Measurement of the δ 34 S value in methionine by double spike multi‐collector thermal ionization mass spectrometry using Carius tube digestion

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 δ 34 S and sulfur concentration. The mean δ 34 S value, relative to Vienna Canyon Diablo Troilite (VCDT), determined was 10.34 ± 0.11‰ (n = 9) with the uncertainty reported as expanded uncertainties (U). These δ 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 µg/g. The isotope composition and concentration results demonstrate the high accuracy and precision of the DS‐MC‐TIMS technique for measuring sulfur in methionine. Published in 2010 by John Wiley & Sons, Ltd.