zoltán
authors.initials: Z
authors.lastname: Mester
authors.forename: Scott
authors.initials: S
authors.lastname: Willie
authors.forename: Lu
authors.initials: L
authors.lastname: Yang
authors.forename: Ralph
authors.initials: R
authors.lastname: Sturgeon
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Caruso
authors.forename: María Luisa
authors.initials: ML
authors.lastname: Fernández
authors.forename: Peter
authors.initials: P
authors.lastname: Fodor
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Goldschmidt
authors.forename: Heidi
authors.initials: H
authors.lastname: Goenaga-Infante
authors.forename: Ryszard
authors.initials: R
authors.lastname: Lobinski
authors.forename: Paulette
authors.initials: P
authors.lastname: Maxwell
authors.forename: Shona
authors.initials: S
authors.lastname: McSheehy
authors.forename: Aleksandra
authors.initials: A
authors.lastname: Polatajko
authors.forename: Baki B M
authors.initials: BB
authors.lastname: Sadi
authors.forename: Alfredo
authors.initials: A
authors.lastname: Sanz-Medel
authors.forename: Christine
authors.initials: C
authors.lastname: Scriver
authors.forename: Joanna
authors.initials: J
authors.lastname: Szpunar
authors.forename: Raimund
authors.initials: R
authors.lastname: Wahlen
authors.forename: Wayne
authors.initials: W
authors.lastname: Wolf
mesh_terms: D002853:Chromatography, Liquid / Q000379:methods*; D013058:Mass Spectrometry / Q000379:methods*; D008715:Methionine / Q000032:analysis* / Q000737:chemistry; D012015:Reference Standards; D012441:Saccharomyces cerevisiae / Q000737:chemistry*; D012643:Selenium / Q000032:analysis* / Q000737:chemistry; D012645:Selenomethionine / Q000032:analysis* / Q000737:chemistry
chemical_list: D012645:Selenomethionine; D008715:Methionine; D012643:Selenium