VSMOW , hydrogen isotopes

FIGURE 15.2 Potential variation in the hydrogen isotopic composition of a range of different materials. Reprinted from T.B. Coplen et al. [16], with permission from Coplen. SLAP, Standard Light Antarctic Precipitation GISP, Greenland Ice Sheet Precipitation VSMOW, Vienna Standard Mean Ocean Water NBS, National Bureau of Standards NGS, natural gas standards. 

These delta values (read delta C-13 , or delta carbon-13 ) are typically given in parts per thousand ( permil , %o). For historical reasons, carbon stable isotopes are reported relative to the PDB (Pee Dee Belemnite, a fossil) or the equivalent VPDB (Vienna PDB) standard. Oxygen and hydrogen stable isotopes are reported relative to SMOW (Standard Mean Ocean Water) or the equivalent VSMOW (Vienna SMOW). The VPDB and VSMOW standards are preferred, not only because the original standards, PDB and SMOW, are no longer available, but also because they imply that the measurements have been calibrated according to international conventions. 

Seed oils were characterized by fatty acid composition as well as bulk and compound-specific isotopic analyses. After fatty acid saponification and derivatization with methanolic sodium hydroxide and methanolic boron trifluoride, the fatty acid composition was assessed by GC-FID equipped with a 30 m Supelcowax-10 column. For the determination of bulk carbon, oxygen and hydrogen composition values in %o VPDB, and values in %o VSMOW), a continuous He-flow... 

---