Remy,

Interesting question.

I only kinda, sorta, know an answer, so I'll foolishly wade in anyway.

We enrich tritium at low temperature by alkaline hydrolysis.  Our 
system is only about 85% efficient in retaining 3H.  We don't measure 
dD of the remaining water to calculate our enrichment.  We calibrate 
our system directly by enriching standards.   But some folks do measure 
enrichment by measuring dD and the water remaining after reducing, say, 
250 ml to 25 ml or so is extremely heavy.

Of course, you are asking about oxygen rather than hydrogen.  But my 
gut feeling is that unless you quantitatively electrolyze all of the 
water and quantitatively recover all of the oxygen, the fractionation 
could be large.

On Feb 28, 2007, at 1:55 PM, Remy Okazaki wrote:

> I would like to isolate oxygen from water for isotopic analysis, so I 
> can
> calibrate the oxygen standard in a mass spectrometer.  I was thinking
> electrolysis to separate H and O, but would any fractionation occur 
> during this
> process?
>
> Conversely, if anyone knows where/how I can purchase an oxygen gas 
> standard to
> calibrate the mass spec, I would appreciate any input.  Thanks,
> Remy Okazaki
>
>
-- 
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