Dear Wolfram,

I have a preprint of a paper by Ahmad Tanweer and Liang-feng Han on
"Reduction of microlitre amounts of water with manganese for D/H isotope
ratio measurement by mass spectrometry". It was submitted to Isotopenpraxis.
I don't know wether or not it was ever published. The results are very
similar to those obtained with Zn reduction with a precision on the order of
+/- 1 per mille. These authors used a 100:1 wt ratio of Mn:water but did
report that there was no amount effect, thus weighing of the Mn was not
critical. They also reported that no reagent pre-treatment was necessary as
you suggested in your note.

Unfortunately the paper does not report on any results from either low pH,
or high salinity waters, so it is difficult to say if it would solve
Natalies problems. I suspect that in this particular case it is the salinity
rather than the pH that is the problem and that using a U furnace would help
matters greatly. Personally I would not want to go down the route of
distillation unless it was a last option.

Perhaps Mannfred Groenning or Kaz Rozanski at the IAEA could comment further
on the Mn method. I think it was developed in the Vienna Lab.

Regards,

Paul
Stable Isotope Laboratory,
Environmental Sciences,
UEA