Recently I have been puzzled trying to understand what was the zero scale
value of some reference materials commonly used for 18O analysis.

According to Items 011796 Gerard Olack, Item 011666-009992 and 009492 by
Willi Brand (and related items on Isogeochem historical record), the new
benzoic acids IAEA-601 and 602 are vs. SMOW. But surfing the internet I
have found that the values were vs. PDB.

At present I am outside my office and I cannot check the IAEA catalogue,
but I have been told that the general list of IR products does not specify
if the value is against SMOW or PDB.

In older time there was the golden rule that water has to be reported against
SMOW and rocks and carbonates against PDB. But what about new applications,
where the two "fields" might converge? Is ther any attempt to unify all
this?
Thanks
Francesca Serra