One possible cause would be mass discrimination during the purge & trap
step.

I suspect the same to be case for SPME as this technique already affects
/ alters 13C values of BTEX's to a significant degree (relative to the
13C scale). Obviously, any isotopic fraction visibly affecting 13C
abundance will wreak havoc with 2H.


Wolfram




> -----Original Message-----
> From: Stable Isotope Geochemistry
> [mailto:[log in to unmask]] On Behalf Of DUCLERC Dominique
> Sent: 24 June 2004 11:54
> To: [log in to unmask]
> Subject: delta D on BTEX
>
>
> We are working on BTEX dissolved in water .
> We want to measure isotopic value of Hydrogene ,using an
> isoprime gc  with chromium furnace. We have standard
> compounds ,delta D values  are known . we obtain good results
> on isoprime gc (between 12 and -80 ) when we inject them pure
> or in solution in n-pentane . We dissolve them in water and
> inject them with spme or purge and trap and we obtain delta
> values between 200 and 800... Masse 3 is really high  in that
> case. I know this kind of measurement is good with gc-tc
> delta plus XL and  I don't understand what is happening on
> isoprime gc. thanks for you ideas...
>
>
> Dominique Duclerc
>
> TOTAL. SA
> Exploration & Production
> Geoscience Technologies
> Fluids and Organic Geochemistry
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>