title: Evaluation of commercially available reagents as a reference material for intramolecular carbon isotopic measurements of acetic acid.
abstract: BACKGROUND
  Recent advances in analytical techniques for the intramolecular carbon isotopic ratio measurement of some organic compounds have provided important information on carbon cycles in biochemistry, organic geochemistry and food chemistry. These advances have made it necessary to prepare intramolecular isotopic reference materials (RMs) to use for inter-laboratory calibration and/or inter-calibration among different analytical methods.
  
  
  METHODS
  We evaluated the feasibility of preparing RMs using commercially available reagents for intramolecular carbon isotopic ratio measurement of acetic acid. The intramolecular carbon isotopic distribution of nine acetic acid and four sodium acetate reagents was determined with high precision using off-line pyrolysis combined with gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS). We also evaluated the potential alteration in the isotopic signature of acetic acid reagents by evaporation.
  
  
  RESULTS
  The intramolecular carbon isotopic distributions for the acetic acid and sodium acetate reagents were determined with a precision of better than 0.45‰. We found that the isotopic values of these reagents spanned the carbon isotopic range of acetic acid in biological and environmental samples. We also found that the isotope fractionation associated with the evaporation of acetic acid occurs solely on the methyl position, the carboxyl position being unaffected.
  
  
  CONCLUSIONS
  These commercially available reagents will be used as RMs in the future for inter-laboratory calibration and/or inter-calibration with another intramolecular isotopic measurement technique, namely quantitative (13) C NMR. In cases where acetic acid is being used as a RM, its storage must be carefully controlled to prevent evaporation.
authors.affiliation: Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama, 226-8503, Japan.
authors.forename: Keita
authors.initials: K
authors.lastname: Yamada
authors.forename: Makiko
authors.initials: M
authors.lastname: Kikuchi
authors.forename: Alexis
authors.initials: A
authors.lastname: Gilbert
authors.forename: Naohiro
authors.initials: N
authors.lastname: Yoshida
authors.forename: Nariaki
authors.initials: N
authors.lastname: Wasano
authors.forename: Ryota
authors.initials: R
authors.lastname: Hattori
authors.forename: Satoshi
authors.initials: S
authors.lastname: Hirano
mesh_terms: D019342:Acetic Acid / Q000737:chemistry*; D002247:Carbon Isotopes / Q000032:analysis* / Q000737:chemistry; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods / Q000592:standards; D006358:Hot Temperature; D016014:Linear Models; D019346:Sodium Acetate / Q000737:chemistry; D012972:Sodium Hydroxide / Q000737:chemistry
chemical_list: D002247:Carbon Isotopes; D019346:Sodium Acetate; D012972:Sodium Hydroxide; D019342:Acetic Acid