title: Measurement of the delta34S value in methionine by double spike multi-collector thermal ionization mass spectrometry using Carius tube digestion.
abstract: Methionine is an essential amino acid and is the primary source of sulfur for humans. Using the double spike ((33)S-(36)S) multi-collector thermal ionization mass spectrometry (MC-TIMS) technique, three sample bottles of a methionine material obtained from the Institute for Reference Materials and Measurements have been measured for delta(34)S and sulfur concentration. The mean delta(34)S value, relative to Vienna Canyon Diablo Troilite (VCDT), determined was 10.34 +/- 0.11 per thousand (n = 9) with the uncertainty reported as expanded uncertainties (U). These delta(34)S measurements include a correction for blank which has been previously ignored in studies of sulfur isotopic composition. The sulfur concentrations for the three bottles range from 56 to 88 microg/g. The isotope composition and concentration results demonstrate the high accuracy and precision of the DS-MC-TIMS technique for measuring sulfur in methionine.
authors.affiliation: Inorganic Chemical Metrology Group, Analytical Chemistry Division, National Institute of Standards and Technology, 100 Bureau Drive, MS8391, Gaithersburg, MD 20899, USA. jmann@nist.gov
authors.forename: Jacqueline L
authors.initials: JL
authors.lastname: Mann
authors.forename: W Robert
authors.initials: WR
authors.lastname: Kelly
mesh_terms: D002138:Calibration; D013058:Mass Spectrometry / Q000379:methods*; D008715:Methionine / Q000737:chemistry*; D010084:Oxidation-Reduction; D013460:Sulfur Isotopes / Q000737:chemistry*
chemical_list: D013460:Sulfur Isotopes; D008715:Methionine